HTTP 409 Conflict vs 502 Bad Gateway
HTTP 409 (Conflict) is a 4xx Client Error response, while 502 (Bad Gateway) is a 5xx Server Error response. 409 indicates that the request conflicts with the current state of the server. Often due to concurrent modification or business rule violations. In contrast, 502 means that the server, acting as a gateway or proxy, received an invalid response from the upstream server.
Description
The request conflicts with the current state of the server. Often due to concurrent modification or business rule violations.
When You See It
When trying to create a resource that already exists, or updating a resource that was modified by another request.
How to Fix
Refresh the resource state, resolve conflicts, and retry. Use ETags for optimistic concurrency.
Description
The server, acting as a gateway or proxy, received an invalid response from the upstream server.
When You See It
When Nginx/Apache can't reach the application server (e.g., Gunicorn is down, upstream timeout).
How to Fix
Check if the upstream server is running. Verify proxy configuration. Check for upstream timeouts.
Key Differences
409 is a 4xx Client Error response, while 502 is a 5xx Server Error response.
HTTP 409: The request conflicts with the current state of the server. Often due to concurrent modification or business rule violations.
HTTP 502: The server, acting as a gateway or proxy, received an invalid response from the upstream server.
You encounter 409 when when trying to create a resource that already exists, or updating a resource that was modified by another request.
You encounter 502 when when Nginx/Apache can't reach the application server (e.g., Gunicorn is down, upstream timeout).
When to Use Which
For 409 (Conflict): Refresh the resource state, resolve conflicts, and retry. Use ETags for optimistic concurrency. For 502 (Bad Gateway): Check if the upstream server is running. Verify proxy configuration. Check for upstream timeouts.