tree 5c3ff3da219ea07baffd5aa75029d6e674c9d418
parent dcac41806239d4f3b2de5e4d1bacf9c03ca99efb
author Amaury Denoyelle <adenoyelle@haproxy.com> 1623935689 +0200
committer Amaury Denoyelle <adenoyelle@haproxy.com> 1623945530 +0200

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.