/*
* 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.behaviors;
import akka.actor.ActorRef;
import akka.actor.Cancellable;
import org.opendaylight.controller.cluster.raft.ClientRequestTracker;
import org.opendaylight.controller.cluster.raft.RaftActorContext;
import org.opendaylight.controller.cluster.raft.RaftState;
import org.opendaylight.controller.cluster.raft.ReplicatedLogEntry;
import org.opendaylight.controller.cluster.raft.SerializationUtils;
import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
import org.opendaylight.controller.cluster.raft.base.messages.ElectionTimeout;
import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
import org.opendaylight.controller.cluster.raft.messages.RequestVote;
import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
import scala.concurrent.duration.FiniteDuration;
import java.util.Random;
import java.util.concurrent.TimeUnit;
/**
* Abstract class that represents the behavior of a RaftActor
*
* All Servers:
*
* - If commitIndex > lastApplied: increment lastApplied, apply
* log[lastApplied] to state machine (§5.3)
*
- If RPC request or response contains term T > currentTerm:
* set currentTerm = T, convert to follower (§5.1)
*/
public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
/**
* Information about the RaftActor whose behavior this class represents
*/
protected final RaftActorContext context;
/**
*
*/
private Cancellable electionCancel = null;
/**
*
*/
protected String leaderId = null;
protected AbstractRaftActorBehavior(RaftActorContext context) {
this.context = context;
}
/**
* Derived classes should not directly handle AppendEntries messages it
* should let the base class handle it first. Once the base class handles
* the AppendEntries message and does the common actions that are applicable
* in all RaftState's it will delegate the handling of the AppendEntries
* message to the derived class to do more state specific handling by calling
* this method
*
* @param sender The actor that sent this message
* @param appendEntries The AppendEntries message
* @return
*/
protected abstract RaftState handleAppendEntries(ActorRef sender,
AppendEntries appendEntries);
/**
* appendEntries first processes the AppendEntries message and then
* delegates handling to a specific behavior
*
* @param sender
* @param appendEntries
* @return
*/
protected RaftState appendEntries(ActorRef sender,
AppendEntries appendEntries) {
// 1. Reply false if term < currentTerm (§5.1)
if (appendEntries.getTerm() < currentTerm()) {
context.getLogger().debug(
"Cannot append entries because sender term " + appendEntries
.getTerm() + " is less than " + currentTerm());
sender.tell(
new AppendEntriesReply(context.getId(), currentTerm(), false,
lastIndex(), lastTerm()), actor()
);
return state();
}
return handleAppendEntries(sender, appendEntries);
}
/**
* Derived classes should not directly handle AppendEntriesReply messages it
* should let the base class handle it first. Once the base class handles
* the AppendEntriesReply message and does the common actions that are
* applicable in all RaftState's it will delegate the handling of the
* AppendEntriesReply message to the derived class to do more state specific
* handling by calling this method
*
* @param sender The actor that sent this message
* @param appendEntriesReply The AppendEntriesReply message
* @return
*/
protected abstract RaftState handleAppendEntriesReply(ActorRef sender,
AppendEntriesReply appendEntriesReply);
/**
* requestVote handles the RequestVote message. This logic is common
* for all behaviors
*
* @param sender
* @param requestVote
* @return
*/
protected RaftState requestVote(ActorRef sender,
RequestVote requestVote) {
context.getLogger().debug(requestVote.toString());
boolean grantVote = false;
// Reply false if term < currentTerm (§5.1)
if (requestVote.getTerm() < currentTerm()) {
grantVote = false;
// If votedFor is null or candidateId, and candidate’s log is at
// least as up-to-date as receiver’s log, grant vote (§5.2, §5.4)
} else if (votedFor() == null || votedFor()
.equals(requestVote.getCandidateId())) {
boolean candidateLatest = false;
// From §5.4.1
// Raft determines which of two logs is more up-to-date
// by comparing the index and term of the last entries in the
// logs. If the logs have last entries with different terms, then
// the log with the later term is more up-to-date. If the logs
// end with the same term, then whichever log is longer is
// more up-to-date.
