/*
* 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.ActorSelection;
import akka.actor.Cancellable;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableMap.Builder;
import com.google.protobuf.ByteString;
import java.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import javax.annotation.Nullable;
import org.opendaylight.controller.cluster.raft.ClientRequestTracker;
import org.opendaylight.controller.cluster.raft.ClientRequestTrackerImpl;
import org.opendaylight.controller.cluster.raft.FollowerLogInformation;
import org.opendaylight.controller.cluster.raft.FollowerLogInformationImpl;
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.Replicate;
import org.opendaylight.controller.cluster.raft.base.messages.SendHeartBeat;
import org.opendaylight.controller.cluster.raft.base.messages.SendInstallSnapshot;
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;
import scala.concurrent.duration.FiniteDuration;
/**
* The behavior of a RaftActor when it is in the Leader state
*
* Leaders:
*
* - Upon election: send initial empty AppendEntries RPCs
* (heartbeat) to each server; repeat during idle periods to
* prevent election timeouts (§5.2)
*
- If command received from client: append entry to local log,
* respond after entry applied to state machine (§5.3)
*
- If last log index ≥ nextIndex for a follower: send
* AppendEntries RPC with log entries starting at nextIndex
*
* - If successful: update nextIndex and matchIndex for
* follower (§5.3)
*
- If AppendEntries fails because of log inconsistency:
* decrement nextIndex and retry (§5.3)
*
* - If there exists an N such that N > commitIndex, a majority
* of matchIndex[i] ≥ N, and log[N].term == currentTerm:
* set commitIndex = N (§5.3, §5.4).
*/
public abstract class AbstractLeader extends AbstractRaftActorBehavior {
// The index of the first chunk that is sent when installing a snapshot
public static final int FIRST_CHUNK_INDEX = 1;
// The index that the follower should respond with if it needs the install snapshot to be reset
public static final int INVALID_CHUNK_INDEX = -1;
// This would be passed as the hash code of the last chunk when sending the first chunk
public static final int INITIAL_LAST_CHUNK_HASH_CODE = -1;
private final Map followerToLog;
private final Map mapFollowerToSnapshot = new HashMap<>();
private Cancellable heartbeatSchedule = null;
private final Collection trackerList = new LinkedList<>();
protected final int minReplicationCount;
protected final int minIsolatedLeaderPeerCount;
private Optional snapshot;
public AbstractLeader(RaftActorContext context) {
super(context, RaftState.Leader);
setLeaderPayloadVersion(context.getPayloadVersion());
final Builder ftlBuilder = ImmutableMap.builder();
for (String followerId : context.getPeerAddresses().keySet()) {
FollowerLogInformation followerLogInformation =
new FollowerLogInformationImpl(followerId, -1, context);
ftlBuilder.put(followerId, followerLogInformation);
}
followerToLog = ftlBuilder.build();
leaderId = context.getId();
LOG.debug("{}: Election: Leader has following peers: {}", logName(), getFollowerIds());
minReplicationCount = getMajorityVoteCount(getFollowerIds().size());
// the isolated Leader peer count will be 1 less than the majority vote count.
// this is because the vote count has the self vote counted in it
// for e.g
// 0 peers = 1 votesRequired , minIsolatedLeaderPeerCount = 0
// 2 peers = 2 votesRequired , minIsolatedLeaderPeerCount = 1
// 4 peers = 3 votesRequired, minIsolatedLeaderPeerCount = 2
minIsolatedLeaderPeerCount = minReplicationCount > 0 ? (minReplicationCount - 1) : 0;
snapshot = Optional.absent();
// Immediately schedule a heartbeat
// Upon election: send initial empty AppendEntries RPCs
// (heartbeat) to each server; repeat during idle periods to
// prevent election timeouts (§5.2)
sendAppendEntries(0, false);
// It is important to schedule this heartbeat here
scheduleHeartBeat(context.getConfigParams().getHeartBeatInterval());
}
/**
* Return an immutable collection of follower identifiers.
