doc/lua-api/index.rst

.. toctree::
   :maxdepth: 2


How Lua runs in HAProxy
=======================

HAProxy Lua running contexts
----------------------------

The Lua code executed in HAProxy can be processed in 2 main modes. The first one
is the **initialisation mode**, and the second is the **runtime mode**.

* In the **initialisation mode**, we can perform DNS solves, but we cannot
  perform socket I/O. In this initialisation mode, HAProxy still blocked during
  the execution of the Lua program.

* In the **runtime mode**, we cannot perform DNS solves, but we can use sockets.
  The execution of the Lua code is multiplexed with the requests processing, so
  the Lua code seems to be run in blocking, but it is not the case.

The Lua code is loaded in one or more files. These files contains main code and
functions. Lua has 8 execution contexts.

1. The Lua file **body context**. It is executed during the load of the Lua file
   in the HAProxy `[global]` section with the directive `lua-load`. It is
   executed in initialisation mode. This section is use for configuring Lua
   bindings in HAProxy.

2. The Lua **init context**. It is a Lua function executed just after the
   HAProxy configuration parsing. The execution is in initialisation mode. In
   this context the HAProxy environment are already initialized. It is useful to
   check configuration, or initializing socket connections or tasks. These
   functions are declared in the body context with the Lua function
   `core.register_init()`. The prototype of the function is a simple function
   without return value and without parameters, like this: `function fcn()`.

3. The Lua **task context**. It is a Lua function executed after the start
   of the HAProxy scheduler, and just after the declaration of the task with the
   Lua function `core.register_task()`. This context can be concurrent with the
   traffic processing. It is executed in runtime mode. The prototype of the
   function is a simple function without return value and without parameters,
   like this: `function fcn()`.

4. The **action context**. It is a Lua function conditionally executed. These
   actions are registered by the Lua directives "`core.register_action()`". The
   prototype of the Lua called function is a function with doesn't returns
   anything and that take an object of class TXN as entry. `function fcn(txn)`.

5. The **sample-fetch context**. This function takes a TXN object as entry
   argument and returns a string. These types of function cannot execute any
   blocking function. They are useful to aggregate some of original HAProxy
   sample-fetches and return the result. The prototype of the function is
   `function string fcn(txn)`. These functions can be registered with the Lua
   function `core.register_fetches()`. Each declared sample-fetch is prefixed by
   the string "lua.".

   .. note::
      It is possible that this function cannot found the required data in the
      original HAProxy sample-fetches, in this case, it cannot return the
      result. This case is not yet supported

6. The **converter context**. It is a Lua function that takes a string as input
   and returns another string as output. These types of function are stateless,
   it cannot access to any context. They don't execute any blocking function.
   The call prototype is `function string fcn(string)`. This function can be
   registered with the Lua function `core.register_converters()`. Each declared
   converter is prefixed by the string "lua.".

7. The **filter context**: It is a Lua object based on a class defining filter
   callback functions. Lua filters are registered using
   `core.register_filter()`. Each declared filter is prefixed by the string
   "lua.".

8. The **event context**: Inside a function that handles events subscribed
   through `core.event_sub()` or `Server.event_sub()`.


HAProxy Lua Hello world
-----------------------

HAProxy configuration file (`hello_world.conf`):

::

    global
       lua-load hello_world.lua

    listen proxy
       bind 127.0.0.1:10001
       tcp-request inspect-delay 1s
       tcp-request content use-service lua.hello_world

HAProxy Lua file (`hello_world.lua`):

.. code-block:: lua

    core.register_service("hello_world", "tcp", function(applet)
       applet:send("hello world\n")
    end)

How to start HAProxy for testing this configuration:

::

    ./haproxy -f hello_world.conf

On other terminal, you can test with telnet:

::

    #:~ telnet 127.0.0.1 10001
    hello world

Usage of load parameters
------------------------

HAProxy lua-load(-per-thread) directives allow a list of parameters after
the lua file name. These parameters are accessible through an array of args
using this code `local args = table.pack(...)` in the body of loaded file.

Below, a new version of the hello world using load parameters

HAProxy configuration file (`hello_world.conf`):

::

    global
       lua-load hello_world.lua "this is not an hello world"

    listen proxy
       bind 127.0.0.1:10001
       tcp-request inspect-delay 1s
       tcp-request content use-service lua.hello_world

HAProxy Lua file (`hello_world.lua`):

.. code-block:: lua

    local args = table.pack(...)

    core.register_service("hello_world", "tcp", function(applet)
       applet:send(args[1] .. "\n")
    end)


Core class
==========

.. js:class:: core

   The "core" class contains all the HAProxy core functions. These function are
   useful for the controlling of the execution flow, registering hooks,
   manipulating global maps or ACL, ...

   "core" class is basically provided with HAProxy. No `require` line is
   required to uses these function.

   The "core" class is static, it is not possible to create a new object of this
   type.

.. js:attribute:: core.emerg

  :returns: integer

  This attribute is an integer, it contains the value of the loglevel
  "emergency" (0).

.. js:attribute:: core.alert

  :returns: integer

  This attribute is an integer, it contains the value of the loglevel
  "alert" (1).

.. js:attribute:: core.crit

  :returns: integer

  This attribute is an integer, it contains the value of the loglevel
  "critical" (2).

.. js:attribute:: core.err

  :returns: integer

  This attribute is an integer, it contains the value of the loglevel
  "error" (3).

.. js:attribute:: core.warning

  :returns: integer

  This attribute is an integer, it contains the value of the loglevel
  "warning" (4).

.. js:attribute:: core.notice

  :returns: integer

  This attribute is an integer, it contains the value of the loglevel
  "notice" (5).

.. js:attribute:: core.info

  :returns: integer

  This attribute is an integer, it contains the value of the loglevel
  "info" (6).

.. js:attribute:: core.debug

  :returns: integer

  This attribute is an integer, it contains the value of the loglevel
  "debug" (7).

.. js:attribute:: core.proxies

  **context**: task, action, sample-fetch, converter

  This attribute is a table of declared proxies (frontend and backends). Each
  proxy give an access to his list of listeners and servers. The table is
  indexed by proxy name, and each entry is of type :ref:`proxy_class`.

  .. Warning::
     if you declared a frontend and backend with the same name, only one of
     them will be listed.

  :see: :js:attr:`core.backends`
  :see: :js:attr:`core.frontends`

.. js:attribute:: core.backends

  **context**: task, action, sample-fetch, converter

  This attribute is a table of declared proxies with backend capability. Each
  proxy give an access to his list of listeners and servers. The table is
  indexed by the backend name, and each entry is of type :ref:`proxy_class`.

  :see: :js:attr:`core.proxies`
  :see: :js:attr:`core.frontends`

.. js:attribute:: core.frontends

  **context**: task, action, sample-fetch, converter

  This attribute is a table of declared proxies with frontend capability. Each
  proxy give an access to his list of listeners and servers. The table is
  indexed by the frontend name, and each entry is of type :ref:`proxy_class`.

  :see: :js:attr:`core.proxies`
  :see: :js:attr:`core.backends`

.. js:attribute:: core.thread

  **context**: task, action, sample-fetch, converter, applet

  This variable contains the executing thread number starting at 1. 0 is a
  special case for the common lua context. So, if thread is 0, Lua scope is
  shared by all threads, otherwise the scope is dedicated to a single thread.
  A program which needs to execute some parts exactly once regardless of the
  number of threads can check that core.thread is 0 or 1.

.. js:function:: core.log(loglevel, msg)

  **context**: body, init, task, action, sample-fetch, converter

  This function sends a log. The log is sent, according with the HAProxy
  configuration file, on the default syslog server if it is configured and on
  the stderr if it is allowed.

  :param integer loglevel: Is the log level associated with the message. It is a
   number between 0 and 7.
  :param string msg: The log content.
  :see: :js:attr:`core.emerg`, :js:attr:`core.alert`, :js:attr:`core.crit`,
    :js:attr:`core.err`, :js:attr:`core.warning`, :js:attr:`core.notice`,
    :js:attr:`core.info`, :js:attr:`core.debug` (log level definitions)
  :see: :js:func:`core.Debug`
  :see: :js:func:`core.Info`
  :see: :js:func:`core.Warning`
  :see: :js:func:`core.Alert`

.. js:function:: core.Debug(msg)

  **context**: body, init, task, action, sample-fetch, converter

  :param string msg: The log content.
  :see: :js:func:`core.log`

  Does the same job than:

.. code-block:: lua

  function Debug(msg)
    core.log(core.debug, msg)
  end
..

.. js:function:: core.Info(msg)

  **context**: body, init, task, action, sample-fetch, converter

  :param string msg: The log content.
  :see: :js:func:`core.log`

.. code-block:: lua

  function Info(msg)
    core.log(core.info, msg)
  end
..

.. js:function:: core.Warning(msg)

  **context**: body, init, task, action, sample-fetch, converter

  :param string msg: The log content.
  :see: :js:func:`core.log`

.. code-block:: lua

  function Warning(msg)
    core.log(core.warning, msg)
  end
..

.. js:function:: core.Alert(msg)

  **context**: body, init, task, action, sample-fetch, converter

  :param string msg: The log content.
  :see: :js:func:`core.log`

.. code-block:: lua

  function Alert(msg)
    core.log(core.alert, msg)
  end
..

.. js:function:: core.add_acl(filename, key)

  **context**: init, task, action, sample-fetch, converter

  Add the ACL *key* in the ACLs list referenced by the file *filename*.

  :param string filename: the filename that reference the ACL entries.
  :param string key: the key which will be added.

.. js:function:: core.del_acl(filename, key)

  **context**: init, task, action, sample-fetch, converter

  Delete the ACL entry referenced by the key *key* in the list of ACLs
  referenced by *filename*.

  :param string filename: the filename that reference the ACL entries.
  :param string key: the key which will be deleted.

.. js:function:: core.del_map(filename, key)

  **context**: init, task, action, sample-fetch, converter

  Delete the map entry indexed with the specified key in the list of maps
  referenced by his filename.

  :param string filename: the filename that reference the map entries.
  :param string key: the key which will be deleted.

.. js:function:: core.get_info()

  **context**: body, init, task, action, sample-fetch, converter

  Returns HAProxy core information. We can find information like the uptime,
  the pid, memory pool usage, tasks number, ...

  This information is also returned by the management socket via the command
  "show info". See the management socket documentation for more information
  about the content of these variables.

  :returns: an array of values.

.. js:function:: core.now()

  **context**: body, init, task, action

  This function returns the current time. The time returned is fixed by the
  HAProxy core and assures than the hour will be monotonic and that the system
  call 'gettimeofday' will not be called too. The time is refreshed between each
  Lua execution or resume, so two consecutive call to the function "now" will
  probably returns the same result.

  :returns: a table which contains two entries "sec" and "usec". "sec"
   contains the current at the epoch format, and "usec" contains the
   current microseconds.

.. js:function:: core.http_date(date)

  **context**: body, init, task, action

  This function take a string representing http date, and returns an integer
  containing the corresponding date with a epoch format. A valid http date
  me respect the format IMF, RFC850 or ASCTIME.

  :param string date: a date http-date formatted
  :returns: integer containing epoch date
  :see: :js:func:`core.imf_date`.
  :see: :js:func:`core.rfc850_date`.
  :see: :js:func:`core.asctime_date`.
  :see: https://tools.ietf.org/html/rfc7231#section-7.1.1.1

.. js:function:: core.imf_date(date)

  **context**: body, init, task, action

  This function take a string representing IMF date, and returns an integer
  containing the corresponding date with a epoch format.

  :param string date: a date IMF formatted
  :returns: integer containing epoch date
  :see: https://tools.ietf.org/html/rfc7231#section-7.1.1.1

  The IMF format is like this:

.. code-block:: text

	Sun, 06 Nov 1994 08:49:37 GMT
..

.. js:function:: core.rfc850_date(date)

  **context**: body, init, task, action

  This function take a string representing RFC850 date, and returns an integer
  containing the corresponding date with a epoch format.

  :param string date: a date RFC859 formatted
  :returns: integer containing epoch date
  :see: https://tools.ietf.org/html/rfc7231#section-7.1.1.1

  The RFC850 format is like this:

.. code-block:: text

	Sunday, 06-Nov-94 08:49:37 GMT
..

.. js:function:: core.asctime_date(date)

  **context**: body, init, task, action

  This function take a string representing ASCTIME date, and returns an integer
  containing the corresponding date with a epoch format.

  :param string date: a date ASCTIME formatted
  :returns: integer containing epoch date
  :see: https://tools.ietf.org/html/rfc7231#section-7.1.1.1

  The ASCTIME format is like this:

.. code-block:: text

	Sun Nov  6 08:49:37 1994
..

.. js:function:: core.msleep(milliseconds)

  **context**: body, init, task, action

  The `core.msleep()` stops the Lua execution between specified milliseconds.

  :param integer milliseconds: the required milliseconds.

.. js:function:: core.register_action(name, actions, func [, nb_args])

  **context**: body

  Register a Lua function executed as action. All the registered action can be
  used in HAProxy with the prefix "lua.". An action gets a TXN object class as
  input.

  :param string name: is the name of the converter.
  :param table actions: is a table of string describing the HAProxy actions who
   want to register to. The expected actions are 'tcp-req', 'tcp-res', 'http-req'
   or 'http-res'.
  :param function func: is the Lua function called to work as converter.
  :param integer nb_args: is the expected number of argument for the action.
   By default the value is 0.

  The prototype of the Lua function used as argument is:

.. code-block:: lua

  function(txn [, arg1 [, arg2]])
..

  * **txn** (:ref:`txn_class`): this is a TXN object used for manipulating the
            current request or TCP stream.

  * **argX**: this is argument provided through the HAProxy configuration file.

  Here, an example of action registration. The action just send an 'Hello world'
  in the logs.

.. code-block:: lua

  core.register_action("hello-world", { "tcp-req", "http-req" }, function(txn)
     txn:Info("Hello world")
  end)
..

