commit 4e172c93f9f28c2cc3d1af3a36dec5be62b077d3
author Tim Duesterhus <tim@bastelstu.be> Tue May 19 13:49:42 2020 +0200
committer Christopher Faulet <cfaulet@haproxy.com> Mon May 25 08:12:35 2020 +0200
tree f6598fd6ca356fcfadaaa37617bbab27cfa9b50e
parent 84ebc136a135c708744f98f742e866bd14e2e31e

MEDIUM: lua: Add `ifexist` parameter to `set_var`

As discussed in GitHub issue #624 Lua scripts should not use
variables that are never going to be read, because the memory
for variable names is never going to be freed.

Add an optional `ifexist` parameter to the `set_var` function
that allows a Lua developer to set variables that are going to
be ignored if the variable name was not used elsewhere before.

Usually this mean that there is no `var()` sample fetch for the
variable in question within the configuration.

doc/lua-api/index.rst

diff --git a/doc/lua-api/index.rst b/doc/lua-api/index.rst
index f3e5cb7..3d8282c 100644
--- a/doc/lua-api/index.rst
+++ b/doc/lua-api/index.rst
@@ -1710,7 +1710,7 @@
   :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)
+.. js:function:: TXN.set_var(TXN, var, value[, ifexist])
 
   Converts a Lua type in a HAProxy type and store it in a variable <var>.
 
@@ -1718,6 +1718,10 @@
   :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 a truthy value the variable
+                          will only be set if it was defined elsewhere (i.e. used
+                          within the configuration). It is highly recommended to
+                          always set this to true.
 
 .. js:function:: TXN.unset_var(TXN, var)
 
@@ -2513,7 +2517,7 @@
   :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)
+.. js:function:: AppletHTTP.set_var(applet, var, value[, ifexist])
 
   Converts a Lua type in a HAProxy type and store it in a variable <var>.
 
@@ -2521,6 +2525,10 @@
   :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 a truthy value the variable
+                          will only be set if it was defined elsewhere (i.e. used
+                          within the configuration). It is highly recommended to
+                          always set this to true.
   :see: :js:func:`AppletHTTP.unset_var`
   :see: :js:func:`AppletHTTP.get_var`
 
@@ -2624,7 +2632,7 @@
   :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)
+.. js:function:: AppletTCP.set_var(applet, var, value[, ifexist])
 
   Converts a Lua type in a HAProxy type and stores it in a variable <var>.
 
@@ -2632,6 +2640,10 @@
   :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 a truthy value the variable
+                          will only be set if it was defined elsewhere (i.e. used
+                          within the configuration). It is highly recommended to
+                          always set this to true.
   :see: :js:func:`AppletTCP.unset_var`
   :see: :js:func:`AppletTCP.get_var`