/*
* 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 java.util.Random;
import java.util.concurrent.TimeUnit;
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.ApplyJournalEntries;
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 org.slf4j.Logger;
import scala.concurrent.duration.FiniteDuration;
/**
* 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 {
protected static final ElectionTimeout ELECTION_TIMEOUT = new ElectionTimeout();
/**
* Information about the RaftActor whose behavior this class represents
*/
protected final RaftActorContext context;
/**
*
*/
protected final Logger LOG;
/**
*
*/
private Cancellable electionCancel = null;
/**
*
*/
protected String leaderId = null;
private short leaderPayloadVersion = -1;
private long replicatedToAllIndex = -1;
private final String logName;
private final RaftState state;
protected AbstractRaftActorBehavior(RaftActorContext context, RaftState state) {
this.context = context;
this.state = state;
this.LOG = context.getLogger();
logName = String.format("%s (%s)", context.getId(), state);
}
@Override
public RaftState state() {
return state;
}
public String logName() {
return logName;
}
@Override
public void setReplicatedToAllIndex(long replicatedToAllIndex) {
this.replicatedToAllIndex = replicatedToAllIndex;
}
@Override
public long getReplicatedToAllIndex() {
return replicatedToAllIndex;
}
/**
* 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 RaftActorBehavior 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 RaftActorBehavior appendEntries(ActorRef sender,
AppendEntries appendEntries) {
// 1. Reply false if term < currentTerm (§5.1)
if (appendEntries.getTerm() < currentTerm()) {
if(LOG.isDebugEnabled()) {
LOG.debug("{}: Cannot append entries because sender term {} is less than {}",
logName(), appendEntries.getTerm(), currentTerm());
}
sender.tell(
new AppendEntriesReply(context.getId(), currentTerm(), false,
lastIndex(), lastTerm(), context.getPayloadVersion()), actor()
);
return this;
}
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 RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
AppendEntriesReply appendEntriesReply);
/**
* requestVote handles the RequestVote message. This logic is common
* for all behaviors
*
* @param sender
* @param requestVote
* @return
*/
protected RaftActorBehavior requestVote(ActorRef sender, RequestVote requestVote) {
LOG.debug("{}: In requestVote: {}", logName(), requestVote);
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());
}
}
RequestVoteReply reply = new RequestVoteReply(currentTerm(), grantVote);
LOG.debug("{}: requestVote returning: {}", logName(), reply);
sender.tell(reply, actor());
return this;
}
/**
* 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 RaftActorBehavior 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(), ELECTION_TIMEOUT,
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 client request tracker for a specific logIndex
*
* @param logIndex
* @return
*/
protected ClientRequestTracker removeClientRequestTracker(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 = removeClientRequestTracker(i);
if (tracker != null) {
clientActor = tracker.getClientActor();
identifier = tracker.getIdentifier();
}
ReplicatedLogEntry replicatedLogEntry =
context.getReplicatedLog().get(i);
if (replicatedLogEntry != null) {
// Send a local message to the local RaftActor (it's derived class to be
// specific to apply the log to it's index)
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
LOG.warn(
"{}: Missing index {} from log. Cannot apply state. Ignoring {} to {}",
logName(), i, i, index);
break;
}
}
if(LOG.isDebugEnabled()) {
LOG.debug("{}: Setting last applied to {}", logName(), newLastApplied);
}
context.setLastApplied(newLastApplied);
// send a message to persist a ApplyLogEntries marker message into akka's persistent journal
// will be used during recovery
//in case if the above code throws an error and this message is not sent, it would be fine
// as the append entries received later would initiate add this message to the journal
actor().tell(new ApplyJournalEntries(context.getLastApplied()), actor());
}
protected Object fromSerializableMessage(Object serializable){
return SerializationUtils.fromSerializable(serializable);
}
@Override
public RaftActorBehavior 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 this;
}
@Override public String getLeaderId() {
return leaderId;
}
@Override
public short getLeaderPayloadVersion() {
return leaderPayloadVersion;
}
public void setLeaderPayloadVersion(short leaderPayloadVersion) {
this.leaderPayloadVersion = leaderPayloadVersion;
}
protected RaftActorBehavior switchBehavior(RaftActorBehavior behavior) {
LOG.info("{} :- Switching from behavior {} to {}", logName(), this.state(), behavior.state());
try {
close();
} catch (Exception e) {
LOG.error("{}: Failed to close behavior : {}", logName(), this.state(), e);
}
return behavior;
}
protected int getMajorityVoteCount(int numPeers) {
// Votes are required from a majority of the peers including self.
// The numMajority field therefore stores a calculated value
// of the number of votes required for this candidate to win an
// election based on it's known peers.
// If a peer was added during normal operation and raft replicas
// came to know about them then the new peer would also need to be
// taken into consideration when calculating this value.
// Here are some examples for what the numMajority would be for n
// peers
// 0 peers = 1 numMajority -: (0 + 1) / 2 + 1 = 1
// 2 peers = 2 numMajority -: (2 + 1) / 2 + 1 = 2
// 4 peers = 3 numMajority -: (4 + 1) / 2 + 1 = 3
int numMajority = 0;
if (numPeers > 0) {
int self = 1;
numMajority = (numPeers + self) / 2 + 1;
}
return numMajority;
}
/**
* Performs a snapshot with no capture on the replicated log.
* It clears the log from the supplied index or last-applied-1 which ever is minimum.
*
* @param snapshotCapturedIndex
*/
protected void performSnapshotWithoutCapture(final long snapshotCapturedIndex) {
long actualIndex = context.getSnapshotManager().trimLog(snapshotCapturedIndex, this);
if(actualIndex != -1){
setReplicatedToAllIndex(actualIndex);
}
}
protected String getId(){
return context.getId();
}
}