  This example code is used in HAProxy configuration like this:

::

  frontend tcp_frt
    mode tcp
    tcp-request content lua.hello-world

  frontend http_frt
    mode http
    http-request lua.hello-world

..

  A second example using arguments

.. code-block:: lua

  function hello_world(txn, arg)
     txn:Info("Hello world for " .. arg)
  end
  core.register_action("hello-world", { "tcp-req", "http-req" }, hello_world, 2)

..

  This example code is used in HAProxy configuration like this:

::

  frontend tcp_frt
    mode tcp
    tcp-request content lua.hello-world everybody

..

.. js:function:: core.register_converters(name, func)

  **context**: body

  Register a Lua function executed as converter. All the registered converters
  can be used in HAProxy with the prefix "lua.". A converter gets a string as
  input and returns a string as output. The registered function can take up to 9
  values as parameter. All the values are strings.

  :param string name: is the name of the converter.
  :param function func: is the Lua function called to work as converter.

  The prototype of the Lua function used as argument is:

.. code-block:: lua

  function(str, [p1 [, p2 [, ... [, p5]]]])
..

  * **str** (*string*): this is the input value automatically converted in
    string.
  * **p1** .. **p5** (*string*): this is a list of string arguments declared in
    the HAProxy configuration file. The number of arguments doesn't exceed 5.
    The order and the nature of these is conventionally chosen by the
    developer.

.. js:function:: core.register_fetches(name, func)

  **context**: body

  Register a Lua function executed as sample fetch. All the registered sample
  fetch can be used in HAProxy with the prefix "lua.". A Lua sample fetch
  returns a string as output. The registered function can take up to 9 values as
  parameter. All the values are strings.

  :param string name: is the name of the sample fetch.
  :param function func: is the Lua function called to work as sample fetch.

  The prototype of the Lua function used as argument is:

.. code-block:: lua

    string function(txn, [p1 [, p2 [, ... [, p5]]]])
..

  * **txn** (:ref:`txn_class`): this is the txn object associated with the
    current request.
  * **p1** .. **p5** (*string*): this is a list of string arguments declared in
    the HAProxy configuration file. The number of arguments doesn't exceed 5.
    The order and the nature of these is conventionally chosen by the
    developer.
  * **Returns**: A string containing some data, or nil if the value cannot be
    returned now.

  lua example code:

.. code-block:: lua

    core.register_fetches("hello", function(txn)
        return "hello"
    end)
..

  HAProxy example configuration:

::

    frontend example
       http-request redirect location /%[lua.hello]

.. js:function:: core.register_filter(name, Flt, func)

  **context**: body

  Register a Lua function used to declare a filter. All the registered filters
  can by used in HAProxy with the prefix "lua.".

  :param string name: is the name of the filter.
  :param table Flt: is a Lua class containing the filter definition (id, flags,
   callbacks).
  :param function func: is the Lua function called to create the Lua filter.

  The prototype of the Lua function used as argument is:

.. code-block:: lua

  function(flt, args)
..

  * **flt** : Is a filter object based on the class provided in
    :js:func:`core.register_filter()` function.

  * **args**: Is a table of strings containing all arguments provided through
    the HAProxy configuration file, on the filter line.

  It must return the filter to use or nil to ignore it. Here, an example of
  filter registration.

.. code-block:: lua

  core.register_filter("my-filter", MyFilter, function(flt, args)
     flt.args = args -- Save arguments
     return flt
  end)
..

  This example code is used in HAProxy configuration like this:

::

  frontend http
    mode http
    filter lua.my-filter arg1 arg2 arg3

..

  :see: :js:class:`Filter`

.. js:function:: core.register_service(name, mode, func)

  **context**: body

  Register a Lua function executed as a service. All the registered services
  can be used in HAProxy with the prefix "lua.". A service gets an object class
  as input according with the required mode.

  :param string name: is the name of the service.
  :param string mode: is string describing the required mode. Only 'tcp' or
   'http' are allowed.
  :param function func: is the Lua function called to work as service.

  The prototype of the Lua function used as argument is:

.. code-block:: lua

  function(applet)
..

  * **applet** *applet*  will be a :ref:`applettcp_class` or a
    :ref:`applethttp_class`. It depends the type of registered applet. An applet
    registered with the 'http' value for the *mode* parameter will gets a
    :ref:`applethttp_class`. If the *mode* value is 'tcp', the applet will gets
    a :ref:`applettcp_class`.

  .. warning::
     Applets of type 'http' cannot be called from 'tcp-*' rulesets. Only the
     'http-*' rulesets are authorized, this means that is not possible to call
     a HTTP applet from a proxy in tcp mode. Applets of type 'tcp' can be
     called from anywhere.

  Here, an example of service registration. The service just send an
  'Hello world' as an http response.

.. code-block:: lua

  core.register_service("hello-world", "http", function(applet)
     local response = "Hello World !"
     applet:set_status(200)
     applet:add_header("content-length", string.len(response))
     applet:add_header("content-type", "text/plain")
     applet:start_response()
     applet:send(response)
  end)
..

  This example code is used in HAProxy configuration like this:

::

    frontend example
       http-request use-service lua.hello-world

.. js:function:: core.register_init(func)

  **context**: body

  Register a function executed after the configuration parsing. This is useful
  to check any parameters.

  :param function func: is the Lua function called to work as initializer.

  The prototype of the Lua function used as argument is:

.. code-block:: lua

    function()
..

  It takes no input, and no output is expected.

.. js:function:: core.register_task(func[, arg1[, arg2[, ...[, arg4]]]])

  **context**: body, init, task, action, sample-fetch, converter, event

  Register and start independent task. The task is started when the HAProxy
  main scheduler starts. For example this type of tasks can be executed to
  perform complex health checks.

  :param function func: is the Lua function called to work as an async task.

  Up to 4 optional arguments (all types supported) may be passed to the
  function. (They will be passed as-is to the task function)

  The prototype of the Lua function used as argument is:

.. code-block:: lua

    function([arg1[, arg2[, ...[, arg4]]]])
..

  It takes up to 4 optional arguments (provided when registering), and no
  output is expected.

.. js:function:: core.register_cli([path], usage, func)

  **context**: body

  Register a custom cli that will be available from haproxy stats socket.

  :param array path: is the sequence of word for which the cli execute the Lua
   binding.
  :param string usage: is the usage message displayed in the help.
  :param function func: is the Lua function called to handle the CLI commands.

  The prototype of the Lua function used as argument is:

.. code-block:: lua

    function(AppletTCP, [arg1, [arg2, [...]]])
..

  I/O are managed with the :ref:`applettcp_class` object. Args are given as
  parameter. The args embed the registered path. If the path is declared like
  this:

.. code-block:: lua

    core.register_cli({"show", "ssl", "stats"}, "Display SSL stats..", function(applet, arg1, arg2, arg3, arg4, arg5)
	 end)
..

  And we execute this in the prompt:

.. code-block:: text

    > prompt
    > show ssl stats all
..

  Then, arg1, arg2 and arg3 will contains respectively "show", "ssl" and
  "stats".
  arg4 will contain "all". arg5 contains nil.

.. js:function:: core.set_nice(nice)

  **context**: task, action, sample-fetch, converter

  Change the nice of the current task or current session.

  :param integer nice: the nice value, it must be between -1024 and 1024.

.. js:function:: core.set_map(filename, key, value)

  **context**: init, task, action, sample-fetch, converter

  Set the value *value* associated to the key *key* in the map referenced by
  *filename*.

  :param string filename: the Map reference
  :param string key: the key to set or replace
  :param string value: the associated value

.. js:function:: core.sleep(int seconds)

  **context**: body, init, task, action

  The `core.sleep()` functions stop the Lua execution between specified seconds.

  :param integer seconds: the required seconds.

.. js:function:: core.tcp()

  **context**: init, task, action

  This function returns a new object of a *socket* class.

  :returns: A :ref:`socket_class` object.

.. js:function:: core.httpclient()

  **context**: init, task, action

  This function returns a new object of a *httpclient* class.

  :returns: A :ref:`httpclient_class` object.

.. js:function:: core.concat()

  **context**: body, init, task, action, sample-fetch, converter

  This function returns a new concat object.

  :returns: A :ref:`concat_class` object.

.. js:function:: core.done(data)

  **context**: body, init, task, action, sample-fetch, converter

  :param any data: Return some data for the caller. It is useful with
   sample-fetches and sample-converters.

  Immediately stops the current Lua execution and returns to the caller which
  may be a sample fetch, a converter or an action and returns the specified
  value (ignored for actions and init). It is used when the LUA process finishes
  its work and wants to give back the control to HAProxy without executing the
  remaining code. It can be seen as a multi-level "return".

.. js:function:: core.yield()

  **context**: task, action, sample-fetch, converter

  Give back the hand at the HAProxy scheduler. It is used when the LUA
  processing consumes a lot of processing time.

.. js:function:: core.parse_addr(address)

  **context**: body, init, task, action, sample-fetch, converter

  :param network: is a string describing an ipv4 or ipv6 address and optionally
   its network length, like this: "127.0.0.1/8" or "aaaa::1234/32".
  :returns: a userdata containing network or nil if an error occurs.

  Parse ipv4 or ipv6 addresses and its facultative associated network.

.. js:function:: core.match_addr(addr1, addr2)

  **context**: body, init, task, action, sample-fetch, converter

  :param addr1: is an address created with "core.parse_addr".
  :param addr2: is an address created with "core.parse_addr".
  :returns: boolean, true if the network of the addresses match, else returns
   false.

  Match two networks. For example "127.0.0.1/32" matches "127.0.0.0/8". The
  order of network is not important.

.. js:function:: core.tokenize(str, separators [, noblank])

  **context**: body, init, task, action, sample-fetch, converter

  This function is useful for tokenizing an entry, or splitting some messages.
  :param string str: The string which will be split.
  :param string separators: A string containing a list of separators.
  :param boolean noblank: Ignore empty entries.
  :returns: an array of string.

  For example:

.. code-block:: lua

	local array = core.tokenize("This function is useful, for tokenizing an entry.", "., ", true)
	print_r(array)
..

  Returns this array:

.. code-block:: text

	(table) table: 0x21c01e0 [
	    1: (string) "This"
	    2: (string) "function"
	    3: (string) "is"
	    4: (string) "useful"
	    5: (string) "for"
	    6: (string) "tokenizing"
	    7: (string) "an"
	    8: (string) "entry"
	]
..

.. js:function:: core.event_sub(event_types, func)

  **context**: body, init, task, action, sample-fetch, converter

  Register a function that will be called on specific system events.

  :param array event_types: array of string containing the event types you want
   to subscribe to
  :param function func: is the Lua function called when one of the subscribed
   events occur.
  :returns: A :ref:`event_sub_class` object.
  :see: :js:func:`Server.event_sub()`.

  List of available event types :

   **SERVER** Family:

    * **SERVER_ADD**: when a server is added
    * **SERVER_DEL**: when a server is removed
    * **SERVER_DOWN**: when a server state goes from UP to DOWN
    * **SERVER_UP**: when a server state goes from DOWN to UP

   .. Note::
     You may also use **SERVER** in **event_types** to subscribe to all server
     events types at once.

  The prototype of the Lua function used as argument is:

.. code-block:: lua

    function(event, event_data, sub, when)
..

  * **event** (*string*): the event type (one of the **event_types** specified
    when subscribing)
  * **event_data**: specific to each event family (For **SERVER** family,
    a :ref:`server_event_class` object)
  * **sub**: class to manage the subscription from within the event
    (a :ref:`event_sub_class` object)
  * **when**: timestamp corresponding to the date when the event was generated.
    It is an integer representing the number of seconds elapsed since Epoch.
    It may be provided as optional argument to `os.date()` lua function to
    convert it to a string according to a given format string.

  .. Warning::
    The callback function will only be scheduled on the very same thread that
    performed the subscription.

    Moreover, each thread treats events sequentially. It means that if you
    have, let's say SERVER_UP followed by a SERVER_DOWN in a short timelapse,
    then the cb function will first be called with SERVER_UP, and once it's
    done handling the event, the cb function will be called again with
    SERVER_DOWN.

    This is to ensure event consistency when it comes to logging / triggering
    logic from lua.

    Your lua cb function may yield if needed, but you're pleased to process the
    event as fast as possible to prevent the event queue from growing up,
    depending on the event flow that is expected for the given subscription.

    To prevent abuses, if the event queue for the current subscription goes
    over a certain amount of unconsumed events, the subscription will pause
    itself automatically for as long as it takes for your handler to catch up.
    This would lead to events being missed, so an error will be reported in the
    logs to warn you about that.
    This is not something you want to let happen too often, it may indicate
    that you subscribed to an event that is occurring too frequently or/and
    that your callback function is too slow to keep up the pace and you should
    review it.

    If you want to do some parallel processing because your callback functions
    are slow: you might want to create subtasks from lua using
    :js:func:`core.register_task()` from within your callback function to
    perform the heavy job in a dedicated task and allow remaining events to be
    processed more quickly.

.. _proxy_class:

Proxy class
============

.. js:class:: Proxy

  This class provides a way for manipulating proxy and retrieving information
  like statistics.

.. js:attribute:: Proxy.name

  Contain the name of the proxy.

  .. warning::
     This attribute is now deprecated and will eventually be removed.
     Please use :js:func:`Proxy.get_name()` function instead.

.. js:function:: Proxy.get_name()

  Returns the name of the proxy.

.. js:attribute:: Proxy.uuid

  Contain the unique identifier of the proxy.

  .. warning::
     This attribute is now deprecated and will eventually be removed.
     Please use :js:func:`Proxy.get_uuid()` function instead.

.. js:function:: Proxy.get_uuid()

  Returns the unique identifier of the proxy.

.. js:attribute:: Proxy.servers

  Contain a table with the attached servers. The table is indexed by server
  name, and each server entry is an object of type :ref:`server_class`.

.. js:attribute:: Proxy.stktable

  Contains a stick table object attached to the proxy.

