package org.opendaylight.controller.cluster.raft.behaviors;
import akka.actor.ActorRef;
+import com.google.common.annotations.VisibleForTesting;
+import java.util.ArrayList;
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.Snapshot;
+import org.opendaylight.controller.cluster.raft.base.messages.ApplySnapshot;
+import org.opendaylight.controller.cluster.raft.base.messages.ElectionTimeout;
+import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
+import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
+import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
+import org.opendaylight.controller.cluster.raft.messages.InstallSnapshot;
+import org.opendaylight.controller.cluster.raft.messages.InstallSnapshotReply;
+import org.opendaylight.controller.cluster.raft.messages.RaftRPC;
+import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
/**
* The behavior of a RaftActor in the Follower state
+ * <p/>
+ * <ul>
+ * <li> Respond to RPCs from candidates and leaders
+ * <li> If election timeout elapses without receiving AppendEntries
+ * RPC from current leader or granting vote to candidate:
+ * convert to candidate
+ * </ul>
*/
public class Follower extends AbstractRaftActorBehavior {
+
+
+
+ private SnapshotTracker snapshotTracker = null;
+
+ private final InitialSyncStatusTracker initialSyncStatusTracker;
+
public Follower(RaftActorContext context) {
- super(context);
+ super(context, RaftState.Follower);
+
+ scheduleElection(electionDuration());
+
+ initialSyncStatusTracker = new InitialSyncStatusTracker(context.getActor());
+ }
+
+ private boolean isLogEntryPresent(long index){
+ if(index == context.getReplicatedLog().getSnapshotIndex()){
+ return true;
+ }
+
+ ReplicatedLogEntry previousEntry = context.getReplicatedLog()
+ .get(index);
+
+ return previousEntry != null;
+
+ }
+
+ private long getLogEntryTerm(long index){
+ if(index == context.getReplicatedLog().getSnapshotIndex()){
+ return context.getReplicatedLog().getSnapshotTerm();
+ }
+
+ ReplicatedLogEntry previousEntry = context.getReplicatedLog()
+ .get(index);
+
+ if(previousEntry != null){
+ return previousEntry.getTerm();
+ }
+
+ return -1;
+ }
+
+ private void updateInitialSyncStatus(long currentLeaderCommit, String leaderId){
+ initialSyncStatusTracker.update(leaderId, currentLeaderCommit, context.getCommitIndex());
+ }
+
+ @Override protected RaftActorBehavior handleAppendEntries(ActorRef sender,
+ AppendEntries appendEntries) {
+
+ int numLogEntries = appendEntries.getEntries() != null ? appendEntries.getEntries().size() : 0;
+ if(LOG.isTraceEnabled()) {
+ LOG.trace("{}: handleAppendEntries: {}", logName(), appendEntries);
+ } else if(LOG.isDebugEnabled() && numLogEntries > 0) {
+ LOG.debug("{}: handleAppendEntries: {}", logName(), appendEntries);
+ }
+
+ // TODO : Refactor this method into a bunch of smaller methods
+ // to make it easier to read. Before refactoring ensure tests
+ // cover the code properly
+
+ // 1. Reply false if term < currentTerm (§5.1)
+ // This is handled in the appendEntries method of the base class
+
+ // If we got here then we do appear to be talking to the leader
+ leaderId = appendEntries.getLeaderId();
+
+ // 2. Reply false if log doesn’t contain an entry at prevLogIndex
+ // whose term matches prevLogTerm (§5.3)
+
+ long prevLogTerm = getLogEntryTerm(appendEntries.getPrevLogIndex());
+ boolean prevEntryPresent = isLogEntryPresent(appendEntries.getPrevLogIndex());
+
+ updateInitialSyncStatus(appendEntries.getLeaderCommit(), appendEntries.getLeaderId());
+
+ boolean outOfSync = true;
+
+ // First check if the logs are in sync or not
+ long lastIndex = lastIndex();
+ if (lastIndex == -1 && appendEntries.getPrevLogIndex() != -1) {
+
+ // The follower's log is out of sync because the leader does have
+ // an entry at prevLogIndex and this follower has no entries in
+ // it's log.
