Problem: Nginx Upstream Connection Error
The "Nginx upstream prematurely closed connection while reading response header from upstream" error happens when Nginx can't get a full response from an upstream server. This problem can interrupt web applications and services. It often leads to incomplete or failed requests, affecting the system's performance and reliability.
Solution: Adjusting Nginx Configuration
Increasing timeout settings
To fix the "Upstream Prematurely Closed Connection" error, you can adjust the timeout settings in your Nginx configuration:
- Modify proxy_read_timeout: This setting controls how long Nginx waits for the upstream server to send data. Increase this value to allow more time for large responses:
proxy_read_timeout 300s;- Adjust proxy_connect_timeout: This setting determines how long Nginx waits to establish a connection with the upstream server. Increase this value if your upstream server takes longer to respond:
proxy_connect_timeout 75s;- Set send_timeout: This setting specifies how long Nginx waits for the client to accept data. Adjust this value based on your application's needs:
send_timeout 60s;Tip: Monitor and adjust
After making changes to timeout settings, monitor your server's performance and adjust the values as needed. Start with conservative increases and gradually fine-tune based on your specific requirements and traffic patterns.
Optimizing buffer settings
Optimizing buffer settings can help prevent the "Upstream Prematurely Closed Connection" error:
- Configure proxy_buffers: This setting determines the number and size of buffers for reading the response from the upstream server. Adjust these values based on your server's resources and typical response sizes:
proxy_buffers 8 16k;- Adjust proxy_buffer_size: This setting specifies the size of the buffer used for reading the first part of the response from the upstream server. Increase this value for larger headers:
proxy_buffer_size 32k;- Fine-tune large_client_header_buffers: This setting controls the maximum number and size of buffers used for reading large client request headers. Adjust these values if you're dealing with requests containing large headers:
large_client_header_buffers 4 32k;By adjusting these Nginx configuration settings, you can often fix the "Upstream Prematurely Closed Connection" error and improve your server's ability to handle large responses and complex requests.
