How to Fix Nginx Error "upstream timed out (110: Connection timed out) while reading response header from upstream"

Experiencing an Nginx upstream timeout error can disrupt your website's performance. This guide will explain how to resolve the "upstream timed out" error in Nginx. We'll use clear steps and keep it brief.

What Causes the Error?

The "upstream timed out" error occurs when Nginx cannot get a response from a server upstream within a set time. This can be due to server overload, network issues, or slow processes.

Step 1: Check Nginx and Upstream Server Logs

Start by reviewing the Nginx logs:

• Access your server via SSH.
• Use the command:

tail -f /var/log/nginx/error.log

Look for any patterns or repeat errors. Do the same for your upstream servers. Logs can point you to whether the issue lies with network, configuration, or server overload.

Step 2: Increase the Timeout Settings

If logs show timeout issues, increase the timeout settings in Nginx:

• Open your Nginx configuration file.
• Find the proxy_read_timeout setting.
• Set it to a higher value (e.g., 300 seconds).
• Reload Nginx: sudo systemctl reload nginx

Step 3: Optimize Upstream Server Performance

Ensure the upstream server is not overburdened:

• Check server load and resource usage.
• Upgrade hardware if necessary.
• Optimize application code and databases.

Step 4: Adjust Proxy Buffers

Adjust the proxy buffer settings in Nginx:

• Open the Nginx configuration file.
• Modify proxy_buffers and proxy_buffer_size.
• Example:

  proxy_buffers 16 32k;
  proxy_buffer_size 64k;
  

• Reload Nginx to apply changes.

Step 5: Check for Network Issues

Inspect your network settings:

• Test network speed and stability.
• Check for any rate limiting or firewall rules.
• Ensure DNS settings are correct.

Step 6: Use Upstream Keepalive

Enable upstream keepalive connections:

• Add keepalive to your upstream block:

  upstream backend {
      server backend1.example.com;
      keepalive 32;
  }
  

• This can reduce connection overhead.

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Step 7: Monitor and Debug

After making changes, monitor the server:

• Keep an eye on the logs.
• Use monitoring tools to track performance.
• Adjust configurations as needed based on observations.

Conclusion

Fixing the Nginx "upstream timed out" error involves several steps from logging to configuration. By increasing timeout settings, optimizing server performance, and ensuring robust network conditions, you can mitigate this error effectively. Regular monitoring will help prevent future occurrences.

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