Re: [lvs-users] Persistent connections not persisting after failover

To: " users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] Persistent connections not persisting after failover
From: Joseph Mack NA3T <jmack@xxxxxxxx>
Date: Tue, 19 Aug 2008 10:56:18 -0700 (PDT)
On Tue, 19 Aug 2008, Nicholas Guarracino wrote:

> I have a cluster set up for load balancing a web based application
> that requires persistent connections. I'm using the ipvs sync daemon
> to keep the connection state information consistent between director
> and backup director. However, many times after a failover, the
> persistence does not work and clients end up connected to a different
> realserver. I'm running this on kernel 2.6.18 (RHEL 5, so not exactly
> bleeding edge.)

thanks for the nice description


> So after the failover, the clients' connections have been reversed:
> is now connected to
> is now connected to
> If I run ipvsadm -L on the backup director before the failover, I do
> see the proper connections so I know the multicast is getting through.

is there persistence on the backup director?

> Any thoughts on what I might be doing wrong?

Possibly nothing. It may be a bug. persistence has a lot of 
problems. I personally suggest using the -SH scheduler for 
your type of setup, but it hasn't been extensively tested 
under the synch demon, so I don't know what will happen 
there. There has been updates (not much) to the synch demon 
since your kernel (and I don't know if they address your 
problem). I can put the ball back in your court by asking 
you to try a recent kernel. I remember something about 
persistence and the synchd recently, but I looked back in my 
list of open problems and didn't see it, so I don't know 
what it might have been.

        do you know any problems with the synchd not 
transfering persistent state info to the backup director on 


Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at
Homepage It's GNU/Linux!

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