*
* @return Collection of follower IDs
*/
public final Collection getFollowerIds() {
return followerToLog.keySet();
}
@VisibleForTesting
void setSnapshot(@Nullable Snapshot snapshot) {
if(snapshot != null) {
this.snapshot = Optional.of(new SnapshotHolder(snapshot));
} else {
this.snapshot = Optional.absent();
}
}
@Override
protected RaftActorBehavior handleAppendEntries(ActorRef sender,
AppendEntries appendEntries) {
LOG.debug("{}: handleAppendEntries: {}", logName(), appendEntries);
return this;
}
@Override
protected RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
AppendEntriesReply appendEntriesReply) {
if(LOG.isTraceEnabled()) {
LOG.trace("{}: handleAppendEntriesReply: {}", logName(), appendEntriesReply);
}
// Update the FollowerLogInformation
String followerId = appendEntriesReply.getFollowerId();
FollowerLogInformation followerLogInformation =
followerToLog.get(followerId);
if(followerLogInformation == null){
LOG.error("{}: handleAppendEntriesReply - unknown follower {}", logName(), followerId);
return this;
}
if(followerLogInformation.timeSinceLastActivity() >
context.getConfigParams().getElectionTimeOutInterval().toMillis()) {
LOG.warn("{} : handleAppendEntriesReply delayed beyond election timeout, " +
"appendEntriesReply : {}, timeSinceLastActivity : {}, lastApplied : {}, commitIndex : {}",
logName(), appendEntriesReply, followerLogInformation.timeSinceLastActivity(),
context.getLastApplied(), context.getCommitIndex());
}
followerLogInformation.markFollowerActive();
followerLogInformation.setPayloadVersion(appendEntriesReply.getPayloadVersion());
boolean updated = false;
if (appendEntriesReply.isSuccess()) {
updated = updateFollowerLogInformation(followerLogInformation, appendEntriesReply);
} else {
LOG.debug("{}: handleAppendEntriesReply: received unsuccessful reply: {}", logName(), appendEntriesReply);
long followerLastLogIndex = appendEntriesReply.getLogLastIndex();
ReplicatedLogEntry followersLastLogEntry = context.getReplicatedLog().get(followerLastLogIndex);
if(appendEntriesReply.isForceInstallSnapshot()) {
// Reset the followers match and next index. This is to signal that this follower has nothing
// in common with this Leader and so would require a snapshot to be installed
followerLogInformation.setMatchIndex(-1);
followerLogInformation.setNextIndex(-1);
// Force initiate a snapshot capture
initiateCaptureSnapshot(followerId);
} else if(followerLastLogIndex < 0 || (followersLastLogEntry != null &&
followersLastLogEntry.getTerm() == appendEntriesReply.getLogLastTerm())) {
// The follower's log is empty or the last entry is present in the leader's journal
// and the terms match so the follower is just behind the leader's journal from
// the last snapshot, if any. We'll catch up the follower quickly by starting at the
// follower's last log index.
updated = updateFollowerLogInformation(followerLogInformation, appendEntriesReply);
} else {
// TODO: When we find that the follower is out of sync with the
// Leader we simply decrement that followers next index by 1.
// Would it be possible to do better than this? The RAFT spec
// does not explicitly deal with it but may be something for us to
// think about.
followerLogInformation.decrNextIndex();
}
}
// Now figure out if this reply warrants a change in the commitIndex
// If there exists an N such that N > commitIndex, a majority
// of matchIndex[i] ≥ N, and log[N].term == currentTerm:
// set commitIndex = N (§5.3, §5.4).
