Multiple Queue improvements: LevelDB Wait on empty, shutdown empty shadow level queue, reduce goroutines etc

modules/graceful/context.go

@@ -6,17 +6,9 @@ package graceful
 
 import (
 	"context"
-	"fmt"
 	"time"
 )
 
-// Errors for context.Err()
-var (
-	ErrShutdown  = fmt.Errorf("Graceful Manager called Shutdown")
-	ErrHammer    = fmt.Errorf("Graceful Manager called Hammer")
-	ErrTerminate = fmt.Errorf("Graceful Manager called Terminate")
-)
-
 // ChannelContext is a context that wraps a channel and error as a context
 type ChannelContext struct {
 	done <-chan struct{}
@@ -63,28 +55,19 @@ func (ctx *ChannelContext) Value(key interface{}) interface{} {
 // Callers using this context should ensure that they are registered as a running server
 // in order that they are waited for.
 func (g *Manager) ShutdownContext() context.Context {
-	return &ChannelContext{
-		done: g.IsShutdown(),
-		err:  ErrShutdown,
-	}
+	return g.shutdown
 }
 
 // HammerContext returns a context.Context that is Done at hammer
 // Callers using this context should ensure that they are registered as a running server
 // in order that they are waited for.
 func (g *Manager) HammerContext() context.Context {
-	return &ChannelContext{
-		done: g.IsHammer(),
-		err:  ErrHammer,
-	}
+	return g.hammer
 }
 
 // TerminateContext returns a context.Context that is Done at terminate
 // Callers using this context should ensure that they are registered as a terminating server
 // in order that they are waited for.
 func (g *Manager) TerminateContext() context.Context {
-	return &ChannelContext{
-		done: g.IsTerminate(),
-		err:  ErrTerminate,
-	}
+	return g.terminate
 }

modules/graceful/manager.go

@@ -54,16 +54,16 @@ func InitManager(ctx context.Context) {
 	})
 }
 
-// CallbackWithContext is combined runnable and context to watch to see if the caller has finished
-type CallbackWithContext func(ctx context.Context, callback func())
+// WithCallback is a runnable to call when the caller has finished
+type WithCallback func(callback func())
 
 // RunnableWithShutdownFns is a runnable with functions to run at shutdown and terminate
 // After the callback to atShutdown is called and is complete, the main function must return.
 // Similarly the callback function provided to atTerminate must return once termination is complete.
 // Please note that use of the atShutdown and atTerminate callbacks will create go-routines that will wait till their respective signals
 // - users must therefore be careful to only call these as necessary.
 // If run is not expected to run indefinitely RunWithShutdownChan is likely to be more appropriate.
-type RunnableWithShutdownFns func(atShutdown, atTerminate func(context.Context, func()))
+type RunnableWithShutdownFns func(atShutdown, atTerminate func(func()))
 
 // RunWithShutdownFns takes a function that has both atShutdown and atTerminate callbacks
 // After the callback to atShutdown is called and is complete, the main function must return.
@@ -80,17 +80,21 @@ func (g *Manager) RunWithShutdownFns(run RunnableWithShutdownFns) {
 			g.doShutdown()
 		}
 	}()
-	run(func(ctx context.Context, atShutdown func()) {
-		go func() {
-			select {
-			case <-g.IsShutdown():
+	run(func(atShutdown func()) {
+		g.lock.Lock()
+		defer g.lock.Unlock()
+		g.toRunAtShutdown = append(g.toRunAtShutdown,
+			func() {
+				defer func() {
+					if err := recover(); err != nil {
+						log.Critical("PANIC during RunWithShutdownFns: %v\nStacktrace: %s", err, log.Stack(2))
+						g.doShutdown()
+					}
+				}()
 				atShutdown()
-			case <-ctx.Done():
-				return
-			}
-		}()
-	}, func(ctx context.Context, atTerminate func()) {
-		g.RunAtTerminate(ctx, atTerminate)
+			})
+	}, func(atTerminate func()) {
+		g.RunAtTerminate(atTerminate)
 	})
 }
 
@@ -99,7 +103,7 @@ func (g *Manager) RunWithShutdownFns(run RunnableWithShutdownFns) {
 // (Optionally IsHammer may be waited for instead however, this should be avoided if possible.)
 // The callback function provided to atTerminate must return once termination is complete.
 // Please note that use of the atTerminate function will create a go-routine that will wait till terminate - users must therefore be careful to only call this as necessary.
-type RunnableWithShutdownChan func(atShutdown <-chan struct{}, atTerminate CallbackWithContext)
+type RunnableWithShutdownChan func(atShutdown <-chan struct{}, atTerminate WithCallback)
 
