Add ability to specify Client capabilities (#106)

Resolves #98

client/clientimpl_test.go

@@ -332,6 +332,7 @@ func TestFirstStatusReport(t *testing.T) {
 					atomic.AddInt64(&remoteConfigReceived, 1)
 				},
 			},
+			Capabilities: protobufs.AgentCapabilities_AcceptsRemoteConfig,
 		}
 		settings.OpAMPServerURL = "ws://" + srv.Endpoint
 		startClient(t, settings, client)
@@ -430,6 +431,7 @@ func TestSetEffectiveConfig(t *testing.T) {
 					return sendConfig, nil
 				},
 			},
+			Capabilities: protobufs.AgentCapabilities_ReportsEffectiveConfig,
 		}
 		settings.OpAMPServerURL = "ws://" + srv.Endpoint
 		prepareClient(t, &settings, client)
@@ -655,6 +657,11 @@ func TestConnectionSettings(t *testing.T) {
 					return nil
 				},
 			},
+			Capabilities: protobufs.AgentCapabilities_ReportsOwnTraces |
+				protobufs.AgentCapabilities_ReportsOwnMetrics |
+				protobufs.AgentCapabilities_ReportsOwnLogs |
+				protobufs.AgentCapabilities_AcceptsOtherConnectionSettings |
+				protobufs.AgentCapabilities_AcceptsOpAMPConnectionSettings,
 		}
 		settings.OpAMPServerURL = "ws://" + srv.Endpoint
 		prepareClient(t, &settings, client)
@@ -685,6 +692,7 @@ func TestReportAgentDescription(t *testing.T) {
 		// Start a client.
 		settings := types.StartSettings{
 			OpAMPServerURL: "ws://" + srv.Endpoint,
+			Capabilities:   protobufs.AgentCapabilities_ReportsEffectiveConfig,
 		}
 		prepareClient(t, &settings, client)
 
@@ -747,6 +755,7 @@ func TestReportAgentHealth(t *testing.T) {
 		// Start a client.
 		settings := types.StartSettings{
 			OpAMPServerURL: "ws://" + srv.Endpoint,
+			Capabilities:   protobufs.AgentCapabilities_ReportsEffectiveConfig | protobufs.AgentCapabilities_ReportsHealth,
 		}
 		prepareClient(t, &settings, client)
 
@@ -906,6 +915,7 @@ func verifyRemoteConfigUpdate(t *testing.T, successCase bool, expectStatus *prot
 					}
 				},
 			},
+			Capabilities: protobufs.AgentCapabilities_AcceptsRemoteConfig,
 		}
 		prepareClient(t, &settings, client)
 
@@ -1056,6 +1066,7 @@ func verifyUpdatePackages(t *testing.T, testCase packageTestCase) {
 				OnMessageFunc: onMessageFunc,
 			},
 			PackagesStateProvider: localPackageState,
+			Capabilities:          protobufs.AgentCapabilities_AcceptsPackages | protobufs.AgentCapabilities_ReportsPackageStatuses,
 		}
 		prepareClient(t, &settings, client)
 
