Understanding 503s

[Maninder Singh]

Apache runs on port 8080 and is not open to the outside world.
All requests are routed through varnish but then not all requests are
cached.

I guess in that case, varnish becomes the only client for apache.
So, I should increase the KeepAliveTimeout.



On Thu, 15 Apr 2021 at 13:45, Dridi Boukelmoune <dridi at varni.sh> wrote:

> On Thu, Apr 15, 2021 at 7:27 AM Maninder Singh <mandys at gmail.com> wrote:
> >
> > Thank you Dridi.
> > This is very helpful.
> >
> > FYI - My apache keepalive is
> > KeepAliveTimeout 3
> >
> > You would suggest increasing this to 5-10 ?
>
> If varnish is httpd´s only client then increase it to 70s. Varnish
> will close unused connections after 60s by default, and if it´s really
> really busy that gives a 10s window for the actual shutdown to happen.
>
> If there are other direct clients in front of your httpd server, then
> decrease backend_idle_timeout in varnishd to 2s, but then you will
> force varnish to establish connections more often. This is already the
> case of course, but at least that will reduce the risk of reusing a
> closed connection and failing backend fetches for this reason.
>
> > We had lowered the KeepAliveTimeout as the server is a very busy one and
> we want to handle many connections.
>
> I understand, and there´s a good reason to have a low default when you
> can´t trust the clients. It boils down to whether your httpd server is
> openly accessible to more than just varnish, including potentially
> malicious clients.
>
> Dridi
>
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