feat(supervisor): optional idle shutdown

Makefile

@@ -33,6 +33,7 @@ API_DISABLE_HEALTH_CHECK_ROUTE_TELEMETRY=false
 API_ENABLE_DEBUG_ROUTE=false
 CHROMIUM_RESTART_AFTER=100
 CHROMIUM_MAX_QUEUE_SIZE=0
+CHROMIUM_IDLE_SHUTDOWN_TIMEOUT=0
 CHROMIUM_MAX_CONCURRENCY=6
 CHROMIUM_AUTO_START=false
 CHROMIUM_START_TIMEOUT=20s
@@ -50,6 +51,7 @@ CHROMIUM_DISABLE_JAVASCRIPT=false
 CHROMIUM_DISABLE_ROUTES=false
 LIBREOFFICE_RESTART_AFTER=10
 LIBREOFFICE_MAX_QUEUE_SIZE=0
+LIBREOFFICE_IDLE_SHUTDOWN_TIMEOUT=0
 LIBREOFFICE_AUTO_START=false
 LIBREOFFICE_START_TIMEOUT=20s
 LIBREOFFICE_DISABLE_ROUTES=false

compose.yaml

@@ -36,6 +36,7 @@ services:
       - "--chromium-restart-after=${CHROMIUM_RESTART_AFTER}"
       - "--chromium-auto-start=${CHROMIUM_AUTO_START}"
       - "--chromium-max-queue-size=${CHROMIUM_MAX_QUEUE_SIZE}"
+      - "--chromium-idle-shutdown-timeout=${CHROMIUM_IDLE_SHUTDOWN_TIMEOUT}"
       - "--chromium-max-concurrency=${CHROMIUM_MAX_CONCURRENCY}"
       - "--chromium-start-timeout=${CHROMIUM_START_TIMEOUT}"
       - "--chromium-allow-insecure-localhost=${CHROMIUM_ALLOW_INSECURE_LOCALHOST}"
@@ -52,6 +53,7 @@ services:
       - "--chromium-disable-routes=${CHROMIUM_DISABLE_ROUTES}"
       - "--libreoffice-restart-after=${LIBREOFFICE_RESTART_AFTER}"
       - "--libreoffice-max-queue-size=${LIBREOFFICE_MAX_QUEUE_SIZE}"
+      - "--libreoffice-idle-shutdown-timeout=${LIBREOFFICE_IDLE_SHUTDOWN_TIMEOUT}"
       - "--libreoffice-auto-start=${LIBREOFFICE_AUTO_START}"
       - "--libreoffice-start-timeout=${LIBREOFFICE_START_TIMEOUT}"
       - "--libreoffice-disable-routes=${LIBREOFFICE_DISABLE_ROUTES}"

pkg/gotenberg/supervisor.go

@@ -91,28 +91,33 @@ type processSupervisor struct {
 	// via firstStartOnce. Subsequent callers that enter the !firstStart block
 	// need to observe this value after the Once has completed, without
 	// re-executing the closure.
-	firstStartErr   error
-	reqCounter      atomic.Int64
-	reqQueueSize    atomic.Int64
-	restartsCounter atomic.Int64
-	isRestarting    atomic.Bool
-	activeTasks     atomic.Int64
-	restartMutex    sync.Mutex
+	firstStartErr       error
+	reqCounter          atomic.Int64
+	reqQueueSize        atomic.Int64
+	restartsCounter     atomic.Int64
+	isRestarting        atomic.Bool
+	activeTasks         atomic.Int64
+	restartMutex        sync.Mutex
+	idleShutdownTimeout time.Duration
+	lastActivity        atomic.Int64  // unix nano timestamp of last completed task
+	idleMu              sync.Mutex    // protects idleStopChan
+	idleStopChan        chan struct{} // signal to stop the idle ticker goroutine
 }
 
