Zero-Downtime Servicing of a Varnish Server Behind a F5 BIG-IP

[Steven Engelhardt]

Because of the usage patterns of the web service, I'm not sure that even a
1-second timeout would be sufficient to get all HTTP client connections to
close.

The idea of setting sess_timeout to be 0 was strictly in the context of
taking a Varnish server out of service, in order to (somewhat indirectly)
force the out of service Varnish server to close all its HTTP connections.
 We would restore sess_timeout to a sensible value before putting it back
in service.

Steve

On Mon, Jul 9, 2012 at 4:07 PM, Javier Casares <javier at casares.org> wrote:

> If  sess_timeout  is set by default to 5 seconds, you could try to set
> this to 4, 3, 2 or 1 and test if has a better performance... i suposse
> that set this to 0 will close all connectiond and seems to be an epic
> fail...
>
> Javier Casares
> http://javiercasares.com/
>
>
> 2012/7/9 Steven Engelhardt <sengelha at gmail.com>:
> > Just to be clear, would you suggest something like:
> > 1. Mark the Varnish server as disabled in the BIG-IP
> > 2. Use varnishadm to set sess_timeout to 0 to start aggressively closing
> > HTTP requests?
> > 3. Wait for connections to drain
> >
> > Steve
> >
> > On Mon, Jul 9, 2012 at 3:59 PM, Javier Casares <javier at casares.org>
> wrote:
> >>
> >> https://www.varnish-cache.org/docs/3.0/reference/varnishd.html
> >>
> >> sess_timeout
> >>
> >>         Units: seconds
> >>         Default: 5
> >>
> >>     Idle timeout for persistent sessions. If a HTTP request has not
> >> been received in this many seconds, the session is closed.
> >>
> >> ¿?
> >>
> >> Javier Casares
> >> http://javiercasares.com/
> >>
> >>
> >> 2012/7/9 Steven Engelhardt <sengelha at gmail.com>:
> >> > I have two Varnish servers behind a F5 BIG-IP load balancer.  Both
> >> > servers
> >> > are constantly active and serving ~5,000 requests/second 24x7.
>  Clients
> >> > aggressively use HTTP 1.1 Keep-Alives.
> >> >
> >> > I'm looking to develop a process for servicing and upgrading the
> Varnish
> >> > servers which results in 0 downtime to the client.  Our normal process
> >> > for
> >> > performing changes on production servers is:
> >> > 1. Mark the server as disabled in the BIG-IP
> >> > 2. Wait for the connections on the server to drop to 0
> >> > 3. Service the machine
> >> >
> >> > However, because of the aggressive and constant use of HTTP
> Keep-Alives,
> >> > clients virtually never drop their connections, and the machine
> >> > continues to
> >> > serve traffic for quite a long time after it is disabled in the
> BIG-IP.
> >> >
> >> > Is there a way to tell Varnish to aggressively close all client HTTP
> >> > connections?
> >> >
> >> > Thank you,
> >> > Steve
> >> >
> >> > --
> >> > Steven Engelhardt
> >> > sengelha at gmail.com
> >> >
> >> > _______________________________________________
> >> > varnish-misc mailing list
> >> > varnish-misc at varnish-cache.org
> >> > https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
> >>
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> >
> >
> >
> >
> > --
> > Steven Engelhardt
> > sengelha at gmail.com
> >
> > _______________________________________________
> > varnish-misc mailing list
> > varnish-misc at varnish-cache.org
> > https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
>
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-- 
Steven Engelhardt
sengelha at gmail.com
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