/* * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved. * * This program and the accompanying materials are made available under the * terms of the Eclipse Public License v1.0 which accompanies this distribution, * and is available at http://www.eclipse.org/legal/epl-v10.html */ package org.opendaylight.controller.cluster.raft; import akka.actor.ActorRef; import akka.actor.ActorSelection; import akka.japi.Procedure; import akka.persistence.SnapshotSelectionCriteria; import com.google.common.annotations.VisibleForTesting; import com.google.common.base.Objects; import com.google.common.base.Optional; import com.google.common.collect.ImmutableMap; import com.google.common.collect.Lists; import java.io.Serializable; import java.util.Collection; import java.util.List; import java.util.Map; import java.util.concurrent.TimeUnit; import javax.annotation.Nonnull; import org.apache.commons.lang3.time.DurationFormatUtils; import org.opendaylight.controller.cluster.DataPersistenceProvider; import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider; import org.opendaylight.controller.cluster.NonPersistentDataProvider; import org.opendaylight.controller.cluster.PersistentDataProvider; import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor; import org.opendaylight.controller.cluster.notifications.LeaderStateChanged; import org.opendaylight.controller.cluster.notifications.RoleChanged; import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries; import org.opendaylight.controller.cluster.raft.base.messages.ApplyState; import org.opendaylight.controller.cluster.raft.base.messages.Replicate; import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader; import org.opendaylight.controller.cluster.raft.behaviors.DelegatingRaftActorBehavior; import org.opendaylight.controller.cluster.raft.behaviors.Follower; import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior; import org.opendaylight.controller.cluster.raft.client.messages.FindLeader; import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply; import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo; import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState; import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState; import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * RaftActor encapsulates a state machine that needs to be kept synchronized * in a cluster. It implements the RAFT algorithm as described in the paper * * In Search of an Understandable Consensus Algorithm *

* RaftActor has 3 states and each state has a certain behavior associated * with it. A Raft actor can behave as, *

*

*

* A RaftActor MUST be a Leader in order to accept requests from clients to * change the state of it's encapsulated state machine. Once a RaftActor becomes * a Leader it is also responsible for ensuring that all followers ultimately * have the same log and therefore the same state machine as itself. *

*

* The current behavior of a RaftActor determines how election for leadership * is initiated and how peer RaftActors react to request for votes. *

*

* Each RaftActor also needs to know the current election term. It uses this * information for a couple of things. One is to simply figure out who it * voted for in the last election. Another is to figure out if the message * it received to update it's state is stale. *

*

* The RaftActor uses akka-persistence to store it's replicated log. * Furthermore through it's behaviors a Raft Actor determines *