@@ -1257,3 +1268,112 @@ func TestUpdatePackages(t *testing.T) {
 		})
 	}
 }
+
+func TestMissingCapabilities(t *testing.T) {
+	testClients(t, func(t *testing.T, client OpAMPClient) {
+		// Start a server.
+		srv := internal.StartMockServer(t)
+		srv.EnableExpectMode()
+
+		// Start a client.
+		settings := types.StartSettings{
+			Callbacks: types.CallbacksStruct{
+				OnMessageFunc: func(ctx context.Context, msg *types.MessageData) {
+					// These fields must not be set since we did not define the capabilities to accept them.
+					assert.Nil(t, msg.RemoteConfig)
+					assert.Nil(t, msg.OwnLogsConnSettings)
+					assert.Nil(t, msg.OwnMetricsConnSettings)
+					assert.Nil(t, msg.OwnTracesConnSettings)
+					assert.Nil(t, msg.OtherConnSettings)
+					assert.Nil(t, msg.PackagesAvailable)
+				},
+				OnOpampConnectionSettingsFunc: func(
+					ctx context.Context, settings *protobufs.OpAMPConnectionSettings,
+				) error {
+					assert.Fail(t, "should not be called since capability is not set to accept it")
+					return nil
+				},
+			},
+		}
+		settings.OpAMPServerURL = "ws://" + srv.Endpoint
+		prepareClient(t, &settings, client)
+
+		require.NoError(t, client.Start(context.Background(), settings))
+
+		// Change the config.
+		err := client.UpdateEffectiveConfig(context.Background())
+
+		assert.ErrorIs(t, err, internal.ErrReportsEffectiveConfigNotSet)
+
+		remoteCfg := createRemoteConfig()
+		// ---> Server
+		srv.Expect(func(msg *protobufs.AgentToServer) *protobufs.ServerToAgent {
+			opampSettings := &protobufs.OpAMPConnectionSettings{DestinationEndpoint: "http://opamp.com"}
+			metricsSettings := &protobufs.TelemetryConnectionSettings{DestinationEndpoint: "http://metrics.com"}
+			tracesSettings := &protobufs.TelemetryConnectionSettings{DestinationEndpoint: "http://traces.com"}
+			logsSettings := &protobufs.TelemetryConnectionSettings{DestinationEndpoint: "http://logs.com"}
+			otherSettings := &protobufs.OtherConnectionSettings{DestinationEndpoint: "http://other.com"}
+			hash := []byte{1, 2, 3}
+
+			return &protobufs.ServerToAgent{
+				InstanceUid:  msg.InstanceUid,
+				RemoteConfig: remoteCfg,
+				ConnectionSettings: &protobufs.ConnectionSettingsOffers{
+					Hash:       hash,
+					Opamp:      opampSettings,
+					OwnMetrics: metricsSettings,
+					OwnTraces:  tracesSettings,
+					OwnLogs:    logsSettings,
+					OtherConnections: map[string]*protobufs.OtherConnectionSettings{
+						"other": otherSettings,
+					},
+				},
+				PackagesAvailable: &protobufs.PackagesAvailable{
+					Packages:        map[string]*protobufs.PackageAvailable{},
+					AllPackagesHash: []byte{1, 2, 3, 4, 5},
+				},
+			}
+		})
+
+		// Shutdown the Server.
+		srv.Close()
+
+		// Shutdown the client.
+		err = client.Stop(context.Background())
+		assert.NoError(t, err)
+	})
+}
+
+func TestMissingPackagesStateProvider(t *testing.T) {
+	testClients(t, func(t *testing.T, client OpAMPClient) {
+		// Start a client.
+		settings := types.StartSettings{
+			Callbacks:    types.CallbacksStruct{},
+			Capabilities: protobufs.AgentCapabilities_AcceptsPackages | protobufs.AgentCapabilities_ReportsPackageStatuses,
+		}
+		prepareClient(t, &settings, client)
+
+		assert.ErrorIs(t, client.Start(context.Background(), settings), internal.ErrPackagesStateProviderNotSet)
+
+		// Start a client.
+		localPackageState := internal.NewInMemPackagesStore()
+		settings = types.StartSettings{
+			Callbacks:             types.CallbacksStruct{},
+			PackagesStateProvider: localPackageState,
+			Capabilities:          protobufs.AgentCapabilities_AcceptsPackages,
+		}
+		prepareClient(t, &settings, client)
+
+		assert.ErrorIs(t, client.Start(context.Background(), settings), internal.ErrAcceptsPackagesNotSet)
+
+		// Start a client.
+		settings = types.StartSettings{
+			Callbacks:             types.CallbacksStruct{},
+			PackagesStateProvider: localPackageState,
+			Capabilities:          protobufs.AgentCapabilities_ReportsPackageStatuses,
+		}
+		prepareClient(t, &settings, client)
+
+		assert.ErrorIs(t, client.Start(context.Background(), settings), internal.ErrAcceptsPackagesNotSet)
+	})
+}

client/httpclient.go

@@ -94,5 +94,6 @@ func (c *httpClient) runUntilStopped(ctx context.Context) {
 		c.common.Callbacks,
 		&c.common.ClientSyncedState,
 		c.common.PackagesStateProvider,
+		c.common.Capabilities,
 	)
 }

client/internal/clientcommon.go

@@ -15,9 +15,13 @@ var (
 	ErrAgentDescriptionMissing      = errors.New("AgentDescription is nil")
 	ErrAgentDescriptionNoAttributes = errors.New("AgentDescription has no attributes defined")
 	ErrAgentHealthMissing           = errors.New("AgentHealth is nil")
+	ErrReportsEffectiveConfigNotSet = errors.New("ReportsEffectiveConfig capability is not set")
+	ErrPackagesStateProviderNotSet  = errors.New("PackagesStateProvider must be set")
+	ErrAcceptsPackagesNotSet        = errors.New("AcceptsPackages and ReportsPackageStatuses must be set")
 
