How to Use tcp_nodelay in Nginx for Better TCP Performance

To use tcp_nodelay in Nginx, add the directive tcp_nodelay on; inside the server or location block of your configuration. This disables Nagle's algorithm, allowing small packets to be sent immediately, which reduces latency for TCP connections.

Syntax

The tcp_nodelay directive controls whether Nginx disables Nagle's algorithm on TCP sockets. It accepts on or off values.

• tcp_nodelay on; - disables Nagle's algorithm, sending packets immediately.
• tcp_nodelay off; - enables Nagle's algorithm, buffering small packets.

This directive is typically placed inside server or location blocks for HTTP or stream modules.

nginx

server {
    listen 80;
    tcp_nodelay on;
    location / {
        proxy_pass http://backend;
    }
}

Example

This example shows how to enable tcp_nodelay in an Nginx HTTP server block to reduce latency by sending TCP packets immediately without delay.

nginx

http {
    upstream backend {
        server 127.0.0.1:8080;
    }

    server {
        listen 80;
        tcp_nodelay on;

        location / {
            proxy_pass http://backend;
        }
    }
}

Common Pitfalls

Common mistakes when using tcp_nodelay include:

• Placing tcp_nodelay outside of valid contexts like server or location blocks, causing configuration errors.
• Forgetting to reload or restart Nginx after changing the configuration, so changes don't take effect.
• Using tcp_nodelay unnecessarily on connections where latency is not critical, which may increase network overhead.

Always test your configuration with nginx -t before reloading.

nginx

## Wrong placement example (will cause error):
server {
    tcp_nodelay on;
    listen 80;
}

## Correct placement:
server {
    listen 80;
    tcp_nodelay on;
}

Output

nginx: [emerg] "tcp_nodelay" directive is not allowed here in /etc/nginx/nginx.conf:2

Quick Reference

tcp_nodelay directive summary:

Directive	Context	Default	Description
tcp_nodelay	server, location	off	Disables Nagle's algorithm to send TCP packets immediately

Key Takeaways

Enable tcp_nodelay with 'tcp_nodelay on;' inside server or location blocks to reduce TCP latency.

Place tcp_nodelay only in valid contexts like server or location to avoid configuration errors.

Reload Nginx after changes using 'nginx -s reload' to apply tcp_nodelay settings.

Use tcp_nodelay when low latency is important, such as real-time applications.

Test configuration syntax with 'nginx -t' before restarting Nginx.