 // RunWithShutdownChan takes a function that has channel to watch for shutdown and atTerminate callbacks
 // After the atShutdown channel is closed, the main function must return once shutdown is complete.
@@ -115,8 +119,8 @@ func (g *Manager) RunWithShutdownChan(run RunnableWithShutdownChan) {
 			g.doShutdown()
 		}
 	}()
-	run(g.IsShutdown(), func(ctx context.Context, atTerminate func()) {
-		g.RunAtTerminate(ctx, atTerminate)
+	run(g.IsShutdown(), func(atTerminate func()) {
+		g.RunAtTerminate(atTerminate)
 	})
 }
 
@@ -136,60 +140,65 @@ func (g *Manager) RunWithShutdownContext(run func(context.Context)) {
 }
 
 // RunAtTerminate adds to the terminate wait group and creates a go-routine to run the provided function at termination
-func (g *Manager) RunAtTerminate(ctx context.Context, terminate func()) {
+func (g *Manager) RunAtTerminate(terminate func()) {
 	g.terminateWaitGroup.Add(1)
-	go func() {
-		defer g.terminateWaitGroup.Done()
-		defer func() {
-			if err := recover(); err != nil {
-				log.Critical("PANIC during RunAtTerminate: %v\nStacktrace: %s", err, log.Stack(2))
-			}
-		}()
-		select {
-		case <-g.IsTerminate():
+	g.lock.Lock()
+	defer g.lock.Unlock()
+	g.toRunAtTerminate = append(g.toRunAtTerminate,
+		func() {
+			defer g.terminateWaitGroup.Done()
+			defer func() {
+				if err := recover(); err != nil {
+					log.Critical("PANIC during RunAtTerminate: %v\nStacktrace: %s", err, log.Stack(2))
+				}
+			}()
 			terminate()
-		case <-ctx.Done():
-		}
-	}()
+		})
 }
 
 // RunAtShutdown creates a go-routine to run the provided function at shutdown
 func (g *Manager) RunAtShutdown(ctx context.Context, shutdown func()) {
-	go func() {
-		defer func() {
-			if err := recover(); err != nil {
-				log.Critical("PANIC during RunAtShutdown: %v\nStacktrace: %s", err, log.Stack(2))
+	g.lock.Lock()
+	defer g.lock.Unlock()
+	g.toRunAtShutdown = append(g.toRunAtShutdown,
+		func() {
+			defer func() {
+				if err := recover(); err != nil {
+					log.Critical("PANIC during RunAtShutdown: %v\nStacktrace: %s", err, log.Stack(2))
+				}
+			}()
+			select {
+			case <-ctx.Done():
+				return
+			default:
+				shutdown()
 			}
-		}()
-		select {
-		case <-g.IsShutdown():
-			shutdown()
-		case <-ctx.Done():
-		}
-	}()
+		})
 }
 
 // RunAtHammer creates a go-routine to run the provided function at shutdown
-func (g *Manager) RunAtHammer(ctx context.Context, hammer func()) {
-	go func() {
-		defer func() {
-			if err := recover(); err != nil {
-				log.Critical("PANIC during RunAtHammer: %v\nStacktrace: %s", err, log.Stack(2))
-			}
-		}()
-		select {
-		case <-g.IsHammer():
+func (g *Manager) RunAtHammer(hammer func()) {
+	g.lock.Lock()
+	defer g.lock.Unlock()
+	g.toRunAtHammer = append(g.toRunAtHammer,
+		func() {
+			defer func() {
+				if err := recover(); err != nil {
+					log.Critical("PANIC during RunAtHammer: %v\nStacktrace: %s", err, log.Stack(2))
+				}
+			}()
 			hammer()
-		case <-ctx.Done():
-		}
-	}()
+		})
 }
 func (g *Manager) doShutdown() {
 	if !g.setStateTransition(stateRunning, stateShuttingDown) {
 		return
 	}
 	g.lock.Lock()
-	close(g.shutdown)
+	g.shutdownCancel()
+	for _, fn := range g.toRunAtShutdown {
+		go fn()
+	}
 	g.lock.Unlock()
 
