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From Gary Smith <gary.sm...@holdstead.com>
Subject RE: [users@httpd] Apache Server status page shows uneven number of requests across load balanced web servers
Date Wed, 27 Jan 2010 17:25:14 GMT
Arunkumar,

There is no problem with what I see.  The load balancer will balance a requester to a machine
for a period of time.  So if my web clients makes a request to your server, I will probably
have a higher probability of getting that same server.  It's like iptables connection tracking.
 Load balance doesn't necessarily mean equality service.  There is also an unfair comparison
going on here.  The servers that are seeing all of the connections were restarted 1.5 days
ago and the two that are working fine were started 6 days ago.  If you are going to restart
and then compare, restart all of them to compare.  You mentioned that you are using weight
load sharing algorithm.  It is possible that when the two servers were restarted that the
balancer is trying to give them a bigger weighted share to "catch up" to the other servers.
 I had a problem with this using ipvsadm some time ago when I would add a new server and give
it the same schedule as the others it would be slammed for a while.

When you see a lot of connections like that, do an netstat -atunep and see what the IP address
and states are.  Check to see if you have a bunch of duplicate IP's.  If this is the case,
it's because the load balancer is gluing the connections during a session and that the IP's
are also making multiple requests.

That's a place to start at least.

Gary Smith

From: Arunkumar Janarthanan [mailto:arunkumar.webadmin@gmail.com]
Sent: Wednesday, January 27, 2010 6:36 AM
To: users@httpd.apache.org
Subject: [users@httpd] Apache Server status page shows uneven number of requests across load
balanced web servers

Hello All,

We have apache servers running on RedHat Linux physical servers, all 4 servers are balanced
by Citrix Netscaler 8.1 load balancer with round robin weight load sharing algorithm.

However when I check the server status page to find the number of requests are served by each
Apache server is showing uneven load / number of requests being processed by each Apache.

I notice the load always getting processed by two specific Apache instances, here are the
configuration details.

Attached here the server status screen shot page of all 4 web servers.

[root@web bin]# ./apachectl -version
Server version: Apache/2.2.6 (Unix)
Server built:   Sep 26 2007 11:18:50
[root@web bin]#

Operating System:

Linux Host1 2.4.21-53.ELsmp #1 SMP Wed Nov 14 03:54:12 EST 2007 i686 i686 i386 GNU/Linux


Hardware configuration are same for all 4 physical Linux servers.

Please advice.

Best Regards,
Arun J

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