[Emu] MutexExecutionService for running tasks that need to run only on a single instance.
Change-Id: Idf9fedbbf15c014e97c77db25aa608cd1db53b27
diff --git a/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/MutexExecutionManager.java b/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/MutexExecutionManager.java
new file mode 100644
index 0000000..d8593e3
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/MutexExecutionManager.java
@@ -0,0 +1,315 @@
+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.store.consistent.impl;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.apache.felix.scr.annotations.Service;
+import org.onlab.util.Tools;
+import org.onosproject.cluster.ClusterEvent;
+import org.onosproject.cluster.ClusterEventListener;
+import org.onosproject.cluster.ClusterService;
+import org.onosproject.cluster.ControllerNode.State;
+import org.onosproject.cluster.NodeId;
+import org.onosproject.store.serializers.KryoNamespaces;
+import org.onosproject.store.service.ConsistentMap;
+import org.onosproject.store.service.ConsistentMapException;
+import org.onosproject.store.service.MapEvent;
+import org.onosproject.store.service.MapEventListener;
+import org.onosproject.store.service.MutexExecutionService;
+import org.onosproject.store.service.MutexTask;
+import org.onosproject.store.service.Serializer;
+import org.onosproject.store.service.StorageService;
+import org.onosproject.store.service.Versioned;
+import org.slf4j.Logger;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+
+/**
+ * Implementation of a MutexExecutionService.
+ */
+@Component(immediate = true)
+@Service
+public class MutexExecutionManager implements MutexExecutionService {
+
+ private final Logger log = getLogger(getClass());
+
+ protected ConsistentMap<String, MutexState> lockMap;
+ protected NodeId localNodeId;
+
+ @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+ protected ClusterService clusterService;
+
+ @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+ protected StorageService storageService;
+
+ private final MapEventListener<String, MutexState> mapEventListener = new InternalLockMapEventListener();
+ private final ClusterEventListener clusterEventListener = new InternalClusterEventListener();
+
+ private Map<String, CompletableFuture<MutexState>> pending = Maps.newConcurrentMap();
+ private Map<String, InnerMutexTask> activeTasks = Maps.newConcurrentMap();
+
+ @Activate
+ public void activate() {
+ localNodeId = clusterService.getLocalNode().id();
+ lockMap = storageService.<String, MutexState>consistentMapBuilder()
+ .withName("onos-mutexes")
+ .withSerializer(Serializer.using(Arrays.asList(KryoNamespaces.API), MutexState.class))
+ .withPartitionsDisabled()
+ .build();
+ lockMap.addListener(mapEventListener);
+ clusterService.addListener(clusterEventListener);
+ releaseOldLocks();
+ log.info("Started");
+ }
+
+ @Deactivate
+ public void deactivate() {
+ lockMap.removeListener(mapEventListener);
+ pending.values().forEach(future -> future.cancel(true));
+ activeTasks.forEach((k, v) -> {
+ v.stop();
+ unlock(k);
+ });
+ clusterService.removeListener(clusterEventListener);
+ log.info("Stopped");
+ }
+
+ @Override
+ public CompletableFuture<Void> execute(MutexTask task, String exclusionPath, Executor executor) {
+ return lock(exclusionPath)
+ .thenApply(state -> activeTasks.computeIfAbsent(exclusionPath,
+ k -> new InnerMutexTask(exclusionPath,
+ task,
+ state.term())))
+ .thenAcceptAsync(t -> t.start(), executor)
+ .whenComplete((r, e) -> unlock(exclusionPath));
+ }
+
+ protected CompletableFuture<MutexState> lock(String exclusionPath) {
+ CompletableFuture<MutexState> future =
+ pending.computeIfAbsent(exclusionPath, k -> new CompletableFuture<>());
+ tryLock(exclusionPath);
+ return future;
+ }
+
+ /**
+ * Attempts to acquire lock for a path. If lock is held by some other node, adds this node to
+ * the wait list.
+ * @param exclusionPath exclusion path
+ */
+ protected void tryLock(String exclusionPath) {
+ Tools.retryable(() -> lockMap.asJavaMap()
+ .compute(exclusionPath,
+ (k, v) -> MutexState.admit(v, localNodeId)),
+ ConsistentMapException.ConcurrentModification.class,
+ Integer.MAX_VALUE,
+ 100).get();
+ }
+
+ /**
+ * Releases lock for the specific path. This operation is idempotent.
+ * @param exclusionPath exclusion path
+ */
+ protected void unlock(String exclusionPath) {
+ Tools.retryable(() -> lockMap.asJavaMap()
+ .compute(exclusionPath, (k, v) -> MutexState.evict(v, localNodeId)),
+ ConsistentMapException.ConcurrentModification.class,
+ Integer.MAX_VALUE,
+ 100).get();
+ }
+
+ /**
+ * Detects and releases all locks held by this node.
