/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.zookeeper.server.quorum;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.BindException;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketAddress;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ConcurrentMap;
import org.apache.jute.BinaryOutputArchive;
import org.apache.zookeeper.ZooDefs.OpCode;
import org.apache.zookeeper.common.Time;
import org.apache.zookeeper.server.FinalRequestProcessor;
import org.apache.zookeeper.server.Request;
import org.apache.zookeeper.server.RequestProcessor;
import org.apache.zookeeper.server.ZooKeeperCriticalThread;
import org.apache.zookeeper.server.quorum.QuorumPeer.LearnerType;
import org.apache.zookeeper.server.quorum.flexible.QuorumVerifier;
import org.apache.zookeeper.server.util.ZxidUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This class has the control logic for the Leader.
*/
public class Leader {
private static final Logger LOG = LoggerFactory.getLogger(Leader.class);
static final private boolean nodelay = System.getProperty("leader.nodelay", "true").equals("true");
static {
LOG.info("TCP NoDelay set to: " + nodelay);
}
static public class Proposal extends SyncedLearnerTracker {
public QuorumPacket packet;
public Request request;
@Override
public String toString() {
return packet.getType() + ", " + packet.getZxid() + ", " + request;
}
}
// Throttle when there are too many concurrent snapshots being sent to observers
private static final String MAX_CONCURRENT_SNAPSHOTS = "zookeeper.leader.maxConcurrentSnapshots";
private static final int maxConcurrentSnapshots;
private static final String MAX_CONCURRENT_SNAPSHOT_TIMEOUT = "zookeeper.leader.maxConcurrentSnapshotTimeout";
private static final long maxConcurrentSnapshotTimeout;
static {
maxConcurrentSnapshots = Integer.getInteger(MAX_CONCURRENT_SNAPSHOTS, 10);
LOG.info(MAX_CONCURRENT_SNAPSHOTS + " = " + maxConcurrentSnapshots);
maxConcurrentSnapshotTimeout = Long.getLong(MAX_CONCURRENT_SNAPSHOT_TIMEOUT, 5);
LOG.info(MAX_CONCURRENT_SNAPSHOT_TIMEOUT + " = " + maxConcurrentSnapshotTimeout);
}
private final LearnerSnapshotThrottler learnerSnapshotThrottler =
new LearnerSnapshotThrottler(maxConcurrentSnapshots, maxConcurrentSnapshotTimeout);
final LeaderZooKeeperServer zk;
final QuorumPeer self;
private boolean quorumFormed = false;
// the follower acceptor thread
volatile LearnerCnxAcceptor cnxAcceptor = null;
// list of all the followers
private final HashSet<LearnerHandler> learners =
new HashSet<LearnerHandler>();
/**
* Returns a copy of the current learner snapshot
*/
public List<LearnerHandler> getLearners() {
synchronized (learners) {
return new ArrayList<LearnerHandler>(learners);
}
}
// list of followers that are ready to follow (i.e synced with the leader)
private final HashSet<LearnerHandler> forwardingFollowers =
new HashSet<LearnerHandler>();
/**
* Returns a copy of the current forwarding follower snapshot
*/
public List<LearnerHandler> getForwardingFollowers() {
synchronized (forwardingFollowers) {
return new ArrayList<LearnerHandler>(forwardingFollowers);
}
}
private void addForwardingFollower(LearnerHandler lh) {
synchronized (forwardingFollowers) {
forwardingFollowers.add(lh);
}
}
private final HashSet<LearnerHandler> observingLearners =
new HashSet<LearnerHandler>();
/**
* Returns a copy of the current observer snapshot
*/
public List<LearnerHandler> getObservingLearners() {
synchronized (observingLearners) {
return new ArrayList<LearnerHandler>(observingLearners);
}
}
private void addObserverLearnerHandler(LearnerHandler lh) {
synchronized (observingLearners) {
observingLearners.add(lh);
}
}
// Pending sync requests. Must access under 'this' lock.
private final HashMap<Long,List<LearnerSyncRequest>> pendingSyncs =
new HashMap<Long,List<LearnerSyncRequest>>();
synchronized public int getNumPendingSyncs() {
return pendingSyncs.size();
}
//Follower counter
final AtomicLong followerCounter = new AtomicLong(-1);
/**
* Adds peer to the leader.
