[cmd/opampsupervisor] Report AvailableComponents via OpAMP supervisor (#37250)

#### Description
This feature implements support for the new AvailableComponents message
in opamp-go for the OpAMP supervisor:
open-telemetry/opamp-go#340

~~Since the AvailableComponents message has not yet been released, this
PR contains replace directives for testing purposes. This PR will not be
merged until opamp-go has been released with the new AvailableComponents
message implementation, at which point the replace directives will be
removed.~~ opamp-go v0.19.0 has been released.

This PR is one of two that make up
#37248

#### Link to tracking issue
Fixes
#37247

#### Testing
Updated unit tests
Manual end-to-end testing using the OpAMP extension and an external
OpAMP server.

#### Documentation
Updated README

---------

Co-authored-by: Daniel Jaglowski <[email protected]>

Author: mrsillydog

.chloggen/report-available-components-opamp-supervisor.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: opampsupervisor
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Support retrieval of available components via the OpAMP supervisor.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [37247]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

cmd/opampsupervisor/README.md

@@ -77,6 +77,7 @@ For a list of open issues related to the Supervisor, see [these issues](https://
 | AcceptsRestartCommand          | <https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/21077> |
 | ReportsHealth                  | ⚠️                                                                               |
 | ReportsRemoteConfig            | <https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/21079> |
+| ReportsAvailableComponents     | <https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/37247> |
 
 ### Supervisor specification features
 

cmd/opampsupervisor/e2e_test.go

@@ -598,6 +598,104 @@ func TestSupervisorBootstrapsCollector(t *testing.T) {
 	}, 5*time.Second, 250*time.Millisecond)
 }
 
+func TestSupervisorBootstrapsCollectorAvailableComponents(t *testing.T) {
+	agentDescription := atomic.Value{}
+	availableComponents := atomic.Value{}
+
+	// Load the Supervisor config so we can get the location of
+	// the Collector that will be run.
+	var cfg config.Supervisor
+	cfgFile := getSupervisorConfig(t, "reports_available_components", map[string]string{})
+	k := koanf.New("::")
+	err := k.Load(file.Provider(cfgFile.Name()), yaml.Parser())
+	require.NoError(t, err)
+	err = k.UnmarshalWithConf("", &cfg, koanf.UnmarshalConf{
+		Tag: "mapstructure",
+	})
+	require.NoError(t, err)
+
+	// Get the binary name and version from the Collector binary
+	// using the `components` command that prints a YAML-encoded
+	// map of information about the Collector build. Some of this
+	// information will be used as defaults for the telemetry
+	// attributes.
+	agentPath := cfg.Agent.Executable
+	componentsInfo, err := exec.Command(agentPath, "components").Output()
+	require.NoError(t, err)
+	k = koanf.New("::")
+	err = k.Load(rawbytes.Provider(componentsInfo), yaml.Parser())
+	require.NoError(t, err)
+	buildinfo := k.StringMap("buildinfo")
+	command := buildinfo["command"]
+	version := buildinfo["version"]
+
+	server := newOpAMPServer(
+		t,
+		defaultConnectingHandler,
+		types.ConnectionCallbacks{
+			OnMessage: func(_ context.Context, _ types.Connection, message *protobufs.AgentToServer) *protobufs.ServerToAgent {
+				if message.AgentDescription != nil {
+					agentDescription.Store(message.AgentDescription)
+				}
+
+				response := &protobufs.ServerToAgent{}
+				if message.AvailableComponents != nil {
+					availableComponents.Store(message.AvailableComponents)
+
+					if message.GetAvailableComponents().GetComponents() == nil {
+						response.Flags = uint64(protobufs.ServerToAgentFlags_ServerToAgentFlags_ReportAvailableComponents)
+					}
+				}
+
+				return response
+			},
+		})
+
+	s := newSupervisor(t, "reports_available_components", map[string]string{"url": server.addr})
+
+	require.Nil(t, s.Start())
+	defer s.Shutdown()
+
+	waitForSupervisorConnection(server.supervisorConnected, true)
+
+	require.Eventually(t, func() bool {
+		ac, ok := availableComponents.Load().(*protobufs.AvailableComponents)
+		if !ok {
+			return false
+		}
+
+		if ac.GetComponents() == nil {
+			return false
+		}
+
+		require.Len(t, ac.GetComponents(), 5) // connectors, exporters, extensions, processors, receivers
+		require.NotNil(t, ac.GetComponents()["extensions"])
+		require.NotNil(t, ac.GetComponents()["extensions"].GetSubComponentMap())
+		require.NotNil(t, ac.GetComponents()["extensions"].GetSubComponentMap()["opamp"])
+
+		ad, ok := agentDescription.Load().(*protobufs.AgentDescription)
+		if !ok {
+			return false
+		}
+
+		var agentName, agentVersion string
+		identAttr := ad.IdentifyingAttributes
+		for _, attr := range identAttr {
+			switch attr.Key {
+			case semconv.AttributeServiceName:
+				agentName = attr.Value.GetStringValue()
+			case semconv.AttributeServiceVersion:
+				agentVersion = attr.Value.GetStringValue()
+			}
+		}
+
+		// By default the Collector should report its name and version
+		// from the component.BuildInfo struct built into the Collector
+		// binary.
+		return agentName == command && agentVersion == version
+	}, 10*time.Second, 250*time.Millisecond)
+}
+
 func TestSupervisorReportsEffectiveConfig(t *testing.T) {
 	var agentConfig atomic.Value
 	server := newOpAMPServer(

