MINOR: vars: make the vars() sample fetch function support a default value
It is quite common to see in configurations constructions like the
following one:
http-request set-var(txn.bodylen) 0
http-request set-var(txn.bodylen) req.hdr(content-length)
...
http-request set-header orig-len %[var(txn.bodylen)]
The set-var() rules are almost always duplicated when manipulating
integers or any other value that is mandatory along operations. This is
a problem because it makes the configurations complicated to maintain
and slower than needed. And it becomes even more complicated when several
conditions may set the same variable because the risk of forgetting to
initialize it or to accidentally reset it is high.
This patch extends the var() sample fetch function to take an optional
argument which contains a default value to be returned if the variable
was not set. This way it becomes much simpler to use the variable, just
set it where needed, and read it with a fall back to the default value:
http-request set-var(txn.bodylen) req.hdr(content-length)
...
http-request set-header orig-len %[var(txn.bodylen,0)]
The default value is always passed as a string, thus it will experience
a cast to the output type. It doesn't seem userful to complicate the
configuration to pass an explicit type at this point.
The vars.vtc regtest was updated accordingly.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index f664175..1a8eb5b 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -17764,10 +17764,11 @@
specified, a UUID version 4 (fully random) is returned.
Currently, only version 4 is supported.
-var(<var-name>) : undefined
+var(<var-name>[,<default>]) : undefined
Returns a variable with the stored type. If the variable is not set, the
- sample fetch fails. The name of the variable starts with an indication
- about its scope. The scopes allowed are:
+ sample fetch fails, unless a default value is provided, in which case it will
+ return it as a string. Empty strings are permitted. The name of the variable
+ starts with an indication about its scope. The scopes allowed are:
"proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and
diff --git a/reg-tests/sample_fetches/vars.vtc b/reg-tests/sample_fetches/vars.vtc
index 5dc7b44..8a04718 100644
--- a/reg-tests/sample_fetches/vars.vtc
+++ b/reg-tests/sample_fetches/vars.vtc
@@ -5,8 +5,9 @@
haproxy h1 -conf {
global
+ # note below, str60 is purposely not defined so that the default is used
set-var proc.int12 int(12)
- set-var proc.int5 str(60),div(proc.int12)
+ set-var proc.int5 var(proc.str60,60),div(proc.int12)
set-var proc.str1 str("this is")
set-var proc.str2 str("a string")
set-var proc.str var(proc.str1)
diff --git a/src/vars.c b/src/vars.c
index df421f7..1e8e1bd 100644
--- a/src/vars.c
+++ b/src/vars.c
@@ -339,8 +339,12 @@
static int smp_fetch_var(const struct arg *args, struct sample *smp, const char *kw, void *private)
{
const struct var_desc *var_desc = &args[0].data.var;
+ const struct buffer *def = NULL;
- return vars_get_by_desc(var_desc, smp, NULL);
+ if (args[1].type == ARGT_STR)
+ def = &args[1].data.str;
+
+ return vars_get_by_desc(var_desc, smp, def);
}
/* This function search in the <head> a variable with the same
@@ -1193,7 +1197,7 @@
static struct sample_fetch_kw_list sample_fetch_keywords = {ILH, {
- { "var", smp_fetch_var, ARG1(1,STR), smp_check_var, SMP_T_STR, SMP_USE_CONST },
+ { "var", smp_fetch_var, ARG2(1,STR,STR), smp_check_var, SMP_T_STR, SMP_USE_CONST },
{ /* END */ },
}};