*

*/ public abstract class RaftActor extends AbstractUntypedPersistentActor { private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis protected final Logger LOG = LoggerFactory.getLogger(getClass()); /** * The current state determines the current behavior of a RaftActor * A Raft Actor always starts off in the Follower State */ private final DelegatingRaftActorBehavior currentBehavior = new DelegatingRaftActorBehavior(); /** * This context should NOT be passed directly to any other actor it is * only to be consumed by the RaftActorBehaviors */ private final RaftActorContextImpl context; private final DelegatingPersistentDataProvider delegatingPersistenceProvider = new DelegatingPersistentDataProvider(null); private RaftActorRecoverySupport raftRecovery; private RaftActorSnapshotMessageSupport snapshotSupport; private final BehaviorStateHolder reusableBehaviorStateHolder = new BehaviorStateHolder(); public RaftActor(String id, Map peerAddresses) { this(id, peerAddresses, Optional.absent()); } public RaftActor(String id, Map peerAddresses, Optional configParams) { context = new RaftActorContextImpl(this.getSelf(), this.getContext(), id, new ElectionTermImpl(delegatingPersistenceProvider, id, LOG), -1, -1, peerAddresses, (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()), LOG); context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, delegatingPersistenceProvider, currentBehavior)); } @Override public void preStart() throws Exception { LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(), context.getConfigParams().getJournalRecoveryLogBatchSize()); super.preStart(); } @Override public void postStop() { if(currentBehavior.getDelegate() != null) { try { currentBehavior.close(); } catch (Exception e) { LOG.debug("{}: Error closing behavior {}", persistenceId(), currentBehavior.state()); } } super.postStop(); } @Override public void handleRecover(Object message) { if(raftRecovery == null) { raftRecovery = new RaftActorRecoverySupport(delegatingPersistenceProvider, context, currentBehavior, getRaftActorRecoveryCohort()); } boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message); if(recoveryComplete) { if(!persistence().isRecoveryApplicable()) { // Delete all the messages from the akka journal so that we do not end up with consistency issues // Note I am not using the dataPersistenceProvider and directly using the akka api here deleteMessages(lastSequenceNr()); // Delete all the akka snapshots as they will not be needed deleteSnapshots(new SnapshotSelectionCriteria(scala.Long.MaxValue(), scala.Long.MaxValue())); } onRecoveryComplete(); initializeBehavior(); raftRecovery = null; } } protected void initializeBehavior(){ changeCurrentBehavior(new Follower(context)); } protected void changeCurrentBehavior(RaftActorBehavior newBehavior){ reusableBehaviorStateHolder.init(getCurrentBehavior()); setCurrentBehavior(newBehavior); handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior()); } @Override public void handleCommand(Object message) { if(snapshotSupport == null) { snapshotSupport = new RaftActorSnapshotMessageSupport(delegatingPersistenceProvider, context, currentBehavior, getRaftActorSnapshotCohort(), self()); } boolean handled = snapshotSupport.handleSnapshotMessage(message); if(handled) { return; } if (message instanceof ApplyState){ ApplyState applyState = (ApplyState) message; long elapsedTime = (System.nanoTime() - applyState.getStartTime()); if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){ LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}", TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState); } if(LOG.isDebugEnabled()) { LOG.debug("{}: Applying state for log index {} data {}", persistenceId(), applyState.getReplicatedLogEntry().getIndex(), applyState.getReplicatedLogEntry().getData()); } applyState(applyState.getClientActor(), applyState.getIdentifier(), applyState.getReplicatedLogEntry().getData()); } else if (message instanceof ApplyJournalEntries){ ApplyJournalEntries applyEntries = (ApplyJournalEntries) message; if(LOG.isDebugEnabled()) { LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex()); } persistence().persist(applyEntries, NoopProcedure.instance()); } else if (message instanceof FindLeader) { getSender().tell( new FindLeaderReply(getLeaderAddress()), getSelf() ); } else if(message instanceof GetOnDemandRaftState) { onGetOnDemandRaftStats(); } else { reusableBehaviorStateHolder.init(getCurrentBehavior()); setCurrentBehavior(currentBehavior.handleMessage(getSender(), message)); handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior()); } } private void onGetOnDemandRaftStats() { // Debugging message to retrieve raft stats. OnDemandRaftState.Builder builder = OnDemandRaftState.builder() .commitIndex(context.getCommitIndex()) .currentTerm(context.getTermInformation().getCurrentTerm()) .inMemoryJournalDataSize(replicatedLog().dataSize()) .inMemoryJournalLogSize(replicatedLog().size()) .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing()) .lastApplied(context.getLastApplied()) .lastIndex(replicatedLog().lastIndex()) .lastTerm(replicatedLog().lastTerm()) .leader(getLeaderId()) .raftState(currentBehavior.state().toString()) .