cmd/opampsupervisor/supervisor/config/config.go

@@ -95,6 +95,7 @@ type Capabilities struct {
 	ReportsOwnMetrics              bool `mapstructure:"reports_own_metrics"`
 	ReportsHealth                  bool `mapstructure:"reports_health"`
 	ReportsRemoteConfig            bool `mapstructure:"reports_remote_config"`
+	ReportsAvailableComponents     bool `mapstructure:"reports_available_components"`
 }
 
 func (c Capabilities) SupportedCapabilities() protobufs.AgentCapabilities {
@@ -128,6 +129,10 @@ func (c Capabilities) SupportedCapabilities() protobufs.AgentCapabilities {
 		supportedCapabilities |= protobufs.AgentCapabilities_AgentCapabilities_AcceptsOpAMPConnectionSettings
 	}
 
+	if c.ReportsAvailableComponents {
+		supportedCapabilities |= protobufs.AgentCapabilities_AgentCapabilities_ReportsAvailableComponents
+	}
+
 	return supportedCapabilities
 }
 
@@ -245,6 +250,7 @@ func DefaultSupervisor() Supervisor {
 			ReportsOwnMetrics:              true,
 			ReportsHealth:                  true,
 			ReportsRemoteConfig:            false,
+			ReportsAvailableComponents:     false,
 		},
 		Storage: Storage{
 			Directory: defaultStorageDir,

cmd/opampsupervisor/supervisor/config/config_test.go

@@ -460,6 +460,7 @@ func TestCapabilities_SupportedCapabilities(t *testing.T) {
 				ReportsOwnMetrics:              true,
 				ReportsHealth:                  true,
 				ReportsRemoteConfig:            true,
+				ReportsAvailableComponents:     true,
 			},
 			expectedAgentCapabilities: protobufs.AgentCapabilities_AgentCapabilities_ReportsStatus |
 				protobufs.AgentCapabilities_AgentCapabilities_ReportsEffectiveConfig |
@@ -468,7 +469,8 @@ func TestCapabilities_SupportedCapabilities(t *testing.T) {
 				protobufs.AgentCapabilities_AgentCapabilities_AcceptsRemoteConfig |
 				protobufs.AgentCapabilities_AgentCapabilities_ReportsRemoteConfig |
 				protobufs.AgentCapabilities_AgentCapabilities_AcceptsRestartCommand |
-				protobufs.AgentCapabilities_AgentCapabilities_AcceptsOpAMPConnectionSettings,
+				protobufs.AgentCapabilities_AgentCapabilities_AcceptsOpAMPConnectionSettings |
+				protobufs.AgentCapabilities_AgentCapabilities_ReportsAvailableComponents,
 		},
 	}
 

cmd/opampsupervisor/supervisor/server.go

@@ -13,7 +13,7 @@ import (
 )
 
