import scala.concurrent.duration.FiniteDuration;
/**
- * Abstract class that represents the behavior of a RaftActor
- * <p/>
- * All Servers:
- * <ul>
- * <li> If commitIndex > lastApplied: increment lastApplied, apply
- * log[lastApplied] to state machine (§5.3)
- * <li> If RPC request or response contains term T > currentTerm:
- * set currentTerm = T, convert to follower (§5.1)
+ * Abstract class that provides common code for a RaftActor behavior.
*/
public abstract class AbstractRaftActorBehavior implements RaftActorBehavior {
/**
- * Information about the RaftActor whose behavior this class represents
+ * Information about the RaftActor whose behavior this class represents.
*/
protected final RaftActorContext context;
/**
- *
+ * Used for message logging.
*/
- protected final Logger LOG;
+ protected final Logger log;
/**
- *
+ * Prepended to log messages to provide appropriate context.
*/
- private Cancellable electionCancel = null;
-
- private long replicatedToAllIndex = -1;
-
private final String logName;
+ /**
+ * The RaftState corresponding to his behavior.
+ */
private final RaftState state;
+ /**
+ * Used to cancel a scheduled election.
+ */
+ private Cancellable electionCancel = null;
+
+ /**
+ * The index of the last log entry that has been replicated to all raft peers.
+ */
+ private long replicatedToAllIndex = -1;
+
AbstractRaftActorBehavior(final RaftActorContext context, final RaftState state) {
this.context = Preconditions.checkNotNull(context);
this.state = Preconditions.checkNotNull(state);
- this.LOG = context.getLogger();
+ this.log = context.getLogger();
logName = String.format("%s (%s)", context.getId(), state);
}
protected abstract RaftActorBehavior handleAppendEntries(ActorRef sender,
AppendEntries appendEntries);
-
/**
- * appendEntries first processes the AppendEntries message and then
- * delegates handling to a specific behavior
+ * Handles the common logic for the AppendEntries message and delegates handling to the derived class.
*
- * @param sender
- * @param appendEntries
+ * @param sender the ActorRef that sent the message
+ * @param appendEntries the message
* @return a new behavior if it was changed or the current behavior
*/
- protected RaftActorBehavior appendEntries(ActorRef sender,
- AppendEntries appendEntries) {
+ 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());
- }
+ 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()
- );
+ sender.tell(new AppendEntriesReply(context.getId(), currentTerm(), false, lastIndex(), lastTerm(),
+ context.getPayloadVersion()), actor());
return this;
}
AppendEntriesReply appendEntriesReply);
/**
- * requestVote handles the RequestVote message. This logic is common
- * for all behaviors
+ * Handles the logic for the RequestVote message that is common for all behaviors.
*
- * @param sender
- * @param requestVote
+ * @param sender the ActorRef that sent the message
+ * @param requestVote the message
* @return a new behavior if it was changed or the current behavior
*/
protected RaftActorBehavior requestVote(ActorRef sender, RequestVote requestVote) {
- LOG.debug("{}: In requestVote: {}", logName(), requestVote);
+ log.debug("{}: In requestVote: {}", logName(), requestVote);
boolean grantVote = canGrantVote(requestVote);
- if(grantVote) {
+ if (grantVote) {
context.getTermInformation().updateAndPersist(requestVote.getTerm(), requestVote.getCandidateId());
}
RequestVoteReply reply = new RequestVoteReply(currentTerm(), grantVote);
- LOG.debug("{}: requestVote returning: {}", logName(), reply);
+ log.debug("{}: requestVote returning: {}", logName(), reply);
sender.tell(reply, actor());
return this;
}
- protected boolean canGrantVote(RequestVote requestVote){
+ protected boolean canGrantVote(RequestVote requestVote) {
boolean grantVote = false;
// Reply false if term < currentTerm (§5.1)
// more up-to-date.
if (requestVote.getLastLogTerm() > lastTerm()) {
candidateLatest = true;
- } else if ((requestVote.getLastLogTerm() == lastTerm())
+ } else if (requestVote.getLastLogTerm() == lastTerm()
&& requestVote.getLastLogIndex() >= lastIndex()) {
candidateLatest = true;
}
RequestVoteReply requestVoteReply);
/**
+ * Returns a duration for election with an additional variance for randomness.
*
* @return a random election duration
*/
}
/**
- * stop the scheduled election
+ * Stops the currently scheduled election.
*/
protected void stopElection() {
if (electionCancel != null && !electionCancel.isCancelled()) {
}
/**
- * schedule a new election
+ * Schedule a new election.