 // NewProcessSupervisor initializes a new [ProcessSupervisor].
-func NewProcessSupervisor(logger *slog.Logger, process Process, maxReqLimit, maxQueueSize, maxConcurrency int64) ProcessSupervisor {
+func NewProcessSupervisor(logger *slog.Logger, process Process, maxReqLimit, maxQueueSize, maxConcurrency int64, idleShutdownTimeout time.Duration) ProcessSupervisor {
 	if maxConcurrency < 1 {
 		maxConcurrency = 1
 	}
 
 	b := &processSupervisor{
-		logger:         logger,
-		process:        process,
-		semaphore:      make(chan struct{}, maxConcurrency),
-		maxReqLimit:    maxReqLimit,
-		maxQueueSize:   maxQueueSize,
-		maxConcurrency: maxConcurrency,
+		logger:              logger,
+		process:             process,
+		semaphore:           make(chan struct{}, maxConcurrency),
+		maxReqLimit:         maxReqLimit,
+		maxQueueSize:        maxQueueSize,
+		maxConcurrency:      maxConcurrency,
+		idleShutdownTimeout: idleShutdownTimeout,
 	}
 	b.reqCounter.Store(0)
 	b.reqQueueSize.Store(0)
@@ -131,6 +136,12 @@ func (s *processSupervisor) Launch() error {
 	}
 
 	s.firstStart.Store(true)
+
+	if s.idleShutdownTimeout > 0 {
+		s.lastActivity.Store(time.Now().UnixNano())
+		s.startIdleTicker()
+	}
+
 	s.logger.DebugContext(context.Background(), "process successfully started")
 
 	return nil
@@ -138,6 +149,9 @@ func (s *processSupervisor) Launch() error {
 
 func (s *processSupervisor) Shutdown() error {
 	s.logger.DebugContext(context.Background(), "shutdown process")
+
+	s.stopIdleTicker()
+
 	err := s.process.Stop(s.logger)
 	if err != nil {
 		return fmt.Errorf("shutdown process: %w", err)
@@ -220,6 +234,9 @@ func (s *processSupervisor) Run(ctx context.Context, logger *slog.Logger, task f
 
 			defer func() {
 				s.activeTasks.Add(-1)
+				if s.idleShutdownTimeout > 0 {
+					s.lastActivity.Store(time.Now().UnixNano())
+				}
 				if semaphoreOwned {
 					logger.DebugContext(ctx, "process lock released")
 					<-s.semaphore
@@ -255,6 +272,87 @@ func (s *processSupervisor) Run(ctx context.Context, logger *slog.Logger, task f
 	}
 }
 
+// startIdleTicker starts a background goroutine that periodically checks
+// whether the process has been idle long enough to shut down.
+func (s *processSupervisor) startIdleTicker() {
+	stopChan := make(chan struct{})
+
+	s.idleMu.Lock()
+	s.idleStopChan = stopChan
+	s.idleMu.Unlock()
+
+	go func() {
+		ticker := time.NewTicker(s.idleShutdownTimeout)
+		defer ticker.Stop()
+		for {
+			select {
+			case <-ticker.C:
+				s.maybeIdleShutdown()
+			case <-stopChan:
+				return
+			}
+		}
+	}()
+}
+
+// stopIdleTicker signals the idle ticker goroutine to exit, if one is running.
+func (s *processSupervisor) stopIdleTicker() {
+	s.idleMu.Lock()
+	defer s.idleMu.Unlock()
+
+	if s.idleStopChan != nil {
+		close(s.idleStopChan)
+		s.idleStopChan = nil
+	}
+}
+
+// maybeIdleShutdown stops the process if it has been idle for longer than
+// the configured timeout. It is safe to call concurrently with Run and
+// restart.
+func (s *processSupervisor) maybeIdleShutdown() {
+	if !s.firstStart.Load() || s.isRestarting.Load() {
+		return
+	}
+
+	if s.activeTasks.Load() > 0 || s.reqQueueSize.Load() > 0 {
+		return
+	}
+
+	lastNano := s.lastActivity.Load()
+	if lastNano == 0 || time.Since(time.Unix(0, lastNano)) < s.idleShutdownTimeout {
+		return
+	}
+
+	if !s.restartMutex.TryLock() {
+		return
+	}
+	defer s.restartMutex.Unlock()
+
+	// Double-check after acquiring the lock.
+	if s.activeTasks.Load() > 0 || s.reqQueueSize.Load() > 0 {
+		return
+	}
+
+	s.logger.InfoContext(context.Background(), "idle shutdown timeout reached, stopping process")
+
+	// Stop the ticker — it will be restarted on the next Launch().
+	s.stopIdleTicker()
+
+	err := s.process.Stop(s.logger)
+	if err != nil {
+		s.logger.WarnContext(context.Background(), fmt.Sprintf("idle shutdown: %s", err))
+		return
+	}
+
+	// Reset state so ensureStarted() re-launches on next request.
+	s.firstStart.Store(false)
+	s.firstStartOnce = sync.Once{}
+	s.firstStartErr = nil
+	s.reqCounter.Store(0)
+
+	s.logger.InfoContext(context.Background(), "process stopped due to idle timeout")
+}
+
 // acquireSlot attempts to acquire a semaphore slot, yielding it back if a
 // restart drain is in progress.
 func (s *processSupervisor) acquireSlot(ctx context.Context, logger *slog.Logger) error {