if (requestVote.getLastLogTerm() > lastTerm()) {
candidateLatest = true;
} else if ((requestVote.getLastLogTerm() == lastTerm())
&& requestVote.getLastLogIndex() >= lastIndex()) {
candidateLatest = true;
}
if (candidateLatest) {
grantVote = true;
context.getTermInformation().updateAndPersist(requestVote.getTerm(),
requestVote.getCandidateId());
}
}
sender.tell(new RequestVoteReply(currentTerm(), grantVote), actor());
return state();
}
/**
* Derived classes should not directly handle RequestVoteReply messages it
* should let the base class handle it first. Once the base class handles
* the RequestVoteReply message and does the common actions that are
* applicable in all RaftState's it will delegate the handling of the
* RequestVoteReply message to the derived class to do more state specific
* handling by calling this method
*
* @param sender The actor that sent this message
* @param requestVoteReply The RequestVoteReply message
* @return
*/
protected abstract RaftState handleRequestVoteReply(ActorRef sender,
RequestVoteReply requestVoteReply);
/**
* Creates a random election duration
*
* @return
*/
protected FiniteDuration electionDuration() {
long variance = new Random().nextInt(context.getConfigParams().getElectionTimeVariance());
return context.getConfigParams().getElectionTimeOutInterval().$plus(
new FiniteDuration(variance, TimeUnit.MILLISECONDS));
}
/**
* stop the scheduled election
*/
protected void stopElection() {
if (electionCancel != null && !electionCancel.isCancelled()) {
electionCancel.cancel();
}
}
/**
* schedule a new election
*
* @param interval
*/
protected void scheduleElection(FiniteDuration interval) {
stopElection();
// Schedule an election. When the scheduler triggers an ElectionTimeout
// message is sent to itself
electionCancel =
context.getActorSystem().scheduler().scheduleOnce(interval,
context.getActor(), new ElectionTimeout(),
context.getActorSystem().dispatcher(), context.getActor());
}
/**
* Get the current term
* @return
*/
protected long currentTerm() {
return context.getTermInformation().getCurrentTerm();
}
/**
* Get the candidate for whom we voted in the current term
* @return
*/
protected String votedFor() {
return context.getTermInformation().getVotedFor();
}
/**
* Get the actor associated with this behavior
* @return
*/
protected ActorRef actor() {
return context.getActor();
}
/**
* Get the term from the last entry in the log
*
* @return
*/
protected long lastTerm() {
return context.getReplicatedLog().lastTerm();
}
/**
* Get the index from the last entry in the log
*
* @return
*/
protected long lastIndex() {
return context.getReplicatedLog().lastIndex();
}
/**
* Find the client request tracker for a specific logIndex
*
* @param logIndex
* @return
*/
protected ClientRequestTracker findClientRequestTracker(long logIndex) {
return null;
}
/**
* Find the log index from the previous to last entry in the log
*
* @return
*/
protected long prevLogIndex(long index){
ReplicatedLogEntry prevEntry =
context.getReplicatedLog().get(index - 1);
if (prevEntry != null) {
return prevEntry.getIndex();
}
return -1;
}
/**
* Find the log term from the previous to last entry in the log
* @return
*/
protected long prevLogTerm(long index){
ReplicatedLogEntry prevEntry =
context.getReplicatedLog().get(index - 1);
if (prevEntry != null) {
return prevEntry.getTerm();
}
return -1;
}
/**
* Apply the provided index to the state machine
*
* @param index a log index that is known to be committed
*/
protected void applyLogToStateMachine(final long index) {
long newLastApplied = context.getLastApplied();
// Now maybe we apply to the state machine
for (long i = context.getLastApplied() + 1;
i < index + 1; i++) {
ActorRef clientActor = null;
String identifier = null;
ClientRequestTracker tracker = findClientRequestTracker(i);
if (tracker != null) {
clientActor = tracker.getClientActor();
identifier = tracker.getIdentifier();
}
ReplicatedLogEntry replicatedLogEntry =
context.getReplicatedLog().get(i);
if (replicatedLogEntry != null) {
actor().tell(new ApplyState(clientActor, identifier,
replicatedLogEntry), actor());
newLastApplied = i;
} else {
//if one index is not present in the log, no point in looping
// around as the rest wont be present either
context.getLogger().error(
"Missing index {} from log. Cannot apply state. Ignoring {} to {}", i, i, index );
break;
}
}
// Send a local message to the local RaftActor (it's derived class to be
// specific to apply the log to it's index)
context.getLogger().debug("Setting last applied to {}", newLastApplied);
context.setLastApplied(newLastApplied);
}
protected Object fromSerializableMessage(Object serializable){
return SerializationUtils.fromSerializable(serializable);
}
@Override
public RaftState handleMessage(ActorRef sender, Object message) {
if (message instanceof AppendEntries) {
return appendEntries(sender, (AppendEntries) message);
} else if (message instanceof AppendEntriesReply) {
return handleAppendEntriesReply(sender, (AppendEntriesReply) message);
} else if (message instanceof RequestVote) {
return requestVote(sender, (RequestVote) message);
} else if (message instanceof RequestVoteReply) {
return handleRequestVoteReply(sender, (RequestVoteReply) message);
}
return state();
}
@Override public String getLeaderId() {
return leaderId;
}
}