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I'm trying to use NginX to replace Apache as a load-balancer/reverse-proxy to a highly loaded service. Currently I have Apache configured with a maximum of 1024 workers on each proxy server - where I have several of them so the actual capacity is much higher. Still, at times there are more then n * 1024 simultaneous connections and in such cases Apache will queue incoming requests and will serve them once workers become available again.

With NginX it is not so, as if a connection is coming in when all the worker processes have all their connections taken - then NginX will reject the connection outright (not even a 500 error response). Is there a way to configure NginX to queue the new request instead of rejecting it?

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up vote 2 down vote accepted

No. Increase the amount of connections a worker may handle. 1024 is much lower than Nginx can handle.

If you need to limit the amount concurrent of concurrent requests passed to a back end then you need a 3rd party module like:

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Ok, but I still need a queuing mechanism to limit the number of workers on my backend - I was using Apache for this but Apache takes too much memory (~4M per worker), hence Nginx. What can I use instead? – Guss May 7 '11 at 16:09
You'll need to install a 3rd party plugin then, I have edited my answer to include the plugin link. – Martin Fjordvald May 7 '11 at 17:27
Ah, this is not exactly what I was looking for - I was more about queueing of the incoming connections while nginx-ey-balancer is about queueing outgoing connections, but I guess that if I increase the incoming max_connections to some ridiculous value and set up upstream max_connections to 1024/workers/upstream servers and assuming uniform distribution (which I know is not the case because I'm using ip_hash, but hopefully it won't matter much) then I should be OK. Its going a bit backwards about the whole thing, but it just might work well enough - thanks! – Guss May 7 '11 at 18:38

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