for (long N = context.getCommitIndex() + 1; ; N++) {
int replicatedCount = 1;
for (FollowerLogInformation info : followerToLog.values()) {
if (info.getMatchIndex() >= N) {
replicatedCount++;
}
}
if (replicatedCount >= minReplicationCount) {
ReplicatedLogEntry replicatedLogEntry = context.getReplicatedLog().get(N);
if (replicatedLogEntry != null &&
replicatedLogEntry.getTerm() == currentTerm()) {
context.setCommitIndex(N);
}
} else {
break;
}
}
// Apply the change to the state machine
if (context.getCommitIndex() > context.getLastApplied()) {
if(LOG.isDebugEnabled()) {
LOG.debug("{}: handleAppendEntriesReply from {}: applying to log - commitIndex: {}, lastAppliedIndex: {}",
logName(), followerId, context.getCommitIndex(), context.getLastApplied());
}
applyLogToStateMachine(context.getCommitIndex());
}
if (!context.getSnapshotManager().isCapturing()) {
purgeInMemoryLog();
}
//Send the next log entry immediately, if possible, no need to wait for heartbeat to trigger that event
sendUpdatesToFollower(followerId, followerLogInformation, false, !updated);
return this;
}
private boolean updateFollowerLogInformation(FollowerLogInformation followerLogInformation,
AppendEntriesReply appendEntriesReply) {
boolean updated = followerLogInformation.setMatchIndex(appendEntriesReply.getLogLastIndex());
updated = followerLogInformation.setNextIndex(appendEntriesReply.getLogLastIndex() + 1) || updated;
if(updated && LOG.isDebugEnabled()) {
LOG.debug("{}: handleAppendEntriesReply - FollowerLogInformation for {} updated: matchIndex: {}, nextIndex: {}",
logName(), followerLogInformation.getId(), followerLogInformation.getMatchIndex(),
followerLogInformation.getNextIndex());
}
return updated;
}
private void purgeInMemoryLog() {
//find the lowest index across followers which has been replicated to all.
// lastApplied if there are no followers, so that we keep clearing the log for single-node
// we would delete the in-mem log from that index on, in-order to minimize mem usage
// we would also share this info thru AE with the followers so that they can delete their log entries as well.
long minReplicatedToAllIndex = followerToLog.isEmpty() ? context.getLastApplied() : Long.MAX_VALUE;
for (FollowerLogInformation info : followerToLog.values()) {
minReplicatedToAllIndex = Math.min(minReplicatedToAllIndex, info.getMatchIndex());
}
super.performSnapshotWithoutCapture(minReplicatedToAllIndex);
}
@Override
protected ClientRequestTracker removeClientRequestTracker(long logIndex) {
final Iterator it = trackerList.iterator();
while (it.hasNext()) {
final ClientRequestTracker t = it.next();
if (t.getIndex() == logIndex) {
it.remove();
return t;
}
}
return null;
}
@Override
protected ClientRequestTracker findClientRequestTracker(long logIndex) {
for (ClientRequestTracker tracker : trackerList) {
if (tracker.getIndex() == logIndex) {
return tracker;
}
}
return null;
}
@Override
protected RaftActorBehavior handleRequestVoteReply(ActorRef sender,
RequestVoteReply requestVoteReply) {
return this;
}
protected void beforeSendHeartbeat(){}
@Override
public RaftActorBehavior handleMessage(ActorRef sender, Object originalMessage) {
Preconditions.checkNotNull(sender, "sender should not be null");
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 leader's term {} - switching to Follower",
logName(), rpc.getTerm(), rpc, context.getTermInformation().getCurrentTerm());
context.getTermInformation().updateAndPersist(rpc.getTerm(), null);
return internalSwitchBehavior(RaftState.Follower);
}
}
if (message instanceof SendHeartBeat) {
beforeSendHeartbeat();
sendHeartBeat();
scheduleHeartBeat(context.getConfigParams().getHeartBeatInterval());
return this;
} else if(message instanceof SendInstallSnapshot) {
// received from RaftActor
setSnapshot(((SendInstallSnapshot) message).getSnapshot());
sendInstallSnapshot();
} else if (message instanceof Replicate) {
replicate((Replicate) message);
} else if (message instanceof InstallSnapshotReply){
handleInstallSnapshotReply((InstallSnapshotReply) message);
}
return super.handleMessage(sender, message);
}
