[transport/http] adding request and response encoders for Protobuf

transport/http/proto/client.go

@@ -0,0 +1,37 @@
+package proto
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"io/ioutil"
+	"net/http"
+
+	httptransport "github.com/go-kit/kit/transport/http"
+	"github.com/golang/protobuf/proto"
+)
+
+// EncodeProtoRequest is an EncodeRequestFunc that serializes the request as Protobuf.
+// If the request implements Headerer, the provided headers will be applied
+// to the request. If the given request does not implement proto.Message, an error will
+// be returned.
+func EncodeProtoRequest(_ context.Context, r *http.Request, preq interface{}) error {
+	r.Header.Set("Content-Type", "application/x-protobuf")
+	if headerer, ok := preq.(httptransport.Headerer); ok {
+		for k := range headerer.Headers() {
+			r.Header.Set(k, headerer.Headers().Get(k))
+		}
+	}
+	req, ok := preq.(proto.Message)
+	if !ok {
+		return errors.New("response does not implement proto.Message")
+	}
+
+	b, err := proto.Marshal(req)
+	if err != nil {
+		return err
+	}
+	r.ContentLength = int64(len(b))
+	r.Body = ioutil.NopCloser(bytes.NewReader(b))
+	return nil
+}

transport/http/proto/proto_test.go

@@ -0,0 +1,95 @@
+package proto
+
+import (
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/golang/protobuf/proto"
+)
+
+func TestEncodeProtoRequest(t *testing.T) {
+	cat := &Cat{Name: "Ziggy", Age: 13, Breed: "Lumpy"}
+
+	r := httptest.NewRequest(http.MethodGet, "/cat", nil)
+
+	err := EncodeProtoRequest(nil, r, cat)
+	if err != nil {
+		t.Errorf("expected no encoding errors but got: %s", err)
+		return
+	}
+
+	const xproto = "application/x-protobuf"
+	if typ := r.Header.Get("Content-Type"); typ != xproto {
+		t.Errorf("expected content type of %q, got %q", xproto, typ)
+		return
+	}
+
+	bod, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		t.Errorf("expected no read errors but got: %s", err)
+		return
+	}
+	defer r.Body.Close()
+
+	var got Cat
+	err = proto.Unmarshal(bod, &got)
+	if err != nil {
+		t.Errorf("expected no proto errors but got: %s", err)
+		return
+	}
+
+	if !proto.Equal(&got, cat) {
+		t.Errorf("expected cats to be equal but got:\n\n%#v\n\nwant:\n\n%#v", got, cat)
+		return
+	}
+}
+
+func TestEncodeProtoResponse(t *testing.T) {
+	cat := &Cat{Name: "Ziggy", Age: 13, Breed: "Lumpy"}
+
+	wr := httptest.NewRecorder()
+
+	err := EncodeProtoResponse(nil, wr, cat)
+	if err != nil {
+		t.Errorf("expected no encoding errors but got: %s", err)
+		return
+	}
+
+	w := wr.Result()
+
+	const xproto = "application/x-protobuf"
+	if typ := w.Header.Get("Content-Type"); typ != xproto {
+		t.Errorf("expected content type of %q, got %q", xproto, typ)
+		return
+	}
+
+	if w.StatusCode != http.StatusTeapot {
+		t.Errorf("expected status code of %d, got %d", http.StatusTeapot, w.StatusCode)
+		return
+	}
+
+	bod, err := ioutil.ReadAll(w.Body)
+	if err != nil {
+		t.Errorf("expected no read errors but got: %s", err)
+		return
+	}
+	defer w.Body.Close()
+
+	var got Cat
+	err = proto.Unmarshal(bod, &got)
+	if err != nil {
+		t.Errorf("expected no proto errors but got: %s", err)
+		return
+	}
+
+	if !proto.Equal(&got, cat) {
+		t.Errorf("expected cats to be equal but got:\n\n%#v\n\nwant:\n\n%#v", got, cat)
+		return
+	}
+}
+
+func (c *Cat) StatusCode() int {
+	return http.StatusTeapot
+}

transport/http/proto/proto_test.proto

@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+message Cat {
+    int32 Age = 1;
+    string Breed = 2;
+    string Name = 3;
+}

transport/http/proto/server.go

@@ -0,0 +1,47 @@
+package proto
+
+import (
+	"context"
+	"errors"
+	"net/http"
+
+	httptransport "github.com/go-kit/kit/transport/http"
+	"github.com/golang/protobuf/proto"
+)
+
+// EncodeProtoResponse is an EncodeResponseFunc that serializes the response as Protobuf.
+// Many Proto-over-HTTP services can use it as a sensible default. If the response
+// implements Headerer, the provided headers will be applied to the response. If the
+// response implements StatusCoder, the provided StatusCode will be used instead of 200.
+func EncodeProtoResponse(ctx context.Context, w http.ResponseWriter, pres interface{}) error {
+	res, ok := pres.(proto.Message)
+	if !ok {
+		return errors.New("response does not implement proto.Message")
+	}
+	w.Header().Set("Content-Type", "application/x-protobuf")
+	if headerer, ok := w.(httptransport.Headerer); ok {
+		for k := range headerer.Headers() {
+			w.Header().Set(k, headerer.Headers().Get(k))
+		}
+	}
+	code := http.StatusOK
+	if sc, ok := pres.(httptransport.StatusCoder); ok {
+		code = sc.StatusCode()
+	}
+	w.WriteHeader(code)
+	if code == http.StatusNoContent {
+		return nil
+	}
+	if res == nil {
+		return nil
+	}
+	b, err := proto.Marshal(res)
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(b)
+	if err != nil {
+		return err
+	}
+	return nil
+}