How to Optimize Nginx: Custom 404 Pages, Status Monitoring, and High‑Concurrency Tuning

1. Custom 404 Error Page

Before the change, a request to a non‑existent URL returns the default 404 message. Edit /usr/local/nginx/conf/nginx.conf and add error_page 404 /404.html;. Create the custom page at /usr/local/nginx/html/404.html (e.g., containing "Oops, No page …"). Reload Nginx with nginx -s reload. After reloading, the browser shows the custom 40x page.

2. Viewing Server Status

Compile Nginx with the --with-http_stub_status_module flag to enable the status page. After installation, add a location block in nginx.conf:

location /status {
    stub_status on;
    #allow IP;
    #deny IP;
}

Reload Nginx and query the page: curl http://192.168.4.5/status The output shows active connections, accepts, handled, requests, and the numbers of reading, writing, and waiting connections, providing a quick health check.

3. Increasing Concurrency

Initial load testing with ab -n 2000 -c 2000 http://192.168.4.5/ may hit "Too many open files". Increase worker processes and connections in nginx.conf:

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

Reload Nginx, then retest with ab. To raise the OS file descriptor limit, edit /etc/security/limits.conf:

* soft nofile 100000
* hard nofile 100000

Apply the new limits with ulimit -Hn 100000 and ulimit -Sn 100000.

4. Expanding Header Buffer Cache

When a long URL triggers "414 Request‑URI Too Large", increase the header buffers:

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

Reload Nginx and re‑run the script that builds a 5,000‑parameter URL; the request now succeeds.

5. Browser‑Side Static Asset Caching

In Firefox, open about:cache to view cached entries. To set a 30‑day cache for static files, add a location block:

location ~* \.(jpg|jpeg|gif|png|css|js|ico|xml)$ {
    expires 30d;
}

Reload Nginx, then access an image (e.g., http://192.168.4.5/day.jpg) and verify the cache entry and expiration time in Firefox.