private void handleInstallSnapshotReply(InstallSnapshotReply reply) {
LOG.debug("{}: handleInstallSnapshotReply: {}", logName(), reply);
String followerId = reply.getFollowerId();
FollowerToSnapshot followerToSnapshot = mapFollowerToSnapshot.get(followerId);
if (followerToSnapshot == null) {
LOG.error("{}: FollowerId {} in InstallSnapshotReply not known to Leader",
logName(), followerId);
return;
}
FollowerLogInformation followerLogInformation = followerToLog.get(followerId);
followerLogInformation.markFollowerActive();
if (followerToSnapshot.getChunkIndex() == reply.getChunkIndex()) {
boolean wasLastChunk = false;
if (reply.isSuccess()) {
if(followerToSnapshot.isLastChunk(reply.getChunkIndex())) {
//this was the last chunk reply
if(LOG.isDebugEnabled()) {
LOG.debug("{}: InstallSnapshotReply received, " +
"last chunk received, Chunk: {}. Follower: {} Setting nextIndex: {}",
logName(), reply.getChunkIndex(), followerId,
context.getReplicatedLog().getSnapshotIndex() + 1
);
}
long followerMatchIndex = snapshot.get().getLastIncludedIndex();
followerLogInformation.setMatchIndex(followerMatchIndex);
followerLogInformation.setNextIndex(followerMatchIndex + 1);
mapFollowerToSnapshot.remove(followerId);
LOG.debug("{}: follower: {}, matchIndex set to {}, nextIndex set to {}",
logName(), followerId, followerLogInformation.getMatchIndex(),
followerLogInformation.getNextIndex());
if (mapFollowerToSnapshot.isEmpty()) {
// once there are no pending followers receiving snapshots
// we can remove snapshot from the memory
setSnapshot(null);
}
wasLastChunk = true;
} else {
followerToSnapshot.markSendStatus(true);
}
} else {
LOG.info("{}: InstallSnapshotReply received sending snapshot chunk failed, Will retry, Chunk: {}",
logName(), reply.getChunkIndex());
followerToSnapshot.markSendStatus(false);
}
if (wasLastChunk && !context.getSnapshotManager().isCapturing()) {
// Since the follower is now caught up try to purge the log.
purgeInMemoryLog();
} else if (!wasLastChunk && followerToSnapshot.canSendNextChunk()) {
ActorSelection followerActor = context.getPeerActorSelection(followerId);
if(followerActor != null) {
sendSnapshotChunk(followerActor, followerId);
}
}
} else {
LOG.error("{}: Chunk index {} in InstallSnapshotReply from follower {} does not match expected index {}",
logName(), reply.getChunkIndex(), followerId,
followerToSnapshot.getChunkIndex());
if(reply.getChunkIndex() == INVALID_CHUNK_INDEX){
// Since the Follower did not find this index to be valid we should reset the follower snapshot
// so that Installing the snapshot can resume from the beginning
followerToSnapshot.reset();
}
}
}
private void replicate(Replicate replicate) {
long logIndex = replicate.getReplicatedLogEntry().getIndex();
LOG.debug("{}: Replicate message: identifier: {}, logIndex: {}", logName(),
replicate.getIdentifier(), logIndex);
// Create a tracker entry we will use this later to notify the
// client actor
trackerList.add(
new ClientRequestTrackerImpl(replicate.getClientActor(),
replicate.getIdentifier(),
logIndex)
);
boolean applyModificationToState = followerToLog.isEmpty()
|| context.getRaftPolicy().applyModificationToStateBeforeConsensus();
if(applyModificationToState){
context.setCommitIndex(logIndex);
applyLogToStateMachine(logIndex);
}
if (!followerToLog.isEmpty()) {
sendAppendEntries(0, false);
}
}
private void sendAppendEntries(long timeSinceLastActivityInterval, boolean isHeartbeat) {
// Send an AppendEntries to all followers
for (Entry e : followerToLog.entrySet()) {
final String followerId = e.getKey();
final FollowerLogInformation followerLogInformation = e.getValue();
// This checks helps not to send a repeat message to the follower
if(!followerLogInformation.isFollowerActive() ||
followerLogInformation.timeSinceLastActivity() >= timeSinceLastActivityInterval) {
sendUpdatesToFollower(followerId, followerLogInformation, true, isHeartbeat);
}
}
}
/**
*
* This method checks if any update needs to be sent to the given follower. This includes append log entries,
* sending next snapshot chunk, and initiating a snapshot.
