2 * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
9 package org.opendaylight.controller.cluster.raft.behaviors;
11 import akka.actor.ActorRef;
12 import akka.actor.Cancellable;
13 import java.util.Random;
14 import java.util.concurrent.TimeUnit;
15 import org.opendaylight.controller.cluster.raft.ClientRequestTracker;
16 import org.opendaylight.controller.cluster.raft.RaftActorContext;
17 import org.opendaylight.controller.cluster.raft.RaftState;
18 import org.opendaylight.controller.cluster.raft.ReplicatedLogEntry;
19 import org.opendaylight.controller.cluster.raft.SerializationUtils;
20 import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
21 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
22 import org.opendaylight.controller.cluster.raft.base.messages.ElectionTimeout;
23 import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
24 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
25 import org.opendaylight.controller.cluster.raft.messages.RequestVote;
26 import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
27 import org.slf4j.Logger;
28 import scala.concurrent.duration.FiniteDuration;
31 * Abstract class that represents the behavior of a RaftActor
35 * <li> If commitIndex > lastApplied: increment lastApplied, apply
36 * log[lastApplied] to state machine (§5.3)
37 * <li> If RPC request or response contains term T > currentTerm:
38 * set currentTerm = T, convert to follower (§5.1)
40 public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
42 * Information about the RaftActor whose behavior this class represents
44 protected final RaftActorContext context;
49 protected final Logger LOG;
54 private Cancellable electionCancel = null;
59 protected String leaderId = null;
61 private short leaderPayloadVersion = -1;
63 private long replicatedToAllIndex = -1;
65 private final String logName;
67 private final RaftState state;
69 protected AbstractRaftActorBehavior(RaftActorContext context, RaftState state) {
70 this.context = context;
72 this.LOG = context.getLogger();
74 logName = String.format("%s (%s)", context.getId(), state);
78 public RaftState state() {
82 public String logName() {
87 public void setReplicatedToAllIndex(long replicatedToAllIndex) {
88 this.replicatedToAllIndex = replicatedToAllIndex;
92 public long getReplicatedToAllIndex() {
93 return replicatedToAllIndex;
97 * Derived classes should not directly handle AppendEntries messages it
98 * should let the base class handle it first. Once the base class handles
99 * the AppendEntries message and does the common actions that are applicable
100 * in all RaftState's it will delegate the handling of the AppendEntries
101 * message to the derived class to do more state specific handling by calling
104 * @param sender The actor that sent this message
105 * @param appendEntries The AppendEntries message
106 * @return a new behavior if it was changed or the current behavior
108 protected abstract RaftActorBehavior handleAppendEntries(ActorRef sender,
109 AppendEntries appendEntries);
113 * appendEntries first processes the AppendEntries message and then
114 * delegates handling to a specific behavior
117 * @param appendEntries
118 * @return a new behavior if it was changed or the current behavior
120 protected RaftActorBehavior appendEntries(ActorRef sender,
121 AppendEntries appendEntries) {
123 // 1. Reply false if term < currentTerm (§5.1)
124 if (appendEntries.getTerm() < currentTerm()) {
125 if(LOG.isDebugEnabled()) {
126 LOG.debug("{}: Cannot append entries because sender term {} is less than {}",
127 logName(), appendEntries.getTerm(), currentTerm());
131 new AppendEntriesReply(context.getId(), currentTerm(), false,
132 lastIndex(), lastTerm(), context.getPayloadVersion()), actor()
138 return handleAppendEntries(sender, appendEntries);
142 * Derived classes should not directly handle AppendEntriesReply messages it
143 * should let the base class handle it first. Once the base class handles
144 * the AppendEntriesReply message and does the common actions that are
145 * applicable in all RaftState's it will delegate the handling of the
146 * AppendEntriesReply message to the derived class to do more state specific
147 * handling by calling this method
149 * @param sender The actor that sent this message
150 * @param appendEntriesReply The AppendEntriesReply message
151 * @return a new behavior if it was changed or the current behavior
153 protected abstract RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
154 AppendEntriesReply appendEntriesReply);
157 * requestVote handles the RequestVote message. This logic is common
162 * @return a new behavior if it was changed or the current behavior
