[extension/opampextension]: Adding AcceptsRestartCommand capability

.chloggen/opamp-extension-accepts-remote-config.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. receiver/filelog)
+component: extension/opamp
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: This change adds support for the OpAMP AcceptsRemoteConfig capability. This capability has been implemented in the OpAMP supervisor, but this adds functionality to the extension which sends the SIGHUP signal to restart the collector which will reload the config on startup.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [45056]
+
+# (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: [user]

extension/opampextension/README.md

@@ -47,6 +47,7 @@ The following settings are optional for both transports:
   - `reports_effective_config`: Whether to enable the OpAMP ReportsEffectiveConfig capability. Default is `true`.
   - `reports_health`: Whether to enable the OpAMP ReportsHealth capability. Default is `true`.
   - `reports_available_components`: Whether to enable the OpAMP ReportsAvailableComponents capability. Default is `true`.
+  - `accepts_remote_config`: Whether to enable the OpAMP AcceptsRemoteConfig capability. Default is `false`. The extension sends a `SIGHUP` signal to the collector to initiate a restart in order to reload the updated remote config.
 - `agent_description`: Setting that modifies the agent description reported to the OpAMP server.
   - `include_resource_attributes`: Copy the Collector's resource attributes into the set of non-identifying attributes in the agent description.
   - `non_identifying_attributes`: A map of key value pairs that will be added to the [non-identifying attributes](https://github.com/open-telemetry/opamp-spec/blob/main/specification.md#agentdescriptionnon_identifying_attributes) reported to the OpAMP server. If an attribute collides with the default non-identifying attributes that are automatically added, the ones specified here take precedence.

extension/opampextension/config.go

@@ -64,6 +64,8 @@ type Capabilities struct {
 	ReportsHealth bool `mapstructure:"reports_health"`
 	// ReportsAvailableComponents enables the OpAMP ReportsAvailableComponents Capability (default: true)
 	ReportsAvailableComponents bool `mapstructure:"reports_available_components"`
+	// AcceptsRemoteConfig enables the OpAMP AcceptsRemoteConfig Capability (default: false)
+	AcceptsRemoteConfig bool `mapstructure:"accepts_remote_config"`
 }
 
 func (caps Capabilities) toAgentCapabilities() protobufs.AgentCapabilities {
@@ -76,10 +78,12 @@ func (caps Capabilities) toAgentCapabilities() protobufs.AgentCapabilities {
 	if caps.ReportsHealth {
 		agentCapabilities |= protobufs.AgentCapabilities_AgentCapabilities_ReportsHealth
 	}
-
 	if caps.ReportsAvailableComponents {
 		agentCapabilities |= protobufs.AgentCapabilities_AgentCapabilities_ReportsAvailableComponents
 	}
+	if caps.AcceptsRemoteConfig {
+		agentCapabilities |= protobufs.AgentCapabilities_AgentCapabilities_AcceptsRemoteConfig
+	}
 
 	return agentCapabilities
 }

extension/opampextension/factory.go

@@ -29,6 +29,7 @@ func createDefaultConfig() component.Config {
 			ReportsEffectiveConfig:     true,
 			ReportsHealth:              true,
 			ReportsAvailableComponents: true,
+			AcceptsRemoteConfig:        false,
 		},
 		PPIDPollInterval: 5 * time.Second,
 	}

extension/opampextension/opamp_agent.go

@@ -15,6 +15,7 @@ import (
 	"sort"
 	"strings"
 	"sync"
+	"syscall"
 
 	"github.com/google/uuid"
 	"github.com/oklog/ulid/v2"
@@ -464,6 +465,12 @@ func (o *opampAgent) onMessage(_ context.Context, msg *types.MessageData) {
 	if msg.CustomMessage != nil {
 		o.customCapabilityRegistry.ProcessMessage(msg.CustomMessage)
 	}
+	if msg.RemoteConfig != nil {
+		o.logger.Info("received remote config — sending SIGHUP to reload")
+		if err := syscall.Kill(os.Getpid(), syscall.SIGHUP); err != nil {
+			o.logger.Error("sending sighup signal", zap.Error(err))
+		}
+	}
 }
 
 func (o *opampAgent) setHealth(ch *protobufs.ComponentHealth) {

extension/opampextension/opamp_agent_test.go

@@ -6,13 +6,16 @@
 import (
 	"context"
 	"errors"
+	"go.uber.org/zap/zaptest"
 	"os"
+	"os/signal"
 	"path/filepath"
 	"runtime"
 	"sync"
+	"syscall"
 	"testing"
 	"time"
 
 	"github.com/google/uuid"
 	"github.com/open-telemetry/opamp-go/client/types"
 	"github.com/open-telemetry/opamp-go/protobufs"
@@ -775,6 +778,58 @@
 	})
 }
 
+func TestOpAMPAgent_onMessage(t *testing.T) {
+	t.Run("happy path - SIGHUP signal", func(t *testing.T) {
+		agent := opampAgent{
+			logger: zaptest.NewLogger(t),
+		}
+
+		ctx, cancel := context.WithCancel(context.Background())
+		t.Cleanup(cancel)
+
+		sighupReceived := make(chan bool, 1)
+		setupSignalHandler(t, ctx, func() {
+			sighupReceived <- true
+		})
+
+		agent.onMessage(ctx, &types.MessageData{
+			RemoteConfig: &protobufs.AgentRemoteConfig{},
+		})
+
+		select {
+		case <-sighupReceived:
+			// Success
+		case <-time.After(500 * time.Millisecond):
+			t.Error("Timed out waiting for SIGHUP reload")
+		}
+	})
+}
+
+func setupSignalHandler(t testing.TB, ctx context.Context, signalCallback func()) {
+	t.Helper()
+
+	sigChan := make(chan os.Signal, 1)
+	// Notify sigChan when SIGHUP is received
+	signal.Notify(sigChan, syscall.SIGHUP)
+
+	go func() {
+		t.Cleanup(func() {
+			signal.Stop(sigChan)
+		})
+
+		for {
+			select {
+			case sig := <-sigChan:
+				if sig == syscall.SIGHUP {
+					signalCallback()
+				}
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+}
+
 type mockStatusAggregator struct {
 	statusChan     chan *status.AggregateStatus
 	receivedEvents []eventSourcePair