 type flattenedSettings struct {
-	onMessage         func(conn serverTypes.Connection, message *protobufs.AgentToServer)
+	onMessage         func(conn serverTypes.Connection, message *protobufs.AgentToServer) *protobufs.ServerToAgent
 	onConnecting      func(request *http.Request) (shouldConnect bool, rejectStatusCode int)
 	onConnectionClose func(conn serverTypes.Connection)
 	endpoint          string
@@ -54,7 +54,7 @@ func (fs flattenedSettings) OnConnected(_ context.Context, _ serverTypes.Connect
 
 func (fs flattenedSettings) OnMessage(_ context.Context, conn serverTypes.Connection, message *protobufs.AgentToServer) *protobufs.ServerToAgent {
 	if fs.onMessage != nil {
-		fs.onMessage(conn, message)
+		return fs.onMessage(conn, message)
 	}
 
 	return &protobufs.ServerToAgent{}

cmd/opampsupervisor/supervisor/server_test.go

@@ -60,8 +60,9 @@ func Test_flattenedSettings_OnConnecting(t *testing.T) {
 func Test_flattenedSettings_OnMessage(t *testing.T) {
 	onMessageFuncCalled := false
 	fs := flattenedSettings{
-		onMessage: func(_ serverTypes.Connection, _ *protobufs.AgentToServer) {
+		onMessage: func(_ serverTypes.Connection, _ *protobufs.AgentToServer) *protobufs.ServerToAgent {
 			onMessageFuncCalled = true
+			return &protobufs.ServerToAgent{}
 		},
 	}
 

cmd/opampsupervisor/supervisor/supervisor.go

@@ -103,7 +103,8 @@ type Supervisor struct {
 	// Supervisor's own config.
 	config config.Supervisor
 
-	agentDescription *atomic.Value
+	agentDescription    *atomic.Value
+	availableComponents *atomic.Value
 
 	// Supervisor's persistent state
 	persistentState *persistentState
@@ -174,6 +175,7 @@ func NewSupervisor(logger *zap.Logger, cfg config.Supervisor) (*Supervisor, erro
 		cfgState:                     &atomic.Value{},
 		effectiveConfig:              &atomic.Value{},
 		agentDescription:             &atomic.Value{},
+		availableComponents:          &atomic.Value{},
 		doneChan:                     make(chan struct{}),
 		customMessageToServer:        make(chan *protobufs.CustomMessage, maxBufferedCustomMessages),
 		agentConn:                    &atomic.Value{},
@@ -300,16 +302,22 @@ func (s *Supervisor) getBootstrapInfo() (err error) {
 
 	done := make(chan error, 1)
 	var connected atomic.Bool
+	var doneReported atomic.Bool
 
 	// Start a one-shot server to get the Collector's agent description
-	// using the Collector's OpAMP extension.
+	// and available components using the Collector's OpAMP extension.
 	err = srv.Start(flattenedSettings{
 		endpoint: fmt.Sprintf("localhost:%d", s.opampServerPort),
 		onConnecting: func(_ *http.Request) (bool, int) {
 			connected.Store(true)
 			return true, http.StatusOK
 		},
-		onMessage: func(_ serverTypes.Connection, message *protobufs.AgentToServer) {
+		onMessage: func(_ serverTypes.Connection, message *protobufs.AgentToServer) *protobufs.ServerToAgent {
+			response := &protobufs.ServerToAgent{}
+			if message.GetAvailableComponents() != nil {
+				s.setAvailableComponents(message.AvailableComponents)
+			}
+
 			if message.AgentDescription != nil {
 				instanceIDSeen := false
 				s.setAgentDescription(message.AgentDescription)
@@ -324,19 +332,47 @@ func (s *Supervisor) getBootstrapInfo() (err error) {
 								"the Collector's instance ID (%s) does not match with the instance ID set by the Supervisor (%s)",
 								attr.Value.GetStringValue(),
 								s.persistentState.InstanceID.String())
-							return
+							return response
 						}
 						instanceIDSeen = true
 					}
 				}
 
 				if !instanceIDSeen {
 					done <- errors.New("the Collector did not specify an instance ID in its AgentDescription message")
-					return
+					return response
 				}
+			}
+
+			// agent description must be defined
+			_, ok := s.agentDescription.Load().(*protobufs.AgentDescription)
+			if !ok {
+				return response
+			}
+
+			// if available components have not been reported, agent description is sufficient to continue
+			availableComponents, availableComponentsOk := s.availableComponents.Load().(*protobufs.AvailableComponents)
+			if availableComponentsOk {
+				// must have a full list of components if available components have been reported
+				if availableComponents.GetComponents() != nil {
+					if !doneReported.Load() {
+						done <- nil
+						doneReported.Store(true)
+					}
+				} else {
+					// if we don't have a full component list, ask for it
+					response.Flags = uint64(protobufs.ServerToAgentFlags_ServerToAgentFlags_ReportAvailableComponents)
+				}
+				return response
+			}
 