* @return true if any update is sent, false otherwise
*/
private void sendUpdatesToFollower(String followerId, FollowerLogInformation followerLogInformation,
boolean sendHeartbeat, boolean isHeartbeat) {
ActorSelection followerActor = context.getPeerActorSelection(followerId);
if (followerActor != null) {
long followerNextIndex = followerLogInformation.getNextIndex();
boolean isFollowerActive = followerLogInformation.isFollowerActive();
boolean sendAppendEntries = false;
List entries = Collections.emptyList();
if (mapFollowerToSnapshot.get(followerId) != null) {
// if install snapshot is in process , then sent next chunk if possible
if (isFollowerActive && mapFollowerToSnapshot.get(followerId).canSendNextChunk()) {
sendSnapshotChunk(followerActor, followerId);
} else if(sendHeartbeat) {
// we send a heartbeat even if we have not received a reply for the last chunk
sendAppendEntries = true;
}
} else {
long leaderLastIndex = context.getReplicatedLog().lastIndex();
long leaderSnapShotIndex = context.getReplicatedLog().getSnapshotIndex();
if((!isHeartbeat && LOG.isDebugEnabled()) || LOG.isTraceEnabled()) {
LOG.debug("{}: Checking sendAppendEntries for follower {}: active: {}, followerNextIndex: {}, leaderLastIndex: {}, leaderSnapShotIndex: {}",
logName(), followerId, isFollowerActive, followerNextIndex, leaderLastIndex, leaderSnapShotIndex);
}
if (isFollowerActive && context.getReplicatedLog().isPresent(followerNextIndex)) {
LOG.debug("{}: sendAppendEntries: {} is present for follower {}", logName(),
followerNextIndex, followerId);
if(followerLogInformation.okToReplicate()) {
// Try to send all the entries in the journal but not exceeding the max data size
// for a single AppendEntries message.
int maxEntries = (int) context.getReplicatedLog().size();
entries = context.getReplicatedLog().getFrom(followerNextIndex, maxEntries,
context.getConfigParams().getSnapshotChunkSize());
sendAppendEntries = true;
}
} else if (isFollowerActive && followerNextIndex >= 0 &&
leaderLastIndex > followerNextIndex && !context.getSnapshotManager().isCapturing()) {
// if the followers next index is not present in the leaders log, and
// if the follower is just not starting and if leader's index is more than followers index
// then snapshot should be sent
if (LOG.isDebugEnabled()) {
LOG.debug(String.format("%s: InitiateInstallSnapshot to follower: %s," +
"follower-nextIndex: %d, leader-snapshot-index: %d, " +
"leader-last-index: %d", logName(), followerId,
followerNextIndex, leaderSnapShotIndex, leaderLastIndex));
}
// Send heartbeat to follower whenever install snapshot is initiated.
