grpc-ecosystem#4238 Added the WithWriteContentLength ServerMuxOption,…

… which if set will write a Content-Length header before calling w.Write on non-streaming responses

runtime/handler.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"net/textproto"
+	"strconv"
 	"strings"
 
 	"google.golang.org/genproto/googleapis/api/httpbody"
@@ -176,6 +177,10 @@ func ForwardResponseMessage(ctx context.Context, mux *ServeMux, marshaler Marsha
 		return
 	}
 
+	if mux.writeContentLength {
+		w.Header().Set("Content-Length", strconv.Itoa(len(buf)))
+	}
+
 	if _, err = w.Write(buf); err != nil {
 		grpclog.Infof("Failed to write response: %v", err)
 	}

runtime/mux.go

@@ -64,6 +64,7 @@ type ServeMux struct {
 	routingErrorHandler       RoutingErrorHandlerFunc
 	disablePathLengthFallback bool
 	unescapingMode            UnescapingMode
+	writeContentLength        bool
 }
 
 // ServeMuxOption is an option that can be given to a ServeMux on construction.
@@ -224,6 +225,13 @@ func WithDisablePathLengthFallback() ServeMuxOption {
 	}
 }
 
+// WithWriteContentLength returns a ServeMuxOption to enable writing content length on non-streaming responses
+func WithWriteContentLength() ServeMuxOption {
+	return func(serveMux *ServeMux) {
+		serveMux.writeContentLength = true
+	}
+}
+
 // WithHealthEndpointAt returns a ServeMuxOption that will add an endpoint to the created ServeMux at the path specified by endpointPath.
 // When called the handler will forward the request to the upstream grpc service health check (defined in the
 // gRPC Health Checking Protocol).