+			// need to only report done once, not on each message - otherwise, we get a hung thread
+			if !doneReported.Load() {
 				done <- nil
+				doneReported.Store(true)
 			}
+
+			return response
 		},
 	}.toServerSettings())
 	if err != nil {
@@ -456,6 +492,12 @@ func (s *Supervisor) startOpAMPClient() error {
 		return err
 	}
 
+	if ac, ok := s.availableComponents.Load().(*protobufs.AvailableComponents); ok && ac != nil {
+		if err = s.opampClient.SetAvailableComponents(ac); err != nil {
+			return err
+		}
+	}
+
 	s.logger.Debug("Starting OpAMP client...")
 	if err = s.opampClient.Start(context.Background(), settings); err != nil {
 		return err
@@ -505,7 +547,7 @@ func (s *Supervisor) startOpAMPServer() error {
 	return nil
 }
 
-func (s *Supervisor) handleAgentOpAMPMessage(conn serverTypes.Connection, message *protobufs.AgentToServer) {
+func (s *Supervisor) handleAgentOpAMPMessage(conn serverTypes.Connection, message *protobufs.AgentToServer) *protobufs.ServerToAgent {
 	s.agentConn.Store(conn)
 
 	s.logger.Debug("Received OpAMP message from the agent")
@@ -551,6 +593,8 @@ func (s *Supervisor) handleAgentOpAMPMessage(conn serverTypes.Connection, messag
 		s.logger.Debug("Received health status from agent", zap.Bool("healthy", message.Health.Healthy))
 		s.lastHealthFromClient = message.Health
 	}
+
+	return &protobufs.ServerToAgent{}
 }
 
 func (s *Supervisor) forwardCustomMessagesToServerLoop() {
@@ -584,6 +628,11 @@ func (s *Supervisor) setAgentDescription(ad *protobufs.AgentDescription) {
 	s.agentDescription.Store(ad)
 }
 
+// setAvailableComponents sets the available components of the OpAMP agent
+func (s *Supervisor) setAvailableComponents(ac *protobufs.AvailableComponents) {
+	s.availableComponents.Store(ac)
+}
+
 // applyKeyValueOverrides merges the overrides map into the array of key value pairs.
 // If a key from overrides already exists in the array of key value pairs, it is overwritten by the value from the overrides map.
 // An array of KeyValue pair is returned, with each key value pair having a distinct key.
@@ -766,10 +815,11 @@ func (s *Supervisor) composeOpAMPExtensionConfig() []byte {
 
 	var cfg bytes.Buffer
 	tplVars := map[string]any{
-		"InstanceUid":      s.persistentState.InstanceID.String(),
-		"SupervisorPort":   s.opampServerPort,
-		"PID":              s.pidProvider.PID(),
-		"PPIDPollInterval": orphanPollInterval,
+		"InstanceUid":                s.persistentState.InstanceID.String(),
+		"SupervisorPort":             s.opampServerPort,
+		"PID":                        s.pidProvider.PID(),
+		"PPIDPollInterval":           orphanPollInterval,
+		"ReportsAvailableComponents": s.config.Capabilities.ReportsAvailableComponents,
 	}
 	err := s.opampextensionTemplate.Execute(
 		&cfg,
@@ -1020,7 +1070,7 @@ func (s *Supervisor) startAgent() (agentStartStatus, error) {
 	err := s.commander.Start(context.Background())
 	if err != nil {
 		s.logger.Error("Cannot start the agent", zap.Error(err))
-		startErr := fmt.Errorf("Cannot start the agent: %w", err)
+		startErr := fmt.Errorf("cannot start the agent: %w", err)
 		err = s.opampClient.SetHealth(&protobufs.ComponentHealth{Healthy: false, LastError: startErr.Error()})
 		if err != nil {
 			s.logger.Error("Failed to report OpAMP client health", zap.Error(err))