Add fscontext.AfterFuncDelayed function

This is useful in scenarios where a context gets canceled, but the code bound to the lifetime of the context does not return within a reasonable time. `AfterFuncDelayed` can be used to try exit the code more aggressively.

PiperOrigin-RevId: 686477044

fleetspeak/src/common/fscontext/fscontext.go

@@ -21,6 +21,7 @@ import (
 	"context"
 	"fmt"
 	"sync"
+	"time"
 )
 
 // ErrStopRequested is the cancelation cause to be used when callers
@@ -60,3 +61,30 @@ func WithDoneChan(ctx context.Context, cause error, done <-chan struct{}) (newCt
 		wg.Wait()
 	}
 }
+
+// AfterFuncDelayed behaves like context.AfterFunc, but with a delay.
+// The returned stop function must be called eventually to free resources.
+func AfterFuncDelayed(ctx context.Context, f func(), delay time.Duration) func() bool {
+	stopCh := make(chan func() bool)
+
+	cancelInitiation := context.AfterFunc(ctx, func() {
+		timer := time.AfterFunc(delay, f)
+		stopCh <- timer.Stop
+		close(stopCh)
+	})
+
+	return func() bool {
+		if cancelInitiation() {
+			// context.AfterFunc will not fire
+			close(stopCh)
+			return true
+		}
+
+		stop, ok := <-stopCh
+		if ok {
+			return stop()
+		}
+
+		return false
+	}
+}

fleetspeak/src/common/fscontext/fscontext_test.go

@@ -17,6 +17,7 @@ package fscontext_test
 import (
 	"context"
 	"errors"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -30,7 +31,7 @@ var (
 
 var shortDuration = 100 * time.Millisecond
 
-func TestWithDoneChanNotCanceled(t *testing.T) {
+func TestWithDoneChan_NotCanceled(t *testing.T) {
 	// Given
 	doneCh := make(chan struct{})
 	defer close(doneCh)
@@ -49,7 +50,7 @@ func TestWithDoneChanNotCanceled(t *testing.T) {
 	}
 }
 
-func TestWithDoneChanCanceledThroughChannel(t *testing.T) {
+func TestWithDoneChan_CanceledThroughChannel(t *testing.T) {
 	// Given
 	doneCh := make(chan struct{})
 
@@ -73,7 +74,7 @@ func TestWithDoneChanCanceledThroughChannel(t *testing.T) {
 	}
 }
 
-func TestWithDoneChanCanceledThroughOuterContext(t *testing.T) {
+func TestWithDoneChan_CanceledThroughOuterContext(t *testing.T) {
 	// Given
 	doneCh := make(chan struct{})
 	defer close(doneCh)
@@ -100,7 +101,7 @@ func TestWithDoneChanCanceledThroughOuterContext(t *testing.T) {
 	}
 }
 
-func TestWithDoneChanCanceledThroughOwnContext(t *testing.T) {
+func TestWithDoneChan_CanceledThroughOwnContext(t *testing.T) {
 	// Given
 	doneCh := make(chan struct{})
 	defer close(doneCh)
@@ -124,3 +125,123 @@ func TestWithDoneChanCanceledThroughOwnContext(t *testing.T) {
 		}
 	}
 }
+
+func TestAfterFuncDelayed_DelayReached(t *testing.T) {
+	// Given
+	const delay = 100 * time.Millisecond
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	flag := atomic.Bool{}
+	setFlag := func() {
+		flag.Store(true)
+	}
+
+	stop := fscontext.AfterFuncDelayed(ctx, setFlag, delay)
+	defer stop()
+
+	// When
+	cancel()
+	time.Sleep(2 * delay)
+
+	// Then
+	if !flag.Load() {
+		t.Errorf("flag not set after %v", delay)
+	}
+	if stop() {
+		t.Errorf("stop() returned true, but flag was set")
+	}
+}
+
+func TestAfterFuncDelayed_StopBeforeCancel(t *testing.T) {
+	// Given
+	const delay = 100 * time.Millisecond
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	flag := atomic.Bool{}
+	setFlag := func() {
+		flag.Store(true)
+	}
+
+	stop := fscontext.AfterFuncDelayed(ctx, setFlag, delay)
+	defer stop()
+
+	// When
+	stopped := stop()
+	cancel()
+	time.Sleep(2 * delay)
+
+	// Then
+	if !stopped {
+		t.Errorf("stop() returned false, but context was not canceled")
+	}
+	if flag.Load() {
+		t.Errorf("flag was set, but stop() was called before")
+	}
+	if stop() {
+		t.Errorf("stop() returned true, but stop() was called before")
+	}
+}
+
+func TestAfterFuncDelayed_StopAfterCancel(t *testing.T) {
+	// Given
+	const delay = 100 * time.Millisecond
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	flag := atomic.Bool{}
+	setFlag := func() {
+		flag.Store(true)
+	}
+
+	stop := fscontext.AfterFuncDelayed(ctx, setFlag, delay)
+	defer stop()
+
+	// When
+	cancel()
+	stopped := stop()
+	time.Sleep(2 * delay)
+
+	// Then
+	if !stopped {
+		t.Errorf("stop() returned false, but delay was not reached")
+	}
+	if flag.Load() {
+		t.Errorf("flag was set, but stop() was called before")
+	}
+	if stop() {
+		t.Errorf("stop() returned true, but stop() was called before")
+	}
+}
+
+func TestAfterFuncDelayed_StopAfterDelay(t *testing.T) {
+	// Given
+	const delay = 100 * time.Millisecond
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	flag := atomic.Bool{}
+	setFlag := func() {
+		flag.Store(true)
+	}
+
+	stop := fscontext.AfterFuncDelayed(ctx, setFlag, delay)
+	defer stop()
+
+	// When
+	cancel()
+	time.Sleep(2 * delay)
+	stopped := stop()
+
+	// Then
+	if stopped {
+		t.Errorf("stop() returned true, but delay was reached")
+	}
+	if !flag.Load() {
+		t.Errorf("flag was not set, but delay was reached")
+	}
+	if stop() {
+		t.Errorf("stop() returned true, but stop() was called before")
+	}
+}