+ */
+ private void releaseOldLocks() {
+ Maps.filterValues(lockMap.asJavaMap(), state -> localNodeId.equals(state.holder()))
+ .keySet()
+ .forEach(path -> {
+ log.info("Detected zombie task still holding lock for {}. Releasing lock.", path);
+ unlock(path);
+ });
+ }
+
+ private class InternalLockMapEventListener implements MapEventListener<String, MutexState> {
+
+ @Override
+ public void event(MapEvent<String, MutexState> event) {
+ log.debug("Received {}", event);
+ if (event.type() == MapEvent.Type.UPDATE || event.type() == MapEvent.Type.INSERT) {
+ pending.computeIfPresent(event.key(), (k, future) -> {
+ MutexState state = Versioned.valueOrElse(event.value(), null);
+ if (state != null && localNodeId.equals(state.holder())) {
+ log.debug("Local node is now owner for {}", event.key());
+ future.complete(state);
+ return null;
+ } else {
+ return future;
+ }
+ });
+ InnerMutexTask task = activeTasks.get(event.key());
+ if (task != null && task.term() < Versioned.valueOrElse(event.value(), null).term()) {
+ task.stop();
+ }
+ }
+ }
+ }
+
+ private class InternalClusterEventListener implements ClusterEventListener {
+
+ @Override
+ public void event(ClusterEvent event) {
+ if (event.type() == ClusterEvent.Type.INSTANCE_DEACTIVATED ||
+ event.type() == ClusterEvent.Type.INSTANCE_REMOVED) {
+ NodeId nodeId = event.subject().id();
+ log.debug("{} is no longer active. Attemping to clean up its locks.", nodeId);
+ lockMap.asJavaMap().forEach((k, v) -> {
+ if (v.contains(nodeId)) {
+ lockMap.compute(k, (path, state) -> MutexState.evict(v, nodeId));
+ }
+ });
+ }
+ long activeNodes = clusterService.getNodes()
+ .stream()
+ .map(node -> clusterService.getState(node.id()))
+ .filter(State.ACTIVE::equals)
+ .count();
+ if (clusterService.getNodes().size() > 1 && activeNodes == 1) {
+ log.info("This node is partitioned away from the cluster. Stopping all inflight executions");
+ activeTasks.forEach((k, v) -> {
+ v.stop();
+ });
+ }
+ }
+ }
+
+ private static final class MutexState {
+
+ private final NodeId holder;
+ private final List<NodeId> waitList;
+ private final long term;
+
+ public static MutexState admit(MutexState state, NodeId nodeId) {
+ if (state == null) {
+ return new MutexState(nodeId, 1L, Lists.newArrayList());
+ } else if (state.holder() == null) {
+ return new MutexState(nodeId, state.term() + 1, Lists.newArrayList());
+ } else {
+ if (!state.contains(nodeId)) {
+ NodeId newHolder = state.holder();
+ List<NodeId> newWaitList = Lists.newArrayList(state.waitList());
+ newWaitList.add(nodeId);
+ return new MutexState(newHolder, state.term(), newWaitList);
+ } else {
+ return state;
+ }
+ }
+ }
+
+ public static MutexState evict(MutexState state, NodeId nodeId) {
+ return state.evict(nodeId);
+ }
+
+ public MutexState evict(NodeId nodeId) {
+ if (nodeId.equals(holder)) {
+ if (waitList.isEmpty()) {
+ return new MutexState(null, term, waitList);
+ }
+ List<NodeId> newWaitList = Lists.newArrayList(waitList);
+ NodeId newHolder = newWaitList.remove(0);
+ return new MutexState(newHolder, term + 1, newWaitList);
+ } else {
+ NodeId newHolder = holder;
+ List<NodeId> newWaitList = Lists.newArrayList(waitList);
+ newWaitList.remove(nodeId);
+ return new MutexState(newHolder, term, newWaitList);
+ }
+ }
+
+ public NodeId holder() {
+ return holder;
+ }
+
+ public List<NodeId> waitList() {
+ return waitList;
+ }
+
+ public long term() {
+ return term;
+ }
+
+ private boolean contains(NodeId nodeId) {
+ return (nodeId.equals(holder) || waitList.contains(nodeId));
+ }
+
+ private MutexState(NodeId holder, long term, List<NodeId> waitList) {
+ this.holder = holder;
+ this.term = term;
+ this.waitList = Lists.newArrayList(waitList);
+ }
+
+ @Override
+ public String toString() {
+ return MoreObjects.toStringHelper(getClass())
+ .add("holder", holder)
+ .add("term", term)
+ .add("waitList", waitList)
+ .toString();
+ }
+ }
+
+ private class InnerMutexTask implements MutexTask {
+ private final MutexTask task;
+ private final String mutexPath;
+ private final long term;
+
+ public InnerMutexTask(String mutexPath, MutexTask task, long term) {
+ this.mutexPath = mutexPath;
+ this.term = term;
+ this.task = task;
+ }
+
+ public long term() {
+ return term;
+ }
+
+ @Override
+ public void start() {
+ log.debug("Starting execution for mutex task guarded by {}", mutexPath);
+ task.start();
+ log.debug("Finished execution for mutex task guarded by {}", mutexPath);
+ }
+
+ @Override
+ public void stop() {
+ log.debug("Stopping execution for mutex task guarded by {}", mutexPath);
+ task.stop();
+ }
+ }
+}
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