Nginx configuring worker_rlimit_nofile and worker_processes

nginx

My site recently got lots and lots of traffic and I think the issue was the nginx was spending too much time scheduling requests. I increased my worker_processes and that seemed to fix the problem.

Honestly, I do not really understand why.

I was wondering if someone could point me to/explain how nginx workers work, and what the worker_rlimit_nofile is, so I could have a better conceptual understanding for future changes I have to make.

Best Answer

In nginx worker_processes are the number of processes nginx will spawn. Default is 1 , worker_rlimit_nofile is the maximum file descriptors that can be opened by each worker process. Be careful when you increase worker_processes, because this will impact in the number of max. clients your server will handle. worker_processes values of 2 or 4 are ok when working on multiprocessor machines.

Also you can change the worker_connections parameter which is the maximun number of connections for each worker process.

It seems that in your case the number of requests was serving a big number of request per second and the default nginx worker was spending too much time blocked on disk IO.

Related Solutions

Nginx / uWsgi / Django site can handle more traffic with rewrite URL

The answer is pretty simple, actually. In your first test (the redirect) ab is only benchmarking a "301 Moved Permanently" request. The second test is testing your actual content.

To illustrate what I mean, curl your redirect URL. You'll get something like:

<html>
<head><title>301 Moved Permanently</title></head>
<body bgcolor="white">
<center><h1>301 Moved Permanently</h1></center>
<hr><center>nginx/0.8.52</center>
</body>
</html>

It's not hard to handle 15000 concurrent requests for just that! ;)

Nginx – Disable caching when serving static files with Nginx (for development)

Since the answer is somehow hidden in the question - here is the solution for nginx in a VirtualBox environment as standalone answer.

In your nginx config (usally /etc/nginx/nginx.conf) or vhost config file change the sendfile parameter to off:

sendfile  off;

While sendfile is at the heart of Nginx's fame (blazing-fast low-level static file serving efficiency) it might be a bane for local development, e.g. Javascripts that change often and need to be reloaded. Nonetheless Nginx sendfile is smart and probably isn't most people's issue; check your browser's "disable cache" options as well!

Best Answer

Related Solutions

Nginx / uWsgi / Django site can handle more traffic with rewrite URL

Nginx – Disable caching when serving static files with Nginx (for development)

Related Topic