How to Optimize Nginx for High Concurrency, Custom Errors, and Better Caching

Custom 404 Error Page

Before modification, browsers display a generic "404 Not Found" page when accessing a missing resource. By editing /usr/local/nginx/conf/nginx.conf and adding error_page 404 /404.html;, you can serve a custom HTML file (e.g., /usr/local/nginx/html/404.html) and reload Nginx with nginx -s reload.

# vim /usr/local/nginx/conf/nginx.conf
    ...
    error_page   404  /404.html;
    ...
# vim /usr/local/nginx/html/404.html
    Oops, No page …
# nginx -s reload

Viewing Server Status

Enable the http_stub_status_module during compilation (e.g., --with-http_stub_status_module) and add a location block in the configuration:

location /status {
    stub_status on;
    #allow 127.0.0.1;
    #deny all;
}

After reloading, request http://<em>server_ip</em>/status to see metrics such as active connections, accepts, handled requests, reading, writing, and waiting.

Increasing Nginx Concurrency

Adjust the number of worker processes to match CPU cores and raise worker_connections to a high value (e.g., 65535). Then reload Nginx.

worker_processes  2;   # match CPU cores
events {
    worker_connections 65535;
}

Test concurrency with ab -n 2000 -c 2000 http://<em>server_ip</em>/. If you encounter "Too many open files", increase the file descriptor limits:

# ulimit -Hn 100000   # hard limit
# ulimit -Sn 100000   # soft limit
# edit /etc/security/limits.conf
* soft nofile 100000
* hard nofile 100000

Optimizing Client Header Buffers

Modify the http block to enlarge header buffers, preventing "414 Request-URI Too Large" errors for long URLs.

http {
    client_header_buffer_size    1k;
    large_client_header_buffers  4 4k;
}

Browser Local Caching of Static Assets

Configure Nginx to set an expiration time for static file types, allowing browsers (e.g., Firefox) to cache them for 30 days.

server {
    listen 80;
    server_name localhost;
    location / {
        root html;
        index index.html index.htm;
    }
    location ~* \.(jpg|jpeg|gif|png|css|js|ico|xml)$ {
        expires 30d;
    }
}

After reloading, verify the cache via about:cache in Firefox.