sendAppendEntries = true;
if (canInstallSnapshot(followerNextIndex)) {
initiateCaptureSnapshot(followerId);
}
} else if(sendHeartbeat) {
// we send an AppendEntries, even if the follower is inactive
// in-order to update the followers timestamp, in case it becomes active again
sendAppendEntries = true;
}
}
if(sendAppendEntries) {
sendAppendEntriesToFollower(followerActor, followerNextIndex,
entries, followerId);
}
}
}
private void sendAppendEntriesToFollower(ActorSelection followerActor, long followerNextIndex,
List entries, String followerId) {
AppendEntries appendEntries = new AppendEntries(currentTerm(), context.getId(),
prevLogIndex(followerNextIndex),
prevLogTerm(followerNextIndex), entries,
context.getCommitIndex(), super.getReplicatedToAllIndex(), context.getPayloadVersion());
if(!entries.isEmpty() || LOG.isTraceEnabled()) {
LOG.debug("{}: Sending AppendEntries to follower {}: {}", logName(), followerId,
appendEntries);
}
followerActor.tell(appendEntries.toSerializable(), actor());
}
/**
* Install Snapshot works as follows
* 1. Leader initiates the capture snapshot by sending a CaptureSnapshot message to actor
* 2. RaftActor on receipt of the CaptureSnapshotReply (from Shard), stores the received snapshot in the replicated log
* and makes a call to Leader's handleMessage , with SendInstallSnapshot message.
* 3. Leader , picks the snapshot from im-mem ReplicatedLog and sends it in chunks to the Follower
* 4. On complete, Follower sends back a InstallSnapshotReply.
* 5. On receipt of the InstallSnapshotReply for the last chunk, Leader marks the install complete for that follower
* and replenishes the memory by deleting the snapshot in Replicated log.
* 6. If another follower requires a snapshot and a snapshot has been collected (via CaptureSnapshotReply)
* then send the existing snapshot in chunks to the follower.
* @param followerId
*/
private void initiateCaptureSnapshot(String followerId) {
if (snapshot.isPresent()) {
// if a snapshot is present in the memory, most likely another install is in progress
// no need to capture snapshot.
// This could happen if another follower needs an install when one is going on.
final ActorSelection followerActor = context.getPeerActorSelection(followerId);
sendSnapshotChunk(followerActor, followerId);
} else {
context.getSnapshotManager().captureToInstall(context.getReplicatedLog().last(),
this.getReplicatedToAllIndex(), followerId);
}
}
private boolean canInstallSnapshot(long nextIndex){
// If the follower's nextIndex is -1 then we might as well send it a snapshot
// Otherwise send it a snapshot only if the nextIndex is not present in the log but is present
// in the snapshot
return (nextIndex == -1 ||
(!context.getReplicatedLog().isPresent(nextIndex)
&& context.getReplicatedLog().isInSnapshot(nextIndex)));
}
private void sendInstallSnapshot() {
LOG.debug("{}: sendInstallSnapshot", logName());
for (Entry e : followerToLog.entrySet()) {
ActorSelection followerActor = context.getPeerActorSelection(e.getKey());
if (followerActor != null) {
long nextIndex = e.getValue().getNextIndex();
if (canInstallSnapshot(nextIndex)) {
sendSnapshotChunk(followerActor, e.getKey());
}
}
}
}
/**
* Sends a snapshot chunk to a given follower
* InstallSnapshot should qualify as a heartbeat too.
*/
private void sendSnapshotChunk(ActorSelection followerActor, String followerId) {
try {
if (snapshot.isPresent()) {
ByteString nextSnapshotChunk = getNextSnapshotChunk(followerId, snapshot.get().getSnapshotBytes());
// Note: the previous call to getNextSnapshotChunk has the side-effect of adding
// followerId to the followerToSnapshot map.
