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Add helper to write RPC errors from HTTP middleware (#337)
Add a protocol-aware helper type to write RPC errors from net/http middleware. The new ErrorWriter struct accepts HandlerOptions, so that it's fully aware of the supported Codecs and RPC protocols, and it supports gRPC, gRPC-Web, and Connect clients. Co-authored-by: Akshay Shah <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,168 @@ | ||
| // Copyright 2021-2022 Buf Technologies, Inc. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package connect | ||
|
|
||
| import ( | ||
| "encoding/json" | ||
| "fmt" | ||
| "net/http" | ||
| "strings" | ||
| ) | ||
|
|
||
| // An ErrorWriter writes errors to an [http.ResponseWriter] in the format | ||
| // expected by an RPC client. This is especially useful in server-side net/http | ||
| // middleware, where you may wish to handle requests from RPC and non-RPC | ||
| // clients with the same code. | ||
| // | ||
| // ErrorWriters are safe to use concurrently. | ||
| type ErrorWriter struct { | ||
| bufferPool *bufferPool | ||
| protobuf Codec | ||
| allContentTypes map[string]struct{} | ||
| grpcContentTypes map[string]struct{} | ||
| grpcWebContentTypes map[string]struct{} | ||
| unaryConnectContentTypes map[string]struct{} | ||
| streamingConnectContentTypes map[string]struct{} | ||
| } | ||
|
|
||
| // NewErrorWriter constructs an ErrorWriter. To properly recognize supported | ||
| // RPC Content-Types in net/http middleware, you must pass the same | ||
| // HandlerOptions to NewErrorWriter and any wrapped Connect handlers. | ||
| func NewErrorWriter(opts ...HandlerOption) *ErrorWriter { | ||
| config := newHandlerConfig("", opts) | ||
| writer := &ErrorWriter{ | ||
| bufferPool: config.BufferPool, | ||
| protobuf: newReadOnlyCodecs(config.Codecs).Protobuf(), | ||
| allContentTypes: make(map[string]struct{}), | ||
| grpcContentTypes: make(map[string]struct{}), | ||
| grpcWebContentTypes: make(map[string]struct{}), | ||
| unaryConnectContentTypes: make(map[string]struct{}), | ||
| streamingConnectContentTypes: make(map[string]struct{}), | ||
| } | ||
| for name := range config.Codecs { | ||
| unary := connectContentTypeFromCodecName(StreamTypeUnary, name) | ||
| writer.allContentTypes[unary] = struct{}{} | ||
| writer.unaryConnectContentTypes[unary] = struct{}{} | ||
| streaming := connectContentTypeFromCodecName(StreamTypeBidi, name) | ||
| writer.streamingConnectContentTypes[streaming] = struct{}{} | ||
| writer.allContentTypes[streaming] = struct{}{} | ||
| } | ||
| if config.HandleGRPC { | ||
| writer.grpcContentTypes[grpcContentTypeDefault] = struct{}{} | ||
| writer.allContentTypes[grpcContentTypeDefault] = struct{}{} | ||
| for name := range config.Codecs { | ||
| ct := grpcContentTypeFromCodecName(false /* web */, name) | ||
| writer.grpcContentTypes[ct] = struct{}{} | ||
| writer.allContentTypes[ct] = struct{}{} | ||
| } | ||
| } | ||
| if config.HandleGRPCWeb { | ||
| writer.grpcWebContentTypes[grpcWebContentTypeDefault] = struct{}{} | ||
| writer.allContentTypes[grpcWebContentTypeDefault] = struct{}{} | ||
| for name := range config.Codecs { | ||
| ct := grpcContentTypeFromCodecName(true /* web */, name) | ||
| writer.grpcWebContentTypes[ct] = struct{}{} | ||
| writer.allContentTypes[ct] = struct{}{} | ||
| } | ||
| } | ||
| return writer | ||
| } | ||
|
|
||
| // IsSupported checks whether a request is using one of the ErrorWriter's | ||
| // supported RPC protocols. | ||
| func (w *ErrorWriter) IsSupported(request *http.Request) bool { | ||
| ctype := request.Header.Get(headerContentType) | ||
| _, ok := w.allContentTypes[ctype] | ||
| return ok | ||
| } | ||
|
|
||
| // Write an error, using the format appropriate for the RPC protocol in use. | ||
| // Callers should first use IsSupported to verify that the request is using one | ||
| // of the ErrorWriter's supported RPC protocols. | ||
| // | ||
| // Write does not read or close the request body. | ||
| func (w *ErrorWriter) Write(response http.ResponseWriter, request *http.Request, err error) error { | ||
| ctype := request.Header.Get(headerContentType) | ||
| if _, ok := w.unaryConnectContentTypes[ctype]; ok { | ||
| // Unary errors are always JSON. | ||
| response.Header().Set(headerContentType, connectUnaryContentTypeJSON) | ||
| return w.writeConnectUnary(response, err) | ||
| } | ||
| if _, ok := w.streamingConnectContentTypes[ctype]; ok { | ||
| response.Header().Set(headerContentType, ctype) | ||
| return w.writeConnectStreaming(response, err) | ||
| } | ||
| if _, ok := w.grpcContentTypes[ctype]; ok { | ||
| response.Header().Set(headerContentType, ctype) | ||
| return w.writeGRPC(response, err) | ||