pkg/gotenberg/supervisor_test.go

@@ -45,7 +45,7 @@ func TestProcessSupervisor_Launch(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 5, 0, 1).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, 5, 0, 1, 0).(*processSupervisor)
 			if tc.firstStartSet {
 				ps.firstStart.Store(true)
 			}
@@ -93,7 +93,7 @@ func TestProcessSupervisor_Shutdown(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 5, 0, 1)
+			ps := NewProcessSupervisor(logger, process, 5, 0, 1, 0)
 			err := ps.Shutdown()
 
 			if !tc.expectError && err != nil {
@@ -145,7 +145,7 @@ func TestProcessSupervisor_restart(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 5, 0, 1).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, 5, 0, 1, 0).(*processSupervisor)
 
 			err := ps.restart()
 
@@ -201,7 +201,7 @@ func TestProcessSupervisor_Healthy(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 5, 0, 1).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, 5, 0, 1, 0).(*processSupervisor)
 			if tc.initiallyStarted {
 				ps.firstStart.Store(true)
 			}
@@ -386,7 +386,7 @@ func TestProcessSupervisor_Run(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, tc.maxReqLimit, tc.maxQueueSize, 1).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, tc.maxReqLimit, tc.maxQueueSize, 1, 0).(*processSupervisor)
 			if tc.initiallyStarted {
 				ps.firstStart.Store(true)
 			}
@@ -470,7 +470,7 @@ func TestProcessSupervisor_runWithDeadline(t *testing.T) {
 		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
-			ps := NewProcessSupervisor(slog.New(slog.DiscardHandler), new(ProcessMock), 0, 0, 1).(*processSupervisor)
+			ps := NewProcessSupervisor(slog.New(slog.DiscardHandler), new(ProcessMock), 0, 0, 1, 0).(*processSupervisor)
 
 			ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 			if tc.ctxDone {
@@ -504,7 +504,7 @@ func TestProcessSupervisor_ReqQueueSize(t *testing.T) {
 			return true
 		},
 	}
-	ps := NewProcessSupervisor(logger, process, 0, 0, 1).(*processSupervisor)
+	ps := NewProcessSupervisor(logger, process, 0, 0, 1, 0).(*processSupervisor)
 
 	// Simulating a lock.
 	ps.semaphore <- struct{}{}
@@ -565,7 +565,7 @@ func TestProcessSupervisor_QueueSizeCAS(t *testing.T) {
 
 	maxQueueSize := int64(50)
 	// maxConcurrency=1 so all goroutines block on the semaphore, exercising queue logic.
-	ps := NewProcessSupervisor(logger, process, 0, maxQueueSize, 1).(*processSupervisor)
+	ps := NewProcessSupervisor(logger, process, 0, maxQueueSize, 1, 0).(*processSupervisor)
 
 	// Simulating a lock so that all goroutines queue up.
 	ps.semaphore <- struct{}{}
@@ -619,7 +619,7 @@ func TestProcessSupervisor_QueueSizeIncludesActiveTasks(t *testing.T) {
 	}
 
 	// maxQueueSize=1, maxConcurrency=1: only one request at a time.
-	ps := NewProcessSupervisor(logger, process, 0, 1, 1)
+	ps := NewProcessSupervisor(logger, process, 0, 1, 1, 0)
 
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
@@ -708,7 +708,7 @@ func TestProcessSupervisor_RestartsCount(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 0, 0, 1).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, 0, 0, 1, 0).(*processSupervisor)
 			ps.restartsCounter.Store(tc.initialRestartsCount)
 
 			for i := 0; i < tc.restartAttempts; i++ {
@@ -741,7 +741,7 @@ func TestProcessSupervisor_ConcurrentRun(t *testing.T) {
 	}
 
 	maxConcurrency := int64(3)
-	ps := NewProcessSupervisor(logger, process, 0, 0, maxConcurrency).(*processSupervisor)
+	ps := NewProcessSupervisor(logger, process, 0, 0, maxConcurrency, 0).(*processSupervisor)
 
