imap proxy limited to about 210 connections

Maxim Dounin mdounin at
Tue Jan 21 11:39:27 UTC 2014


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 Dounin

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