Probing to see if Varnish is Alive.

Richard Chiswell richard.chiswell at
Wed Sep 15 16:59:11 CEST 2010

  I've got our load balancer requesting a MySQL driven PHP page via 
Apache and via Varnish.

Every second, our load balancer probes a page on our site. This page is 
set to "pass" through Varnish to Apache which then asks PHP to check 
MySQL. If all is ok, the page returns the text "All checks passed" - if 
that text isn't there within 0.5s (for example, Varnish is unavailable, 
Apache is unavailable, MySQL is unavailable etc), then that server is 
removed from our load balanced pool. If we do maintenance, we just kill 
Varnish (our site is still accessible to ourselves via port 8080 which 
the Apache port), bring Varnish back up and then wait a couple of 
seconds for the load balancer to notice the "All checks passed" text is 
being returned.


On 15/09/2010 15:55, Caunter, Stefan wrote:
> If your load balancer can do a port 80 check (or whatever port you are 
> using), you can block port 80 with pf to stop traffic flow, do your 
> updating, and return it to service by unblocking the port.
> Stefan Caunter :: Senior Systems Administrator :: TOPS
> e: scaunter at  ::  m: (416) 561-4871
> *From:* varnish-misc-bounces at 
> [mailto:varnish-misc-bounces at] *On Behalf Of *Mohan Rao
> *Sent:* September-15-10 9:26 AM
> *To:* varnish-misc at
> *Subject:* Probing to see if Varnish is Alive.
> Hi,
> Is there a way to probe a varnish server to see if it is alive ? We 
> have a couple of varnish servers that are load balanced. We would like 
> the load balancer to stop sending traffic to a particular varnish 
> server if we are updating that server. Is there a recommended way to 
> do this ?
> Thanks & Regards,
> Mohan
> _______________________________________________
> varnish-misc mailing list
> varnish-misc at

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