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
@@ -803,7 +803,7 @@ func TestProcessSupervisor_RestartDrainsAllSlots(t *testing.T) {
 	}
 
 	maxConcurrency := int64(3)
-	ps := NewProcessSupervisor(logger, process, 3, 0, maxConcurrency).(*processSupervisor)
+	ps := NewProcessSupervisor(logger, process, 3, 0, maxConcurrency, 0).(*processSupervisor)
 	ps.firstStart.Store(true)
 
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
@@ -841,3 +841,103 @@ func TestProcessSupervisor_RestartDrainsAllSlots(t *testing.T) {
 		t.Fatalf("expected 1 restart, got %d", ps.RestartsCount())
 	}
 }
+
+func TestProcessSupervisor_IdleShutdown(t *testing.T) {
+	logger := slog.New(slog.DiscardHandler)
+
+	var stopCalls atomic.Int64
+	process := &ProcessMock{
+		StartMock: func(logger *slog.Logger) error {
+			return nil
+		},
+		StopMock: func(logger *slog.Logger) error {
+			stopCalls.Add(1)
+			return nil
+		},
+		HealthyMock: func(logger *slog.Logger) bool {
+			return true
+		},
+	}
+
+	idleTimeout := 50 * time.Millisecond
+	ps := NewProcessSupervisor(logger, process, 0, 0, 1, idleTimeout).(*processSupervisor)
+
+	ctx := context.Background()
+	err := ps.Run(ctx, logger, func() error {
+		return nil
+	})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	// Wait for idle shutdown to fire.
+	deadline := time.After(2 * time.Second)
+	for ps.firstStart.Load() {
+		select {
+		case <-deadline:
+			t.Fatal("timed out waiting for idle shutdown")
+		default:
+			time.Sleep(10 * time.Millisecond)
+		}
+	}
+
+	if stopCalls.Load() < 1 {
+		t.Fatal("expected process to be stopped via idle shutdown")
+	}
+
+	// Verify re-launch on next request.
+	err = ps.Run(ctx, logger, func() error {
+		return nil
+	})
+	if err != nil {
+		t.Fatalf("unexpected error on re-launch: %v", err)
+	}
+
+	if !ps.firstStart.Load() {
+		t.Fatal("expected process to be re-launched after idle shutdown")
+	}
+}
+
+func TestProcessSupervisor_IdleShutdownSkippedWhenActive(t *testing.T) {
+	logger := slog.New(slog.DiscardHandler)
+
+	var stopCalls atomic.Int64
+	taskRunning := make(chan struct{})
+	taskDone := make(chan struct{})
+
+	process := &ProcessMock{
+		StartMock: func(logger *slog.Logger) error {
+			return nil
+		},
+		StopMock: func(logger *slog.Logger) error {
+			stopCalls.Add(1)
+			return nil
+		},
+		HealthyMock: func(logger *slog.Logger) bool {
+			return true
+		},
+	}
+
+	idleTimeout := 50 * time.Millisecond
+	ps := NewProcessSupervisor(logger, process, 0, 0, 1, idleTimeout)
+
+	ctx := context.Background()
+	go func() {
+		_ = ps.Run(ctx, logger, func() error {
+			close(taskRunning)
+			<-taskDone
+			return nil
+		})
+	}()
+
+	<-taskRunning
+
+	// Wait longer than the idle timeout while a task is active.
+	time.Sleep(idleTimeout * 3)
+
+	if stopCalls.Load() > 0 {
+		t.Fatal("idle shutdown should not fire while a task is active")
+	}
+
+	close(taskDone)
+}

pkg/modules/chromium/chromium.go

@@ -435,6 +435,7 @@ func (mod *Chromium) Descriptor() gotenberg.ModuleDescriptor {
 			fs := flag.NewFlagSet("chromium", flag.ExitOnError)
 			fs.Int64("chromium-restart-after", 100, "Number of conversions after which Chromium will automatically restart. Set to 0 to disable this feature")
 			fs.Int64("chromium-max-queue-size", 0, "Maximum request queue size for Chromium. Set to 0 to disable this feature")
+			fs.Duration("chromium-idle-shutdown-timeout", 0, "Shutdown Chromium after being idle for the given duration. Set to 0 to disable this feature")
 			fs.Int64("chromium-max-concurrency", 6, "Maximum number of concurrent conversions. Chromium supports up to 6")
 			fs.Bool("chromium-auto-start", false, "Automatically launch Chromium upon initialization if set to true; otherwise, Chromium will start at the time of the first conversion")
 			fs.Duration("chromium-start-timeout", time.Duration(20)*time.Second, "Maximum duration to wait for Chromium to start or restart")
@@ -504,7 +505,7 @@ func (mod *Chromium) Provision(ctx *gotenberg.Context) error {
 