+
+ LOG.debug("{}: The followers log is empty and the senders prevLogIndex is {}",
+ logName(), appendEntries.getPrevLogIndex());
+ } else if (lastIndex > -1 && appendEntries.getPrevLogIndex() != -1 && !prevEntryPresent) {
+
+ // The follower's log is out of sync because the Leader's
+ // prevLogIndex entry was not found in it's log
+
+ LOG.debug("{}: The log is not empty but the prevLogIndex {} was not found in it",
+ logName(), appendEntries.getPrevLogIndex());
+ } else if (lastIndex > -1 && prevEntryPresent && prevLogTerm != appendEntries.getPrevLogTerm()) {
+
+ // The follower's log is out of sync because the Leader's
+ // prevLogIndex entry does exist in the follower's log but it has
+ // a different term in it
+
+ LOG.debug(
+ "{}: Cannot append entries because previous entry term {} is not equal to append entries prevLogTerm {}",
+ logName(), prevLogTerm, appendEntries.getPrevLogTerm());
+ } else {
+ outOfSync = false;
+ }
+
+ if (outOfSync) {
+ // We found that the log was out of sync so just send a negative
+ // reply and return
+
+ LOG.debug("{}: Follower is out-of-sync, so sending negative reply, lastIndex: {}, lastTerm: {}",
+ logName(), lastIndex, lastTerm());
+
+ sender.tell(new AppendEntriesReply(context.getId(), currentTerm(), false, lastIndex,
+ lastTerm()), actor());
+ return this;
+ }
+
+ if (appendEntries.getEntries() != null && appendEntries.getEntries().size() > 0) {
+
+ LOG.debug("{}: Number of entries to be appended = {}", logName(),
+ appendEntries.getEntries().size());
+
+ // 3. If an existing entry conflicts with a new one (same index
+ // but different terms), delete the existing entry and all that
+ // follow it (§5.3)
+ int addEntriesFrom = 0;
+ if (context.getReplicatedLog().size() > 0) {
+
+ // Find the entry up until which the one that is not in the follower's log
+ for (int i = 0;i < appendEntries.getEntries().size(); i++, addEntriesFrom++) {
+ ReplicatedLogEntry matchEntry = appendEntries.getEntries().get(i);
+ ReplicatedLogEntry newEntry = context.getReplicatedLog().get(matchEntry.getIndex());
+
+ if (newEntry == null) {
+ //newEntry not found in the log
+ break;
+ }
+
+ if (newEntry.getTerm() == matchEntry.getTerm()) {
+ continue;
+ }
+
+ LOG.debug("{}: Removing entries from log starting at {}", logName(),
+ matchEntry.getIndex());
+
+ // Entries do not match so remove all subsequent entries
+ context.getReplicatedLog().removeFromAndPersist(matchEntry.getIndex());
+ break;
+ }
+ }
+
+ lastIndex = lastIndex();
+ LOG.debug("{}: After cleanup entries to be added from = {}", logName(),
+ (addEntriesFrom + lastIndex));
+
+ // 4. Append any new entries not already in the log
+ for (int i = addEntriesFrom; i < appendEntries.getEntries().size(); i++) {
+ ReplicatedLogEntry entry = appendEntries.getEntries().get(i);
+
+ LOG.debug("{}: Append entry to log {}", logName(), entry.getData());
+
+ context.getReplicatedLog().appendAndPersist(entry);
+ }
+
+ LOG.debug("{}: Log size is now {}", logName(), context.getReplicatedLog().size());
+ }
+
+ // 5. If leaderCommit > commitIndex, set commitIndex =
+ // min(leaderCommit, index of last new entry)
+
+ lastIndex = lastIndex();
+ long prevCommitIndex = context.getCommitIndex();
+
+ context.setCommitIndex(Math.min(appendEntries.getLeaderCommit(), lastIndex));
+
+ if (prevCommitIndex != context.getCommitIndex()) {
+ LOG.debug("{}: Commit index set to {}", logName(), context.getCommitIndex());
+ }
+
+ // If commitIndex > lastApplied: increment lastApplied, apply
+ // log[lastApplied] to state machine (§5.3)
+ // check if there are any entries to be applied. last-applied can be equal to last-index
+ if (appendEntries.getLeaderCommit() > context.getLastApplied() &&
+ context.getLastApplied() < lastIndex) {
+ if(LOG.isDebugEnabled()) {
+ LOG.debug("{}: applyLogToStateMachine, " +
+ "appendEntries.getLeaderCommit(): {}," +
+ "context.getLastApplied(): {}, lastIndex(): {}", logName(),
+ appendEntries.getLeaderCommit(), context.getLastApplied(), lastIndex);
+ }
+
+ applyLogToStateMachine(appendEntries.getLeaderCommit());
+ }
+
+ AppendEntriesReply reply = new AppendEntriesReply(context.getId(), currentTerm(), true,
+ lastIndex, lastTerm());
+
+ if(LOG.isTraceEnabled()) {
+ LOG.trace("{}: handleAppendEntries returning : {}", logName(), reply);
+ } else if(LOG.isDebugEnabled() && numLogEntries > 0) {
+ LOG.debug("{}: handleAppendEntries returning : {}", logName(), reply);
+ }
+
+ sender.tell(reply, actor());
+
+ if (!context.isSnapshotCaptureInitiated()) {