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex()) .snapshotIndex(replicatedLog().getSnapshotIndex()) .snapshotTerm(replicatedLog().getSnapshotTerm()) .votedFor(context.getTermInformation().getVotedFor()) .peerAddresses(ImmutableMap.copyOf(context.getPeerAddresses())); ReplicatedLogEntry lastLogEntry = getLastLogEntry(); if (lastLogEntry != null) { builder.lastLogIndex(lastLogEntry.getIndex()); builder.lastLogTerm(lastLogEntry.getTerm()); } if(getCurrentBehavior() instanceof AbstractLeader) { AbstractLeader leader = (AbstractLeader)getCurrentBehavior(); Collection followerIds = leader.getFollowerIds(); List followerInfoList = Lists.newArrayListWithCapacity(followerIds.size()); for(String id: followerIds) { final FollowerLogInformation info = leader.getFollower(id); followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(), info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity()))); } builder.followerInfoList(followerInfoList); } sender().tell(builder.build(), self()); } private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) { RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior(); if (oldBehavior != currentBehavior){ onStateChanged(); } String oldBehaviorLeaderId = oldBehavior == null ? null : oldBehaviorState.getLeaderId(); String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name(); // it can happen that the state has not changed but the leader has changed. Optional roleChangeNotifier = getRoleChangeNotifier(); if(!Objects.equal(oldBehaviorLeaderId, currentBehavior.getLeaderId())) { if(roleChangeNotifier.isPresent()) { roleChangeNotifier.get().tell(new LeaderStateChanged(getId(), currentBehavior.getLeaderId()), getSelf()); } onLeaderChanged(oldBehaviorLeaderId, currentBehavior.getLeaderId()); } if (roleChangeNotifier.isPresent() && (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) { roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName , currentBehavior.state().name()), getSelf()); } } /** * When a derived RaftActor needs to persist something it must call * persistData. * * @param clientActor * @param identifier * @param data */ protected void persistData(final ActorRef clientActor, final String identifier, final Payload data) { ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry( context.getReplicatedLog().lastIndex() + 1, context.getTermInformation().getCurrentTerm(), data); if(LOG.isDebugEnabled()) { LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry); } final RaftActorContext raftContext = getRaftActorContext(); replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure() { @Override public void apply(ReplicatedLogEntry replicatedLogEntry) throws Exception { if(!hasFollowers()){ // Increment the Commit Index and the Last Applied values raftContext.setCommitIndex(replicatedLogEntry.getIndex()); raftContext.setLastApplied(replicatedLogEntry.getIndex()); // Apply the state immediately applyState(clientActor, identifier, data); // Send a ApplyJournalEntries message so that we write the fact that we applied // the state to durable storage self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self()); context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior); } else if (clientActor != null) { // Send message for replication currentBehavior.handleMessage(getSelf(), new Replicate(clientActor, identifier, replicatedLogEntry)); } } }); } private ReplicatedLog replicatedLog() { return context.getReplicatedLog(); } protected String getId() { return context.getId(); } @VisibleForTesting void setCurrentBehavior(RaftActorBehavior behavior) { currentBehavior.setDelegate(behavior); } protected RaftActorBehavior getCurrentBehavior() { return currentBehavior.getDelegate(); } /** * Derived actors can call the isLeader method to check if the current * RaftActor is the Leader or not * * @return true it this RaftActor is a Leader false otherwise */ protected boolean isLeader() { return context.getId().equals(currentBehavior.getLeaderId()); } /** * Derived actor can call getLeader if they need a reference to the Leader. * This would be useful for example in forwarding a request to an actor * which is the leader * * @return A reference to the leader if known, null otherwise */ protected ActorSelection getLeader(){ String leaderAddress = getLeaderAddress(); if(leaderAddress == null){ return null; } return context.actorSelection(leaderAddress); } /** * * @return the current leader's id */ protected String getLeaderId(){ return currentBehavior.getLeaderId(); } protected RaftState getRaftState() { return currentBehavior.state(); } protected ReplicatedLogEntry getLastLogEntry() { return replicatedLog().last(); } protected Long getCurrentTerm(){ return context.getTermInformation().getCurrentTerm(); } protected Long getCommitIndex(){ return context.getCommitIndex(); } protected Long getLastApplied(){ return context.getLastApplied(); } protected RaftActorContext getRaftActorContext() { return context; } protected void updateConfigParams(ConfigParams configParams) { context.setConfigParams(configParams); } public final DataPersistenceProvider persistence() { return delegatingPersistenceProvider.getDelegate(); } public void setPersistence(DataPersistenceProvider provider) { delegatingPersistenceProvider.setDelegate(provider); } protected void setPersistence(boolean persistent) { if(persistent) { setPersistence(new PersistentDataProvider(this)); } else { setPersistence(new NonPersistentDataProvider() { /** * The way snapshotting works is, *
    *
  1. RaftActor calls createSnapshot on the Shard *
  2. Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot *
  3. When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This * commitSnapshot is mimicking what is done in SaveSnapshotSuccess. *
*/ @Override public void saveSnapshot(Object o) { // Make saving Snapshot successful // Committing the snapshot here would end up calling commit in the creating state which would // be a state violation. That's why now we send a message to commit the snapshot. self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self()); } }); } } /** * setPeerAddress sets the address of a known peer at a later time. *