.. js:attribute:: Proxy.listeners

  Contain a table with the attached listeners. The table is indexed by listener
  name, and each each listeners entry is an object of type
  :ref:`listener_class`.

.. js:function:: Proxy.pause(px)

  Pause the proxy. See the management socket documentation for more information.

  :param class_proxy px: A :ref:`proxy_class` which indicates the manipulated
   proxy.

.. js:function:: Proxy.resume(px)

  Resume the proxy. See the management socket documentation for more
  information.

  :param class_proxy px: A :ref:`proxy_class` which indicates the manipulated
   proxy.

.. js:function:: Proxy.stop(px)

  Stop the proxy. See the management socket documentation for more information.

  :param class_proxy px: A :ref:`proxy_class` which indicates the manipulated
   proxy.

.. js:function:: Proxy.shut_bcksess(px)

  Kill the session attached to a backup server. See the management socket
  documentation for more information.

  :param class_proxy px: A :ref:`proxy_class` which indicates the manipulated
   proxy.

.. js:function:: Proxy.get_cap(px)

  Returns a string describing the capabilities of the proxy.

  :param class_proxy px: A :ref:`proxy_class` which indicates the manipulated
   proxy.
  :returns: a string "frontend", "backend", "proxy" or "ruleset".

.. js:function:: Proxy.get_mode(px)

  Returns a string describing the mode of the current proxy.

  :param class_proxy px: A :ref:`proxy_class` which indicates the manipulated
   proxy.
  :returns: a string "tcp", "http", "health" or "unknown"

.. js:function:: Proxy.get_stats(px)

  Returns a table containing the proxy statistics. The statistics returned are
  not the same if the proxy is frontend or a backend.

  :param class_proxy px: A :ref:`proxy_class` which indicates the manipulated
   proxy.
  :returns: a key/value table containing stats

.. _server_class:

Server class
============

.. js:class:: Server

  This class provides a way for manipulating servers and retrieving information.

.. js:attribute:: Server.name

  Contain the name of the server.

  .. warning::
     This attribute is now deprecated and will eventually be removed.
     Please use :js:func:`Server.get_name()` function instead.

.. js:function:: Server.get_name(sv)

  Returns the name of the server.

.. js:attribute:: Server.puid

  Contain the proxy unique identifier of the server.

  .. warning::
     This attribute is now deprecated and will eventually be removed.
     Please use :js:func:`Server.get_puid()` function instead.

.. js:function:: Server.get_puid(sv)

  Returns the proxy unique identifier of the server.

.. js:function:: Server.get_rid(sv)

  Returns the rid (revision ID) of the server.
  It is an unsigned integer that is set upon server creation. Value is derived
  from a global counter that starts at 0 and is incremented each time one or
  multiple server deletions are followed by a server addition (meaning that
  old name/id reuse could occur).

  Combining server name/id with server rid yields a process-wide unique
  identifier.

.. js:function:: Server.is_draining(sv)

  Return true if the server is currently draining sticky connections.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: a boolean

.. js:function:: Server.is_backup(sv)

  Return true if the server is a backup server

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: a boolean

.. js:function:: Server.is_dynamic(sv)

  Return true if the server was instantiated at runtime (e.g.: from the cli)

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: a boolean

.. js:function:: Server.set_maxconn(sv, weight)

  Dynamically change the maximum connections of the server. See the management
  socket documentation for more information about the format of the string.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :param string maxconn: A string describing the server maximum connections.

.. js:function:: Server.get_maxconn(sv, weight)

  This function returns an integer representing the server maximum connections.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: an integer.

.. js:function:: Server.set_weight(sv, weight)

  Dynamically change the weight of the server. See the management socket
  documentation for more information about the format of the string.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :param string weight: A string describing the server weight.

.. js:function:: Server.get_weight(sv)

  This function returns an integer representing the server weight.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: an integer.

.. js:function:: Server.set_addr(sv, addr[, port])

  Dynamically change the address of the server. See the management socket
  documentation for more information about the format of the string.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :param string addr: A string describing the server address.

.. js:function:: Server.get_addr(sv)

  Returns a string describing the address of the server.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: A string

.. js:function:: Server.get_stats(sv)

  Returns server statistics.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: a key/value table containing stats

.. js:function:: Server.get_proxy(sv)

  Returns the parent proxy to which the server belongs.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: a :ref:`proxy_class` or nil if not available

.. js:function:: Server.shut_sess(sv)

  Shutdown all the sessions attached to the server. See the management socket
  documentation for more information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.set_drain(sv)

  Drain sticky sessions. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.set_maint(sv)

  Set maintenance mode. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.set_ready(sv)

  Set normal mode. See the management socket documentation for more information
  about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.check_enable(sv)

  Enable health checks. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.check_disable(sv)

  Disable health checks. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.check_force_up(sv)

  Force health-check up. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.check_force_nolb(sv)

  Force health-check nolb mode. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.check_force_down(sv)

  Force health-check down. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.agent_enable(sv)

  Enable agent check. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.agent_disable(sv)

  Disable agent check. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.agent_force_up(sv)

  Force agent check up. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.agent_force_down(sv)

  Force agent check down. See the management socket documentation for more
  information about this function.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.

.. js:function:: Server.tracking(sv)

  Check if the current server is tracking another server.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: A :ref:`server_class` which indicates the tracked server or nil if
   the server doesn't track another one.

.. js:function:: Server.get_trackers(sv)

  Check if the current server is being tracked by other servers.

  :param class_server sv: A :ref:`server_class` which indicates the manipulated
   server.
  :returns: An array of :ref:`server_class` which indicates the tracking
   servers (might be empty)

.. js:function:: Server.event_sub(sv, event_types, func)

  Register a function that will be called on specific server events.
  It works exactly like :js:func:`core.event_sub()` except that the subscription
  will be performed within the server dedicated subscription list instead of the
  global one.
  (Your callback function will only be called for server events affecting sv)

  See :js:func:`core.event_sub()` for function usage.

  A key advantage to using :js:func:`Server.event_sub()` over
  :js:func:`core.event_sub()` for servers is that :js:func:`Server.event_sub()`
  allows you to be notified for servers events of a single server only.
  It removes the needs for extra filtering in your callback function if you only
  care about a single server, and also prevents useless wakeups.

  For instance, if you want to be notified for UP/DOWN events on a given set of
  servers, it is recommended to perform multiple per-server subscriptions since
  it will be more efficient that doing a single global subscription that will
  filter the received events.
  Unless you really want to be notified for servers events of ALL servers of
  course, which could make sense given you setup but should be avoided if you
  have an important number of servers as it will add a significant load on your
  haproxy process in case of multiple servers state change in a short amount of
  time.

  .. Note::
     You may also combine :js:func:`core.event_sub()` with
     :js:func:`Server.event_sub()`.

     Also, don't forget that you can use :js:func:`core.register_task()` from
     your callback function if needed. (ie: parallel work)

  Here is a working example combining :js:func:`core.event_sub()` with
  :js:func:`Server.event_sub()` and :js:func:`core.register_task()`
  (This only serves as a demo, this is not necessarily useful to do so)

.. code-block:: lua

  core.event_sub({"SERVER_ADD"}, function(event, data, sub)
    -- in the global event handler
    if data["reference"] ~= nil then
      print("Tracking new server: ", data["name"])
      data["reference"]:event_sub({"SERVER_UP", "SERVER_DOWN"}, function(event, data, sub)
        -- in the per-server event handler
	if data["reference"] ~= nil then
          core.register_task(function(server)
            -- subtask to perform some async work (e.g.: HTTP API calls, sending emails...)
            print("ASYNC: SERVER ", server:get_name(), " is ", event == "SERVER_UP" and "UP" or "DOWN")
          end, data["reference"])
        end
      end)
    end
  end)

..

  In this example, we will first track global server addition events.
  For each newly added server ("add server" on the cli), we will register a
  UP/DOWN server subscription.
  Then, the callback function will schedule the event handling in an async
  subtask which will receive the server reference as an argument.

.. _listener_class:

Listener class
==============

.. js:function:: Listener.get_stats(ls)

  Returns server statistics.

  :param class_listener ls: A :ref:`listener_class` which indicates the
   manipulated listener.
  :returns: a key/value table containing stats

.. _event_sub_class:

EventSub class
==============

.. js:function:: EventSub.unsub()

  End the subscription, the callback function will not be called again.

.. _server_event_class:

ServerEvent class
=================

.. js:attribute:: ServerEvent.name

  Contains the name of the server.

.. js:attribute:: ServerEvent.puid

  Contains the proxy-unique uid of the server

.. js:attribute:: ServerEvent.rid

  Contains the revision ID of the server

.. js:attribute:: ServerEvent.proxy_name

  Contains the name of the proxy to which the server belongs

.. js:attribute:: ServerEvent.proxy_uuid

  Contains the uuid of the proxy to which the server belongs

.. js:attribute:: ServerEvent.reference

  Reference to the live server (A :ref:`server_class`).

  .. Warning::
     Not available if the server was removed in the meantime.
     (Will never be set for SERVER_DEL event since the server does not exist
     anymore)

.. _concat_class:

Concat class
============

.. js:class:: Concat

  This class provides a fast way for string concatenation. The way using native
  Lua concatenation like the code below is slow for some reasons.

.. code-block:: lua

  str = "string1"
  str = str .. ", string2"
  str = str .. ", string3"
..

  For each concatenation, Lua:
  - allocates memory for the result,
  - catenates the two string copying the strings in the new memory block,
  - frees the old memory block containing the string which is no longer used.

  This process does many memory move, allocation and free. In addition, the
  memory is not really freed, it is just marked as unused and waits for the
  garbage collector.

  The Concat class provides an alternative way to concatenate strings. It uses
  the internal Lua mechanism (it does not allocate memory), but it doesn't copy
  the data more than once.

  On my computer, the following loops spends 0.2s for the Concat method and
  18.5s for the pure Lua implementation. So, the Concat class is about 1000x
  faster than the embedded solution.

.. code-block:: lua

  for j = 1, 100 do
    c = core.concat()
    for i = 1, 20000 do
      c:add("#####")
    end
  end
..

.. code-block:: lua

  for j = 1, 100 do
    c = ""
    for i = 1, 20000 do
      c = c .. "#####"
    end
  end
..

.. js:function:: Concat.add(concat, string)

  This function adds a string to the current concatenated string.

  :param class_concat concat: A :ref:`concat_class` which contains the currently
   built string.
  :param string string: A new string to concatenate to the current built
   string.

.. js:function:: Concat.dump(concat)

  This function returns the concatenated string.

  :param class_concat concat: A :ref:`concat_class` which contains the currently
   built string.
  :returns: the concatenated string

.. _fetches_class:

Fetches class
=============

.. js:class:: Fetches

  This class contains a lot of internal HAProxy sample fetches. See the
  HAProxy "configuration.txt" documentation for more information.
  (chapters 7.3.2 to 7.3.6)

  .. warning::
     some sample fetches are not available in some context. These limitations
     are specified in this documentation when they're useful.

  :see: :js:attr:`TXN.f`
  :see: :js:attr:`TXN.sf`

  Fetches are useful to:

  * get system time,
  * get environment variable,
  * get random numbers,
  * know backend status like the number of users in queue or the number of
    connections established,
  * get client information like ip source or destination,
  * deal with stick tables,
  * fetch established SSL information,
  * fetch HTTP information like headers or method.

.. code-block:: lua

  function action(txn)
    -- Get source IP
    local clientip = txn.f:src()
  end
..

.. _converters_class:

Converters class
================

.. js:class:: Converters

  This class contains a lot of internal HAProxy sample converters. See the
  HAProxy documentation "configuration.txt" for more information about her
  usage. Its the chapter 7.3.1.

  :see: :js:attr:`TXN.c`
  :see: :js:attr:`TXN.sc`

  Converters provides stateful transformation. They are useful to:

  * convert input to base64,
  * apply hash on input string (djb2, crc32, sdbm, wt6),
  * format date,
  * json escape,
  * extract preferred language comparing two lists,
  * turn to lower or upper chars,
  * deal with stick tables.

.. _channel_class:

Channel class
=============

.. js:class:: Channel

  **context**: action, sample-fetch, convert, filter

  HAProxy uses two buffers for the processing of the requests. The first one is
  used with the request data (from the client to the server) and the second is
  used for the response data (from the server to the client).

  Each buffer contains two types of data. The first type is the incoming data
  waiting for a processing. The second part is the outgoing data already
  processed. Usually, the incoming data is processed, after it is tagged as
  outgoing data, and finally it is sent. The following functions provides tools
  for manipulating these data in a buffer.

  The following diagram shows where the channel class function are applied.

  .. image:: _static/channel.png

  .. warning::
    It is not possible to read from the response in request action, and it is
    not possible to read from the request channel in response action.

  .. warning::
    It is forbidden to alter the Channels buffer from HTTP contexts.  So only
    :js:func:`Channel.input`, :js:func:`Channel.output`,
    :js:func:`Channel.may_recv`, :js:func:`Channel.is_full` and
    :js:func:`Channel.is_resp` can be called from a HTTP context.

  All the functions provided by this class are available in the
  **sample-fetches**, **actions** and **filters** contexts. For **filters**,
  incoming data (offset and length) are relative to the filter. Some functions
  may yield, but only for **actions**. Yield is not possible for
  **sample-fetches**, **converters** and **filters**.

.. js:function:: Channel.append(channel, string)

  This function copies the string **string** at the end of incoming data of the
  channel buffer. The function returns the copied length on success or -1 if
  data cannot be copied.

  Same that :js:func:`Channel.insert(channel, string, channel:input())`.

  :param class_channel channel: The manipulated Channel.
  :param string string: The data to copy at the end of incoming data.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: Channel.data(channel [, offset [, length]])

  This function returns **length** bytes of incoming data from the channel
  buffer, starting at the offset **offset**. The data are not removed from the
  buffer.

  By default, if no length is provided, all incoming data found, starting at the
  given offset, are returned. If **length** is set to -1, the function tries to
  retrieve a maximum of data and, if called by an action, it yields if
  necessary. It also waits for more data if the requested length exceeds the
  available amount of incoming data. Not providing an offset is the same as
  setting it to 0. A positive offset is relative to the beginning of incoming
  data of the channel buffer while negative offset is relative to the end.

