fix(compute): flakey cache test (#15520)

core/capabilities/compute/cache.go

@@ -38,8 +38,9 @@ type moduleCache struct {
 	timeout        time.Duration
 	evictAfterSize int
 
-	clock    clockwork.Clock
-	onReaper chan struct{}
+	clock      clockwork.Clock
+	reapTicker <-chan time.Time
+	onReaper   chan struct{}
 }
 
 func newModuleCache(clock clockwork.Clock, tick, timeout time.Duration, evictAfterSize int) *moduleCache {
@@ -49,6 +50,7 @@ func newModuleCache(clock clockwork.Clock, tick, timeout time.Duration, evictAft
 		timeout:        timeout,
 		evictAfterSize: evictAfterSize,
 		clock:          clock,
+		reapTicker:     clock.NewTicker(tick).Chan(),
 		stopChan:       make(chan struct{}),
 	}
 }
@@ -67,10 +69,9 @@ func (mc *moduleCache) close() {
 }
 
 func (mc *moduleCache) reapLoop() {
-	ticker := mc.clock.NewTicker(mc.tickInterval)
 	for {
 		select {
-		case <-ticker.Chan():
+		case <-mc.reapTicker:
 			mc.evictOlderThan(mc.timeout)
 			if mc.onReaper != nil {
 				mc.onReaper <- struct{}{}
@@ -84,7 +85,7 @@ func (mc *moduleCache) reapLoop() {
 func (mc *moduleCache) add(id string, mod *module) {
 	mc.mu.Lock()
 	defer mc.mu.Unlock()
-	mod.lastFetchedAt = time.Now()
+	mod.lastFetchedAt = mc.clock.Now()
 	mc.m[id] = mod
 	moduleCacheAddition.Inc()
 }

core/capabilities/compute/cache_test.go

@@ -20,14 +20,17 @@ const (
 	binaryCmd      = "core/capabilities/compute/test/simple/cmd"
 )
 
+// Verify that cache evicts an expired module.
 func TestCache(t *testing.T) {
 	t.Parallel()
 	clock := clockwork.NewFakeClock()
 	tick := 1 * time.Second
 	timeout := 1 * time.Second
+	reapTicker := make(chan time.Time)
 
 	cache := newModuleCache(clock, tick, timeout, 0)
 	cache.onReaper = make(chan struct{}, 1)
+	cache.reapTicker = reapTicker
 	cache.start()
 	defer cache.close()
 
@@ -50,20 +53,24 @@ func TestCache(t *testing.T) {
 	assert.Equal(t, got, mod)
 
 	clock.Advance(15 * time.Second)
+	reapTicker <- time.Now()
 	<-cache.onReaper
 	_, ok = cache.get(id)
 	assert.False(t, ok)
 }
 
+// Verify that an expired module is not evicted because evictAfterSize is 1
 func TestCache_EvictAfterSize(t *testing.T) {
 	t.Parallel()
 	ctx := tests.Context(t)
 	clock := clockwork.NewFakeClock()
 	tick := 1 * time.Second
 	timeout := 1 * time.Second
+	reapTicker := make(chan time.Time)
 
 	cache := newModuleCache(clock, tick, timeout, 1)
 	cache.onReaper = make(chan struct{}, 1)
+	cache.reapTicker = reapTicker
 	cache.start()
 	defer cache.close()
 
@@ -79,13 +86,15 @@ func TestCache_EvictAfterSize(t *testing.T) {
 		module: hmod,
 	}
 	cache.add(id, mod)
+	assert.Len(t, cache.m, 1)
 
 	got, ok := cache.get(id)
 	assert.True(t, ok)
 
 	assert.Equal(t, got, mod)
 
 	clock.Advance(15 * time.Second)
+	reapTicker <- time.Now()
 	select {
 	case <-ctx.Done():
 		return