Avoid race condition when updating equivalence cache.

pkg/scheduler/core/equivalence_cache.go

@@ -75,9 +75,12 @@ func (ec *EquivalenceCache) UpdateCachedPredicateItem(
 	fit bool,
 	reasons []algorithm.PredicateFailureReason,
 	equivalenceHash uint64,
+	needLock bool,
 ) {
-	ec.Lock()
-	defer ec.Unlock()
+	if needLock {
+		ec.Lock()
+		defer ec.Unlock()
+	}
 	if _, exist := ec.algorithmCache[nodeName]; !exist {
 		ec.algorithmCache[nodeName] = newAlgorithmCache()
 	}
@@ -106,10 +109,12 @@ func (ec *EquivalenceCache) UpdateCachedPredicateItem(
 // based on cached predicate results
 func (ec *EquivalenceCache) PredicateWithECache(
 	podName, nodeName, predicateKey string,
-	equivalenceHash uint64,
+	equivalenceHash uint64, needLock bool,
 ) (bool, []algorithm.PredicateFailureReason, bool) {
-	ec.RLock()
-	defer ec.RUnlock()
+	if needLock {
+		ec.RLock()
+		defer ec.RUnlock()
+	}
 	glog.V(5).Infof("Begin to calculate predicate: %v for pod: %s on node: %s based on equivalence cache",
 		predicateKey, podName, nodeName)
 	if algorithmCache, exist := ec.algorithmCache[nodeName]; exist {

pkg/scheduler/core/equivalence_cache_test.go

@@ -90,6 +90,7 @@ func TestUpdateCachedPredicateItem(t *testing.T) {
 			test.fit,
 			test.reasons,
 			test.equivalenceHash,
+			true,
 		)
 
 		value, ok := ecache.algorithmCache[test.nodeName].predicatesCache.Get(test.predicateKey)
@@ -201,6 +202,7 @@ func TestPredicateWithECache(t *testing.T) {
 			test.cachedItem.fit,
 			test.cachedItem.reasons,
 			test.equivalenceHashForUpdatePredicate,
+			true,
 		)
 		// if we want to do invalid, invalid the cached item
 		if test.expectedInvalidPredicateKey {
@@ -213,6 +215,7 @@ func TestPredicateWithECache(t *testing.T) {
 			test.nodeName,
 			test.predicateKey,
 			test.equivalenceHashForCalPredicate,
+			true,
 		)
 		// returned invalid should match expectedInvalidPredicateKey or expectedInvalidEquivalenceHash
 		if test.equivalenceHashForUpdatePredicate != test.equivalenceHashForCalPredicate {
@@ -564,6 +567,7 @@ func TestInvalidateCachedPredicateItemOfAllNodes(t *testing.T) {
 			test.cachedItem.fit,
 			test.cachedItem.reasons,
 			test.equivalenceHashForUpdatePredicate,
+			true,
 		)
 	}
 
@@ -632,6 +636,7 @@ func TestInvalidateAllCachedPredicateItemOfNode(t *testing.T) {
 			test.cachedItem.fit,
 			test.cachedItem.reasons,
 			test.equivalenceHashForUpdatePredicate,
+			true,
 		)
 	}
 

pkg/scheduler/core/generic_scheduler.go

@@ -108,7 +108,7 @@ type genericScheduler struct {
 
 // Schedule tries to schedule the given pod to one of node in the node list.
 // If it succeeds, it will return the name of the node.
-// If it fails, it will return a Fiterror error with reasons.
+// If it fails, it will return a FitError error with reasons.
 func (g *genericScheduler) Schedule(pod *v1.Pod, nodeLister algorithm.NodeLister) (string, error) {
 	trace := utiltrace.New(fmt.Sprintf("Scheduling %s/%s", pod.Namespace, pod.Name))
 	defer trace.LogIfLong(100 * time.Millisecond)
@@ -469,8 +469,11 @@ func podFitsOnNode(
 			//TODO (yastij) : compute average predicate restrictiveness to export it as Prometheus metric
 			if predicate, exist := predicateFuncs[predicateKey]; exist {
 				if eCacheAvailable {
+					// Lock ecache here to avoid a race condition against cache invalidation invoked
+					// in event handlers. This race has existed despite locks in eCache implementation.
+					ecache.Lock()
 					// PredicateWithECache will return its cached predicate results.
-					fit, reasons, invalid = ecache.PredicateWithECache(pod.GetName(), info.Node().GetName(), predicateKey, equivCacheInfo.hash)
+					fit, reasons, invalid = ecache.PredicateWithECache(pod.GetName(), info.Node().GetName(), predicateKey, equivCacheInfo.hash, false)
 				}
 
 				if !eCacheAvailable || invalid {
@@ -488,8 +491,15 @@ func podFitsOnNode(
 						} else {
 							predicateResults[predicateKey] = HostPredicate{Fit: fit, FailReasons: reasons}
 						}
+						result := predicateResults[predicateKey]
+						ecache.UpdateCachedPredicateItem(pod.GetName(), info.Node().GetName(), predicateKey, result.Fit, result.FailReasons, equivCacheInfo.hash, false)
 					}
 				}
+
+				if eCacheAvailable {
+					ecache.Unlock()
+				}
+
 				if !fit {
 					// eCache is available and valid, and predicates result is unfit, record the fail reasons
 					failedPredicates = append(failedPredicates, reasons...)
@@ -503,18 +513,6 @@ func podFitsOnNode(
 		}
 	}
 
-	// TODO(bsalamat): This way of updating equiv. cache has a race condition against
-	// cache invalidations invoked in event handlers. This race has existed despite locks
-	// in eCache implementation. If cache is invalidated after a predicate is executed
-	// and before we update the cache, the updates should not be written to the cache.
-	if eCacheAvailable {
-		nodeName := info.Node().GetName()
-		for predKey, result := range predicateResults {
-			// update equivalence cache with newly computed fit & reasons
-			// TODO(resouer) should we do this in another thread? any race?
-			ecache.UpdateCachedPredicateItem(pod.GetName(), nodeName, predKey, result.Fit, result.FailReasons, equivCacheInfo.hash)
-		}
-	}
 	return len(failedPredicates) == 0, failedPredicates, nil
 }