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[lvs-users] Weird problem after realserver crashes

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: [lvs-users] Weird problem after realserver crashes
From: Janar Kartau <janar.kartau@xxxxxxxxx>
Date: Thu, 10 Apr 2008 13:18:16 +0300
Hi,
We're using LVS-DR to loadbalance HTTP/HTTPS requests to three 
webservers. Both active and backup LVS servers have fully updated CentOS 
5.1.  ARP problem is solved with arptables_jf. All this time i have been 
restarting realservers during the night under very little load and s at 
all. But lately one of the realservers crashed during the day and when 
it came back it was automatically added back to the LVS and all but no 
new requests were sent to it. Ipvsadm showed it had a lot of 
ActiveConn's and zero InActConn's. These numbers remained the same for 
10 or more minutes and then ActiveConn started decreasing slowly. Once 
the ActiveConn was lower than the other realservers had, new requests 
started to reach the server and InActConn increased from 0. I could 
reproduce this later when i took a realserver down myself and noticed 
that the more connections there were during the crash and after, the 
bigger static count of ActiveConn's appeared for the crashed server once 
it came back. Neither LVS restart or "ipvsadm --zero" helped.
It seems to me that when one of the realservers disappears, LVS doesn't 
close the open connections and they just hang there until timeout comes. 
Definately doesn't seem like an ARP prolem.
Oh.. and i should mention that i'm using firewall marks and lc scheduler.

Any help would be appreciated!

Thanks,
Janar Kartau


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