feat: Supports callbacks when reading a message fails

server/callbacks.go

@@ -28,9 +28,10 @@ func (c CallbacksStruct) OnConnecting(request *http.Request) types.ConnectionRes
 // ConnectionCallbacksStruct is a struct that implements ConnectionCallbacks interface and allows
 // to override only the methods that are needed.
 type ConnectionCallbacksStruct struct {
-	OnConnectedFunc       func(ctx context.Context, conn types.Connection)
-	OnMessageFunc         func(ctx context.Context, conn types.Connection, message *protobufs.AgentToServer) *protobufs.ServerToAgent
-	OnConnectionCloseFunc func(conn types.Connection)
+	OnConnectedFunc        func(ctx context.Context, conn types.Connection)
+	OnMessageFunc          func(ctx context.Context, conn types.Connection, message *protobufs.AgentToServer) *protobufs.ServerToAgent
+	OnConnectionCloseFunc  func(conn types.Connection)
+	OnReadMessageErrorFunc func(conn types.Connection, mt int, msgByte []byte, err error)
 }
 
 var _ types.ConnectionCallbacks = (*ConnectionCallbacksStruct)(nil)
@@ -61,3 +62,10 @@ func (c ConnectionCallbacksStruct) OnConnectionClose(conn types.Connection) {
 		c.OnConnectionCloseFunc(conn)
 	}
 }
+
+// OnReadMessageError implements types.ConnectionCallbacks.
+func (c ConnectionCallbacksStruct) OnReadMessageError(conn types.Connection, mt int, msgByte []byte, err error) {
+	if c.OnReadMessageErrorFunc != nil {
+		c.OnReadMessageErrorFunc(conn, mt, msgByte, err)
+	}
+}

server/serverimpl.go

@@ -5,6 +5,7 @@ import (
 	"compress/gzip"
 	"context"
 	"errors"
+	"fmt"
 	"io"
 	"net"
 	"net/http"
@@ -19,16 +20,16 @@ import (
 	serverTypes "github.com/open-telemetry/opamp-go/server/types"
 )
 
-var (
-	errAlreadyStarted = errors.New("already started")
-)
+var errAlreadyStarted = errors.New("already started")
 
-const defaultOpAMPPath = "/v1/opamp"
-const headerContentType = "Content-Type"
-const headerContentEncoding = "Content-Encoding"
-const headerAcceptEncoding = "Accept-Encoding"
-const contentEncodingGzip = "gzip"
-const contentTypeProtobuf = "application/x-protobuf"
+const (
+	defaultOpAMPPath      = "/v1/opamp"
+	headerContentType     = "Content-Type"
+	headerContentEncoding = "Content-Encoding"
+	headerAcceptEncoding  = "Accept-Encoding"
+	contentEncodingGzip   = "gzip"
+	contentTypeProtobuf   = "application/x-protobuf"
+)
 
 type server struct {
 	logger   types.Logger
@@ -231,26 +232,39 @@ func (s *server) handleWSConnection(reqCtx context.Context, wsConn *websocket.Co
 	for {
 		msgContext := context.Background()
 		// Block until the next message can be read.
+		request := protobufs.AgentToServer{}
+
 		mt, msgBytes, err := wsConn.ReadMessage()
-		if err != nil {
-			if !websocket.IsUnexpectedCloseError(err) {
-				s.logger.Errorf(msgContext, "Cannot read a message from WebSocket: %v", err)
-				break
+		isBreak, err := func() (bool, error) {
+			if err != nil {
+				if !websocket.IsUnexpectedCloseError(err) {
+					s.logger.Errorf(msgContext, "Cannot read a message from WebSocket: %v", err)
+					return true, err
+				}
+				// This is a normal closing of the WebSocket connection.
+				s.logger.Debugf(msgContext, "Agent disconnected: %v", err)
+				return true, err
+			}
+			if mt != websocket.BinaryMessage {
+				err = fmt.Errorf("Received unexpected message type from WebSocket: %v", mt)
+				s.logger.Errorf(msgContext, err.Error())
+				return false, err
 			}
-			// This is a normal closing of the WebSocket connection.
-			s.logger.Debugf(msgContext, "Agent disconnected: %v", err)
-			break
-		}
-		if mt != websocket.BinaryMessage {
-			s.logger.Errorf(msgContext, "Received unexpected message type from WebSocket: %v", mt)
-			continue
-		}
 
