Nginx Error Code Upstream Timed Out (110): How to Fix It

Q: What causes Nginx upstream timeout errors?

Nginx upstream timeout errors are typically caused by backend servers being slow to respond, overloaded, or completely unresponsive. Network connectivity issues, insufficient timeout settings, and application performance problems are the most common root causes.

Q: How do I find which backend server is causing timeouts?

Check your Nginx error logs (/var/log/nginx/error.log) to identify which upstream server is timing out. You can also enable access logs with response times and use monitoring tools to track backend server performance individually.

Q: What's a reasonable timeout value for proxy_connect_timeout?

A reasonable proxy_connect_timeout value depends on your application, but typically ranges from 60-300 seconds. Start with 120 seconds and adjust based on your backend server's typical response times and performance characteristics.

Q: Can I set different timeout values for different backends?

Yes, you can configure different timeout values for different upstream blocks or location blocks in your Nginx configuration. This allows you to customize timeouts based on the specific requirements of each backend service.

Q: Will increasing timeout values solve all connection issues?

No, increasing timeouts is often a temporary fix. While it may reduce timeout errors, the underlying performance issues with your backend servers should be investigated and resolved for a permanent solution.

Abstract

The Nginx upstream timed out (110: Connection timed out) error occurs when your web server cannot establish a connection to the backend application server within the configured timeout period. This typically happens when the backend server is overloaded, unresponsive, or when network connectivity issues prevent successful communication between Nginx and your application.