Fix log server not exiting properly on SIGINT (#2805)

* Fix log server not exiting properly on SIGINT

Make the tree garbage collection coroutine exit immediately when the
context is cancelled.

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## HEAD
 
+### Misc
+* Fix log server not exiting properly on SIGINT
+
 ## v.1.5.0
 
 ### Storage

server/admin/tree_gc.go

@@ -35,7 +35,7 @@ const (
 
 var (
 	timeNow   = time.Now
-	timeSleep = time.Sleep
+	timeAfter = time.After
 
 	hardDeleteCounter monitoring.Counter
 	metricsOnce       sync.Once
@@ -85,12 +85,6 @@ func NewDeletedTreeGC(admin storage.AdminStorage, threshold, minRunInterval time
 // Run starts the tree garbage collection process. It runs until ctx is cancelled.
 func (gc *DeletedTreeGC) Run(ctx context.Context) {
 	for {
-		select {
-		case <-ctx.Done():
-			return
-		default:
-		}
-
 		count, err := gc.RunOnce(ctx)
 		if err != nil {
 			klog.Errorf("DeletedTreeGC.Run: %v", err)
@@ -100,7 +94,12 @@ func (gc *DeletedTreeGC) Run(ctx context.Context) {
 		}
 
 		d := gc.minRunInterval + time.Duration(rand.Int63n(gc.minRunInterval.Nanoseconds()))
-		timeSleep(d)
+		select {
+		case <-ctx.Done():
+			return
+		case <-timeAfter(d):
+		}
+
 	}
 }
 

server/admin/tree_gc_test.go

@@ -40,7 +40,7 @@ func TestDeletedTreeGC_Run(t *testing.T) {
 	// * Sleep (ctx cancelled)
 	//
 	// DeletedTreeGC.Run() until ctx in cancelled. Since it always sleeps between iterations, we
-	// make "timeSleep" cancel ctx the second time around to break the loop.
+	// make "timeAfter" cancel ctx the second time around to break the loop.
 
 	tree1 := proto.Clone(testonly.LogTree).(*trillian.Tree)
 	tree1.TreeId = 1
@@ -74,10 +74,10 @@ func TestDeletedTreeGC_Run(t *testing.T) {
 	listTX2.EXPECT().Close().Return(nil)
 	listTX2.EXPECT().Commit().Return(nil)
 
-	defer func(now func() time.Time, sleep func(time.Duration)) {
+	defer func(now func() time.Time, after func(time.Duration) <-chan time.Time) {
 		timeNow = now
-		timeSleep = sleep
-	}(timeNow, timeSleep)
+		timeAfter = after
+	}(timeNow, timeAfter)
 
 	const deleteThreshold = 1 * time.Hour
 	const runInterval = 3 * time.Second
@@ -87,14 +87,20 @@ func TestDeletedTreeGC_Run(t *testing.T) {
 	timeNow = func() time.Time { return now }
 
 	calls := 0
-	timeSleep = func(d time.Duration) {
+	timeAfter = func(d time.Duration) <-chan time.Time {
 		calls++
 		if d < runInterval || d >= 2*runInterval {
 			t.Errorf("Called time.Sleep(%v), want %v", d, runInterval)
 		}
 		if calls >= 2 {
 			cancel()
+			// Block to make sure we're exiting because of the cancelled context and
+			// not because the timer elapsed.
+			return make(chan time.Time)
 		}
+		ch := make(chan time.Time, 1)
+		ch <- now
+		return ch
 	}
 
 	NewDeletedTreeGC(as, deleteThreshold, runInterval, nil /* mf */).Run(ctx)