limit_conn is dropping valid connections and causing memory leaks on nginx reload

Anoop Alias anoopalias01 at
Sat Sep 30 10:13:57 UTC 2017

What is the change (workaround) you made ?I don't see a difference?

On Sat, Sep 30, 2017 at 3:35 PM, Dejan Grofelnik Pelzel <
nginx-forum at> wrote:

> Hello,
> We are running the nginx 1.13.5  with HTTP/2 in a proxy_pass proxy_cache
> configuration with clients having relatively long open connections. Our
> system does automatic reloads for any new configuration and we recently
> introduced a limit_conn to some of the config files. After that, I've
> started noticing a rapid drop in connections and outgoing network
> every-time
> the system would perform a configuration reload. Even stranger, on every
> reload the memory usage would go up for about 1-2GB until ultimately
> everything crashed if the reloads were too frequent. The memory usage did
> go
> down after old workers were released, but that could take up to 30 minutes,
> while the configuration could get reloaded up to twice per minute.
> We used the following configuration as recommended by pretty much any
> example:
> limit_conn_zone $binary_remote_addr zone=1234con:10m;
> limit_conn zone1234con 10;
> I was able to verify the connection drop by doing a simple ab test, for
> example, I would run ab -c 100 -n -k 1000
> 990 of the connections went through, however, 10 would still be active.
> Immediately after the reload, those would get dropped as well. Adding -r
> option would help the problem, but that doesn't fix our problem.
> Finally, after I tried to create a workaround, I've configured the limit
> zone to:
> limit_conn_zone "v$binary_remote_addr" zone=1234con:10m;
> Suddenly everything magically started to work. The connections were not
> being dropped, the limit worked as expected and even more surprisingly the
> memory usage was not going up anymore. I've been tearing my hair out almost
> all day yesterday trying to figure this out. While I was very happy to see
> this resolved, I am now confused as to why nginx behaves in such a way.
> I'm thinking this might likely be a bug, so I'm just wondering if anyone
> could explain why it is happening or has a similar problem.
> Thank you!
> Posted at Nginx Forum:
> php?2,276633,276633#msg-276633
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*Anoop P Alias*
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