  If there is no incoming data and the channel can't receive more data, a 'nil'
  value is returned.

  :param class_channel channel: The manipulated Channel.
  :param integer offset: *optional* The offset in incoming data to start to get
   data. 0 by default. May be negative to be relative to the end of incoming
   data.
  :param integer length: *optional* The expected length of data to retrieve. All
   incoming data by default. May be set to -1 to get a maximum of data.
  :returns: a string containing the data found or nil.

.. js:function:: Channel.forward(channel, length)

  This function forwards **length** bytes of data from the channel buffer. If
  the requested length exceeds the available amount of incoming data, and if
  called by an action, the function yields, waiting for more data to forward. It
  returns the amount of data forwarded.

  :param class_channel channel: The manipulated Channel.
  :param integer int: The amount of data to forward.

.. js:function:: Channel.input(channel)

  This function returns the length of incoming data in the channel buffer. When
  called by a filter, this value is relative to the filter.

  :param class_channel channel: The manipulated Channel.
  :returns: an integer containing the amount of available bytes.

.. js:function:: Channel.insert(channel, string [, offset])

  This function copies the string **string** at the offset **offset** in
  incoming data of the channel buffer. The function returns the copied length on
  success or -1 if data cannot be copied.

  By default, if no offset is provided, the string is copied in front of
  incoming data. A positive offset is relative to the beginning of incoming data
  of the channel buffer while negative offset is relative to their end.

  :param class_channel channel: The manipulated Channel.
  :param string string: The data to copy into incoming data.
  :param integer offset: *optional* The offset in incoming data where to copy
   data. 0 by default. May be negative to be relative to the end of incoming
   data.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: Channel.is_full(channel)

  This function returns true if the channel buffer is full.

  :param class_channel channel: The manipulated Channel.
  :returns: a boolean

.. js:function:: Channel.is_resp(channel)

  This function returns true if the channel is the response one.

  :param class_channel channel: The manipulated Channel.
  :returns: a boolean

.. js:function:: Channel.line(channel [, offset [, length]])

  This function parses **length** bytes of incoming data of the channel buffer,
  starting at offset **offset**, and returns the first line found, including the
  '\\n'.  The data are not removed from the buffer. If no line is found, all
  data are returned.

  By default, if no length is provided, all incoming data, starting at the given
  offset, are evaluated. If **length** is set to -1, the function tries to
  retrieve a maximum of data and, if called by an action, yields if
  necessary. It also waits for more data if the requested length exceeds the
  available amount of incoming data. Not providing an offset is the same as
  setting it to 0. A positive offset is relative to the beginning of incoming
  data of the channel buffer while negative offset is relative to the end.

  If there is no incoming data and the channel can't receive more data, a 'nil'
  value is returned.

  :param class_channel channel: The manipulated Channel.
  :param integer offset: *optional* The offset in incoming data to start to
   parse data. 0 by default. May be negative to be relative to the end of
   incoming data.
  :param integer length: *optional* The length of data to parse. All incoming
   data by default. May be set to -1 to get a maximum of data.
  :returns: a string containing the line found or nil.

.. js:function:: Channel.may_recv(channel)

  This function returns true if the channel may still receive data.

  :param class_channel channel: The manipulated Channel.
  :returns: a boolean

.. js:function:: Channel.output(channel)

  This function returns the length of outgoing data of the channel buffer. When
  called by a filter, this value is relative to the filter.

  :param class_channel channel: The manipulated Channel.
  :returns: an integer containing the amount of available bytes.

.. js:function:: Channel.prepend(channel, string)

  This function copies the string **string** in front of incoming data of the
  channel buffer. The function returns the copied length on success or -1 if
  data cannot be copied.

  Same that :js:func:`Channel.insert(channel, string, 0)`.

  :param class_channel channel: The manipulated Channel.
  :param string string: The data to copy in front of incoming data.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: Channel.remove(channel [, offset [, length]])

  This function removes **length** bytes of incoming data of the channel buffer,
  starting at offset **offset**. This function returns number of bytes removed
  on success.

  By default, if no length is provided, all incoming data, starting at the given
  offset, are removed. Not providing an offset is the same as setting it
  to 0. A positive offset is relative to the beginning of incoming data of the
  channel buffer while negative offset is relative to the end.

  :param class_channel channel: The manipulated Channel.
  :param integer offset: *optional* The offset in incoming data where to start
   to remove data. 0 by default. May be negative to be relative to the end of
   incoming data.
  :param integer length: *optional* The length of data to remove. All incoming
   data by default.
  :returns: an integer containing the amount of bytes removed.

.. js:function:: Channel.send(channel, string)

  This function requires immediate send of the string **string**. It means the
  string is copied at the beginning of incoming data of the channel buffer and
  immediately forwarded. Unless if the connection is close, and if called by an
  action, this function yields to copy and forward all the string.

  :param class_channel channel: The manipulated Channel.
  :param string string: The data to send.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: Channel.set(channel, string [, offset [, length]])

  This function replaces **length** bytes of incoming data of the channel
  buffer, starting at offset **offset**, by the string **string**. The function
  returns the copied length on success or -1 if data cannot be copied.

  By default, if no length is provided, all incoming data, starting at the given
  offset, are replaced. Not providing an offset is the same as setting it
  to 0. A positive offset is relative to the beginning of incoming data of the
  channel buffer while negative offset is relative to the end.

  :param class_channel channel: The manipulated Channel.
  :param string string: The data to copy into incoming data.
  :param integer offset: *optional* The offset in incoming data where to start
   the data replacement. 0 by default. May be negative to be relative to the
   end of incoming data.
  :param integer length: *optional* The length of data to replace. All incoming
   data by default.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: Channel.dup(channel)

  **DEPRECATED**

  This function returns all incoming data found in the channel buffer. The data
  are not removed from the buffer and can be reprocessed later.

  If there is no incoming data and the channel can't receive more data, a 'nil'
  value is returned.

  :param class_channel channel: The manipulated Channel.
  :returns: a string containing all data found or nil.

  .. warning::
     This function is deprecated. :js:func:`Channel.data()` must be used
     instead.

.. js:function:: Channel.get(channel)

  **DEPRECATED**

  This function returns all incoming data found in the channel buffer and remove
  them from the buffer.

  If there is no incoming data and the channel can't receive more data, a 'nil'
  value is returned.

  :param class_channel channel: The manipulated Channel.
  :returns: a string containing all the data found or nil.

  .. warning::
     This function is deprecated. :js:func:`Channel.data()` must be used to
     retrieve data followed by a call to :js:func:`Channel:remove()` to remove
     data.

     .. code-block:: lua

       local data = chn:data()
       chn:remove(0, data:len())

     ..

.. js:function:: Channel.getline(channel)

  **DEPRECATED**

  This function returns the first line found in incoming data of the channel
  buffer, including the '\\n'. The returned data are removed from the buffer. If
  no line is found, and if called by an action, this function yields to wait for
  more data, except if the channel can't receive more data. In this case all
  data are returned.

  If there is no incoming data and the channel can't receive more data, a 'nil'
  value is returned.

  :param class_channel channel: The manipulated Channel.
  :returns: a string containing the line found or nil.

  .. warning::
     This function is deprecated. :js:func:`Channel.line()` must be used to
     retrieve a line followed by a call to :js:func:`Channel:remove()` to remove
     data.

     .. code-block:: lua

       local line = chn:line(0, -1)
       chn:remove(0, line:len())

     ..

.. js:function:: Channel.get_in_len(channel)

  **DEPRECATED**

  This function returns the length of the input part of the buffer. When called
  by a filter, this value is relative to the filter.

  :param class_channel channel: The manipulated Channel.
  :returns: an integer containing the amount of available bytes.

  .. warning::
     This function is deprecated. :js:func:`Channel.input()` must be used
     instead.

.. js:function:: Channel.get_out_len(channel)

  **DEPRECATED**

  This function returns the length of the output part of the buffer. When called
  by a filter, this value is relative to the filter.

  :param class_channel channel: The manipulated Channel.
  :returns: an integer containing the amount of available bytes.

  .. warning::
     This function is deprecated. :js:func:`Channel.output()` must be used
     instead.

.. _http_class:

HTTP class
==========

.. js:class:: HTTP

   This class contain all the HTTP manipulation functions.

.. js:function:: HTTP.req_get_headers(http)

  Returns a table containing all the request headers.

  :param class_http http: The related http object.
  :returns: table of headers.
  :see: :js:func:`HTTP.res_get_headers`

  This is the form of the returned table:

.. code-block:: lua

  HTTP:req_get_headers()['<header-name>'][<header-index>] = "<header-value>"

  local hdr = HTTP:req_get_headers()
  hdr["host"][0] = "www.test.com"
  hdr["accept"][0] = "audio/basic q=1"
  hdr["accept"][1] = "audio/*, q=0.2"
  hdr["accept"][2] = "*/*, q=0.1"
..

.. js:function:: HTTP.res_get_headers(http)

  Returns a table containing all the response headers.

  :param class_http http: The related http object.
  :returns: table of headers.
  :see: :js:func:`HTTP.req_get_headers`

  This is the form of the returned table:

.. code-block:: lua

  HTTP:res_get_headers()['<header-name>'][<header-index>] = "<header-value>"

  local hdr = HTTP:req_get_headers()
  hdr["host"][0] = "www.test.com"
  hdr["accept"][0] = "audio/basic q=1"
  hdr["accept"][1] = "audio/*, q=0.2"
  hdr["accept"][2] = "*.*, q=0.1"
..

.. js:function:: HTTP.req_add_header(http, name, value)

  Appends a HTTP header field in the request whose name is
  specified in "name" and whose value is defined in "value".

  :param class_http http: The related http object.
  :param string name: The header name.
  :param string value: The header value.
  :see: :js:func:`HTTP.res_add_header`

.. js:function:: HTTP.res_add_header(http, name, value)

  Appends a HTTP header field in the response whose name is
  specified in "name" and whose value is defined in "value".

  :param class_http http: The related http object.
  :param string name: The header name.
  :param string value: The header value.
  :see: :js:func:`HTTP.req_add_header`

.. js:function:: HTTP.req_del_header(http, name)

  Removes all HTTP header fields in the request whose name is
  specified in "name".

  :param class_http http: The related http object.
  :param string name: The header name.
  :see: :js:func:`HTTP.res_del_header`

.. js:function:: HTTP.res_del_header(http, name)

  Removes all HTTP header fields in the response whose name is
  specified in "name".

  :param class_http http: The related http object.
  :param string name: The header name.
  :see: :js:func:`HTTP.req_del_header`

.. js:function:: HTTP.req_set_header(http, name, value)

  This variable replace all occurrence of all header "name", by only
  one containing the "value".

  :param class_http http: The related http object.
  :param string name: The header name.
  :param string value: The header value.
  :see: :js:func:`HTTP.res_set_header`

  This function does the same work as the following code:

.. code-block:: lua

   function fcn(txn)
      TXN.http:req_del_header("header")
      TXN.http:req_add_header("header", "value")
   end
..

.. js:function:: HTTP.res_set_header(http, name, value)

  This function replaces all occurrence of all header "name", by only
  one containing the "value".

  :param class_http http: The related http object.
  :param string name: The header name.
  :param string value: The header value.
  :see: :js:func:`HTTP.req_rep_header()`

.. js:function:: HTTP.req_rep_header(http, name, regex, replace)

  Matches the regular expression in all occurrences of header field "name"
  according to "regex", and replaces them with the "replace" argument. The
  replacement value can contain back references like \1, \2, ... This
  function works with the request.

  :param class_http http: The related http object.
  :param string name: The header name.
  :param string regex: The match regular expression.
  :param string replace: The replacement value.
  :see: :js:func:`HTTP.res_rep_header()`

.. js:function:: HTTP.res_rep_header(http, name, regex, string)

  Matches the regular expression in all occurrences of header field "name"
  according to "regex", and replaces them with the "replace" argument. The
  replacement value can contain back references like \1, \2, ... This
  function works with the request.

  :param class_http http: The related http object.
  :param string name: The header name.
  :param string regex: The match regular expression.
  :param string replace: The replacement value.
  :see: :js:func:`HTTP.req_rep_header()`

.. js:function:: HTTP.req_set_method(http, method)

  Rewrites the request method with the parameter "method".

  :param class_http http: The related http object.
  :param string method: The new method.

.. js:function:: HTTP.req_set_path(http, path)

  Rewrites the request path with the "path" parameter.

  :param class_http http: The related http object.
  :param string path: The new path.

.. js:function:: HTTP.req_set_query(http, query)

  Rewrites the request's query string which appears after the first question
  mark ("?") with the parameter "query".

  :param class_http http: The related http object.
  :param string query: The new query.

.. js:function:: HTTP.req_set_uri(http, uri)

  Rewrites the request URI with the parameter "uri".

  :param class_http http: The related http object.
  :param string uri: The new uri.

.. js:function:: HTTP.res_set_status(http, status [, reason])

  Rewrites the response status code with the parameter "code".

  If no custom reason is provided, it will be generated from the status.

  :param class_http http: The related http object.
  :param integer status: The new response status code.
  :param string reason: The new response reason (optional).

.. _httpclient_class:

HTTPClient class
================

.. js:class:: HTTPClient

   The httpclient class allows issue of outbound HTTP requests through a simple
   API without the knowledge of HAProxy internals.

.. js:function:: HTTPClient.get(httpclient, request)
.. js:function:: HTTPClient.head(httpclient, request)
.. js:function:: HTTPClient.put(httpclient, request)
.. js:function:: HTTPClient.post(httpclient, request)
.. js:function:: HTTPClient.delete(httpclient, request)

  Send a HTTP request and wait for a response. GET, HEAD PUT, POST and DELETE
  methods can be used.
  The HTTPClient will send asynchronously the data and is able to send and
  receive more than HAProxy bufsize.

