pkg/trace: add support for meta_struct span proto field

pkg/trace/api/api_test.go

@@ -794,7 +794,7 @@ func TestHandleTraces(t *testing.T) {
 		ts, ok := rs.Stats[info.Tags{Lang: lang, EndpointVersion: "v0.4"}]
 		assert.True(ok)
 		assert.Equal(int64(20), ts.TracesReceived)
-		assert.Equal(int64(59222), ts.TracesBytes)
+		assert.Equal(int64(61822), ts.TracesBytes)
 	}
 	// make sure we have all our languages registered
 	assert.Equal("C#|go|java|python|ruby", receiver.Languages())

pkg/trace/api/info.go

@@ -64,20 +64,22 @@ func (r *HTTPReceiver) makeInfoHandler() (hash string, handler http.HandlerFunc)
 		oconf.Memcached = o.Memcached.Enabled
 	}
 	txt, err := json.MarshalIndent(struct {
-		Version       string        `json:"version"`
-		GitCommit     string        `json:"git_commit"`
-		BuildDate     string        `json:"build_date"`
-		Endpoints     []string      `json:"endpoints"`
-		FeatureFlags  []string      `json:"feature_flags,omitempty"`
-		ClientDropP0s bool          `json:"client_drop_p0s"`
-		Config        reducedConfig `json:"config"`
+		Version         string        `json:"version"`
+		GitCommit       string        `json:"git_commit"`
+		BuildDate       string        `json:"build_date"`
+		Endpoints       []string      `json:"endpoints"`
+		FeatureFlags    []string      `json:"feature_flags,omitempty"`
+		ClientDropP0s   bool          `json:"client_drop_p0s"`
+		SpanMetaStructs bool          `json:"span_meta_structs"`
+		Config          reducedConfig `json:"config"`
 	}{
-		Version:       info.Version,
-		GitCommit:     info.GitCommit,
-		BuildDate:     info.BuildDate,
-		Endpoints:     all,
-		FeatureFlags:  features.All(),
-		ClientDropP0s: true,
+		Version:         info.Version,
+		GitCommit:       info.GitCommit,
+		BuildDate:       info.BuildDate,
+		Endpoints:       all,
+		FeatureFlags:    features.All(),
+		ClientDropP0s:   true,
+		SpanMetaStructs: true,
 		Config: reducedConfig{
 			DefaultEnv:             r.conf.DefaultEnv,
 			TargetTPS:              r.conf.TargetTPS,

pkg/trace/api/info_test.go

@@ -136,6 +136,7 @@ func TestInfoHandler(t *testing.T) {
 		"feature_flag"
 	],
 	"client_drop_p0s": true,
+	"span_meta_structs": true,
 	"config": {
 		"default_env": "prod",
 		"target_tps": 11,
@@ -195,6 +196,7 @@ func TestInfoHandler(t *testing.T) {
 		"config_endpoint"
 	],
 	"client_drop_p0s": true,
+	"span_meta_structs": true,
 	"config": {
 		"default_env": "prod",
 		"target_tps": 11,

pkg/trace/pb/decoder_bytes.go

@@ -247,3 +247,20 @@ func parseInt32Bytes(bts []byte) (int32, []byte, error) {
 		return 0, bts, msgp.TypeError{Encoded: t, Method: msgp.IntType}
 	}
 }
+
+// parseBytes reads the next BinType in the msgpack payload.
+func parseBytes(bts []byte) ([]byte, []byte, error) {
+	if msgp.IsNil(bts) {
+		bts, err := msgp.ReadNilBytes(bts)
+		return nil, bts, err
+	}
+	// read the generic representation type without decoding
+	t := msgp.NextType(bts)
+
+	switch t {
+	case msgp.BinType:
+		return msgp.ReadBytesZC(bts)
+	default:
+		return nil, bts, msgp.TypeError{Encoded: t, Method: msgp.BinType}
+	}
+}

pkg/trace/pb/span.proto

@@ -17,4 +17,5 @@ message Span {
     map<string, string> meta = 10 [(gogoproto.jsontag) = "meta", (gogoproto.moretags) = "msg:\"meta\""];
     map<string, double> metrics = 11 [(gogoproto.jsontag) = "metrics", (gogoproto.moretags) = "msg:\"metrics\""];
     string type = 12 [(gogoproto.jsontag) = "type", (gogoproto.moretags) = "msg:\"type\""];
+    map<string, bytes> meta_struct = 13 [(gogoproto.jsontag) = "meta_struct,omitempty", (gogoproto.moretags) = "msg:\"meta_struct\""];
 }