FollowerToSnapshot followerToSnapshot = mapFollowerToSnapshot.get(followerId);
followerActor.tell(
new InstallSnapshot(currentTerm(), context.getId(),
snapshot.get().getLastIncludedIndex(),
snapshot.get().getLastIncludedTerm(),
nextSnapshotChunk,
followerToSnapshot.incrementChunkIndex(),
followerToSnapshot.getTotalChunks(),
Optional.of(followerToSnapshot.getLastChunkHashCode())
).toSerializable(),
actor()
);
if(LOG.isDebugEnabled()) {
LOG.debug("{}: InstallSnapshot sent to follower {}, Chunk: {}/{}",
logName(), followerActor.path(), followerToSnapshot.getChunkIndex(),
followerToSnapshot.getTotalChunks());
}
}
} catch (IOException e) {
LOG.error("{}: InstallSnapshot failed for Leader.", logName(), e);
}
}
/**
* Acccepts snaphot as ByteString, enters into map for future chunks
* creates and return a ByteString chunk
*/
private ByteString getNextSnapshotChunk(String followerId, ByteString snapshotBytes) throws IOException {
FollowerToSnapshot followerToSnapshot = mapFollowerToSnapshot.get(followerId);
if (followerToSnapshot == null) {
followerToSnapshot = new FollowerToSnapshot(snapshotBytes);
mapFollowerToSnapshot.put(followerId, followerToSnapshot);
}
ByteString nextChunk = followerToSnapshot.getNextChunk();
LOG.debug("{}: next snapshot chunk size for follower {}: {}", logName(), followerId, nextChunk.size());
return nextChunk;
}
private void sendHeartBeat() {
if (!followerToLog.isEmpty()) {
LOG.trace("{}: Sending heartbeat", logName());
sendAppendEntries(context.getConfigParams().getHeartBeatInterval().toMillis(), true);
}
}
private void stopHeartBeat() {
if (heartbeatSchedule != null && !heartbeatSchedule.isCancelled()) {
heartbeatSchedule.cancel();
}
}
private void scheduleHeartBeat(FiniteDuration interval) {
if (followerToLog.isEmpty()) {
// Optimization - do not bother scheduling a heartbeat as there are
// no followers
return;
}
stopHeartBeat();
// Schedule a heartbeat. When the scheduler triggers a SendHeartbeat
// message is sent to itself.
// Scheduling the heartbeat only once here because heartbeats do not
// need to be sent if there are other messages being sent to the remote
// actor.
heartbeatSchedule = context.getActorSystem().scheduler().scheduleOnce(
interval, context.getActor(), new SendHeartBeat(),
context.getActorSystem().dispatcher(), context.getActor());
}
@Override
public void close() throws Exception {
stopHeartBeat();
}
@Override
public String getLeaderId() {
return context.getId();
}
protected boolean isLeaderIsolated() {
int minPresent = minIsolatedLeaderPeerCount;
for (FollowerLogInformation followerLogInformation : followerToLog.values()) {
if (followerLogInformation.isFollowerActive()) {
--minPresent;
if (minPresent == 0) {
break;
}
}
}
return (minPresent != 0);
}
/**
* Encapsulates the snapshot bytestring and handles the logic of sending
* snapshot chunks
*/
protected class FollowerToSnapshot {
private final ByteString snapshotBytes;
private int offset = 0;
// the next snapshot chunk is sent only if the replyReceivedForOffset matches offset
private int replyReceivedForOffset;
// if replyStatus is false, the previous chunk is attempted
private boolean replyStatus = false;
private int chunkIndex;
private final int totalChunks;
private int lastChunkHashCode = AbstractLeader.INITIAL_LAST_CHUNK_HASH_CODE;
private int nextChunkHashCode = AbstractLeader.INITIAL_LAST_CHUNK_HASH_CODE;
public FollowerToSnapshot(ByteString snapshotBytes) {
this.snapshotBytes = snapshotBytes;
int size = snapshotBytes.size();
totalChunks = ( size / context.getConfigParams().getSnapshotChunkSize()) +
((size % context.getConfigParams().getSnapshotChunkSize()) > 0 ? 1 : 0);
if(LOG.isDebugEnabled()) {