  The HTTPClient interface is not able to decompress responses, it is not
  recommended to send an Accept-Encoding in the request so the response is
  received uncompressed.

  :param class httpclient: Is the manipulated HTTPClient.
  :param table request: Is a table containing the parameters of the request
   that will be send.
  :param string request.url: Is a mandatory parameter for the request that
   contains the URL.
  :param string request.body: Is an optional parameter for the request that
   contains the body to send.
  :param table request.headers: Is an optional parameter for the request that
   contains the headers to send.
  :param string request.dst: Is an optional parameter for the destination in
   haproxy address format.
  :param integer request.timeout: Optional timeout parameter, set a
   "timeout server" on the connections.
  :returns: Lua table containing the response


.. code-block:: lua

  local httpclient = core.httpclient()
  local response = httpclient:post{url="http://127.0.0.1", body=body, dst="unix@/var/run/http.sock"}

..

.. code-block:: lua

 response = {
    status  = 400,
    reason  = "Bad request",
    headers = {
        ["content-type"]  = { "text/html" },
        ["cache-control"] = { "no-cache", "no-store" },
    },
    body = "<html><body><h1>invalid request<h1></body></html>",
  }
..


.. _txn_class:

TXN class
=========

.. js:class:: TXN

  The txn class contain all the functions relative to the http or tcp
  transaction (Note than a tcp stream is the same than a tcp transaction, but
  a HTTP transaction is not the same than a tcp stream).

  The usage of this class permits to retrieve data from the requests, alter it
  and forward it.

  All the functions provided by this class are available in the context
  **sample-fetches**, **actions** and **filters**.

.. js:attribute:: TXN.c

  :returns: An :ref:`converters_class`.

  This attribute contains a Converters class object.

.. js:attribute:: TXN.sc

  :returns: An :ref:`converters_class`.

  This attribute contains a Converters class object. The functions of
  this object returns always a string.

.. js:attribute:: TXN.f

  :returns: An :ref:`fetches_class`.

  This attribute contains a Fetches class object.

.. js:attribute:: TXN.sf

  :returns: An :ref:`fetches_class`.

  This attribute contains a Fetches class object. The functions of
  this object returns always a string.

.. js:attribute:: TXN.req

  :returns: An :ref:`channel_class`.

  This attribute contains a channel class object for the request buffer.

.. js:attribute:: TXN.res

  :returns: An :ref:`channel_class`.

  This attribute contains a channel class object for the response buffer.

.. js:attribute:: TXN.http

  :returns: An :ref:`http_class`.

  This attribute contains a HTTP class object. It is available only if the
  proxy has the "mode http" enabled.

.. js:attribute:: TXN.http_req

  :returns: An :ref:`httpmessage_class`.

  This attribute contains the request HTTPMessage class object. It is available
  only if the proxy has the "mode http" enabled and only in the **filters**
  context.

.. js:attribute:: TXN.http_res

  :returns: An :ref:`httpmessage_class`.

  This attribute contains the response HTTPMessage class object. It is available
  only if the proxy has the "mode http" enabled and only in the **filters**
  context.

.. js:function:: TXN.log(TXN, loglevel, msg)

  This function sends a log. The log is sent, according with the HAProxy
  configuration file, on the default syslog server if it is configured and on
  the stderr if it is allowed.

  :param class_txn txn: The class txn object containing the data.
  :param integer loglevel: Is the log level associated with the message. It is
   a number between 0 and 7.
  :param string msg: The log content.
  :see: :js:attr:`core.emerg`, :js:attr:`core.alert`, :js:attr:`core.crit`,
    :js:attr:`core.err`, :js:attr:`core.warning`, :js:attr:`core.notice`,
    :js:attr:`core.info`, :js:attr:`core.debug` (log level definitions)
  :see: :js:func:`TXN.deflog`
  :see: :js:func:`TXN.Debug`
  :see: :js:func:`TXN.Info`
  :see: :js:func:`TXN.Warning`
  :see: :js:func:`TXN.Alert`

.. js:function:: TXN.deflog(TXN, msg)

  Sends a log line with the default loglevel for the proxy associated with the
  transaction.

  :param class_txn txn: The class txn object containing the data.
  :param string msg: The log content.
  :see: :js:func:`TXN.log`

.. js:function:: TXN.Debug(txn, msg)

  :param class_txn txn: The class txn object containing the data.
  :param string msg: The log content.
  :see: :js:func:`TXN.log`

  Does the same job as:

.. code-block:: lua

  function Debug(txn, msg)
    TXN.log(txn, core.debug, msg)
  end
..

.. js:function:: TXN.Info(txn, msg)

  :param class_txn txn: The class txn object containing the data.
  :param string msg: The log content.
  :see: :js:func:`TXN.log`

  Does the same job as:

.. code-block:: lua

  function Info(txn, msg)
    TXN.log(txn, core.info, msg)
  end
..

.. js:function:: TXN.Warning(txn, msg)

  :param class_txn txn: The class txn object containing the data.
  :param string msg: The log content.
  :see: :js:func:`TXN.log`

  Does the same job as:

.. code-block:: lua

  function Warning(txn, msg)
    TXN.log(txn, core.warning, msg)
  end
..

.. js:function:: TXN.Alert(txn, msg)

  :param class_txn txn: The class txn object containing the data.
  :param string msg: The log content.
  :see: :js:func:`TXN.log`

  Does the same job as:

.. code-block:: lua

  function Alert(txn, msg)
    TXN.log(txn, core.alert, msg)
  end
..

.. js:function:: TXN.get_priv(txn)

  Return Lua data stored in the current transaction (with the `TXN.set_priv()`)
  function. If no data are stored, it returns a nil value.

  :param class_txn txn: The class txn object containing the data.
  :returns: the opaque data previously stored, or nil if nothing is
   available.

.. js:function:: TXN.set_priv(txn, data)

  Store any data in the current HAProxy transaction. This action replaces the
  old stored data.

  :param class_txn txn: The class txn object containing the data.
  :param opaque data: The data which is stored in the transaction.

.. js:function:: TXN.set_var(TXN, var, value[, ifexist])

  Converts a Lua type in a HAProxy type and store it in a variable <var>.

  :param class_txn txn: The class txn object containing the data.
  :param string var: The variable name according with the HAProxy variable
   syntax.
  :param type value: The value associated to the variable. The type can be
   string or integer.
  :param boolean ifexist: If this parameter is set to true the variable will
   only be set if it was defined elsewhere (i.e. used within the configuration).
   For global variables (using the "proc" scope), they will only be updated and
   never created. It is highly recommended to always set this to true.

.. js:function:: TXN.unset_var(TXN, var)

  Unset the variable <var>.

  :param class_txn txn: The class txn object containing the data.
  :param string var: The variable name according with the HAProxy variable
   syntax.

.. js:function:: TXN.get_var(TXN, var)

  Returns data stored in the variable <var> converter in Lua type.

  :param class_txn txn: The class txn object containing the data.
  :param string var: The variable name according with the HAProxy variable
   syntax.

.. js:function:: TXN.reply([reply])

  Return a new reply object

  :param table reply: A table containing info to initialize the reply fields.
  :returns: A :ref:`reply_class` object.

  The table used to initialized the reply object may contain following entries :

  * status : The reply status code. the code 200 is used by default.
  * reason : The reply reason. The reason corresponding to the status code is
    used by default.
  * headers : A list of headers, indexed by header name. Empty by default. For
    a given name, multiple values are possible, stored in an ordered list.
  * body : The reply body, empty by default.

.. code-block:: lua

  local reply = txn:reply{
      status  = 400,
      reason  = "Bad request",
      headers = {
          ["content-type"]  = { "text/html" },
          ["cache-control"] = {"no-cache", "no-store" }
      },
      body = "<html><body><h1>invalid request<h1></body></html>"
  }
..
  :see: :js:class:`Reply`

.. js:function:: TXN.done(txn[, reply])

  This function terminates processing of the transaction and the associated
  session and optionally reply to the client for HTTP sessions.

  :param class_txn txn: The class txn object containing the data.
  :param class_reply reply: The class reply object to return to the client.

  This functions can be used when a critical error is detected or to terminate
  processing after some data have been returned to the client (eg: a redirect).
  To do so, a reply may be provided. This object is optional and may contain a
  status code, a reason, a header list and a body. All these fields are
  optional. When not provided, the default values are used. By default, with an
  empty reply object, an empty HTTP 200 response is returned to the client. If
  no reply object is provided, the transaction is terminated without any
  reply. If a reply object is provided, it must not exceed the buffer size once
  converted into the internal HTTP representation. Because for now there is no
  easy way to be sure it fits, it is probably better to keep it reasonably
  small.

  The reply object may be fully created in lua or the class Reply may be used to
  create it.

.. code-block:: lua

  local reply = txn:reply()
  reply:set_status(400, "Bad request")
  reply:add_header("content-type", "text/html")
  reply:add_header("cache-control", "no-cache")
  reply:add_header("cache-control", "no-store")
  reply:set_body("<html><body><h1>invalid request<h1></body></html>")
  txn:done(reply)
..

.. code-block:: lua

   txn:done{
       status  = 400,
       reason  = "Bad request",
       headers = {
           ["content-type"]  = { "text/html" },
           ["cache-control"] = { "no-cache", "no-store" },
       },
       body = "<html><body><h1>invalid request<h1></body></html>"
   }
..

  .. warning::
    It does not make sense to call this function from sample-fetches. In this
    case the behavior is the same than core.done(): it finishes the Lua
    execution. The transaction is really aborted only from an action registered
    function.

  :see: :js:func:`TXN.reply`, :js:class:`Reply`

.. js:function:: TXN.set_loglevel(txn, loglevel)

  Is used to change the log level of the current request. The "loglevel" must
  be an integer between 0 and 7.

  :param class_txn txn: The class txn object containing the data.
  :param integer loglevel: The required log level. This variable can be one of
  :see: :js:attr:`core.emerg`, :js:attr:`core.alert`, :js:attr:`core.crit`,
    :js:attr:`core.err`, :js:attr:`core.warning`, :js:attr:`core.notice`,
    :js:attr:`core.info`, :js:attr:`core.debug` (log level definitions)

.. js:function:: TXN.set_tos(txn, tos)

  Is used to set the TOS or DSCP field value of packets sent to the client to
  the value passed in "tos" on platforms which support this.

  :param class_txn txn: The class txn object containing the data.
  :param integer tos: The new TOS os DSCP.

.. js:function:: TXN.set_mark(txn, mark)

  Is used to set the Netfilter MARK on all packets sent to the client to the
  value passed in "mark" on platforms which support it.

  :param class_txn txn: The class txn object containing the data.
  :param integer mark: The mark value.

.. js:function:: TXN.set_priority_class(txn, prio)

  This function adjusts the priority class of the transaction. The value should
  be within the range -2047..2047. Values outside this range will be
  truncated.

  See the HAProxy configuration.txt file keyword "http-request" action
  "set-priority-class" for details.

.. js:function:: TXN.set_priority_offset(txn, prio)

  This function adjusts the priority offset of the transaction. The value
  should be within the range -524287..524287. Values outside this range will be
  truncated.

  See the HAProxy configuration.txt file keyword "http-request" action
  "set-priority-offset" for details.

.. _reply_class:

Reply class
============

.. js:class:: Reply

  **context**: action

  This class represents a HTTP response message. It provides some methods to
  enrich it. Once converted into the internal HTTP representation, the response
  message must not exceed the buffer size. Because for now there is no
  easy way to be sure it fits, it is probably better to keep it reasonably
  small.

  See tune.bufsize in the configuration manual for details.

.. code-block:: lua

  local reply = txn:reply({status = 400}) -- default HTTP 400 reason-phase used
  reply:add_header("content-type", "text/html")
  reply:add_header("cache-control", "no-cache")
  reply:add_header("cache-control", "no-store")
  reply:set_body("<html><body><h1>invalid request<h1></body></html>")
..

  :see: :js:func:`TXN.reply`

.. js:attribute:: Reply.status

  The reply status code. By default, the status code is set to 200.

  :returns: integer

.. js:attribute:: Reply.reason

  The reason string describing the status code.

  :returns: string

.. js:attribute:: Reply.headers

  A table indexing all reply headers by name. To each name is associated an
  ordered list of values.

  :returns: Lua table

.. code-block:: lua

  {
    ["content-type"]  = { "text/html" },
    ["cache-control"] = {"no-cache", "no-store" },
    x_header_name     = { "value1", "value2", ... }
    ...
  }
..

.. js:attribute:: Reply.body

  The reply payload.

  :returns: string

.. js:function:: Reply.set_status(REPLY, status[, reason])

  Set the reply status code and optionally the reason-phrase. If the reason is
  not provided, the default reason corresponding to the status code is used.

  :param class_reply reply: The related Reply object.
  :param integer status: The reply status code.
  :param string reason: The reply status reason (optional).

.. js:function:: Reply.add_header(REPLY, name, value)

  Add a header to the reply object. If the header does not already exist, a new
  entry is created with its name as index and a one-element list containing its
  value as value. Otherwise, the header value is appended to the ordered list of
  values associated to the header name.

  :param class_reply reply: The related Reply object.
  :param string name: The header field name.
  :param string value: The header field value.

.. js:function:: Reply.del_header(REPLY, name)

  Remove all occurrences of a header name from the reply object.

  :param class_reply reply: The related Reply object.
  :param string name: The header field name.

.. js:function:: Reply.set_body(REPLY, body)

  Set the reply payload.

  :param class_reply reply: The related Reply object.
  :param string body: The reply payload.

.. _socket_class:

Socket class
============

.. js:class:: Socket

  This class must be compatible with the Lua Socket class. Only the 'client'
  functions are available. See the Lua Socket documentation:

  `http://w3.impa.br/~diego/software/luasocket/tcp.html
  <http://w3.impa.br/~diego/software/luasocket/tcp.html>`_

.. js:function:: Socket.close(socket)

  Closes a TCP object. The internal socket used by the object is closed and the
  local address to which the object was bound is made available to other
  applications. No further operations (except for further calls to the close
  method) are allowed on a closed Socket.

