From: "Dawid Sieradzki / Gadu-Gadu S.A." <dawid.sieradzki@gxxx-gxxx.pl>
To: "haproxy@formilux.org" <haproxy@formilux.org>
Subject: realtime switch to another backend if got 5xx error?
Message-ID: <4A155FA8.9000602@gadu-gadu.pl>
Date: Thu, 21 May 2009 16:05:28 +0200
User-Agent: Thunderbird 2.0.0.21 (Windows/20090302)

Hi.

The problem is how to silent switch to another backend in realtime if
got 500 answer from backend, without http_client knowledge
Yes i know, httpchk, but the error 500 is 10 per hour, we don't know
when and why.
So, it is a race who get 500 first - httpchk or http_client.

If You don't know what i mean:

example config:

----8<--------

frontend
(..)
default_backend back_1

backend back_1
    option httpchk GET /index.php HTTP/1.1\r\nHost:\ test.pl
    mode http
    retries 10
    balance roundrobin

  server chk1 127.0.0.1:81 weight 1 check
  server chk2 127.0.0.1:82 weight 1 check
  server chk3 127.0.0.1:83 weight 1 check backup

---->8----------

http_client -> haproxy -> (backend1|backend2|backend3)

let's go inside request:

A. haproxy recived request from http_client
B. haproxy sent request from http_client to backend1
C. backend1 said 500 internal server error

I want: :-)
D. haproxy sent request from_http to backend2 (or backup backend or
another one, or one more time to backend1)

I have: :-(
D. haproxy sent 500 internal server error to http_client from backend1
E. haproxy will mark backend1 as down if got 2 > errror 500 from backend1


It is possible to do that?


Thank You

/Dawid Sieradzki