| } | ||
| if _, ok := w.grpcWebContentTypes[ctype]; ok { | ||
| response.Header().Set(headerContentType, ctype) | ||
| return w.writeGRPCWeb(response, err) | ||
| } | ||
| return fmt.Errorf("unsupported Content-Type %q", ctype) | ||
| } | ||
|
|
||
| func (w *ErrorWriter) writeConnectUnary(response http.ResponseWriter, err error) error { | ||
| if connectErr, ok := asError(err); ok { | ||
| mergeHeaders(response.Header(), connectErr.meta) | ||
| } | ||
| response.WriteHeader(connectCodeToHTTP(CodeOf(err))) | ||
| data, marshalErr := json.Marshal(newConnectWireError(err)) | ||
| if marshalErr != nil { | ||
| return fmt.Errorf("marshal error: %w", marshalErr) | ||
| } | ||
| _, writeErr := response.Write(data) | ||
| return writeErr | ||
| } | ||
|
|
||
| func (w *ErrorWriter) writeConnectStreaming(response http.ResponseWriter, err error) error { | ||
| response.WriteHeader(http.StatusOK) | ||
| marshaler := &connectStreamingMarshaler{ | ||
| envelopeWriter: envelopeWriter{ | ||
| writer: response, | ||
| bufferPool: w.bufferPool, | ||
| }, | ||
| } | ||
| // MarshalEndStream returns *Error: check return value to avoid typed nils. | ||
| if marshalErr := marshaler.MarshalEndStream(err, make(http.Header)); marshalErr != nil { | ||
| return marshalErr | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| func (w *ErrorWriter) writeGRPC(response http.ResponseWriter, err error) error { | ||
| trailers := make(http.Header, 2) // need space for at least code & message | ||
| grpcErrorToTrailer(w.bufferPool, trailers, w.protobuf, err) | ||
| // To make net/http reliably send trailers without a body, we must set the | ||
| // Trailers header rather than using http.TrailerPrefix. See | ||
| // https://github.com/golang/go/issues/54723. | ||
| keys := make([]string, 0, len(trailers)) | ||
| for k := range trailers { | ||
| keys = append(keys, k) | ||
| } | ||
| response.Header().Set("Trailer", strings.Join(keys, ",")) | ||
| response.WriteHeader(http.StatusOK) | ||
| mergeHeaders(response.Header(), trailers) | ||
| return nil | ||
| } | ||
|
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||
| func (w *ErrorWriter) writeGRPCWeb(response http.ResponseWriter, err error) error { | ||
| // This is a trailers-only response. To match the behavior of Envoy and | ||
| // protocol_grpc.go, put the trailers in the HTTP headers. | ||
| grpcErrorToTrailer(w.bufferPool, response.Header(), w.protobuf, err) | ||
| response.WriteHeader(http.StatusOK) | ||
| return nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,69 @@ | ||
| // Copyright 2021-2022 Buf Technologies, Inc. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package connect_test | ||
|
|
||
| import ( | ||
| "errors" | ||
| "io" | ||
| "log" | ||
| "net/http" | ||
|
|
||
| "github.com/bufbuild/connect-go" | ||
| ) | ||
|
|
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| // NewHelloHandler is an example HTTP handler. In a real application, it might | ||
| // handle RPCs, requests for HTML, or anything else. | ||
| func NewHelloHandler() http.Handler { | ||
| return http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) { | ||
| io.WriteString(response, "Hello, world!") | ||
| }) | ||
| } | ||
|
|
||
| // NewAuthenticatedHandler is an example of middleware that works with both RPC | ||
| // and non-RPC clients. | ||
| func NewAuthenticatedHandler(handler http.Handler) http.Handler { | ||
| errorWriter := connect.NewErrorWriter() | ||
| return http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) { | ||
| // Dummy authentication logic. | ||
| if request.Header.Get("Token") == "super-secret" { | ||
| handler.ServeHTTP(response, request) | ||
| return | ||
| } | ||
| defer request.Body.Close() | ||
| defer io.Copy(io.Discard, request.Body) | ||
| if errorWriter.IsSupported(request) { | ||
| // Send a protocol-appropriate error to RPC clients, so that they receive | ||
| // the right code, message, and any metadata or error details. | ||
| unauthenticated := connect.NewError(connect.CodeUnauthenticated, errors.New("invalid token")) | ||
| errorWriter.Write(response, request, unauthenticated) | ||
| } else { | ||
| // Send an error to non-RPC clients. | ||
| response.WriteHeader(http.StatusUnauthorized) | ||
| io.WriteString(response, "invalid token") | ||
| } | ||
| }) | ||
| } | ||
|
|
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| func ExampleErrorWriter() { | ||
| mux := http.NewServeMux() | ||
| mux.Handle("/", NewHelloHandler()) | ||
| srv := &http.Server{ | ||
| Addr: ":8080", | ||
| Handler: NewAuthenticatedHandler(mux), | ||
| } | ||
| if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) { | ||
| log.Fatalln(err) | ||
| } | ||
| } |