  :param class_socket socket: Is the manipulated Socket.

  Note: It is important to close all used sockets once they are not needed,
  since, in many systems, each socket uses a file descriptor, which are limited
  system resources. Garbage-collected objects are automatically closed before
  destruction, though.

.. js:function:: Socket.connect(socket, address[, port])

  Attempts to connect a socket object to a remote host.


  In case of error, the method returns nil followed by a string describing the
  error. In case of success, the method returns 1.

  :param class_socket socket: Is the manipulated Socket.
  :param string address: can be an IP address or a host name. See below for more
   information.
  :param integer port: must be an integer number in the range [1..64K].
  :returns: 1 or nil.

  An address field extension permits to use the connect() function to connect to
  other stream than TCP. The syntax containing a simpleipv4 or ipv6 address is
  the basically expected format. This format requires the port.

  Other format accepted are a socket path like "/socket/path", it permits to
  connect to a socket. Abstract namespaces are supported with the prefix
  "abns@", and finally a file descriptor can be passed with the prefix "fd@".
  The prefix "ipv4@", "ipv6@" and "unix@" are also supported. The port can be
  passed int the string. The syntax "127.0.0.1:1234" is valid. In this case, the
  parameter *port* must not be set.

.. js:function:: Socket.connect_ssl(socket, address, port)

  Same behavior than the function socket:connect, but uses SSL.

  :param class_socket socket: Is the manipulated Socket.
  :returns: 1 or nil.

.. js:function:: Socket.getpeername(socket)

  Returns information about the remote side of a connected client object.

  Returns a string with the IP address of the peer, followed by the port number
  that peer is using for the connection. In case of error, the method returns
  nil.

  :param class_socket socket: Is the manipulated Socket.
  :returns: a string containing the server information.

.. js:function:: Socket.getsockname(socket)

  Returns the local address information associated to the object.

  The method returns a string with local IP address and a number with the port.
  In case of error, the method returns nil.

  :param class_socket socket: Is the manipulated Socket.
  :returns: a string containing the client information.

.. js:function:: Socket.receive(socket, [pattern [, prefix]])

  Reads data from a client object, according to the specified read pattern.
  Patterns follow the Lua file I/O format, and the difference in performance
  between all patterns is negligible.

  :param class_socket socket: Is the manipulated Socket.
  :param string|integer pattern: Describe what is required (see below).
  :param string prefix: A string which will be prefix the returned data.
  :returns:  a string containing the required data or nil.

  Pattern can be any of the following:

  * **`*a`**: reads from the socket until the connection is closed. No
              end-of-line translation is performed;

  * **`*l`**: reads a line of text from the Socket. The line is terminated by a
              LF character (ASCII 10), optionally preceded by a CR character
              (ASCII 13). The CR and LF characters are not included in the
              returned line.  In fact, all CR characters are ignored by the
              pattern. This is the default pattern.

  * **number**: causes the method to read a specified number of bytes from the
                Socket. Prefix is an optional string to be concatenated to the
                beginning of any received data before return.

  * **empty**: If the pattern is left empty, the default option is `*l`.

  If successful, the method returns the received pattern. In case of error, the
  method returns nil followed by an error message which can be the string
  'closed' in case the connection was closed before the transmission was
  completed or the string 'timeout' in case there was a timeout during the
  operation. Also, after the error message, the function returns the partial
  result of the transmission.

  Important note: This function was changed severely. It used to support
  multiple patterns (but I have never seen this feature used) and now it
  doesn't anymore.  Partial results used to be returned in the same way as
  successful results. This last feature violated the idea that all functions
  should return nil on error.  Thus it was changed too.

.. js:function:: Socket.send(socket, data [, start [, end ]])

  Sends data through client object.

  :param class_socket socket: Is the manipulated Socket.
  :param string data: The data that will be sent.
  :param integer start: The start position in the buffer of the data which will
   be sent.
  :param integer end: The end position in the buffer of the data which will
   be sent.
  :returns: see below.

  Data is the string to be sent. The optional arguments i and j work exactly
  like the standard string.sub Lua function to allow the selection of a
  substring to be sent.

  If successful, the method returns the index of the last byte within [start,
  end] that has been sent. Notice that, if start is 1 or absent, this is
  effectively the total number of bytes sent. In case of error, the method
  returns nil, followed by an error message, followed by the index of the last
  byte within [start, end] that has been sent. You might want to try again from
  the byte following that. The error message can be 'closed' in case the
  connection was closed before the transmission was completed or the string
  'timeout' in case there was a timeout during the operation.

  Note: Output is not buffered. For small strings, it is always better to
  concatenate them in Lua (with the '..' operator) and send the result in one
  call instead of calling the method several times.

.. js:function:: Socket.setoption(socket, option [, value])

  Just implemented for compatibility, this cal does nothing.

.. js:function:: Socket.settimeout(socket, value [, mode])

  Changes the timeout values for the object. All I/O operations are blocking.
  That is, any call to the methods send, receive, and accept will block
  indefinitely, until the operation completes. The settimeout method defines a
  limit on the amount of time the I/O methods can block. When a timeout time
  has elapsed, the affected methods give up and fail with an error code.

  The amount of time to wait is specified as the value parameter, in seconds.

  The timeout modes are not implemented, the only settable timeout is the
  inactivity time waiting for complete the internal buffer send or waiting for
  receive data.

  :param class_socket socket: Is the manipulated Socket.
  :param float value: The timeout value. Use floating point to specify
   milliseconds.

.. _regex_class:

Regex class
===========

.. js:class:: Regex

  This class allows the usage of HAProxy regexes because classic lua doesn't
  provides regexes. This class inherits the HAProxy compilation options, so the
  regexes can be libc regex, pcre regex or pcre JIT regex.

  The expression matching number is limited to 20 per regex. The only available
  option is case sensitive.

  Because regexes compilation is a heavy process, it is better to define all
  your regexes in the **body context** and use it during the runtime.

.. code-block:: lua

  -- Create the regex
  st, regex = Regex.new("needle (..) (...)", true);

  -- Check compilation errors
  if st == false then
    print "error: " .. regex
  end

  -- Match the regexes
  print(regex:exec("Looking for a needle in the haystack")) -- true
  print(regex:exec("Lokking for a cat in the haystack"))    -- false

  -- Extract words
  st, list = regex:match("Looking for a needle in the haystack")
  print(st)      -- true
  print(list[1]) -- needle in the
  print(list[2]) -- in
  print(list[3]) -- the

.. js:function:: Regex.new(regex, case_sensitive)

  Create and compile a regex.

  :param string regex: The regular expression according with the libc or pcre
   standard
  :param boolean case_sensitive: Match is case sensitive or not.
  :returns: boolean status and :ref:`regex_class` or string containing fail
   reason.

.. js:function:: Regex.exec(regex, str)

  Execute the regex.

  :param class_regex regex: A :ref:`regex_class` object.
  :param string str: The input string will be compared with the compiled regex.
  :returns: a boolean status according with the match result.

.. js:function:: Regex.match(regex, str)

  Execute the regex and return matched expressions.

  :param class_map map: A :ref:`regex_class` object.
  :param string str: The input string will be compared with the compiled regex.
  :returns: a boolean status according with the match result, and
   a table containing all the string matched in order of declaration.

.. _map_class:

Map class
=========

.. js:class:: Map

  This class permits to do some lookups in HAProxy maps. The declared maps can
  be modified during the runtime through the HAProxy management socket.

.. code-block:: lua

  default = "usa"

  -- Create and load map
  geo = Map.new("geo.map", Map._ip);

  -- Create new fetch that returns the user country
  core.register_fetches("country", function(txn)
    local src;
    local loc;

    src = txn.f:fhdr("x-forwarded-for");
    if (src == nil) then
      src = txn.f:src()
      if (src == nil) then
        return default;
      end
    end

    -- Perform lookup
    loc = geo:lookup(src);

    if (loc == nil) then
      return default;
    end

    return loc;
  end);

.. js:attribute:: Map._int

  See the HAProxy configuration.txt file, chapter "Using ACLs and fetching
  samples" and subchapter "ACL basics" to understand this pattern matching
  method.

  Note that :js:attr:`Map.int` is also available for compatibility.

.. js:attribute:: Map._ip

  See the HAProxy configuration.txt file, chapter "Using ACLs and fetching
  samples" and subchapter "ACL basics" to understand this pattern matching
  method.

  Note that :js:attr:`Map.ip` is also available for compatibility.

.. js:attribute:: Map._str

  See the HAProxy configuration.txt file, chapter "Using ACLs and fetching
  samples" and subchapter "ACL basics" to understand this pattern matching
  method.

  Note that :js:attr:`Map.str` is also available for compatibility.

.. js:attribute:: Map._beg

  See the HAProxy configuration.txt file, chapter "Using ACLs and fetching
  samples" and subchapter "ACL basics" to understand this pattern matching
  method.

  Note that :js:attr:`Map.beg` is also available for compatibility.

.. js:attribute:: Map._sub

  See the HAProxy configuration.txt file, chapter "Using ACLs and fetching
  samples" and subchapter "ACL basics" to understand this pattern matching
  method.

  Note that :js:attr:`Map.sub` is also available for compatibility.

.. js:attribute:: Map._dir

  See the HAProxy configuration.txt file, chapter "Using ACLs and fetching
  samples" and subchapter "ACL basics" to understand this pattern matching
  method.

  Note that :js:attr:`Map.dir` is also available for compatibility.

.. js:attribute:: Map._dom

  See the HAProxy configuration.txt file, chapter "Using ACLs and fetching
  samples" and subchapter "ACL basics" to understand this pattern matching
  method.

  Note that :js:attr:`Map.dom` is also available for compatibility.

.. js:attribute:: Map._end

  See the HAProxy configuration.txt file, chapter "Using ACLs and fetching
  samples" and subchapter "ACL basics" to understand this pattern matching
  method.

.. js:attribute:: Map._reg

  See the HAProxy configuration.txt file, chapter "Using ACLs and fetching
  samples" and subchapter "ACL basics" to understand this pattern matching
  method.

  Note that :js:attr:`Map.reg` is also available for compatibility.


.. js:function:: Map.new(file, method)

  Creates and load a map.

  :param string file: Is the file containing the map.
  :param integer method: Is the map pattern matching method. See the attributes
   of the Map class.
  :returns: a class Map object.
  :see: The Map attributes: :js:attr:`Map._int`, :js:attr:`Map._ip`,
    :js:attr:`Map._str`, :js:attr:`Map._beg`, :js:attr:`Map._sub`,
    :js:attr:`Map._dir`, :js:attr:`Map._dom`, :js:attr:`Map._end` and
    :js:attr:`Map._reg`.

.. js:function:: Map.lookup(map, str)

  Perform a lookup in a map.

  :param class_map map: Is the class Map object.
  :param string str: Is the string used as key.
  :returns: a string containing the result or nil if no match.

.. js:function:: Map.slookup(map, str)

  Perform a lookup in a map.

  :param class_map map: Is the class Map object.
  :param string str: Is the string used as key.
  :returns: a string containing the result or empty string if no match.

.. _applethttp_class:

AppletHTTP class
================

.. js:class:: AppletHTTP

  This class is used with applets that requires the 'http' mode. The http applet
  can be registered with the *core.register_service()* function. They are used
  for processing an http request like a server in back of HAProxy.

  This is an hello world sample code:

.. code-block:: lua

  core.register_service("hello-world", "http", function(applet)
     local response = "Hello World !"
     applet:set_status(200)
     applet:add_header("content-length", string.len(response))
     applet:add_header("content-type", "text/plain")
     applet:start_response()
     applet:send(response)
  end)

.. js:attribute:: AppletHTTP.c

  :returns: A :ref:`converters_class`

  This attribute contains a Converters class object.

.. js:attribute:: AppletHTTP.sc

  :returns: A :ref:`converters_class`

  This attribute contains a Converters class object. The
  functions of this object always return a string.

.. js:attribute:: AppletHTTP.f

  :returns: A :ref:`fetches_class`

  This attribute contains a Fetches class object. Note that the
  applet execution place cannot access to a valid HAProxy core HTTP
  transaction, so some sample fetches related to the HTTP dependent
  values (hdr, path, ...) are not available.

.. js:attribute:: AppletHTTP.sf

  :returns: A :ref:`fetches_class`

  This attribute contains a Fetches class object. The functions of
  this object always return a string. Note that the applet
  execution place cannot access to a valid HAProxy core HTTP
  transaction, so some sample fetches related to the HTTP dependent
  values (hdr, path, ...) are not available.

.. js:attribute:: AppletHTTP.method

  :returns: string

  The attribute method returns a string containing the HTTP
  method.

.. js:attribute:: AppletHTTP.version

  :returns: string

  The attribute version, returns a string containing the HTTP
  request version.

.. js:attribute:: AppletHTTP.path

  :returns: string

  The attribute path returns a string containing the HTTP
  request path.

.. js:attribute:: AppletHTTP.qs

  :returns: string

  The attribute qs returns a string containing the HTTP
  request query string.

.. js:attribute:: AppletHTTP.length

  :returns: integer

  The attribute length returns an integer containing the HTTP
  body length.

.. js:attribute:: AppletHTTP.headers

  :returns: table

  The attribute headers returns a table containing the HTTP
  headers. The header names are always in lower case. As the header name can be
  encountered more than once in each request, the value is indexed with 0 as
  first index value. The table has this form:

.. code-block:: lua

  AppletHTTP.headers['<header-name>'][<header-index>] = "<header-value>"

  AppletHTTP.headers["host"][0] = "www.test.com"
  AppletHTTP.headers["accept"][0] = "audio/basic q=1"
  AppletHTTP.headers["accept"][1] = "audio/*, q=0.2"
  AppletHTTP.headers["accept"][2] = "*/*, q=0.1"
..

.. js:function:: AppletHTTP.set_status(applet, code [, reason])

  This function sets the HTTP status code for the response. The allowed code are
  from 100 to 599.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :param integer code: the status code returned to the client.
  :param string reason: the status reason returned to the client (optional).

