Fix concurrent map panic on inject metadata

Signed-off-by: Jin Dong <[email protected]>

go.mod

@@ -9,7 +9,6 @@ require (
 	go.opentelemetry.io/otel/metric v1.19.0
 	go.opentelemetry.io/otel/sdk v1.19.0
 	go.opentelemetry.io/otel/trace v1.19.0
-	golang.org/x/sync v0.10.0
 	google.golang.org/grpc v1.57.0
 	google.golang.org/protobuf v1.30.0
 )

go.sum

@@ -1051,8 +1051,6 @@ golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20220819030929-7fc1605a5dde/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220929204114-8fcdb60fdcc0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.10.0 h1:3NQrjDixjgGwUOCaF8w2+VYHv0Ve/vGYSbdkTa98gmQ=
-golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

interceptor_test.go

@@ -37,6 +37,7 @@ import (
 	"net"
 	"runtime"
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/containerd/otelttrpc/internal"
@@ -47,7 +48,6 @@ import (
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 	"go.opentelemetry.io/otel/sdk/trace/tracetest"
 	"go.opentelemetry.io/otel/trace"
-	"golang.org/x/sync/errgroup"
 )
 
 const serviceName = "testService"
@@ -122,21 +122,28 @@ func TestClientCallServerConcurrent(t *testing.T) {
 		_ = server.Shutdown(ctx)
 	}()
 
-	var eg errgroup.Group
+	var wg sync.WaitGroup
+	var errs []error
+	var mu sync.Mutex
+
 	for _, testClient := range testClients {
 		// capture range variable
 		// TODO: we can remove this once we upgrade golang to >= 1.22
 		testClient := testClient
-		eg.Go(func() error {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
 			if _, err := testClient.Test(ctx, payload); err != nil {
-				return err
+				mu.Lock()
+				defer mu.Unlock()
+				errs = append(errs, err)
 			}
-			return nil
-		})
+		}()
 	}
 
-	if err := eg.Wait(); err != nil {
-		t.Fatal(err)
+	wg.Wait()
+	if len(errs) > 0 {
+		t.Fatalf("unexpected errors: %v", errs)
 	}
 
 	// get exported spans

metadata_supplier.go

@@ -66,10 +66,21 @@ func (s *metadataSupplier) Keys() []string {
 	return out
 }
 
+func copyMD(src ttrpc.MD) ttrpc.MD {
+	md := make(ttrpc.MD, len(src))
+	for k, v := range src {
+		md[k] = append(md[k], v...)
+	}
+	return md
+}
+
 func inject(ctx context.Context, propagators propagation.TextMapPropagator, req *ttrpc.Request) context.Context {
 	md, ok := ttrpc.GetMetadata(ctx)
 	if !ok {
 		md = make(ttrpc.MD)
+	} else {
+		// make a copy to avoid concurrent read/write panic
+		md = copyMD(md)
 	}
 
 	propagators.Inject(ctx, &metadataSupplier{