Forum: NGINX http Keepalive implementation

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prkumar (Guest)
on 2014-06-19 07:25
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I was going through NGINX source code to implement keepalive for nginx
zeromq plugin that I have developed.
I have been inspired by ngx_http_upstream_keepalive_module. Was
why nginx uses a kind of two linkedlist based stack implementation to
implement keepalive connection pool. Why not use  typical linkedlist
queue implementation.
Kindly refer to ngx_http_upstream_keepalive_module.c

I used exactly like this without wondering why, now I kind of want to
the reason.

Posted at Nginx Forum:,251033,251033#msg-251033
Maxim Dounin (Guest)
on 2014-06-19 15:38
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On Thu, Jun 19, 2014 at 01:24:53AM -0400, prkumar wrote:

> I used exactly like this without wondering why, now I kind of want to know
> the reason.

The upstream keepalive module uses the "cache" queue as an LRU
queue, to be able to drop unused connections if there isn't enough
room.  Hence it basically uses it as a stack while storing /
retrieving connections.

The "free" queue is used to avoid runtime allocations.

Maxim Dounin
Lord Nynex (Guest)
on 2014-06-19 23:33
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It seems ZMQ and Nginx keep coming up in conversations lately. There
to be differing opinions on it's performance/feasibility in production.
you plan to open source your code? I'd be curious to look at it.
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