.. js:function:: AppletHTTP.add_header(applet, name, value)

  This function adds a header in the response. Duplicated headers are not
  collapsed. The special header *content-length* is used to determinate the
  response length. If it does not exist, a *transfer-encoding: chunked* is set,
  and all the write from the function *AppletHTTP:send()* become a chunk.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :param string name: the header name
  :param string value: the header value

.. js:function:: AppletHTTP.start_response(applet)

  This function indicates to the HTTP engine that it can process and send the
  response headers. After this called we cannot add headers to the response; We
  cannot use the *AppletHTTP:send()* function if the
  *AppletHTTP:start_response()* is not called.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`

.. js:function:: AppletHTTP.getline(applet)

  This function returns a string containing one line from the http body. If the
  data returned doesn't contains a final '\\n' its assumed than its the last
  available data before the end of stream.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :returns: a string. The string can be empty if we reach the end of the stream.

.. js:function:: AppletHTTP.receive(applet, [size])

  Reads data from the HTTP body, according to the specified read *size*. If the
  *size* is missing, the function tries to read all the content of the stream
  until the end. If the *size* is bigger than the http body, it returns the
  amount of data available.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :param integer size: the required read size.
  :returns: always return a string,the string can be empty is the connection is
   closed.

.. js:function:: AppletHTTP.send(applet, msg)

  Send the message *msg* on the http request body.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :param string msg: the message to send.

.. js:function:: AppletHTTP.get_priv(applet)

  Return Lua data stored in the current transaction. If no data are stored,
  it returns a nil value.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :returns: the opaque data previously stored, or nil if nothing is
   available.
  :see: :js:func:`AppletHTTP.set_priv`

.. js:function:: AppletHTTP.set_priv(applet, data)

  Store any data in the current HAProxy transaction. This action replaces the
  old stored data.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :param opaque data: The data which is stored in the transaction.
  :see: :js:func:`AppletHTTP.get_priv`

.. js:function:: AppletHTTP.set_var(applet, var, value[, ifexist])

  Converts a Lua type in a HAProxy type and store it in a variable <var>.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :param string var: The variable name according with the HAProxy variable
   syntax.
  :param type value: The value associated to the variable. The type ca be string
   or integer.
  :param boolean ifexist: If this parameter is set to true the variable will
   only be set if it was defined elsewhere (i.e. used within the configuration).
   For global variables (using the "proc" scope), they will only be updated and
   never created. It is highly recommended to always set this to true.

  :see: :js:func:`AppletHTTP.unset_var`
  :see: :js:func:`AppletHTTP.get_var`

.. js:function:: AppletHTTP.unset_var(applet, var)

  Unset the variable <var>.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :param string var: The variable name according with the HAProxy variable
   syntax.
  :see: :js:func:`AppletHTTP.set_var`
  :see: :js:func:`AppletHTTP.get_var`

.. js:function:: AppletHTTP.get_var(applet, var)

  Returns data stored in the variable <var> converter in Lua type.

  :param class_AppletHTTP applet: An :ref:`applethttp_class`
  :param string var: The variable name according with the HAProxy variable
   syntax.
  :see: :js:func:`AppletHTTP.set_var`
  :see: :js:func:`AppletHTTP.unset_var`

.. _applettcp_class:

AppletTCP class
===============

.. js:class:: AppletTCP

  This class is used with applets that requires the 'tcp' mode. The tcp applet
  can be registered with the *core.register_service()* function. They are used
  for processing a tcp stream like a server in back of HAProxy.

.. js:attribute:: AppletTCP.c

  :returns: A :ref:`converters_class`

  This attribute contains a Converters class object.

.. js:attribute:: AppletTCP.sc

  :returns: A :ref:`converters_class`

  This attribute contains a Converters class object. The
  functions of this object always return a string.

.. js:attribute:: AppletTCP.f

  :returns: A :ref:`fetches_class`

  This attribute contains a Fetches class object.

.. js:attribute:: AppletTCP.sf

  :returns: A :ref:`fetches_class`

  This attribute contains a Fetches class object.

.. js:function:: AppletTCP.getline(applet)

  This function returns a string containing one line from the stream. If the
  data returned doesn't contains a final '\\n' its assumed than its the last
  available data before the end of stream.

  :param class_AppletTCP applet: An :ref:`applettcp_class`
  :returns: a string. The string can be empty if we reach the end of the stream.

.. js:function:: AppletTCP.receive(applet, [size])

  Reads data from the TCP stream, according to the specified read *size*. If the
  *size* is missing, the function tries to read all the content of the stream
  until the end.

  :param class_AppletTCP applet: An :ref:`applettcp_class`
  :param integer size: the required read size.
  :returns: always return a string, the string can be empty if the connection is
   closed.

.. js:function:: AppletTCP.send(appletmsg)

  Send the message on the stream.

  :param class_AppletTCP applet: An :ref:`applettcp_class`
  :param string msg: the message to send.

.. js:function:: AppletTCP.get_priv(applet)

  Return Lua data stored in the current transaction. If no data are stored,
  it returns a nil value.

  :param class_AppletTCP applet: An :ref:`applettcp_class`
  :returns: the opaque data previously stored, or nil if nothing is
   available.
  :see: :js:func:`AppletTCP.set_priv`

.. js:function:: AppletTCP.set_priv(applet, data)

  Store any data in the current HAProxy transaction. This action replaces the
  old stored data.

  :param class_AppletTCP applet: An :ref:`applettcp_class`
  :param opaque data: The data which is stored in the transaction.
  :see: :js:func:`AppletTCP.get_priv`

.. js:function:: AppletTCP.set_var(applet, var, value[, ifexist])

  Converts a Lua type in a HAProxy type and stores it in a variable <var>.

  :param class_AppletTCP applet: An :ref:`applettcp_class`
  :param string var: The variable name according with the HAProxy variable
   syntax.
  :param type value: The value associated to the variable. The type can be
   string or integer.
  :param boolean ifexist: If this parameter is set to true the variable will
   only be set if it was defined elsewhere (i.e. used within the configuration).
   For global variables (using the "proc" scope), they will only be updated and
   never created. It is highly recommended to always set this to true.

  :see: :js:func:`AppletTCP.unset_var`
  :see: :js:func:`AppletTCP.get_var`

.. js:function:: AppletTCP.unset_var(applet, var)

  Unsets the variable <var>.

  :param class_AppletTCP applet: An :ref:`applettcp_class`
  :param string var: The variable name according with the HAProxy variable
   syntax.
  :see: :js:func:`AppletTCP.unset_var`
  :see: :js:func:`AppletTCP.set_var`

.. js:function:: AppletTCP.get_var(applet, var)

  Returns data stored in the variable <var> converter in Lua type.

  :param class_AppletTCP applet: An :ref:`applettcp_class`
  :param string var: The variable name according with the HAProxy variable
   syntax.
  :see: :js:func:`AppletTCP.unset_var`
  :see: :js:func:`AppletTCP.set_var`

StickTable class
================

.. js:class:: StickTable

  **context**: task, action, sample-fetch

  This class can be used to access the HAProxy stick tables from Lua.

.. js:function:: StickTable.info()

  Returns stick table attributes as a Lua table. See HAProxy documentation for
  "stick-table" for canonical info, or check out example below.

  :returns: Lua table

  Assume our table has IPv4 key and gpc0 and conn_rate "columns":

.. code-block:: lua

  {
    expire=<int>,  # Value in ms
    size=<int>,    # Maximum table size
    used=<int>,    # Actual number of entries in table
    data={         # Data columns, with types as key, and periods as values
                     (-1 if type is not rate counter)
      conn_rate=<int>,
      gpc0=-1
    },
    length=<int>,  # max string length for string table keys, key length
                   # otherwise
    nopurge=<boolean>, # purge oldest entries when table is full
    type="ip"      # can be "ip", "ipv6", "integer", "string", "binary"
  }

.. js:function:: StickTable.lookup(key)

   Returns stick table entry for given <key>

   :param string key: Stick table key (IP addresses and strings are supported)
   :returns: Lua table

.. js:function:: StickTable.dump([filter])

   Returns all entries in stick table. An optional filter can be used
   to extract entries with specific data values. Filter is a table with valid
   comparison operators as keys followed by data type name and value pairs.
   Check out the HAProxy docs for "show table" for more details. For the
   reference, the supported operators are:

     "eq", "ne", "le", "lt", "ge", "gt"

   For large tables, execution of this function can take a long time (for
   HAProxy standards). That's also true when filter is used, so take care and
   measure the impact.

   :param table filter: Stick table filter
   :returns: Stick table entries (table)

   See below for example filter, which contains 4 entries (or comparisons).
   (Maximum number of filter entries is 4, defined in the source code)

.. code-block:: lua

    local filter = {
      {"gpc0", "gt", 30}, {"gpc1", "gt", 20}}, {"conn_rate", "le", 10}
    }

.. _action_class:

Action class
=============

.. js:class:: Act

  **context**: action

  This class contains all return codes an action may return. It is the lua
  equivalent to HAProxy "ACT_RET_*" code.

.. code-block:: lua

  core.register_action("deny", { "http-req" }, function (txn)
      return act.DENY
   end)
..
.. js:attribute:: act.CONTINUE

  This attribute is an integer (0). It instructs HAProxy to continue the
  current ruleset processing on the message. It is the default return code
  for a lua action.

  :returns: integer

.. js:attribute:: act.STOP

  This attribute is an integer (1). It instructs HAProxy to stop the current
  ruleset processing on the message.

.. js:attribute:: act.YIELD

  This attribute is an integer (2). It instructs HAProxy to temporarily pause
  the message processing. It will be resumed later on the same rule. The
  corresponding lua script is re-executed for the start.

.. js:attribute:: act.ERROR

  This attribute is an integer (3). It triggers an internal errors The message
  processing is stopped and the transaction is terminated. For HTTP streams, an
  HTTP 500 error is returned to the client.

  :returns: integer

.. js:attribute:: act.DONE

  This attribute is an integer (4). It instructs HAProxy to stop the message
  processing.

  :returns: integer

.. js:attribute:: act.DENY

  This attribute is an integer (5). It denies the current message. The message
  processing is stopped and the transaction is terminated. For HTTP streams, an
  HTTP 403 error is returned to the client if the deny is returned during the
  request analysis. During the response analysis, a HTTP 502 error is returned
  and the server response is discarded.

  :returns: integer

.. js:attribute:: act.ABORT

  This attribute is an integer (6). It aborts the current message. The message
  processing is stopped and the transaction is terminated. For HTTP streams,
  HAProxy assumes a response was already sent to the client. From the Lua
  actions point of view, when this code is used, the transaction is terminated
  with no reply.

  :returns: integer

.. js:attribute:: act.INVALID

  This attribute is an integer (7). It triggers an internal errors. The message
  processing is stopped and the transaction is terminated. For HTTP streams, an
  HTTP 400 error is returned to the client if the error is returned during the
  request analysis. During the response analysis, a HTTP 502 error is returned
  and the server response is discarded.

  :returns: integer

.. js:function:: act:wake_time(milliseconds)

  **context**: action

  Set the script pause timeout to the specified time, defined in
  milliseconds.

  :param integer milliseconds: the required milliseconds.

  This function may be used when a lua action returns `act.YIELD`, to force its
  wake-up at most after the specified number of milliseconds.

.. _filter_class:

Filter class
=============

.. js:class:: filter

  **context**: filter

  This class contains return codes some filter callback functions may return. It
  also contains configuration flags and some helper functions. To understand how
  the filter API works, see `doc/internal/filters.txt` documentation.

.. js:attribute:: filter.CONTINUE

  This attribute is an integer (1). It may be returned by some filter callback
  functions to instruct this filtering step is finished for this filter.

.. js:attribute:: filter.WAIT

  This attribute is an integer (0). It may be returned by some filter callback
  functions to instruct the filtering must be paused, waiting for more data or
  for an external event depending on this filter.

.. js:attribute:: filter.ERROR

  This attribute is an integer (-1). It may be returned by some filter callback
  functions to trigger an error.

.. js:attribute:: filter.FLT_CFG_FL_HTX

  This attribute is a flag corresponding to the filter flag FLT_CFG_FL_HTX. When
  it is set for a filter, it means the filter is able to filter HTTP streams.

.. js:function:: filter.register_data_filter(chn)

  **context**: filter

  Enable the data filtering on the channel **chn** for the current filter. It
  may be called at any time from any callback functions proceeding the data
  analysis.

  :param class_Channel chn: A :ref:`channel_class`.

.. js:function:: filter.unregister_data_filter(chn)

  **context**: filter

  Disable the data filtering on the channel **chn** for the current filter. It
  may be called at any time from any callback functions.

  :param class_Channel chn: A :ref:`channel_class`.

.. js:function:: filter.wake_time(milliseconds)

  **context**: filter

  Set the script pause timeout to the specified time, defined in
  milliseconds.

  :param integer milliseconds: the required milliseconds.

  This function may be used from any lua filter callback function to force its
  wake-up at most after the specified number of milliseconds. Especially, when
  `filter.CONTINUE` is returned.


A filters is declared using :js:func:`core.register_filter()` function. The
provided class will be used to instantiate filters. It may define following
attributes:

* id: The filter identifier. It is a string that identifies the filter and is
      optional.

* flags: The filter flags. Only :js:attr:`filter.FLT_CFG_FL_HTX` may be set
         for now.

Such filter class must also define all required callback functions in the
following list. Note that :js:func:`Filter.new()` must be defined otherwise the
filter is ignored. Others are optional.

* .. js:function:: FILTER.new()

  Called to instantiate a new filter. This function must be defined.

  :returns: a Lua object that will be used as filter instance for the current
            stream.

* .. js:function:: FILTER.start_analyze(flt, txn, chn)

  Called when the analysis starts on the channel **chn**.

* .. js:function:: FILTER.end_analyze(flt, txn, chn)

  Called when the analysis ends on the channel **chn**.

