Theoretical connections/second limit using Varnish
nick at loman.net
Thu Apr 30 17:10:15 CEST 2009
Michael S. Fischer wrote:
>> I've done that for a specific reason relating to backend PHP processes.
> I don't dispute your reasoning; my employer does this as well.
> KeepAlive with Apache/PHP can be a recipe for resource starvation on
> your origin servers.
Precisely, we only have perhaps 50 PHP children serving requests, so if
these are kept open to serve idle keep-alive connections, that severely
limits the numbers of dynamic page requests we can serve.
>> I typically have thousands of connections in TIME_WAIT mode as a
>> result, which is expected, but I wonder what the solution could be if
>> I ever hit more connections than local ports available.
> I think SO_REUSEADDR is the answer - I'm somewhat surprised that Varnish
> doesn't set it by default for the backend connections.
I've had a browse through the Varnish 2.0.4 source now and have
convinced myself that SO_REUSEADDR isn't set. Can you think of any
specific gotchas I might encounter if I added setsockopt() before the
connect() when getting a backend connection?
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