HTTP 101 Switching Protocols vs 502 Bad Gateway
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 502 (Bad Gateway) is a 5xx Server Error response. 101 indicates that the server understands the Upgrade header field request and indicates which protocol it is switching to. In contrast, 502 means that the server, acting as a gateway or proxy, received an invalid response from the upstream server.
説明
The server understands the Upgrade header field request and indicates which protocol it is switching to.
このコードが表示される場合
When upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
解決方法
This is normal behavior during protocol upgrades. Ensure your client supports the target protocol.
説明
The server, acting as a gateway or proxy, received an invalid response from the upstream server.
このコードが表示される場合
When Nginx/Apache can't reach the application server (e.g., Gunicorn is down, upstream timeout).
解決方法
Check if the upstream server is running. Verify proxy configuration. Check for upstream timeouts.
主な違い
101 is a 1xx Informational response, while 502 is a 5xx Server Error response.
HTTP 101: The server understands the Upgrade header field request and indicates which protocol it is switching to.
HTTP 502: The server, acting as a gateway or proxy, received an invalid response from the upstream server.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 502 when when Nginx/Apache can't reach the application server (e.g., Gunicorn is down, upstream timeout).
どちらをいつ使うか
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 502 (Bad Gateway): Check if the upstream server is running. Verify proxy configuration. Check for upstream timeouts.