A wrong behavior was introduced by
e9544935e8, leading to preventing loading
any configuration where a capture slot id is used in a backend.
IE, the configuration below does not parse:
frontend f
bind *:80
declare capture request len 32
default_backend webserver
backend webserver
http-request capture req.hdr(Host) id 1
The point is that such type of configuration is valid and should run.
This patch enforces the check of capture slot id only if the action rule
is configured in a frontend.
The point is that at configuration parsing time, it is impossible to
check which frontend could point to this backend (furthermore if we use
dynamic backend name resolution at runtime).
The documentation has been updated to warn the user to ensure that
relevant frontends have required declaration when such rule has to be
used in a backend.
If no capture slot can be found, then the action will just not be
executed and HAProxy will process the next one in the list, as expected.
This should be backported to all supported branches (bug created as part
of a bug fix introduced into 1.7 and backported to 1.6).
19a69b3740