Multi-worker statistics and control with nginx “per-worker-listener” patch

Today I’ve written a small nginx patch providing a feature that solves many problems in RTMP-HTTP integration namely statistics and control. Statistics and control is known to work bad in multi-worker mode since HTTP request goes to a random worker. So the client receives random worker statistics or performs a control action with a worker that didn’t receive previous actions from user.

The patch is named per-worker-listener. It can be downloaded here. When applied to nginx it opens ports for connecting to the worker you want, not just a random worker. Each worker has its own port number so you can choose the port to connect. The new syntax extends listen directive with a new option per_worker. The port specified in listen directive becomes base port number for worker listeners.

listen 80; # usual listen directive
listen 9000 per_worker; # per-worker listener

With the above configuration 1st worker will listen to 9000 port, 2nd to 9001 port, 3rd to 9002 port etc. To make that work please turn off accept_mutex. Listeners with no per_worker work as usual.

events {
    worker_connections  1024;
    accept_mutex off;
}

The patch is especially useful with stat and control handlers of nginx-rtmp-module.

server {
    listen   9000 per_worker;
    location /stat {
        rtmp_stat all;
        rtmp_stat_stylesheet stat.xsl;
    }
    location /stat.xsl {
        root /tmp;
    }
    location /control {
        rtmp_control all;
    }
}

Now see 3rd worker stats at the location http://localhost:9002/stat.