Imap proxy limited to about 210 connections

I have nginx proxying imap and pop between 3 different backend servers,
but
it seems to be limited to about 210 concurrent connections. Requests
beyond
this get a connection timed out. I tried adding more worker processes
but
that didn’t do anything. I have multi_accept on and have raised the
number
of worker_connections, but still no luck. I see rate limiting and
connection bandwidth limiting, but these appear to apply to the http
protocol and not the imap/pop protocol. What parameters to I adjust to
increase the number of concurrent sessions to imap/pop?

Posted at Nginx Forum:
http://forum.nginx.org/read.php?2,246642,246642#msg-246642

Hello!

On Mon, Jan 20, 2014 at 05:31:30PM -0500, bidwell wrote:

I have nginx proxying imap and pop between 3 different backend servers, but
it seems to be limited to about 210 concurrent connections. Requests beyond
this get a connection timed out. I tried adding more worker processes but
that didn’t do anything. I have multi_accept on and have raised the number
of worker_connections, but still no luck. I see rate limiting and
connection bandwidth limiting, but these appear to apply to the http
protocol and not the imap/pop protocol. What parameters to I adjust to
increase the number of concurrent sessions to imap/pop?

In nginx itself, tuning worker_connections should be enough. If
it doesn’t help, it indicate the problem is elsewhere - i.e. you
either have to tune some system limit (try looking into error log
to see if there is something there) or your backend servers.


Maxim D.
http://nginx.org/

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