-		// Decode WebSocket message as a Protobuf message.
-		var request protobufs.AgentToServer
-		err = internal.DecodeWSMessage(msgBytes, &request)
+			// Decode WebSocket message as a Protobuf message.
+			err = internal.DecodeWSMessage(msgBytes, &request)
+			if err != nil {
+				s.logger.Errorf(msgContext, "Cannot decode message from WebSocket: %v", err)
+				return false, err
+			}
+			return false, nil
+		}()
+
 		if err != nil {
-			s.logger.Errorf(msgContext, "Cannot decode message from WebSocket: %v", err)
+			connectionCallbacks.OnReadMessageError(agentConn, mt, msgBytes, err)
+			if isBreak {
+				break
+			}
 			continue
 		}
 
@@ -377,7 +391,6 @@ func (s *server) handlePlainHTTPRequest(req *http.Request, w http.ResponseWriter
 		w.Header().Set(headerContentEncoding, contentEncodingGzip)
 	}
 	_, err = w.Write(bodyBytes)
-
 	if err != nil {
 		s.logger.Debugf(req.Context(), "Cannot send HTTP response: %v", err)
 	}

server/serverimpl_test.go

@@ -315,6 +315,52 @@ func TestServerReceiveSendMessage(t *testing.T) {
 	assert.EqualValues(t, settings.CustomCapabilities, response.CustomCapabilities.Capabilities)
 }
 
+func TestServerReceiveSendErrorMessage(t *testing.T) {
+	var rcvMsg atomic.Value
+	type ErrorInfo struct {
+		mt      int
+		msgByte []byte
+		err     error
+	}
+	callbacks := CallbacksStruct{
+		OnConnectingFunc: func(request *http.Request) types.ConnectionResponse {
+			return types.ConnectionResponse{Accept: true, ConnectionCallbacks: ConnectionCallbacksStruct{
+				OnReadMessageErrorFunc: func(conn types.Connection, mt int, msgByte []byte, err error) {
+					rcvMsg.Store(ErrorInfo{
+						mt:      mt,
+						msgByte: msgByte,
+						err:     err,
+					})
+				},
+			}}
+		},
+	}
+
+	// Start a Server.
+	settings := &StartSettings{Settings: Settings{
+		Callbacks:          callbacks,
+		CustomCapabilities: []string{"local.test.capability"},
+	}}
+	srv := startServer(t, settings)
+	defer srv.Stop(context.Background())
+
+	// Connect using a WebSocket client.
+	conn, _, _ := dialClient(settings)
+	require.NotNil(t, conn)
+	defer conn.Close()
+
+	// Send a message to the Server.
+	err := conn.WriteMessage(websocket.TextMessage, []byte(""))
+	require.NoError(t, err)
+
+	// Wait until Server receives the message.
+	eventually(t, func() bool { return rcvMsg.Load() != nil })
+	errInfo := rcvMsg.Load().(ErrorInfo)
+	assert.EqualValues(t, websocket.TextMessage, errInfo.mt)
+	assert.EqualValues(t, []byte(""), errInfo.msgByte)
+	assert.NotNil(t, errInfo.err)
+}
+
 func TestServerReceiveSendMessageWithCompression(t *testing.T) {
 	// Use highly compressible config body.
 	uncompressedCfg := []byte(strings.Repeat("test", 10000))
@@ -620,7 +666,6 @@ func TestServerAttachSendMessagePlainHTTP(t *testing.T) {
 }
 
 func TestServerHonoursClientRequestContentEncoding(t *testing.T) {
-
 	hc := http.Client{}
 	var rcvMsg atomic.Value
 	var onConnectedCalled, onCloseCalled int32
@@ -698,7 +743,6 @@ func TestServerHonoursClientRequestContentEncoding(t *testing.T) {
 }
 
 func TestServerHonoursAcceptEncoding(t *testing.T) {
-
 	hc := http.Client{}
 	var rcvMsg atomic.Value
 	var onConnectedCalled, onCloseCalled int32
@@ -985,7 +1029,6 @@ func BenchmarkSendToClient(b *testing.B) {
 	}
 	srv := New(&sharedinternal.NopLogger{})
 	err := srv.Start(*settings)
-
 	if err != nil {
 		b.Error(err)
 	}
@@ -1017,7 +1060,6 @@ func BenchmarkSendToClient(b *testing.B) {
 
 	for _, conn := range serverConnections {
 		err := conn.Send(context.Background(), &protobufs.ServerToAgent{})
-
 		if err != nil {
 			b.Error(err)
 		}
@@ -1026,5 +1068,4 @@ func BenchmarkSendToClient(b *testing.B) {
 	for _, conn := range clientConnections {
 		conn.Close()
 	}
-
 }

server/types/callbacks.go

@@ -52,4 +52,7 @@ type ConnectionCallbacks interface {
 
 	// OnConnectionClose is called when the OpAMP connection is closed.
 	OnConnectionClose(conn Connection)
+
+	// OnConnectionError is called when an error occurs while reading or serializing a message.
+	OnReadMessageError(conn Connection, mt int, msgByte []byte, err error)
 }