164 protected RaftActorBehavior requestVote(ActorRef sender, RequestVote requestVote) {
166 LOG.debug("{}: In requestVote: {}", logName(), requestVote);
168 boolean grantVote = canGrantVote(requestVote);
171 context.getTermInformation().updateAndPersist(requestVote.getTerm(), requestVote.getCandidateId());
174 RequestVoteReply reply = new RequestVoteReply(currentTerm(), grantVote);
176 LOG.debug("{}: requestVote returning: {}", logName(), reply);
178 sender.tell(reply, actor());
183 protected boolean canGrantVote(RequestVote requestVote){
184 boolean grantVote = false;
186 // Reply false if term < currentTerm (§5.1)
187 if (requestVote.getTerm() < currentTerm()) {
190 // If votedFor is null or candidateId, and candidate’s log is at
191 // least as up-to-date as receiver’s log, grant vote (§5.2, §5.4)
192 } else if (votedFor() == null || votedFor()
193 .equals(requestVote.getCandidateId())) {
195 boolean candidateLatest = false;
198 // Raft determines which of two logs is more up-to-date
199 // by comparing the index and term of the last entries in the
200 // logs. If the logs have last entries with different terms, then
201 // the log with the later term is more up-to-date. If the logs
202 // end with the same term, then whichever log is longer is
204 if (requestVote.getLastLogTerm() > lastTerm()) {
205 candidateLatest = true;
206 } else if ((requestVote.getLastLogTerm() == lastTerm())
207 && requestVote.getLastLogIndex() >= lastIndex()) {
208 candidateLatest = true;
211 if (candidateLatest) {
219 * Derived classes should not directly handle RequestVoteReply messages it
220 * should let the base class handle it first. Once the base class handles
221 * the RequestVoteReply message and does the common actions that are
222 * applicable in all RaftState's it will delegate the handling of the
223 * RequestVoteReply message to the derived class to do more state specific
224 * handling by calling this method
226 * @param sender The actor that sent this message
227 * @param requestVoteReply The RequestVoteReply message
228 * @return a new behavior if it was changed or the current behavior
230 protected abstract RaftActorBehavior handleRequestVoteReply(ActorRef sender,
231 RequestVoteReply requestVoteReply);
235 * @return a random election duration
237 protected FiniteDuration electionDuration() {
238 long variance = new Random().nextInt(context.getConfigParams().getElectionTimeVariance());
239 return context.getConfigParams().getElectionTimeOutInterval().$plus(
240 new FiniteDuration(variance, TimeUnit.MILLISECONDS));
244 * stop the scheduled election
246 protected void stopElection() {
247 if (electionCancel != null && !electionCancel.isCancelled()) {
248 electionCancel.cancel();
252 protected boolean canStartElection() {
253 return context.getRaftPolicy().automaticElectionsEnabled() && context.isVotingMember();
257 * schedule a new election
259 * @param interval the duration after which we should trigger a new election
261 protected void scheduleElection(FiniteDuration interval) {
264 if(canStartElection()) {
265 // Schedule an election. When the scheduler triggers an ElectionTimeout message is sent to itself
266 electionCancel = context.getActorSystem().scheduler().scheduleOnce(interval, context.getActor(),
267 ElectionTimeout.INSTANCE, context.getActorSystem().dispatcher(), context.getActor());
272 * @return the current term
274 protected long currentTerm() {
275 return context.getTermInformation().getCurrentTerm();
279 * @return the candidate for whom we voted in the current term
281 protected String votedFor() {
282 return context.getTermInformation().getVotedFor();
286 * @return the actor associated with this behavior
288 protected ActorRef actor() {
289 return context.getActor();
294 * @return the term from the last entry in the log
296 protected long lastTerm() {
297 return context.getReplicatedLog().lastTerm();
301 * @return the index from the last entry in the log
303 protected long lastIndex() {
304 return context.getReplicatedLog().lastIndex();
309 * @return the client request tracker for the specified logIndex
311 protected ClientRequestTracker findClientRequestTracker(long logIndex) {
317 * @return the client request tracker for the specified logIndex
319 protected ClientRequestTracker removeClientRequestTracker(long logIndex) {
326 * @return log index from the previous to last entry in the log
328 protected long prevLogIndex(long index){
329 ReplicatedLogEntry prevEntry =
330 context.getReplicatedLog().get(index - 1);
331 if (prevEntry != null) {
332 return prevEntry.getIndex();
338 * @return log term from the previous to last entry in the log
340 protected long prevLogTerm(long index){
