Worker processes and connections in Nginx - Commands & Configuration

Introduction

When a web server handles many visitors, it needs to manage how many tasks it can do at once. Worker processes and connections in nginx control how many users can be served at the same time without slowing down.

When your website gets slow because too many people visit at once

When you want to make sure your server uses all CPU cores efficiently

When you need to handle many connections without crashing

When tuning nginx for better performance on busy servers

When setting up nginx on a new server and want it to handle traffic well

Config File - nginx.conf

nginx.conf

worker_processes auto;
events {
    worker_connections 1024;
}
http {
    server {
        listen 80;
        server_name example.com;
        location / {
            root /usr/share/nginx/html;
            index index.html;
        }
    }
}

worker_processes auto; tells nginx to use as many worker processes as CPU cores available, making full use of the server's power.

worker_connections 1024; inside events sets how many connections each worker can handle at once.

This setup helps nginx serve many users efficiently by balancing work across CPU cores and limiting connections per worker.

Commands

This command checks the nginx configuration file for errors before applying changes. It helps avoid server crashes due to bad config.

Terminal

sudo nginx -t

Expected Output

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok

nginx: configuration file /etc/nginx/nginx.conf test is successful

This command reloads nginx to apply the new configuration without stopping the server, so users don't experience downtime.

Terminal

sudo systemctl reload nginx

Expected Output

No output (command runs silently)

This command shows running nginx processes, so you can verify the number of worker processes running.

Terminal

ps aux | grep nginx

Expected Output

root       1234  0.0  0.1  123456  2345 ?        Ss   10:00   0:00 nginx: master process /usr/sbin/nginx

www-data   1235  0.0  0.1  123456  2345 ?        S    10:00   0:00 nginx: worker process

www-data   1236  0.0  0.1  123456  2345 ?        S    10:00   0:00 nginx: worker process

This command counts how many connections are open on port 80, helping you see how many users nginx is currently serving.

Terminal

sudo lsof -i :80 | wc -l

Expected Output

15

Key Concept

If you remember nothing else from this pattern, remember: worker_processes sets how many CPU cores nginx uses, and worker_connections sets how many users each worker can handle at once.

Common Mistakes

Setting worker_processes to a fixed low number like 1 on a multi-core server

This wastes CPU resources and limits how many users nginx can serve at the same time.

Use 'worker_processes auto;' to let nginx use all CPU cores automatically.

Setting worker_connections too low, like 512, on a busy server

Limits the number of simultaneous connections per worker, causing slowdowns or dropped connections.

Increase worker_connections to a higher number like 1024 or more based on expected traffic.

Not testing nginx config with 'nginx -t' before reloading

Bad config changes can cause nginx to fail to reload, leading to downtime.

Always run 'sudo nginx -t' to check config syntax before reloading.

Summary

Set worker_processes to 'auto' to use all CPU cores for better performance.

Set worker_connections to control how many connections each worker can handle.

Test nginx configuration with 'nginx -t' before reloading to avoid errors.

Reload nginx with 'systemctl reload nginx' to apply changes without downtime.

Check running worker processes and active connections to monitor server load.