tree 78a3938df96bc6d9bb4e87a3806c1a4e84e1c29b
parent 4568a4bba6f7e6f19a9f1d184ecf6e572b6942f1
author Amaury Denoyelle <adenoyelle@haproxy.com> 1623935689 +0200
committer Willy Tarreau <w@1wt.eu> 1640271271 +0100
encoding latin1

BUG/MINOR: backend: restore the SF_SRV_REUSED flag original purpose

The SF_SRV_REUSED flag was set if a stream reused a backend connection.
One of its purpose is to count the total reuse on the backend in
opposition to newly instantiated connection.

However, the flag was diverted from its original purpose since the
following commit :

  e8f5f5d8b228d71333fb60229dc908505baf9222
  BUG/MEDIUM: servers: Only set SF_SRV_REUSED if the connection if fully ready.

With this change, the flag is not set anymore if the mux is not ready
when a connection is picked for reuse. This can happen for multiplexed
connections which are inserted in the available list as soon as created
in http-reuse always mode. The goal of this change is to not retry
immediately this request in case on an error on the same server if the
reused connection is not fully ready.

This change is justified for the retry timeout handling but it breaks
other places which still uses the flag for its original purpose. Mainly,
in this case the wrong 'connect' backend counter is incremented instead
of the 'reuse' one. The flag is also used in http_return_srv_error and
may have an impact if a http server error is replied for this stream.

To fix this problem, the original purpose of the flag is restored by
setting it unconditionaly when a connection is reused. Additionally, a
new flag SF_SRV_REUSED_ANTICIPATED is created. This flag is set when the
connection is reused but the mux is not ready yet. For the timeout
handling on error, the request is retried immediately only if the stream
reused a connection without this newly anticipated flag.

This must be backported up to 2.1.

(cherry picked from commit 2b1d91758d74f53df3b9a1dbb1d8e627320b9532)
Signed-off-by: Willy Tarreau <w@1wt.eu>