[missing_worker_processes] Unset `worker_processes` (defaults to 1)

What this check looks for

This plugin warns when worker_processes is not set anywhere in the config.

Why this is a problem

worker_processes controls how many worker processes NGINX starts to accept and process connections.

When the directive is unset, NGINX defaults to 1. On a multi-core system, a single worker can become a bottleneck:

Only one worker -- working on a single CPU -- is available to accept and handle connections.
CPU-bound workloads (TLS, compression, heavy rewrite logic, etc.) can saturate a single core while other cores remain underutilized.
Under load, this often shows up as higher latency and reduced throughput.

In most cases, running one worker per CPU core works well, and setting worker_processes to auto is the simplest way to achieve that.

Bad configuration

# No worker_processes directive anywhere
events { }

http {
    server {
        listen 80;
        return 200 "ok\n";
    }
}

This will run with the default of a single worker process.

Better configuration

worker_processes auto;

events { }

http {
    server {
        listen 80;
        return 200 "ok\n";
    }
}

Additional notes

This check cannot determine how many CPU cores the host has. On a single-core machine, the default of 1 may be fine, and this warning can be considered a false positive.

[missing_worker_processes] Unset worker_processes (defaults to 1)