limit_conn not working

[Maxim Dounin]

Hello!

On Tue, Dec 19, 2017 at 06:36:00AM +0100, Abilio Marques wrote:

> limit_conn is not working for me. I set up a test in nodejs, I'm doing GET
> requests to http://localhost/, they are coming from different connections
> (different origin ports), and all the connections are still open until the
> very end, still, no response other than 200 is received. I double check
> with wireshark.
> 
> What am I missing??
> 
> Minimal configuration I can reproduce it with: https://paste.ngx.cc/70
> Source code for the test: https://paste.ngx.cc/6f

The limit_conn limit only limits connections with active requests.  
Moreover, it only applies after reading request headers - as nginx 
needs to know requested host and URI to check limits appropriate 
for particular server and location blocks.

As a result, it is almost impossible to trigger limit_conn by 
requests to small static files.  To trigger limit_conn, consider 
testing it with files large enough to fill up socket buffers, 
and/or with proxying.

-- 
Maxim Dounin
http://mdounin.ru/