Support SIGHUP configuration reloading (#6000)

* SIGHUP configuration reload

Signed-off-by: Sean Porter <portertech@gmail.com>

* basic SIGHUP reload signal test

Signed-off-by: Sean Porter <portertech@gmail.com>

* always notify with SIGHUP for configuration reloading

Signed-off-by: Sean Porter <portertech@gmail.com>

* sighup reload changelog entry

Signed-off-by: Sean Porter <portertech@gmail.com>

Signed-off-by: Sean Porter <portertech@gmail.com>

.chloggen/sighup-configuration-reloading.yaml

@@ -0,0 +1,16 @@
+# 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. otlpreceiver)
+component: service/collector
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Support SIGHUP configuration reloading"
+
+# One or more tracking issues or pull requests related to the change
+issues: [5966]
+
+# (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:

service/collector.go

@@ -158,6 +158,21 @@ func (col *Collector) setupConfigurationComponents(ctx context.Context) error {
 	return nil
 }
 
+func (col *Collector) reloadConfiguration(ctx context.Context) error {
+	col.service.telemetrySettings.Logger.Warn("Config updated, restart service")
+	col.setCollectorState(Closing)
+
+	if err := col.service.Shutdown(ctx); err != nil {
+		return fmt.Errorf("failed to shutdown the retiring config: %w", err)
+	}
+
+	if err := col.setupConfigurationComponents(ctx); err != nil {
+		return fmt.Errorf("failed to setup configuration components: %w", err)
+	}
+
+	return nil
+}
+
 // Run starts the collector according to the given configuration, and waits for it to complete.
 // Consecutive calls to Run are not allowed, Run shouldn't be called once a collector is shut down.
 func (col *Collector) Run(ctx context.Context) error {
@@ -166,6 +181,9 @@ func (col *Collector) Run(ctx context.Context) error {
 		return err
 	}
 
+	// Always notify with SIGHUP for configuration reloading.
+	signal.Notify(col.signalsChannel, syscall.SIGHUP)
+
 	// Only notify with SIGTERM and SIGINT if graceful shutdown is enabled.
 	if !col.set.DisableGracefulShutdown {
 		signal.Notify(col.signalsChannel, os.Interrupt, syscall.SIGTERM)
@@ -180,21 +198,22 @@ LOOP:
 				break LOOP
 			}
 
-			col.service.telemetrySettings.Logger.Warn("Config updated, restart service")
-			col.setCollectorState(Closing)
-
-			if err = col.service.Shutdown(ctx); err != nil {
-				return fmt.Errorf("failed to shutdown the retiring config: %w", err)
-			}
-			if err = col.setupConfigurationComponents(ctx); err != nil {
-				return fmt.Errorf("failed to setup configuration components: %w", err)
+			if err = col.reloadConfiguration(ctx); err != nil {
+				return err
 			}
 		case err := <-col.asyncErrorChannel:
 			col.service.telemetrySettings.Logger.Error("Asynchronous error received, terminating process", zap.Error(err))
 			break LOOP
 		case s := <-col.signalsChannel:
 			col.service.telemetrySettings.Logger.Info("Received signal from OS", zap.String("signal", s.String()))
-			break LOOP
+			switch s {
+			case syscall.SIGHUP:
+				if err := col.reloadConfiguration(ctx); err != nil {
+					return err
+				}
+			default:
+				break LOOP
+			}
 		case <-col.shutdownChan:
 			col.service.telemetrySettings.Logger.Info("Received shutdown request")
 			break LOOP

service/collector_test.go

@@ -197,6 +197,12 @@ func TestCollectorSendSignal(t *testing.T) {
 		return Running == col.GetState()
 	}, 2*time.Second, 200*time.Millisecond)
 
+	col.signalsChannel <- syscall.SIGHUP
+
+	assert.Eventually(t, func() bool {
+		return Running == col.GetState()
+	}, 2*time.Second, 200*time.Millisecond)
+
 	col.signalsChannel <- syscall.SIGTERM
 
 	wg.Wait()