 	if setting.GracefulHammerTime >= 0 {
@@ -203,7 +212,7 @@ func (g *Manager) doShutdown() {
 		g.doTerminate()
 		g.WaitForTerminate()
 		g.lock.Lock()
-		close(g.done)
+		g.doneCancel()
 		g.lock.Unlock()
 	}()
 }
@@ -212,10 +221,13 @@ func (g *Manager) doHammerTime(d time.Duration) {
 	time.Sleep(d)
 	g.lock.Lock()
 	select {
-	case <-g.hammer:
+	case <-g.hammer.Done():
 	default:
 		log.Warn("Setting Hammer condition")
-		close(g.hammer)
+		g.hammerCancel()
+		for _, fn := range g.toRunAtHammer {
+			go fn()
+		}
 	}
 	g.lock.Unlock()
 }
@@ -226,10 +238,13 @@ func (g *Manager) doTerminate() {
 	}
 	g.lock.Lock()
 	select {
-	case <-g.terminate:
+	case <-g.terminate.Done():
 	default:
 		log.Warn("Terminating")
-		close(g.terminate)
+		g.terminateCancel()
+		for _, fn := range g.toRunAtTerminate {
+			go fn()
+		}
 	}
 	g.lock.Unlock()
 }
@@ -242,22 +257,22 @@ func (g *Manager) IsChild() bool {
 // IsShutdown returns a channel which will be closed at shutdown.
 // The order of closure is IsShutdown, IsHammer (potentially), IsTerminate
 func (g *Manager) IsShutdown() <-chan struct{} {
-	return g.shutdown
+	return g.shutdown.Done()
 }
 
 // IsHammer returns a channel which will be closed at hammer
 // The order of closure is IsShutdown, IsHammer (potentially), IsTerminate
 // Servers running within the running server wait group should respond to IsHammer
 // if not shutdown already
 func (g *Manager) IsHammer() <-chan struct{} {
-	return g.hammer
+	return g.hammer.Done()
 }
 
 // IsTerminate returns a channel which will be closed at terminate
 // The order of closure is IsShutdown, IsHammer (potentially), IsTerminate
 // IsTerminate will only close once all running servers have stopped
 func (g *Manager) IsTerminate() <-chan struct{} {
-	return g.terminate
+	return g.terminate.Done()
 }
 
 // ServerDone declares a running server done and subtracts one from the
@@ -314,25 +329,20 @@ func (g *Manager) InformCleanup() {
 
 // Done allows the manager to be viewed as a context.Context, it returns a channel that is closed when the server is finished terminating
 func (g *Manager) Done() <-chan struct{} {
-	return g.done
+	return g.done.Done()
 }
 
-// Err allows the manager to be viewed as a context.Context done at Terminate, it returns ErrTerminate
+// Err allows the manager to be viewed as a context.Context done at Terminate
 func (g *Manager) Err() error {
-	select {
-	case <-g.Done():
-		return ErrTerminate
-	default:
-		return nil
-	}
+	return g.done.Err()
 }
 
 // Value allows the manager to be viewed as a context.Context done at Terminate, it has no values
 func (g *Manager) Value(key interface{}) interface{} {
-	return nil
+	return g.done.Value(key)
 }
 
 // Deadline returns nil as there is no fixed Deadline for the manager, it allows the manager to be viewed as a context.Context
 func (g *Manager) Deadline() (deadline time.Time, ok bool) {
-	return
+	return g.done.Deadline()
 }

modules/graceful/manager_unix.go

@@ -25,13 +25,21 @@ type Manager struct {
 	forked                 bool
 	lock                   *sync.RWMutex
 	state                  state
-	shutdown               chan struct{}
-	hammer                 chan struct{}
-	terminate              chan struct{}
-	done                   chan struct{}
+	shutdown               context.Context
+	hammer                 context.Context
+	terminate              context.Context
+	done                   context.Context
+	shutdownCancel         context.CancelFunc
+	hammerCancel           context.CancelFunc
+	terminateCancel        context.CancelFunc
+	doneCancel             context.CancelFunc
 	runningServerWaitGroup sync.WaitGroup
 	createServerWaitGroup  sync.WaitGroup
 	terminateWaitGroup     sync.WaitGroup
+
+	toRunAtShutdown  []func()
+	toRunAtHammer    []func()
+	toRunAtTerminate []func()
 }
 
 func newGracefulManager(ctx context.Context) *Manager {
@@ -45,11 +53,11 @@ func newGracefulManager(ctx context.Context) *Manager {
 }
 
 func (g *Manager) start(ctx context.Context) {
-	// Make channels
-	g.terminate = make(chan struct{})
-	g.shutdown = make(chan struct{})
-	g.hammer = make(chan struct{})
-	g.done = make(chan struct{})
+	// Make contexts
+	g.terminate, g.terminateCancel = context.WithCancel(ctx)
+	g.shutdown, g.shutdownCancel = context.WithCancel(ctx)
+	g.hammer, g.hammerCancel = context.WithCancel(ctx)
+	g.done, g.doneCancel = context.WithCancel(ctx)
 
 	// Set the running state & handle signals
 	g.setState(stateRunning)