feat: enable max queue size for chromium and libreoffice

fix gotenberg/gotenberg#463

pkg/gotenberg/supervisor.go

@@ -13,6 +13,10 @@ import (
 // to restart an already restarting [Process].
 var ErrProcessAlreadyRestarting = errors.New("process already restarting")
 
+// ErrMaximumQueueSizeExceeded happens if Run() is called but the maximum queue
+// size is already used.
+var ErrMaximumQueueSizeExceeded = errors.New("maximum queue size exceeded")
+
 // Process is an interface that represents an abstract process
 // and provides methods for starting, stopping, and checking the health of the
 // process.
@@ -74,6 +78,7 @@ type processSupervisor struct {
 	logger          *zap.Logger
 	process         Process
 	maxReqLimit     int64
+	maxQueueSize    int64
 	mutexChan       chan struct{}
 	firstStart      atomic.Bool
 	reqCounter      atomic.Int64
@@ -83,12 +88,13 @@ type processSupervisor struct {
 }
 
 // NewProcessSupervisor initializes a new [ProcessSupervisor].
-func NewProcessSupervisor(logger *zap.Logger, process Process, maxReqLimit int64) ProcessSupervisor {
+func NewProcessSupervisor(logger *zap.Logger, process Process, maxReqLimit int64, maxQueueSize int64) ProcessSupervisor {
 	b := &processSupervisor{
-		logger:      logger,
+		logger:       logger,
-		process:     process,
+		process:      process,
-		mutexChan:   make(chan struct{}, 1),
+		mutexChan:    make(chan struct{}, 1),
-		maxReqLimit: maxReqLimit,
+		maxReqLimit:  maxReqLimit,
+		maxQueueSize: maxQueueSize,
 	}
 	b.reqCounter.Store(0)
 	b.reqQueueSize.Store(0)
@@ -167,6 +173,11 @@ func (s *processSupervisor) Healthy() bool {
 }
 
 func (s *processSupervisor) Run(ctx context.Context, logger *zap.Logger, task func() error) error {
+	currentQueueSize := s.reqQueueSize.Load()
+	if s.maxQueueSize > 0 && currentQueueSize >= s.maxQueueSize {
+		return ErrMaximumQueueSizeExceeded
+	}
+
 	s.reqQueueSize.Add(1)
 
 	for {

pkg/gotenberg/supervisor_test.go

@@ -46,7 +46,7 @@ func TestProcessSupervisor_Launch(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 5).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, 5, 0).(*processSupervisor)
 			if tc.firstStartSet {
 				ps.firstStart.Store(true)
 			}
@@ -94,7 +94,7 @@ func TestProcessSupervisor_Shutdown(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 5)
+			ps := NewProcessSupervisor(logger, process, 5, 0)
 			err := ps.Shutdown()
 
 			if !tc.expectError && err != nil {
@@ -154,7 +154,7 @@ func TestProcessSupervisor_restart(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 5).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, 5, 0).(*processSupervisor)
 			if tc.initiallyRestarting {
 				ps.isRestarting.Store(true)
 			}
@@ -217,7 +217,7 @@ func TestProcessSupervisor_Healthy(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 5).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, 5, 0).(*processSupervisor)
 			if tc.initiallyStarted {
 				ps.firstStart.Store(true)
 			}
@@ -249,6 +249,8 @@ func TestProcessSupervisor_Run(t *testing.T) {
 		expectedStartCalls   int64
 		expectedHealthyCalls int64
 		expectedStopCalls    int64
+		currentQueueSize     int64
+		maxQueueSize         int64
 	}{
 		{
 			scenario:             "successfully run task on non-started process",
@@ -348,6 +350,34 @@ func TestProcessSupervisor_Run(t *testing.T) {
 			expectedHealthyCalls: 1,
 			expectedStopCalls:    0,
 		},
+		{
+			scenario:             "queue size exceeded",
+			initiallyStarted:     false,
+			isRestarting:         false,
+			processHealthy:       true,
+			maxReqLimit:          2,
+			tasksToRun:           1,
+			expectError:          true,
+			expectedStartCalls:   0,
+			expectedHealthyCalls: 0,
+			expectedStopCalls:    0,
+			currentQueueSize:     1,
+			maxQueueSize:         1,
+		},
+		{
+			scenario:             "queue size not exceeded",
+			initiallyStarted:     false,
+			isRestarting:         false,
+			processHealthy:       true,
+			maxReqLimit:          2,
+			tasksToRun:           1,
+			expectError:          true,
+			expectedStartCalls:   1,
+			expectedHealthyCalls: 1,
+			expectedStopCalls:    0,
+			currentQueueSize:     1,
+			maxQueueSize:         2,
+		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
 			logger := zap.NewNop()
@@ -372,13 +402,16 @@ func TestProcessSupervisor_Run(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, tc.maxReqLimit).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, tc.maxReqLimit, tc.maxQueueSize).(*processSupervisor)
 			if tc.initiallyStarted {
 				ps.firstStart.Store(true)
 			}
 			if tc.isRestarting {
 				ps.isRestarting.Store(true)
 			}
+			if tc.currentQueueSize > 0 {
+				ps.reqQueueSize.Store(tc.currentQueueSize)
+			}
 
