F5 XC 503 upstream_reset_before_response_started{protocol_error}
Hello Community, I would like to share some additional information regarding the 503 response code in F5 XC. When the origin server sends a response to XC that is not compliant with HTTP RFC standards, the platform may return a 503. For example, if the origin server responds with a 204 status code but includes a message body, Envoy (the underlying data plane) will treat this as RFC non-compliant and therefore block the content. As a result, XC will return a 503 response to the client. 503 upstream_reset_before_response_started{protocol_error} Check if the http response headers from the origin-server have any invalid field names. Query the the origin-server directly via cURL or something equivalent. Usually indicates that XC is seeing an error in one of the http-headers of the response from the server. We would need to see the http headers that the origin-server is responding with to identify the issue. In one of the scenarios, it was seen that the origin-server may have a total of more than 100 headers (mostly duplicate headers), which XC will treat as failure parsing the response.