* .. js:function:: FILTER.http_headers(flt, txn, http_msg)

  Called just before the HTTP payload analysis and after any processing on the
  HTTP message **http_msg**. This callback functions is only called for HTTP
  streams.

* .. js:function:: FILTER.http_payload(flt, txn, http_msg)

  Called during the HTTP payload analysis on the HTTP message **http_msg**. This
  callback functions is only called for HTTP streams.

* .. js:function:: FILTER.http_end(flt, txn, http_msg)

  Called after the HTTP payload analysis on the HTTP message **http_msg**. This
  callback functions is only called for HTTP streams.

* .. js:function:: FILTER.tcp_payload(flt, txn, chn)

  Called during the TCP payload analysis on the channel **chn**.

Here is a full example:

.. code-block:: lua

  Trace = {}
  Trace.id = "Lua trace filter"
  Trace.flags = filter.FLT_CFG_FL_HTX;
  Trace.__index = Trace

  function Trace:new()
      local trace = {}
      setmetatable(trace, Trace)
      trace.req_len = 0
      trace.res_len = 0
      return trace
  end

  function Trace:start_analyze(txn, chn)
      if chn:is_resp() then
          print("Start response analysis")
      else
          print("Start request analysis")
      end
      filter.register_data_filter(self, chn)
  end

  function Trace:end_analyze(txn, chn)
      if chn:is_resp() then
          print("End response analysis: "..self.res_len.." bytes filtered")
      else
          print("End request analysis: "..self.req_len.." bytes filtered")
      end
  end

  function Trace:http_headers(txn, http_msg)
      stline  = http_msg:get_stline()
      if http_msg.channel:is_resp() then
          print("response:")
          print(stline.version.." "..stline.code.." "..stline.reason)
      else
          print("request:")
          print(stline.method.." "..stline.uri.." "..stline.version)
      end

      for n, hdrs in pairs(http_msg:get_headers()) do
          for i,v in pairs(hdrs) do
              print(n..": "..v)
          end
      end
      return filter.CONTINUE
  end

  function Trace:http_payload(txn, http_msg)
      body = http_msg:body(-20000)
      if http_msg.channel:is_resp() then
          self.res_len = self.res_len + body:len()
      else
          self.req_len = self.req_len + body:len()
      end
  end

  core.register_filter("trace", Trace, function(trace, args)
      return trace
  end)

..

.. _httpmessage_class:

HTTPMessage class
===================

.. js:class:: HTTPMessage

  **context**: filter

  This class contains all functions to manipulate a HTTP message. For now, this
  class is only available from a filter context.

.. js:function:: HTTPMessage.add_header(http_msg, name, value)

  Appends a HTTP header field in the HTTP message **http_msg** whose name is
  specified in **name** and whose value is defined in **value**.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string name: The header name.
  :param string value: The header value.

.. js:function:: HTTPMessage.append(http_msg, string)

  This function copies the string **string** at the end of incoming data of the
  HTTP message **http_msg**. The function returns the copied length on success
  or -1 if data cannot be copied.

  Same that :js:func:`HTTPMessage.insert(http_msg, string, http_msg:input())`.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string string: The data to copy at the end of incoming data.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: HTTPMessage.body(http_msgl[, offset[, length]])

  This function returns **length** bytes of incoming data from the HTTP message
  **http_msg**, starting at the offset **offset**. The data are not removed from
  the buffer.

  By default, if no length is provided, all incoming data found, starting at the
  given offset, are returned. If **length** is set to -1, the function tries to
  retrieve a maximum of data. Because it is called in the filter context, it
  never yield. Not providing an offset is the same as setting it to 0. A
  positive offset is relative to the beginning of incoming data of the
  http_message buffer while negative offset is relative to their end.

  If there is no incoming data and the HTTP message can't receive more data,
  a 'nil' value is returned.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param integer offset: *optional* The offset in incoming data to start to get
   data. 0 by default. May be negative to be relative to the end of incoming
   data.
  :param integer length: *optional* The expected length of data to retrieve.
   All incoming data by default. May be set to -1 to get a maximum of data.
  :returns: a string containing the data found or nil.

.. js:function:: HTTPMessage.eom(http_msg)

  This function returns true if the end of message is reached for the HTTP
  message **http_msg**.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :returns: an integer containing the amount of available bytes.

.. js:function:: HTTPMessage.del_header(http_msg, name)

  Removes all HTTP header fields in the HTTP message **http_msg** whose name is
  specified in **name**.

  :param class_httpmessage http_msg: The manipulated http message.
  :param string name: The header name.

.. js:function:: HTTPMessage.get_headers(http_msg)

  Returns a table containing all the headers of the HTTP message **http_msg**.

  :param class_httpmessage http_msg: The manipulated http message.
  :returns: table of headers.

  This is the form of the returned table:

.. code-block:: lua

  http_msg:get_headers()['<header-name>'][<header-index>] = "<header-value>"

  local hdr = http_msg:get_headers()
  hdr["host"][0] = "www.test.com"
  hdr["accept"][0] = "audio/basic q=1"
  hdr["accept"][1] = "audio/*, q=0.2"
  hdr["accept"][2] = "*.*, q=0.1"
..

.. js:function:: HTTPMessage.get_stline(http_msg)

  Returns a table containing the start-line of the HTTP message **http_msg**.

  :param class_httpmessage http_msg: The manipulated http message.
  :returns: the start-line.

  This is the form of the returned table:

.. code-block:: lua

  -- for the request :
  {"method" = string, "uri" = string, "version" = string}

  -- for the response:
  {"version" = string, "code" = string, "reason" = string}
..

.. js:function:: HTTPMessage.forward(http_msg, length)

  This function forwards **length** bytes of data from the HTTP message
  **http_msg**. Because it is called in the filter context, it never yields. Only
  available incoming data may be forwarded, event if the requested length
  exceeds the available amount of incoming data. It returns the amount of data
  forwarded.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param integer int: The amount of data to forward.

.. js:function:: HTTPMessage.input(http_msg)

  This function returns the length of incoming data in the HTTP message
  **http_msg** from the filter point of view.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :returns: an integer containing the amount of available bytes.

.. js:function:: HTTPMessage.insert(http_msg, string[, offset])

  This function copies the string **string** at the offset **offset** in
  incoming data of the HTTP message **http_msg**. The function returns the
  copied length on success or -1 if data cannot be copied.

  By default, if no offset is provided, the string is copied in front of
  incoming data. A positive offset is relative to the beginning of incoming data
  of the HTTP message while negative offset is relative to their end.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string string: The data to copy into incoming data.
  :param integer offset: *optional* The offset in incoming data where to copy
   data. 0 by default. May be negative to be relative to the end of incoming
   data.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: HTTPMessage.is_full(http_msg)

  This function returns true if the HTTP message **http_msg** is full.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :returns: a boolean

.. js:function:: HTTPMessage.is_resp(http_msg)

  This function returns true if the HTTP message **http_msg** is the response
  one.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :returns: a boolean

.. js:function:: HTTPMessage.may_recv(http_msg)

  This function returns true if the HTTP message **http_msg** may still receive
  data.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :returns: a boolean

.. js:function:: HTTPMessage.output(http_msg)

  This function returns the length of outgoing data of the HTTP message
  **http_msg**.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :returns: an integer containing the amount of available bytes.

.. js:function:: HTTPMessage.prepend(http_msg, string)

  This function copies the string **string** in front of incoming data of the
  HTTP message **http_msg**. The function returns the copied length on success
  or -1 if data cannot be copied.

  Same that :js:func:`HTTPMessage.insert(http_msg, string, 0)`.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string string: The data to copy in front of incoming data.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: HTTPMessage.remove(http_msg[, offset[, length]])

  This function removes **length** bytes of incoming data of the HTTP message
  **http_msg**, starting at offset **offset**. This function returns number of
  bytes removed on success.

  By default, if no length is provided, all incoming data, starting at the given
  offset, are removed. Not providing an offset is the same that setting it
  to 0. A positive offset is relative to the beginning of incoming data of the
  HTTP message while negative offset is relative to the end.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param integer offset: *optional* The offset in incoming data where to start
   to remove data. 0 by default. May be negative to be relative to the end of
   incoming data.
  :param integer length: *optional* The length of data to remove. All incoming
   data by default.
  :returns: an integer containing the amount of bytes removed.

.. js:function:: HTTPMessage.rep_header(http_msg, name, regex, replace)

  Matches the regular expression in all occurrences of header field **name**
  according to regex **regex**, and replaces them with the string **replace**.
  The replacement value can contain back references like \1, \2, ... This
  function acts on whole header lines, regardless of the number of values they
  may contain.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string name: The header name.
  :param string regex: The match regular expression.
  :param string replace: The replacement value.

.. js:function:: HTTPMessage.rep_value(http_msg, name, regex, replace)

  Matches the regular expression on every comma-delimited value of header field
  **name** according to regex **regex**, and replaces them with the string
  **replace**.  The replacement value can contain back references like \1, \2,
  ...

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string name: The header name.
  :param string regex: The match regular expression.
  :param string replace: The replacement value.

.. js:function:: HTTPMessage.send(http_msg, string)

  This function requires immediate send of the string **string**. It means the
  string is copied at the beginning of incoming data of the HTTP message
  **http_msg** and immediately forwarded. Because it is called in the filter
  context, it never yields.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string string: The data to send.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: HTTPMessage.set(http_msg, string[, offset[, length]])

  This function replaces **length** bytes of incoming data of the HTTP message
  **http_msg**, starting at offset **offset**, by the string **string**. The
  function returns the copied length on success or -1 if data cannot be copied.

  By default, if no length is provided, all incoming data, starting at the given
  offset, are replaced. Not providing an offset is the same as setting it
  to 0. A positive offset is relative to the beginning of incoming data of the
  HTTP message while negative offset is relative to the end.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string string: The data to copy into incoming data.
  :param integer offset: *optional* The offset in incoming data where to start
   the data replacement. 0 by default. May be negative to be relative to the
   end of incoming data.
  :param integer length: *optional* The length of data to replace. All incoming
   data by default.
  :returns: an integer containing the amount of bytes copied or -1.

.. js:function:: HTTPMessage.set_eom(http_msg)

  This function set the end of message for the HTTP message **http_msg**.

  :param class_httpmessage http_msg: The manipulated HTTP message.

.. js:function:: HTTPMessage.set_header(http_msg, name, value)

  This variable replace all occurrence of all header matching the name **name**,
  by only one containing the value **value**.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string name: The header name.
  :param string value: The header value.

  This function does the same work as the following code:

.. code-block:: lua

      http_msg:del_header("header")
      http_msg:add_header("header", "value")
..

.. js:function:: HTTPMessage.set_method(http_msg, method)

  Rewrites the request method with the string **method**. The HTTP message
  **http_msg** must be the request.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string method: The new method.

.. js:function:: HTTPMessage.set_path(http_msg, path)

  Rewrites the request path with the string **path**. The HTTP message
  **http_msg** must be the request.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string method: The new method.

.. js:function:: HTTPMessage.set_query(http_msg, query)

  Rewrites the request's query string which appears after the first question
  mark ("?") with the string **query**. The HTTP message **http_msg** must be
  the request.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string query: The new query.

.. js:function:: HTTPMessage.set_status(http_msg, status[, reason])

  Rewrites the response status code with the integer **code** and optional the
  reason **reason**. If no custom reason is provided, it will be generated from
  the status. The HTTP message **http_msg** must be the response.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param integer status: The new response status code.
  :param string reason: The new response reason (optional).

.. js:function:: HTTPMessage.set_uri(http_msg, uri)

  Rewrites the request URI with the string **uri**. The HTTP message
  **http_msg** must be the request.

  :param class_httpmessage http_msg: The manipulated HTTP message.
  :param string uri: The new uri.

.. js:function:: HTTPMessage.unset_eom(http_msg)

  This function remove the end of message for the HTTP message **http_msg**.

  :param class_httpmessage http_msg: The manipulated HTTP message.

.. _CertCache_class:

CertCache class
================

.. js:class:: CertCache

   This class allows to update an SSL certificate file in the memory of the
   current HAProxy process. It will do the same as "set ssl cert" + "commit ssl
   cert" over the HAProxy CLI.

.. js:function:: CertCache.set(certificate)

  This function updates a certificate in memory.

  :param table certificate: A table containing the fields to update.
  :param string certificate.filename: The mandatory filename of the certificate
   to update, it must already exist in memory.
  :param string certificate.crt: A certificate in the PEM format. It can also
   contain a private key.
  :param string certificate.key: A private key in the PEM format.
  :param string certificate.ocsp: An OCSP response in base64. (cf management.txt)
  :param string certificate.issuer: The certificate of the OCSP issuer.
  :param string certificate.sctl: An SCTL file.

.. code-block:: lua

    CertCache.set{filename="certs/localhost9994.pem.rsa", crt=crt}


External Lua libraries
======================

A lot of useful lua libraries can be found here:

* Lua toolbox has been superseded by
  `https://luarocks.org/ <https://luarocks.org/>`_

  The old lua toolbox source code is still available here
  `https://github.com/catwell/lua-toolbox <https://github.com/catwell/lua-toolbox>`_ (DEPRECATED)

Redis client library:

* `https://github.com/nrk/redis-lua <https://github.com/nrk/redis-lua>`_

This is an example about the usage of the Redis library within HAProxy.
Note that each call to any function of this library can throw an error if
the socket connection fails.

.. code-block:: lua

    -- load the redis library
    local redis = require("redis");

    function do_something(txn)

       -- create and connect new tcp socket
       local tcp = core.tcp();
       tcp:settimeout(1);
       tcp:connect("127.0.0.1", 6379);

       -- use the redis library with this new socket
       local client = redis.connect({socket=tcp});
       client:ping();

    end

OpenSSL:

* `http://mkottman.github.io/luacrypto/index.html
  <http://mkottman.github.io/luacrypto/index.html>`_

* `https://github.com/brunoos/luasec/wiki
  <https://github.com/brunoos/luasec/wiki>`_