The 'do-resolve' action is an http-request or tcp-request content action
which allows to run DNS resolution at run time in HAProxy.
The name to be resolved can be picked up in the request sent by the
client and the result of the resolution is stored in a variable.
The time the resolution is being performed, the request is on pause.
If the resolution can't provide a suitable result, then the variable
will be empty. It's up to the admin to take decisions based on this
statement (return 503 to prevent loops).
Read carefully the documentation concerning this feature, to ensure your
setup is secure and safe to be used in production.
This patch creates a global counter to track various errors reported by
the action 'do-resolve'.
Stick and track-sc rules may optionally designate a table in a different
proxy. In this case, a number of verifications are made such as validating
that this proxy actually exists. However, in multi-process mode, the target
table might indeed exist but not be bound to the set of processes the rules
will execute on. This will definitely result in a random behaviour especially
if these tables do require peer synchronization, because some tasks will be
started to try to synchronize form uninitialized areas.
The typical issue looks like this :
peers my-peers
peer foo ...
listen proxy
bind-process 1
stick on src table ip
...
backend ip
bind-process 2
stick-table type ip size 1k peers my-peers
While it appears obvious that the example above will not work, there are
less obvious situations, such as having bind-process in a defaults section
and having a larger set of processes for the referencing proxy than the
referenced one.
The present patch adds checks for such situations by verifying that all
processes from the referencing proxy are present on the other one in all
track-sc* and stick-* rules, and in sample fetch / converters referencing
another table so that sc_inc_gpc0() and similar are safe as well.
This fix must be backported to all maintained versions. It may potentially
disrupt configurations which already randomly crash. There hardly is any
intermediary solution though, such configurations need to be fixed.