+ super.performSnapshotWithoutCapture(appendEntries.getReplicatedToAllIndex());
+ }
+
+ return this;
+ }
+
+ @Override protected RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
+ AppendEntriesReply appendEntriesReply) {
+ return this;
+ }
+
+ @Override protected RaftActorBehavior handleRequestVoteReply(ActorRef sender,
+ RequestVoteReply requestVoteReply) {
+ return this;
}
- @Override public RaftState handleMessage(ActorRef sender, Object message) {
- return RaftState.Follower;
+ @Override public RaftActorBehavior handleMessage(ActorRef sender, Object originalMessage) {
+
+ Object message = fromSerializableMessage(originalMessage);
+
+ if (message instanceof RaftRPC) {
+ RaftRPC rpc = (RaftRPC) message;
+ // 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()) {
+ LOG.debug("{}: Term {} in \"{}\" message is greater than follower's term {} - updating term",
+ logName(), rpc.getTerm(), rpc, context.getTermInformation().getCurrentTerm());
+
+ context.getTermInformation().updateAndPersist(rpc.getTerm(), null);
+ }
+ }
+
+ if (message instanceof ElectionTimeout) {
+ LOG.debug("{}: Received ElectionTimeout - switching to Candidate", logName());
+ return switchBehavior(new Candidate(context));
+
+ } else if (message instanceof InstallSnapshot) {
+ InstallSnapshot installSnapshot = (InstallSnapshot) message;
+ handleInstallSnapshot(sender, installSnapshot);
+ }
+
+ scheduleElection(electionDuration());
+
+ return super.handleMessage(sender, message);
+ }
+
+ private void handleInstallSnapshot(ActorRef sender, InstallSnapshot installSnapshot) {
+
+ LOG.debug("{}: InstallSnapshot received from leader {}, datasize: {} , Chunk: {}/{}",
+ logName(), installSnapshot.getLeaderId(), installSnapshot.getData().size(),
+ installSnapshot.getChunkIndex(), installSnapshot.getTotalChunks());
+
+ if(snapshotTracker == null){
+ snapshotTracker = new SnapshotTracker(LOG, installSnapshot.getTotalChunks());
+ }
+
+ updateInitialSyncStatus(installSnapshot.getLastIncludedIndex(), installSnapshot.getLeaderId());
+
+ try {
+ if(snapshotTracker.addChunk(installSnapshot.getChunkIndex(), installSnapshot.getData(),
+ installSnapshot.getLastChunkHashCode())){
+ Snapshot snapshot = Snapshot.create(snapshotTracker.getSnapshot(),
+ new ArrayList<ReplicatedLogEntry>(),
+ installSnapshot.getLastIncludedIndex(),
+ installSnapshot.getLastIncludedTerm(),
+ installSnapshot.getLastIncludedIndex(),
+ installSnapshot.getLastIncludedTerm());
+
+ actor().tell(new ApplySnapshot(snapshot), actor());
+
+ snapshotTracker = null;
+
+ }
+
+ InstallSnapshotReply reply = new InstallSnapshotReply(
+ currentTerm(), context.getId(), installSnapshot.getChunkIndex(), true);
+
+ LOG.debug("{}: handleInstallSnapshot returning: {}", logName(), reply);
+
+ sender.tell(reply, actor());
+
+ } catch (SnapshotTracker.InvalidChunkException e) {
+ LOG.debug("{}: Exception in InstallSnapshot of follower", logName(), e);
+
+ sender.tell(new InstallSnapshotReply(currentTerm(), context.getId(),
+ -1, false), actor());
+ snapshotTracker = null;
+
+ } catch (Exception e){
+ LOG.error("{}: Exception in InstallSnapshot of follower", logName(), e);
+
+ //send reply with success as false. The chunk will be sent again on failure
+ sender.tell(new InstallSnapshotReply(currentTerm(), context.getId(),
+ installSnapshot.getChunkIndex(), false), actor());
+
+ }
+ }
+
+ @Override
+ public void close() throws Exception {
+ stopElection();
+ }
+
+ @VisibleForTesting
+ SnapshotTracker getSnapshotTracker(){
+ return snapshotTracker;
+ }
+
+ private static class InitialSyncStatusTracker {
+
+ private static final long INVALID_LOG_INDEX = -2L;
+ private long initialLeaderCommit = INVALID_LOG_INDEX;
+ private boolean initialSyncUpDone = false;
+ private String syncedLeaderId = null;
+ private final ActorRef actor;
+
+ public InitialSyncStatusTracker(ActorRef actor) {
+ this.actor = actor;
+ }
+
+ public void update(String leaderId, long leaderCommit, long commitIndex){
+
+ if(!leaderId.equals(syncedLeaderId)){
+ initialSyncUpDone = false;
+ initialLeaderCommit = INVALID_LOG_INDEX;
+ syncedLeaderId = leaderId;
+ }
+
+ if(!initialSyncUpDone){
+ if(initialLeaderCommit == INVALID_LOG_INDEX){
+ actor.tell(new FollowerInitialSyncUpStatus(false), ActorRef.noSender());
+ initialLeaderCommit = leaderCommit;
+ } else if(commitIndex >= initialLeaderCommit){
+ actor.tell(new FollowerInitialSyncUpStatus(true), ActorRef.noSender());
+ initialSyncUpDone = true;
+ }
+ }
+ }
}
}
Code Review / controller.git / blobdiff