 	// Process.
 	mod.browser = newChromiumBrowser(mod.args)
-	mod.supervisor = gotenberg.NewProcessSupervisor(mod.logger, mod.browser, flags.MustInt64("chromium-restart-after"), flags.MustInt64("chromium-max-queue-size"), mod.maxConcurrency)
+	mod.supervisor = gotenberg.NewProcessSupervisor(mod.logger, mod.browser, flags.MustInt64("chromium-restart-after"), flags.MustInt64("chromium-max-queue-size"), mod.maxConcurrency, flags.MustDuration("chromium-idle-shutdown-timeout"))
 
 	// PDF Engine.
 	provider, err := ctx.Module(new(gotenberg.PdfEngineProvider))

pkg/modules/libreoffice/api/api.go

@@ -325,6 +325,7 @@ func (a *Api) Descriptor() gotenberg.ModuleDescriptor {
 			fs := flag.NewFlagSet("api", flag.ExitOnError)
 			fs.Int64("libreoffice-restart-after", 10, "Number of conversions after which LibreOffice will automatically restart. Set to 0 to disable this feature")
 			fs.Int64("libreoffice-max-queue-size", 0, "Maximum request queue size for LibreOffice. Set to 0 to disable this feature")
+			fs.Duration("libreoffice-idle-shutdown-timeout", 0, "Shutdown LibreOffice after being idle for the given duration. Set to 0 to disable this feature")
 			fs.Bool("libreoffice-auto-start", false, "Automatically launch LibreOffice upon initialization if set to true; otherwise, LibreOffice will start at the time of the first conversion")
 			fs.Duration("libreoffice-start-timeout", time.Duration(20)*time.Second, "Maximum duration to wait for LibreOffice to start or restart")
 
@@ -360,7 +361,7 @@ func (a *Api) Provision(ctx *gotenberg.Context) error {
 
 	// Process.
 	a.libreOffice = newLibreOfficeProcess(a.args)
-	a.supervisor = gotenberg.NewProcessSupervisor(a.logger, a.libreOffice, flags.MustInt64("libreoffice-restart-after"), flags.MustInt64("libreoffice-max-queue-size"), 1)
+	a.supervisor = gotenberg.NewProcessSupervisor(a.logger, a.libreOffice, flags.MustInt64("libreoffice-restart-after"), flags.MustInt64("libreoffice-max-queue-size"), 1, flags.MustDuration("libreoffice-idle-shutdown-timeout"))
 
 	// Metrics.
 	meter := gotenberg.Meter()

test/integration/features/debug.feature

@@ -84,6 +84,7 @@ Feature: /debug
           "chromium-disable-web-security": "false",
           "chromium-host-resolver-rules": "",
           "chromium-ignore-certificate-errors": "false",
+          "chromium-idle-shutdown-timeout": "0s",
           "chromium-incognito": "false",
           "chromium-max-concurrency": "6",
           "chromium-max-queue-size": "0",
@@ -94,6 +95,7 @@ Feature: /debug
           "gotenberg-graceful-shutdown-duration": "30s",
           "libreoffice-auto-start": "false",
           "libreoffice-disable-routes": "false",
+          "libreoffice-idle-shutdown-timeout": "0s",
           "libreoffice-max-queue-size": "0",
           "libreoffice-restart-after": "10",
           "libreoffice-start-timeout": "20s",
@@ -210,6 +212,7 @@ Feature: /debug
           "chromium-disable-web-security": "false",
           "chromium-host-resolver-rules": "",
           "chromium-ignore-certificate-errors": "false",
+          "chromium-idle-shutdown-timeout": "0s",
           "chromium-incognito": "false",
           "chromium-max-queue-size": "0",
           "chromium-max-concurrency": "6",
@@ -220,6 +223,7 @@ Feature: /debug
           "gotenberg-graceful-shutdown-duration": "30s",
           "libreoffice-auto-start": "false",
           "libreoffice-disable-routes": "false",
+          "libreoffice-idle-shutdown-timeout": "0s",
           "libreoffice-max-queue-size": "0",
           "libreoffice-restart-after": "10",
           "libreoffice-start-timeout": "20s",