/*
* 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.RaftActorContext;
import org.opendaylight.controller.cluster.raft.RaftState;
import org.opendaylight.controller.cluster.raft.internal.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.RaftRPC;
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;
/**
* The maximum election time variance
*/
private static final int ELECTION_TIME_MAX_VARIANCE = 100;
/**
* The interval in which a new election would get triggered if no leader is found
*/
private static final long ELECTION_TIME_INTERVAL = Leader.HEART_BEAT_INTERVAL.toMillis() * 2;
/**
*
*/
private Cancellable electionCancel = 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
* @param suggestedState The state that the RaftActor should be in based
* on the base class's processing of the AppendEntries
* message
* @return
*/
protected abstract RaftState handleAppendEntries(ActorRef sender,
AppendEntries appendEntries, RaftState suggestedState);
/**
* 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
* @param suggestedState The state that the RaftActor should be in based
* on the base class's processing of the
* AppendEntriesReply message
* @return
*/
protected abstract RaftState handleAppendEntriesReply(ActorRef sender,
AppendEntriesReply appendEntriesReply, RaftState suggestedState);
protected RaftState handleRequestVote(ActorRef sender,
RequestVote requestVote, RaftState suggestedState){
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() >= lastTerm()){
candidateLatest = true;
}
if(candidateLatest) {
grantVote = true;
context.getTermInformation().update(requestVote.getTerm(),
requestVote.getCandidateId());
}
}
sender.tell(new RequestVoteReply(currentTerm(), grantVote), actor());
return suggestedState;
}
/**
* 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
* @param suggestedState The state that the RaftActor should be in based
* on the base class's processing of the RequestVote
* message
* @return
*/
protected abstract RaftState handleRequestVoteReply(ActorRef sender,
RequestVoteReply requestVoteReply, RaftState suggestedState);
/**
* @return The derived class should return the state that corresponds to
* it's behavior
*/
protected abstract RaftState state();
protected FiniteDuration electionDuration(){
long variance = new Random().nextInt(ELECTION_TIME_MAX_VARIANCE);
return new FiniteDuration(ELECTION_TIME_INTERVAL + variance, TimeUnit.MILLISECONDS);
}
protected void scheduleElection(FiniteDuration interval) {
if (electionCancel != null && !electionCancel.isCancelled()) {
electionCancel.cancel();
}
// 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());
}
protected long currentTerm(){
return context.getTermInformation().getCurrentTerm();
}
protected String votedFor(){
return context.getTermInformation().getVotedFor();
}
protected ActorRef actor(){
return context.getActor();
}
protected long lastTerm() {
return context.getReplicatedLog().last().getTerm();
}
protected long lastIndex() {
return context.getReplicatedLog().last().getIndex();
}
@Override
public RaftState handleMessage(ActorRef sender, Object message) {
RaftState raftState = state();
if (message instanceof RaftRPC) {
raftState = applyTerm((RaftRPC) message);
}
if (message instanceof AppendEntries) {
AppendEntries appendEntries = (AppendEntries) message;
if (appendEntries.getLeaderCommit() > context.getLastApplied()) {
applyLogToStateMachine(appendEntries.getLeaderCommit());
}
raftState = handleAppendEntries(sender, appendEntries, raftState);
} else if (message instanceof AppendEntriesReply) {
raftState =
handleAppendEntriesReply(sender, (AppendEntriesReply) message,
raftState);
} else if (message instanceof RequestVote) {
raftState =
handleRequestVote(sender, (RequestVote) message, raftState);
} else if (message instanceof RequestVoteReply) {
raftState =
handleRequestVoteReply(sender, (RequestVoteReply) message,
raftState);
}
return raftState;
}
private RaftState applyTerm(RaftRPC rpc) {
// If RPC request or response contains term T > currentTerm:
// set currentTerm = T, convert to follower (§5.1)
// This applies to all RPC messages and responses
if (rpc.getTerm() > context.getTermInformation().getCurrentTerm()) {
context.getTermInformation().update(rpc.getTerm(), null);
return RaftState.Follower;
}
return state();
}
private void applyLogToStateMachine(long index) {
// Send a local message to the local RaftActor (it's derived class to be
// specific to apply the log to it's index)
context.setLastApplied(index);
}
}