Nginx often acts as a reverse proxy in front of PHP-FPM, Node.js or other backends. If the backend is too slow, Nginx returns a 504 Gateway Timeout error. Here's how to configure correctly.
Symptoms
- "504 Gateway Timeout" error
- Long requests that fail
- Uploads that timeout
- Prematurely closed connections
Common Causes
- Slow backend: PHP-FPM or the application takes too long to respond.
- Timeout too short: Nginx directives configured with values too low.
- Backend connection: Backend socket or port not responding.
Diagnostic Steps
- Check Nginx logs (error.log)
- Test direct backend access (curl localhost:9000)
- Examine current timeout values
- Verify PHP-FPM is running (systemctl status php-fpm)
Automate with MoniTao
MoniTao detects timeouts:
- HTTP monitoring with configurable timeout
- Alerts on 504 errors
- Response time history
Best Practices
- Configure proxy_read_timeout according to your needs
- Align Nginx timeouts with PHP max_execution_time
- Use longer values for uploads
- Put long operations in background (queue)
FAQ
What timeout directives in Nginx?
proxy_connect_timeout, proxy_send_timeout, proxy_read_timeout, fastcgi_read_timeout.
What default value?
60 seconds by default. Adjust according to your longest operations.
How to increase for uploads?
Use client_max_body_size and increase timeouts in the concerned location.
Can MoniTao test with long timeouts?
Yes, configure the timeout in monitor settings.
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