*
* @param interval the duration after which we should trigger a new election
*/
}
/**
+ * Returns the current election term.
+ *
* @return the current term
*/
protected long currentTerm() {
}
/**
+ * Returns the id of the candidate that this server voted for in current term.
+ *
* @return the candidate for whom we voted in the current term
*/
protected String votedFor() {
}
/**
- * @return the actor associated with this behavior
+ * Returns the actor associated with this behavior.
+ *
+ * @return the actor
*/
protected ActorRef actor() {
return context.getActor();
}
/**
+ * Returns the term of the last entry in the log.
*
- * @return the term from the last entry in the log
+ * @return the term
*/
protected long lastTerm() {
return context.getReplicatedLog().lastTerm();
}
/**
- * @return the index from the last entry in the log
+ * Returns the index of the last entry in the log.
+ *
+ * @return the index
*/
protected long lastIndex() {
return context.getReplicatedLog().lastIndex();
}
/**
- * @param logIndex
- * @return the client request tracker for the specified logIndex
+ * Removes and returns the ClientRequestTracker for the specified log index.
+ * @param logIndex the log index
+ * @return the ClientRequestTracker or null if none available
*/
protected ClientRequestTracker removeClientRequestTracker(long logIndex) {
return null;
}
/**
+ * Returns the actual index of the entry in replicated log for the given index or -1 if not found.
*
- * @return the log entry index for the given index or -1 if not found
+ * @return the log entry index or -1 if not found
*/
- protected long getLogEntryIndex(long index){
- if(index == context.getReplicatedLog().getSnapshotIndex()){
+ protected long getLogEntryIndex(long index) {
+ if (index == context.getReplicatedLog().getSnapshotIndex()) {
return context.getReplicatedLog().getSnapshotIndex();
}
ReplicatedLogEntry entry = context.getReplicatedLog().get(index);
- if(entry != null){
+ if (entry != null) {
return entry.getIndex();
}
}
/**
- * @return the log entry term for the given index or -1 if not found
+ * Returns the actual term of the entry in replicated log for the given index or -1 if not found.
+ *
+ * @return the log entry term or -1 if not found
*/
- protected long getLogEntryTerm(long index){
- if(index == context.getReplicatedLog().getSnapshotIndex()){
+ protected long getLogEntryTerm(long index) {
+ if (index == context.getReplicatedLog().getSnapshotIndex()) {
return context.getReplicatedLog().getSnapshotTerm();
}
ReplicatedLogEntry entry = context.getReplicatedLog().get(index);
- if(entry != null){
+ if (entry != null) {
return entry.getTerm();
}
}
/**
- * Apply the provided index to the state machine
+ * Applies the log entries up to the specified index that is known to be committed to the state machine.
*
- * @param index a log index that is known to be committed
+ * @param index the log index
*/
protected void applyLogToStateMachine(final long index) {
long newLastApplied = context.getLastApplied();
} 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 {}",
+ 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);
- }
+
+ 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
return internalSwitchBehavior(createBehavior(context, newState));
}
+ @SuppressWarnings("checkstyle:IllegalCatch")
protected RaftActorBehavior internalSwitchBehavior(RaftActorBehavior newBehavior) {
- if(!context.getRaftPolicy().automaticElectionsEnabled()) {
+ if (!context.getRaftPolicy().automaticElectionsEnabled()) {
return this;
}
- LOG.info("{} :- Switching from behavior {} to {}", logName(), this.state(), newBehavior.state());
+ log.info("{} :- Switching from behavior {} to {}", logName(), this.state(), newBehavior.state());
try {
close();
- } catch (Exception e) {
- LOG.error("{}: Failed to close behavior : {}", logName(), this.state(), e);
+ } catch (RuntimeException e) {
+ log.error("{}: Failed to close behavior : {}", logName(), this.state(), e);
}
return newBehavior;
}
/**
- * 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.
+ * Performs a snapshot with no capture on the replicated log. It clears the log from the supplied index or
+ * lastApplied-1 which ever is minimum.
*
- * @param snapshotCapturedIndex
+ * @param snapshotCapturedIndex the index from which to clear
*/
protected void performSnapshotWithoutCapture(final long snapshotCapturedIndex) {
long actualIndex = context.getSnapshotManager().trimLog(snapshotCapturedIndex);
- if(actualIndex != -1){
+ if (actualIndex != -1) {
setReplicatedToAllIndex(actualIndex);
}
}
- protected String getId(){
+ protected String getId() {
return context.getId();
}
}
Code Review / controller.git / blobdiff