341 ReplicatedLogEntry prevEntry =
342 context.getReplicatedLog().get(index - 1);
343 if (prevEntry != null) {
344 return prevEntry.getTerm();
350 * Apply the provided index to the state machine
352 * @param index a log index that is known to be committed
354 protected void applyLogToStateMachine(final long index) {
355 long newLastApplied = context.getLastApplied();
356 // Now maybe we apply to the state machine
357 for (long i = context.getLastApplied() + 1;
358 i < index + 1; i++) {
359 ActorRef clientActor = null;
360 String identifier = null;
361 ClientRequestTracker tracker = removeClientRequestTracker(i);
363 if (tracker != null) {
364 clientActor = tracker.getClientActor();
365 identifier = tracker.getIdentifier();
367 ReplicatedLogEntry replicatedLogEntry =
368 context.getReplicatedLog().get(i);
370 if (replicatedLogEntry != null) {
371 // Send a local message to the local RaftActor (it's derived class to be
372 // specific to apply the log to it's index)
373 actor().tell(new ApplyState(clientActor, identifier,
374 replicatedLogEntry), actor());
377 //if one index is not present in the log, no point in looping
378 // around as the rest wont be present either
380 "{}: Missing index {} from log. Cannot apply state. Ignoring {} to {}",
381 logName(), i, i, index);
385 if(LOG.isDebugEnabled()) {
386 LOG.debug("{}: Setting last applied to {}", logName(), newLastApplied);
388 context.setLastApplied(newLastApplied);
390 // send a message to persist a ApplyLogEntries marker message into akka's persistent journal
391 // will be used during recovery
392 //in case if the above code throws an error and this message is not sent, it would be fine
393 // as the append entries received later would initiate add this message to the journal
394 actor().tell(new ApplyJournalEntries(context.getLastApplied()), actor());
397 protected Object fromSerializableMessage(Object serializable){
398 return SerializationUtils.fromSerializable(serializable);
402 public RaftActorBehavior handleMessage(ActorRef sender, Object message) {
403 if (message instanceof AppendEntries) {
404 return appendEntries(sender, (AppendEntries) message);
405 } else if (message instanceof AppendEntriesReply) {
406 return handleAppendEntriesReply(sender, (AppendEntriesReply) message);
407 } else if (message instanceof RequestVote) {
408 return requestVote(sender, (RequestVote) message);
409 } else if (message instanceof RequestVoteReply) {
410 return handleRequestVoteReply(sender, (RequestVoteReply) message);
415 @Override public String getLeaderId() {
420 public short getLeaderPayloadVersion() {
421 return leaderPayloadVersion;
424 public void setLeaderPayloadVersion(short leaderPayloadVersion) {
425 this.leaderPayloadVersion = leaderPayloadVersion;
429 public RaftActorBehavior switchBehavior(RaftActorBehavior behavior) {
430 return internalSwitchBehavior(behavior);
433 protected RaftActorBehavior internalSwitchBehavior(RaftState newState) {
434 if(context.getRaftPolicy().automaticElectionsEnabled()){
435 return internalSwitchBehavior(newState.createBehavior(context));
440 private RaftActorBehavior internalSwitchBehavior(RaftActorBehavior newBehavior) {
441 LOG.info("{} :- Switching from behavior {} to {}", logName(), this.state(), newBehavior.state());
444 } catch (Exception e) {
445 LOG.error("{}: Failed to close behavior : {}", logName(), this.state(), e);
451 protected int getMajorityVoteCount(int numPeers) {
452 // Votes are required from a majority of the peers including self.
453 // The numMajority field therefore stores a calculated value
454 // of the number of votes required for this candidate to win an
455 // election based on it's known peers.
456 // If a peer was added during normal operation and raft replicas
457 // came to know about them then the new peer would also need to be
458 // taken into consideration when calculating this value.
459 // Here are some examples for what the numMajority would be for n
461 // 0 peers = 1 numMajority -: (0 + 1) / 2 + 1 = 1
462 // 2 peers = 2 numMajority -: (2 + 1) / 2 + 1 = 2
463 // 4 peers = 3 numMajority -: (4 + 1) / 2 + 1 = 3
468 numMajority = (numPeers + self) / 2 + 1;
476 * Performs a snapshot with no capture on the replicated log.
477 * It clears the log from the supplied index or last-applied-1 which ever is minimum.
479 * @param snapshotCapturedIndex
481 protected void performSnapshotWithoutCapture(final long snapshotCapturedIndex) {
482 long actualIndex = context.getSnapshotManager().trimLog(snapshotCapturedIndex, this);
484 if(actualIndex != -1){
485 setReplicatedToAllIndex(actualIndex);
489 protected String getId(){
490 return context.getId();