-	errAlreadyStarted       = errors.New("already started")
-	errCannotStopNotStarted = errors.New("cannot stop because not started")
+	errAlreadyStarted               = errors.New("already started")
+	errCannotStopNotStarted         = errors.New("cannot stop because not started")
+	errReportsPackageStatusesNotSet = errors.New("ReportsPackageStatuses capability is not set")
 )
 
 // ClientCommon contains the OpAMP logic that is common between WebSocket and
@@ -26,6 +30,9 @@ type ClientCommon struct {
 	Logger    types.Logger
 	Callbacks types.Callbacks
 
+	// Agent's capabilities defined at Start() time.
+	Capabilities protobufs.AgentCapabilities
+
 	// Client state storage. This is needed if the Server asks to report the state.
 	ClientSyncedState ClientSyncedState
 
@@ -62,10 +69,19 @@ func (c *ClientCommon) PrepareStart(
 		return errAlreadyStarted
 	}
 
+	c.Capabilities = settings.Capabilities
+
+	// According to OpAMP spec this capability MUST be set, since all Agents MUST report status.
+	c.Capabilities |= protobufs.AgentCapabilities_ReportsStatus
+
 	if c.ClientSyncedState.AgentDescription() == nil {
 		return ErrAgentDescriptionMissing
 	}
 
+	if c.Capabilities&protobufs.AgentCapabilities_ReportsHealth != 0 && c.ClientSyncedState.Health() == nil {
+		return ErrAgentHealthMissing
+	}
+
 	// Prepare remote config status.
 	if settings.RemoteConfigStatus == nil {
 		// RemoteConfigStatus is not provided. Start with empty.
@@ -82,12 +98,22 @@ func (c *ClientCommon) PrepareStart(
 	c.PackagesStateProvider = settings.PackagesStateProvider
 	var packageStatuses *protobufs.PackageStatuses
 	if settings.PackagesStateProvider != nil {
+		if c.Capabilities&protobufs.AgentCapabilities_AcceptsPackages == 0 ||
+			c.Capabilities&protobufs.AgentCapabilities_ReportsPackageStatuses == 0 {
+			return ErrAcceptsPackagesNotSet
+		}
+
 		// Set package status from the value previously saved in the PackagesStateProvider.
 		var err error
 		packageStatuses, err = settings.PackagesStateProvider.LastReportedStatuses()
 		if err != nil {
 			return err
 		}
+	} else {
+		if c.Capabilities&protobufs.AgentCapabilities_AcceptsPackages != 0 ||
+			c.Capabilities&protobufs.AgentCapabilities_ReportsPackageStatuses != 0 {
+			return ErrPackagesStateProviderNotSet
+		}
 	}
 
 	if packageStatuses == nil {
@@ -234,6 +260,10 @@ func (c *ClientCommon) SetHealth(health *protobufs.AgentHealth) error {
 // UpdateEffectiveConfig fetches the current local effective config using
 // GetEffectiveConfig callback and sends it to the Server using provided Sender.
 func (c *ClientCommon) UpdateEffectiveConfig(ctx context.Context) error {
+	if c.Capabilities&protobufs.AgentCapabilities_ReportsEffectiveConfig == 0 {
+		return ErrReportsEffectiveConfigNotSet
+	}
+
 	// Fetch the locally stored config.
 	cfg, err := c.Callbacks.GetEffectiveConfig(ctx)
 	if err != nil {
@@ -284,6 +314,10 @@ func (c *ClientCommon) SetRemoteConfigStatus(status *protobufs.RemoteConfigStatu
 }
 
 func (c *ClientCommon) SetPackageStatuses(statuses *protobufs.PackageStatuses) error {
+	if c.Capabilities&protobufs.AgentCapabilities_ReportsPackageStatuses == 0 {
+		return errReportsPackageStatusesNotSet
+	}
+
 	if statuses.ServerProvidedAllPackagesHash == nil {
 		return errServerProvidedAllPackagesHashNil
 	}

client/internal/httpsender.go

@@ -65,10 +65,11 @@ func (h *HTTPSender) Run(
 	callbacks types.Callbacks,
 	clientSyncedState *ClientSyncedState,
 	packagesStateProvider types.PackagesStateProvider,
+	capabilities protobufs.AgentCapabilities,
 ) {
 	h.url = url
 	h.callbacks = callbacks
-	h.receiveProcessor = newReceivedProcessor(h.logger, callbacks, h, clientSyncedState, packagesStateProvider)
+	h.receiveProcessor = newReceivedProcessor(h.logger, callbacks, h, clientSyncedState, packagesStateProvider, capabilities)
 
 	for {
 		pollingTimer := time.NewTimer(time.Millisecond * time.Duration(atomic.LoadInt64(&h.pollingIntervalMs)))