LOG.debug("{}: Snapshot {} bytes, total chunks to send:{}",
logName(), size, totalChunks);
}
replyReceivedForOffset = -1;
chunkIndex = AbstractLeader.FIRST_CHUNK_INDEX;
}
public ByteString getSnapshotBytes() {
return snapshotBytes;
}
public int incrementOffset() {
if(replyStatus) {
// if prev chunk failed, we would want to sent the same chunk again
offset = offset + context.getConfigParams().getSnapshotChunkSize();
}
return offset;
}
public int incrementChunkIndex() {
if (replyStatus) {
// if prev chunk failed, we would want to sent the same chunk again
chunkIndex = chunkIndex + 1;
}
return chunkIndex;
}
public int getChunkIndex() {
return chunkIndex;
}
public int getTotalChunks() {
return totalChunks;
}
public boolean canSendNextChunk() {
// we only send a false if a chunk is sent but we have not received a reply yet
return replyReceivedForOffset == offset;
}
public boolean isLastChunk(int chunkIndex) {
return totalChunks == chunkIndex;
}
public void markSendStatus(boolean success) {
if (success) {
// if the chunk sent was successful
replyReceivedForOffset = offset;
replyStatus = true;
lastChunkHashCode = nextChunkHashCode;
} else {
// if the chunk sent was failure
replyReceivedForOffset = offset;
replyStatus = false;
}
}
public ByteString getNextChunk() {
int snapshotLength = getSnapshotBytes().size();
int start = incrementOffset();
int size = context.getConfigParams().getSnapshotChunkSize();
if (context.getConfigParams().getSnapshotChunkSize() > snapshotLength) {
size = snapshotLength;
} else {
if ((start + context.getConfigParams().getSnapshotChunkSize()) > snapshotLength) {
size = snapshotLength - start;
}
}
LOG.debug("{}: Next chunk: length={}, offset={},size={}", logName(),
snapshotLength, start, size);
ByteString substring = getSnapshotBytes().substring(start, start + size);
nextChunkHashCode = substring.hashCode();
return substring;
}
/**
* reset should be called when the Follower needs to be sent the snapshot from the beginning
*/
public void reset(){
offset = 0;
replyStatus = false;
replyReceivedForOffset = offset;
chunkIndex = AbstractLeader.FIRST_CHUNK_INDEX;
lastChunkHashCode = AbstractLeader.INITIAL_LAST_CHUNK_HASH_CODE;
}
public int getLastChunkHashCode() {
return lastChunkHashCode;
}
}
// called from example-actor for printing the follower-states
public String printFollowerStates() {
final StringBuilder sb = new StringBuilder();
sb.append('[');
for (FollowerLogInformation followerLogInformation : followerToLog.values()) {
sb.append('{');
sb.append(followerLogInformation.getId());
sb.append(" state:");
sb.append(followerLogInformation.isFollowerActive());
sb.append("},");
}
sb.append(']');
return sb.toString();
}
@VisibleForTesting
public FollowerLogInformation getFollower(String followerId) {
return followerToLog.get(followerId);
}
@VisibleForTesting
protected void setFollowerSnapshot(String followerId, FollowerToSnapshot snapshot) {
mapFollowerToSnapshot.put(followerId, snapshot);
}
@VisibleForTesting
public int followerSnapshotSize() {
return mapFollowerToSnapshot.size();
}
@VisibleForTesting
public int followerLogSize() {
return followerToLog.size();
}
private static class SnapshotHolder {
private final long lastIncludedTerm;
private final long lastIncludedIndex;
private final ByteString snapshotBytes;
SnapshotHolder(Snapshot snapshot) {
this.lastIncludedTerm = snapshot.getLastAppliedTerm();
this.lastIncludedIndex = snapshot.getLastAppliedIndex();
this.snapshotBytes = ByteString.copyFrom(snapshot.getState());
}
long getLastIncludedTerm() {
return lastIncludedTerm;
}
long getLastIncludedIndex() {
return lastIncludedIndex;
}
ByteString getSnapshotBytes() {
return snapshotBytes;
}
}
}