Add HTTP/JSON to the otlp exporter (#1586)

* Add HTTP/JSON to the otlp exporter

Co-Authored-By: Roy van de Water <72016+royvandewater@users.noreply.github.com>

* PR fixup

Co-authored-by: Roy van de Water <72016+royvandewater@users.noreply.github.com>

CHANGELOG.md

@@ -8,6 +8,9 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+## Added
+
+- Added `Marshler` config option to `otlphttp` to enable otlp over json or protobufs. (#1586)
 ### Removed
 
 - Removed the exported `SimpleSpanProcessor` and `BatchSpanProcessor` structs.

exporters/otlp/otlphttp/driver.go

@@ -28,6 +28,9 @@ import (
 	"strings"
 	"time"
 
+	"github.com/gogo/protobuf/jsonpb"
+	"github.com/gogo/protobuf/proto"
+
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/otlp"
 	colmetricspb "go.opentelemetry.io/otel/exporters/otlp/internal/opentelemetry-proto-gen/collector/metrics/v1"
@@ -37,7 +40,8 @@ import (
 	tracesdk "go.opentelemetry.io/otel/sdk/export/trace"
 )
 
-const contentType = "application/x-protobuf"
+const contentTypeProto = "application/x-protobuf"
+const contentTypeJSON = "application/json"
 
 // Keep it in sync with golang's DefaultTransport from net/http! We
 // have our own copy to avoid handling a situation where the
@@ -142,7 +146,7 @@ func (d *driver) ExportMetrics(ctx context.Context, cps metricsdk.CheckpointSet,
 	pbRequest := &colmetricspb.ExportMetricsServiceRequest{
 		ResourceMetrics: rms,
 	}
-	rawRequest, err := pbRequest.Marshal()
+	rawRequest, err := d.marshal(pbRequest)
 	if err != nil {
 		return err
 	}
@@ -158,13 +162,21 @@ func (d *driver) ExportTraces(ctx context.Context, ss []*tracesdk.SpanSnapshot)
 	pbRequest := &coltracepb.ExportTraceServiceRequest{
 		ResourceSpans: protoSpans,
 	}
-	rawRequest, err := pbRequest.Marshal()
+	rawRequest, err := d.marshal(pbRequest)
 	if err != nil {
 		return err
 	}
 	return d.send(ctx, rawRequest, d.cfg.tracesURLPath)
 }
 
+func (d *driver) marshal(msg proto.Message) ([]byte, error) {
+	if d.cfg.marshaler == MarshalJSON {
+		s, err := (&jsonpb.Marshaler{}).MarshalToString(msg)
+		return []byte(s), err
+	}
+	return proto.Marshal(msg)
+}
+
 func (d *driver) send(ctx context.Context, rawRequest []byte, urlPath string) error {
 	address := fmt.Sprintf("%s://%s%s", d.getScheme(), d.cfg.endpoint, urlPath)
 	var cancel context.CancelFunc
@@ -267,7 +279,11 @@ func (d *driver) prepareBody(rawRequest []byte) (io.ReadCloser, int64, http.Head
 		headers.Set(k, v)
 	}
 	contentLength := (int64)(len(rawRequest))
-	headers.Set("Content-Type", contentType)
+	if d.cfg.marshaler == MarshalJSON {
+		headers.Set("Content-Type", contentTypeJSON)
+	} else {
+		headers.Set("Content-Type", contentTypeProto)
+	}
 	requestReader := bytes.NewBuffer(rawRequest)
 	switch d.cfg.compression {
 	case NoCompression:

exporters/otlp/otlphttp/driver_test.go

@@ -105,6 +105,12 @@ func TestEndToEnd(t *testing.T) {
 				ExpectedHeaders: testHeaders,
 			},
 		},
+		{
+			name: "with json encoding",
+			opts: []otlphttp.Option{
+				otlphttp.WithMarshal(otlphttp.MarshalJSON),
+			},
+		},
 	}
 
 	for _, tc := range tests {

exporters/otlp/otlphttp/mock_collector_test.go

@@ -27,6 +27,7 @@ import (
 	"sync"
 	"testing"
 