* This is to account for situations where a we know that a peer * exists but we do not know an address up-front. This may also be used in * situations where a known peer starts off in a different location and we * need to change it's address *

* Note that if the peerId does not match the list of peers passed to * this actor during construction an IllegalStateException will be thrown. * * @param peerId * @param peerAddress */ protected void setPeerAddress(String peerId, String peerAddress){ context.setPeerAddress(peerId, peerAddress); } /** * The applyState method will be called by the RaftActor when some data * needs to be applied to the actor's state * * @param clientActor A reference to the client who sent this message. This * is the same reference that was passed to persistData * by the derived actor. clientActor may be null when * the RaftActor is behaving as a follower or during * recovery. * @param identifier The identifier of the persisted data. This is also * the same identifier that was passed to persistData by * the derived actor. identifier may be null when * the RaftActor is behaving as a follower or during * recovery * @param data A piece of data that was persisted by the persistData call. * This should NEVER be null. */ protected abstract void applyState(ActorRef clientActor, String identifier, Object data); /** * Returns the RaftActorRecoveryCohort to participate in persistence recovery. */ @Nonnull protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort(); /** * This method is called when recovery is complete. */ protected abstract void onRecoveryComplete(); /** * Returns the RaftActorSnapshotCohort to participate in persistence recovery. */ @Nonnull protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort(); /** * This method will be called by the RaftActor when the state of the * RaftActor changes. The derived actor can then use methods like * isLeader or getLeader to do something useful */ protected abstract void onStateChanged(); /** * Notifier Actor for this RaftActor to notify when a role change happens * @return ActorRef - ActorRef of the notifier or Optional.absent if none. */ protected abstract Optional getRoleChangeNotifier(); protected void onLeaderChanged(String oldLeader, String newLeader){}; private String getLeaderAddress(){ if(isLeader()){ return getSelf().path().toString(); } String leaderId = currentBehavior.getLeaderId(); if (leaderId == null) { return null; } String peerAddress = context.getPeerAddress(leaderId); if(LOG.isDebugEnabled()) { LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}", persistenceId(), leaderId, peerAddress); } return peerAddress; } protected boolean hasFollowers(){ return getRaftActorContext().hasFollowers(); } static class DeleteEntries implements Serializable { private static final long serialVersionUID = 1L; private final int fromIndex; public DeleteEntries(int fromIndex) { this.fromIndex = fromIndex; } public int getFromIndex() { return fromIndex; } } static class UpdateElectionTerm implements Serializable { private static final long serialVersionUID = 1L; private final long currentTerm; private final String votedFor; public UpdateElectionTerm(long currentTerm, String votedFor) { this.currentTerm = currentTerm; this.votedFor = votedFor; } public long getCurrentTerm() { return currentTerm; } public String getVotedFor() { return votedFor; } } private static class BehaviorStateHolder { private RaftActorBehavior behavior; private String leaderId; void init(RaftActorBehavior behavior) { this.behavior = behavior; this.leaderId = behavior != null ? behavior.getLeaderId() : null; } RaftActorBehavior getBehavior() { return behavior; } String getLeaderId() { return leaderId; } } }