Haproxy - http check backend strange problem

Hi,

Today i had strange problem with haproxy (old version: 1.3.15.2 2008/06/21 )

The situation:

Haproxy:80 --------http_roundrobin----> backend-[1-4].atm:80

at 13:00 backend-2.atm is down for 6 sec. haproxy switched off backend-2 for 6 sec, couting the downtime in stats. After 6 sec. backend-2 is up.
Haproxy switch on backend-2

But not correct.
From this time by three hours haproxy sending only ~ 1% /sec packets to backend-2, and the rest to other backends [1,3,4].

I was checked connection to backend manualy, everything work's! On stats haproxy shows backend-2 as enabled.

At 16:00 i did /etc/init.d/haproxy restart And everything come back to work normaly.. backend-2 get 25% traffic.

My God! It was strange!

Look for configuration and the JPG.

-----/ cut here /----

defaults

        log     global
        mode    http
        option  httplog
        option  dontlognull
        retries 3
        option redispatch

        maxconn 2000
        timeout connect    500000
        timeout client     20000
        timeout server     500000

frontend internal_80

    bind XXXXXXXX:80

    log global
    mode http
    no option forceclose
    no option httpclose
    option httplog
    option dontlognull
    maxconn 2000
    option forwardfor

backend backendA

    mode http
    log global

    option redispatch
    option httplog
    option httpclose
    option http_proxy
    option forwardfor
    option forwardfor except 127.0.0.1

    retries 3

    balance roundrobin

    server b-1 backend-1.atm:80 weight 1 maxconn 4096 check
    server b-2 backend-2.atm:80 weight 1 maxconn 4096 check
    server b-3 backend-3.atm:80 weight 1 maxconn 4096 check
    server b-4 backend-4.atm:80 weight 1 maxconn 4096 check

• / cut here /----

-- 
Dawid Sieradzki -  Administrator ds. WWW, Infrastruktura

Gadu-Gadu S.A.
Al. Stanów Zjednoczonych 61 - I piętro 04-028 Warszawa
tel: (22)4277979 fax: (22)5146498 GG: 16200

Spółka zarejestrowana w Sądzie Rejonowym dla m. st. Warszawy, XIII
Wydział Gospodarczy KRS pod numerem 0000264575, NIP 867-19-48-977.
Kapitały zakładowy:  1 758 461,10 zł - wpłacony w całości.