A 504 Gateway Timeout error on Nginx usually means your server took too long to respond. This often happens when PHP-FPM is slow, overloaded, or stuck running heavy scripts. The good news is that you can fix this error with a few configuration changes. In this guide, you’ll learn how to diagnose the cause and apply the right solution on Ubuntu or Virtualmin.
A 504 Gateway Timeout error on Nginx is one of the most frustrating issues you can encounter on an unmanaged VPS. It means Nginx passed the request to your backend (usually PHP-FPM) but didn’t get a response fast enough. This is common on WordPress websites using heavy plugins, slow database queries, or misconfigured timeouts.
Fortunately, the solution is usually straightforward. This guide walks you through the most reliable fixes for Ubuntu and Virtualmin servers running Nginx + PHP-FPM.
What Causes a 504 Gateway Timeout?
This error occurs when PHP-FPM takes too long to process a request. Common causes include:
- Slow WordPress plugins
- Large imports (media, WooCommerce, WP All Import)
- Heavy database queries
- PHP-FPM timeout too low
- Insufficient RAM or CPU
- MySQL slow or overloaded
- A plugin stuck in a loop
- Misconfigured Virtualmin execution mode
- Nginx timeout settings too strict
Let’s diagnose and fix the issue.
🛠️ Step 1: Check PHP-FPM Status
Start by verifying whether PHP-FPM is running normally:
systemctl status php8.1-fpm
If you’re on PHP 8.2:
systemctl status php8.2-fpm
If you see errors like “child exited with signal” or “failed”, restart the service:
systemctl restart php8.1-fpm
🛠️ Step 2: Increase Nginx Timeout Values
Nginx might be giving up too early. Increase key timeout settings in your site config:
Open:
nano /etc/nginx/sites-available/yourdomain.com.conf
Add or update:
proxy_connect_timeout 300;
proxy_send_timeout 300;
proxy_read_timeout 300;
send_timeout 300;
fastcgi_read_timeout 300;
These raise the limit to 5 minutes, ideal for imports or slow operations.
Test config:
nginx -t
Reload:
systemctl reload nginx
🛠️ Step 3: Increase PHP-FPM Timeout
Nginx may wait longer, but PHP-FPM might still terminate requests early.
Edit:
nano /etc/php/8.1/fpm/pool.d/www.conf
Find:
request_terminate_timeout
Set it to:
request_terminate_timeout = 300
Also increase max execution time:
/etc/php/8.1/fpm/php.ini
Modify:
max_execution_time = 300
Restart PHP-FPM:
systemctl restart php8.1-fpm
🛠️ Step 4: Check for Slow WordPress Plugins
Certain plugins frequently trigger 504s:
WooCommerce analytics
WP All Import / Export
Backup plugins
Security scanners
Plugins with remote API calls
Broken caching plugins
Check your logs if a specific plugin is causing long execution times.
Disable suspected plugins in WordPress or temporarily via SFTP by renaming the folder:
wp-content/plugins/plugin-name-disabled
🛠️ Step 5: Check Server Resource Usage
Run:
top
Or:
htop
Look for:
PHP-FPM using 100% CPU
MySQL consuming all resources
High memory usage
Swap usage pushed to the limit
If memory is low, increase swap:
fallocate -l 2G /swapfile
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile
Add to /etc/fstab:
/swapfile none swap sw 0 0
You can also read our full guide on adding swap space on Ubuntu.
🛠️ Step 6: Check MySQL Bottlenecks
MySQL slowdowns can cause PHP-FPM to stall.
Check slow query log:
tail -n 50 /var/log/mysql/mysql-slow.log
If WordPress queries are extremely slow:
optimize database
remove heavy plugins
repair tables
upgrade server resources
🛠️ Step 7: Virtualmin-Specific Fixes
In Virtualmin:
Web Configuration → PHP Options
Set:
PHP execution mode = FPM
PHP script timeout = 300 seconds
Also check:
Web Configuration → PHP-FPM Configuration
Ensure your domain uses the correct PHP version’s socket.
🧪 Final Test
Restart everything:
systemctl restart nginx
systemctl restart php8.1-fpm
systemctl restart mysql
Reload your site.
🎉 Conclusion
A 504 Gateway Timeout usually happens because PHP-FPM or MySQL took too long to respond. By increasing your timeout limits, checking slow plugins, reviewing server performance, and tuning PHP-FPM, you can eliminate this error for good.
If the issue still persists, it’s usually caused by:
A faulty plugin
Long-running WooCommerce/WP All Import tasks
Insufficient VPS resources
Feel free to share your environment details in the forums and I can help you troubleshoot deeper.
