Function Example_logging

mcp/server_example_test.go:90–145

!-prompts !+logging

()

// !+logging

func Example_logging() {
	ctx := context.Background()

	// Create a server.
	s := mcp.NewServer(&mcp.Implementation{Name: "server", Version: "v0.0.1"}, nil)

	// Create a client that displays log messages.
	done := make(chan struct{}) // solely for the example
	var nmsgs atomic.Int32
	c := mcp.NewClient(
		&mcp.Implementation{Name: "client", Version: "v0.0.1"},
		&mcp.ClientOptions{
			LoggingMessageHandler: func(_ context.Context, r *mcp.LoggingMessageRequest) {
				m := r.Params.Data.(map[string]any)
				fmt.Println(m["msg"], m["value"])
				if nmsgs.Add(1) == 2 { // number depends on logger calls below
					close(done)
				}
			},
		})

	// Connect the server and client.
	t1, t2 := mcp.NewInMemoryTransports()
	ss, err := s.Connect(ctx, t1, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer ss.Close()
	cs, err := c.Connect(ctx, t2, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer cs.Close()

	// Set the minimum log level to "info".
	if err := cs.SetLoggingLevel(ctx, &mcp.SetLoggingLevelParams{Level: "info"}); err != nil {
		log.Fatal(err)
	}

	// Get a slog.Logger for the server session.
	logger := slog.New(mcp.NewLoggingHandler(ss, nil))

	// Log some things.
	logger.Info("info shows up", "value", 1)
	logger.Debug("debug doesn't show up", "value", 2)
	logger.Warn("warn shows up", "value", 3)

	// Wait for them to arrive on the client.
	// In a real application, the log messages would appear asynchronously
	// while other work was happening.
	<-done

	// Output:
	// info shows up 1
	// warn shows up 3
}

// !-logging