 			task := func() error {
 				return tc.taskError
@@ -451,7 +484,7 @@ func TestProcessSupervisor_runWithDeadline(t *testing.T) {
 		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
-			ps := NewProcessSupervisor(zap.NewNop(), new(ProcessMock), 0).(*processSupervisor)
+			ps := NewProcessSupervisor(zap.NewNop(), new(ProcessMock), 0, 0).(*processSupervisor)
 
 			ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 			defer cancel()
@@ -485,7 +518,7 @@ func TestProcessSupervisor_ReqQueueSize(t *testing.T) {
 			return true
 		},
 	}
-	ps := NewProcessSupervisor(logger, process, 0).(*processSupervisor)
+	ps := NewProcessSupervisor(logger, process, 0, 0).(*processSupervisor)
 
 	// Simulating a lock.
 	ps.mutexChan <- struct{}{}
@@ -586,7 +619,7 @@ func TestProcessSupervisor_RestartsCount(t *testing.T) {
 				},
 			}
 
-			ps := NewProcessSupervisor(logger, process, 0).(*processSupervisor)
+			ps := NewProcessSupervisor(logger, process, 0, 0).(*processSupervisor)
 			ps.restartsCounter.Store(tc.initialRestartsCount)
 
 			for i := 0; i < tc.restartAttempts; i++ {

pkg/modules/chromium/chromium.go

@@ -295,6 +295,7 @@ func (mod *Chromium) Descriptor() gotenberg.ModuleDescriptor {
 			fs.Bool("chromium-clear-cookies", false, "Clear Chromium cookies between each conversion")
 			fs.Bool("chromium-disable-javascript", false, "Disable JavaScript")
 			fs.Bool("chromium-disable-routes", false, "Disable the routes")
+			fs.Int64("chromium-max-queue-size", 0, "Maximum request queue size for chromium. Set to 0 to disable this feature")
 
 			return fs
 		}(),
@@ -344,7 +345,7 @@ 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"))
+	mod.supervisor = gotenberg.NewProcessSupervisor(mod.logger, mod.browser, flags.MustInt64("chromium-restart-after"), flags.MustInt64("chromium-max-queue-size"))
 
 	// PDF Engine.
 	provider, err := ctx.Module(new(gotenberg.PdfEngineProvider))

pkg/modules/chromium/routes.go

@@ -540,6 +540,16 @@ func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url
 			)
 		}
 
+		if errors.Is(err, gotenberg.ErrMaximumQueueSizeExceeded) {
+			return api.WrapError(
+				fmt.Errorf("convert to PDF: %w", err),
+				api.NewSentinelHttpError(
+					http.StatusTooManyRequests,
+					"The maximum queue size has been reached",
+				),
+			)
+		}
+
 		return fmt.Errorf("convert to PDF: %w", err)
 	}
 

pkg/modules/libreoffice/api/api.go

@@ -80,6 +80,7 @@ func (a *Api) Descriptor() gotenberg.ModuleDescriptor {
 		FlagSet: func() *flag.FlagSet {
 			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.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")
 
@@ -123,7 +124,7 @@ 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"))
+	a.supervisor = gotenberg.NewProcessSupervisor(a.logger, a.libreOffice, flags.MustInt64("libreoffice-restart-after"), flags.MustInt64("libreoffice-max-queue-size"))
 
 	return nil
 }

pkg/modules/libreoffice/routes.go

@@ -68,6 +68,16 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 
 				err = libreOffice.Pdf(ctx, ctx.Log(), inputPath, outputPaths[i], options)
 				if err != nil {
+					if errors.Is(err, gotenberg.ErrMaximumQueueSizeExceeded) {
+						return api.WrapError(
+							fmt.Errorf("convert to PDF: %w", err),
+							api.NewSentinelHttpError(
+								http.StatusTooManyRequests,
+								"The maximum queue size has been reached",
+							),
+						)
+					}
+
 					if errors.Is(err, libreofficeapi.ErrInvalidPdfFormats) {
 						return api.WrapError(
 							fmt.Errorf("convert to PDF: %w", err),