{"record":{"id":"efbc9324a71e3b6b","repo":"grpc/grpc-go","slug":"extproc-invalid-response-trailer-mode-v-must-be","errorCode":null,"errorMessage":"extproc: invalid response trailer mode %v: must be %q when response body mode is %q","messagePattern":"extproc: invalid response trailer mode (.+?): must be %q when response body mode is %q","errorType":"validation","errorClass":null,"httpStatus":null,"severity":"error","filePath":"internal/xds/httpfilter/extproc/ext_proc.go","lineNumber":104,"sourceCode":"func (builder) TypeURLs() []string {\n\treturn []string{\n\t\t\"type.googleapis.com/envoy.extensions.filters.http.ext_proc.v3.ExternalProcessor\",\n\t\t\"type.googleapis.com/envoy.extensions.filters.http.ext_proc.v3.ExtProcPerRoute\",\n\t}\n}\n\n// validateBodyProcessingMode ensures that the body processing mode is either\n// NONE or GRPC. Also ensures that if response body mode is GRPC then response\n// trailer mode must be SEND.\nfunc validateBodyProcessingMode(mode *v3procfilterpb.ProcessingMode) error {\n\tif m := mode.GetRequestBodyMode(); m != v3procfilterpb.ProcessingMode_NONE && m != v3procfilterpb.ProcessingMode_GRPC {\n\t\treturn fmt.Errorf(\"extproc: invalid request body mode %v: want %q or %q\", m, \"NONE\", \"GRPC\")\n\t}\n\tif m := mode.GetResponseBodyMode(); m != v3procfilterpb.ProcessingMode_NONE && m != v3procfilterpb.ProcessingMode_GRPC {\n\t\treturn fmt.Errorf(\"extproc: invalid response body mode %v: want %q or %q\", m, \"NONE\", \"GRPC\")\n\t}\n\tif mode.GetResponseBodyMode() == v3procfilterpb.ProcessingMode_GRPC && mode.GetResponseTrailerMode() != v3procfilterpb.ProcessingMode_SEND {\n\t\treturn fmt.Errorf(\"extproc: invalid response trailer mode %v: must be %q when response body mode is %q\", mode.GetResponseTrailerMode(), \"SEND\", \"GRPC\")\n\t}\n\treturn nil\n}\n\nfunc (builder) ParseFilterConfig(cfg proto.Message) (httpfilter.FilterConfig, error) {\n\tm, ok := cfg.(*anypb.Any)\n\tif !ok {\n\t\treturn nil, fmt.Errorf(\"extproc: error parsing config %v: unknown type %T, want *anypb.Any\", cfg, cfg)\n\t}\n\tmsg := new(v3procfilterpb.ExternalProcessor)\n\tif err := m.UnmarshalTo(msg); err != nil {\n\t\treturn nil, fmt.Errorf(\"extproc: failed to unmarshal config %v: %v\", cfg, err)\n\t}\n\tif msg.GetProcessingMode() == nil {\n\t\treturn nil, fmt.Errorf(\"extproc: missing processing_mode in config %v\", cfg)\n\t}\n\tif err := validateBodyProcessingMode(msg.GetProcessingMode()); err != nil {\n\t\treturn nil, err","sourceCodeStart":86,"sourceCodeEnd":122,"githubUrl":"https://github.com/grpc/grpc-go/blob/03255a9237b6eb32710f6bc4f2de9a675b99fe36/internal/xds/httpfilter/extproc/ext_proc.go#L86-L122","documentation":"Raised by validateBodyProcessingMode (ext_proc.go:104) when response_body_mode is GRPC but response_trailer_mode is not SEND. gRPC needs to send response trailers to the processor whenever it is processing the response body (so it can mark end-of-stream correctly); any other trailer mode in that combination is rejected.","triggerScenarios":"At ext_proc.go:103, mode.GetResponseBodyMode() == GRPC and mode.GetResponseTrailerMode() != SEND (e.g. it is SKIP or DEFAULT-resolved-to-skip).","commonSituations":"Config sets response_body_mode: GRPC for response mutation but explicitly sets response_trailer_mode: SKIP (or relies on the default skip) because trailers weren't wanted; partial config produced by only setting the body mode.","solutions":["Set response_trailer_mode: SEND whenever response_body_mode is GRPC.","If you do not want trailer processing, switch response_body_mode to NONE instead of leaving it GRPC with SKIP trailers.","Re-apply the resource and confirm it is ACKed."],"exampleFix":"// before\n//   processing_mode: { response_body_mode: GRPC, response_trailer_mode: SKIP }   // -> error 374\n//\n// after\n//   processing_mode: { response_body_mode: GRPC, response_trailer_mode: SEND }","handlingStrategy":"validation","validationCode":"// Validate the response body/trailer coupling (ext_proc.go:103-105).\nfunc validateResponseTrailerMode(pm *v3procfilterpb.ProcessingMode) error {\n    if pm.GetResponseBodyMode() == v3procfilterpb.ProcessingMode_GRPC && pm.GetResponseTrailerMode() != v3procfilterpb.ProcessingMode_SEND {\n        return fmt.Errorf(\"response_trailer_mode must be SEND when response_body_mode is GRPC\")\n    }\n    return nil\n}","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Whenever you set response_body_mode: GRPC, also set response_trailer_mode: SEND.","If trailers must be skipped, use response_body_mode: NONE instead of GRPC+SKIP.","Encode this coupling as a schema/CI rule for ext_proc processing_mode."],"tags":["grpc","xds","config","ext-proc","processing-mode"],"analyzedSha":"03255a9237b6eb32710f6bc4f2de9a675b99fe36","analyzedAt":"2026-08-07T00:29:34.215Z","schemaVersion":2},"datasetVersion":"2026-08-07T03:17:09.362Z"}