[lvs-users] Servers unable to flush data to clients

[Brian Staszewski]

----- Original Message -----
From: "Dr. Volker Jaenisch" <volker.jaenisch at inqbus.de>
To: "LinuxVirtualServer.org users mailing list." <lvs-users at LinuxVirtualServer.org>
Sent: Wednesday, May 16, 2007 3:35:36 PM (GMT-0800) America/Los_Angeles
Subject: Re: Servers unable to flush data to clients

Hi Brian!

Brian Staszewski schrieb:
> Hey everyone. I implemented an LVS-NAT/ldirectord setup for a web site and I'm having some strange problems. What appears to be happening is that somehow the real servers are not always able to send data back to the client that made the request. When I view apache's status page (/server-status/) I'll see many connections in the "W" (Sending Reply) state, and they'll stay there until they either time out or I restart apache. 
>
>   
Here a few suggestions:

* Is the loadbalancer able to fetch pages from the reals? Check this 
with lynx.
* Have you checked that the default route on all reals points to the 
loadbalancer? If you use iproute with source routing double check your 
routing table with "ip rule"
* Try turning the apache configuration option keepalive to OFF.


Beste Regards,

Volker Jaenisch

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------------------
Okay, it took me a little bit to respond to this because I was setting this up in a test environment and making sure I could duplicate the results, and I have.

To answer your questions:


* Is the loadbalancer able to fetch pages from the reals? Check this 
with lynx.

Yes. No problems here. I've also got ldirectord fetching pages as it's server check.

* Have you checked that the default route on all reals points to the 
loadbalancer? If you use iproute with source routing double check your 
routing table with "ip rule"

All reals point to the internal virtual IP of the LVS cluster for default gateway. I double checked their routing tables and verified that this is the case.

* Try turning the apache configuration option keepalive to OFF.

This made no difference. The connection problems happened just as often whether keepalives were on or off.


I did note one thing in response to Joe's reply, and that was that if I stop iptables completely the problem goes away.

Thanks,
Brian