+	"github.com/gogo/protobuf/jsonpb"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -109,15 +110,25 @@ func (c *mockCollector) serveMetrics(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
-	request := collectormetricpb.ExportMetricsServiceRequest{}
-	if err := request.Unmarshal(rawRequest); err != nil {
+	request, err := unmarshalMetricsRequest(rawRequest, r.Header.Get("content-type"))
+	if err != nil {
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
 	writeReply(w, rawResponse, 0, c.injectContentType)
 	c.metricLock.Lock()
 	defer c.metricLock.Unlock()
-	c.metricsStorage.AddMetrics(&request)
+	c.metricsStorage.AddMetrics(request)
+}
+
+func unmarshalMetricsRequest(rawRequest []byte, contentType string) (*collectormetricpb.ExportMetricsServiceRequest, error) {
+	request := &collectormetricpb.ExportMetricsServiceRequest{}
+	if contentType == "application/json" {
+		err := jsonpb.UnmarshalString(string(rawRequest), request)
+		return request, err
+	}
+	err := request.Unmarshal(rawRequest)
+	return request, err
 }
 
 func (c *mockCollector) serveTraces(w http.ResponseWriter, r *http.Request) {
@@ -140,15 +151,26 @@ func (c *mockCollector) serveTraces(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
-	request := collectortracepb.ExportTraceServiceRequest{}
-	if err := request.Unmarshal(rawRequest); err != nil {
+
+	request, err := unmarshalTraceRequest(rawRequest, r.Header.Get("content-type"))
+	if err != nil {
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
 	writeReply(w, rawResponse, 0, c.injectContentType)
 	c.spanLock.Lock()
 	defer c.spanLock.Unlock()
-	c.spansStorage.AddSpans(&request)
+	c.spansStorage.AddSpans(request)
+}
+
+func unmarshalTraceRequest(rawRequest []byte, contentType string) (*collectortracepb.ExportTraceServiceRequest, error) {
+	request := &collectortracepb.ExportTraceServiceRequest{}
+	if contentType == "application/json" {
+		err := jsonpb.UnmarshalString(string(rawRequest), request)
+		return request, err
+	}
+	err := request.Unmarshal(rawRequest)
+	return request, err
 }
 
 func (c *mockCollector) checkHeaders(r *http.Request) bool {

exporters/otlp/otlphttp/options.go

@@ -48,6 +48,16 @@ const (
 	DefaultBackoff time.Duration = 300 * time.Millisecond
 )
 
+// Marshaler describes the kind of message format sent to the collector
+type Marshaler int
+
+const (
+	// MarshalProto tells the driver to send using the protobuf binary format.
+	MarshalProto Marshaler = iota
+	// MarshalJSON tells the driver to send using json format.
+	MarshalJSON
+)
+
 type config struct {
 	endpoint       string
 	compression    Compression
@@ -58,6 +68,7 @@ type config struct {
 	tlsCfg         *tls.Config
 	insecure       bool
 	headers        map[string]string
+	marshaler      Marshaler
 }
 
 // Option applies an option to the HTTP driver.
@@ -201,3 +212,16 @@ func (headersOption) private() {}
 func WithHeaders(headers map[string]string) Option {
 	return (headersOption)(headers)
 }
+
+type marshalerOption Marshaler
+
+func (o marshalerOption) Apply(cfg *config) {
+	cfg.marshaler = Marshaler(o)
+}
+func (marshalerOption) private() {}
+
+// WithMarshal tells the driver which wire format to use when sending to the
+// collector.  If unset, MarshalProto will be used
+func WithMarshal(m Marshaler) Option {
+	return marshalerOption(m)
+}