*
* @param learner
* instance of learner handle
*/
void addLearnerHandler(LearnerHandler learner) {
synchronized (learners) {
learners.add(learner);
}
}
/**
* Remove the learner from the learner list
*
* @param peer
*/
void removeLearnerHandler(LearnerHandler peer) {
synchronized (forwardingFollowers) {
forwardingFollowers.remove(peer);
}
synchronized (learners) {
learners.remove(peer);
}
synchronized (observingLearners) {
observingLearners.remove(peer);
}
}
boolean isLearnerSynced(LearnerHandler peer){
synchronized (forwardingFollowers) {
return forwardingFollowers.contains(peer);
}
}
/**
* Returns true if a quorum in qv is connected and synced with the leader
* and false otherwise
*
* @param qv, a QuorumVerifier
*/
public boolean isQuorumSynced(QuorumVerifier qv) {
HashSet<Long> ids = new HashSet<Long>();
if (qv.getVotingMembers().containsKey(self.getId()))
ids.add(self.getId());
synchronized (forwardingFollowers) {
for (LearnerHandler learnerHandler: forwardingFollowers){
if (learnerHandler.synced() && qv.getVotingMembers().containsKey(learnerHandler.getSid())){
ids.add(learnerHandler.getSid());
}
}
}
return qv.containsQuorum(ids);
}
private final ServerSocket ss;
Leader(QuorumPeer self,LeaderZooKeeperServer zk) throws IOException {
this.self = self;
try {
if (self.getQuorumListenOnAllIPs()) {
ss = new ServerSocket(self.getQuorumAddress().getPort());
} else {
ss = new ServerSocket();
}
ss.setReuseAddress(true);
if (!self.getQuorumListenOnAllIPs()) {
ss.bind(self.getQuorumAddress());
}
} catch (BindException e) {
if (self.getQuorumListenOnAllIPs()) {
LOG.error("Couldn't bind to port " + self.getQuorumAddress().getPort(), e);
} else {
LOG.error("Couldn't bind to " + self.getQuorumAddress(), e);
}
throw e;
}
this.zk = zk;
}
/**
* This message is for follower to expect diff
*/
final static int DIFF = 13;
/**
* This is for follower to truncate its logs
*/
final static int TRUNC = 14;
/**
* This is for follower to download the snapshots
*/
final static int SNAP = 15;
/**
* This tells the leader that the connecting peer is actually an observer
*/
final static int OBSERVERINFO = 16;
/**
* This message type is sent by the leader to indicate it's zxid and if
* needed, its database.
*/
final static int NEWLEADER = 10;
/**
* This message type is sent by a follower to pass the last zxid. This is here
* for backward compatibility purposes.
*/
final static int FOLLOWERINFO = 11;
/**
* This message type is sent by the leader to indicate that the follower is
* now uptodate andt can start responding to clients.
*/
final static int UPTODATE = 12;
/**
* This message is the first that a follower receives from the leader.
* It has the protocol version and the epoch of the leader.
*/
public static final int LEADERINFO = 17;
/**
* This message is used by the follow to ack a proposed epoch.
*/
public static final int ACKEPOCH = 18;
/**
* This message type is sent to a leader to request and mutation operation.
* The payload will consist of a request header followed by a request.
*/
final static int REQUEST = 1;
/**
* This message type is sent by a leader to propose a mutation.
*/
public final static int PROPOSAL = 2;
/**
* This message type is sent by a follower after it has synced a proposal.
*/
final static int ACK = 3;
/**
* This message type is sent by a leader to commit a proposal and cause
* followers to start serving the corresponding data.
*/
final static int COMMIT = 4;
/**
* This message type is enchanged between follower and leader (initiated by
* follower) to determine liveliness.
*/
final static int PING = 5;
/**
* This message type is to validate a session that should be active.
*/
final static int REVALIDATE = 6;
/**
* This message is a reply to a synchronize command flushing the pipe
* between the leader and the follower.
*/
final static int SYNC = 7;
/**
* This message type informs observers of a committed proposal.
*/
final static int INFORM = 8;
/**
* Similar to COMMIT, only for a reconfig operation.
*/
final static int COMMITANDACTIVATE = 9;
/**
* Similar to INFORM, only for a reconfig operation.
*/
final static int INFORMANDACTIVATE = 19;
final ConcurrentMap<Long, Proposal> outstandingProposals = new ConcurrentHashMap<Long, Proposal>();
private final ConcurrentLinkedQueue<Proposal> toBeApplied = new ConcurrentLinkedQueue<Proposal>();
private final Proposal newLeaderProposal = new Proposal();
class LearnerCnxAcceptor extends ZooKeeperCriticalThread {
private volatile boolean stop = false;
public LearnerCnxAcceptor() {
super("LearnerCnxAcceptor-" + ss.getLocalSocketAddress(), zk
.getZooKeeperServerListener());
}
@Override
public void run() {
try {
while (!stop) {
try{
Socket s = ss.accept();
// start with the initLimit, once the ack is processed
// in LearnerHandler switch to the syncLimit
s.setSoTimeout(self.tickTime * self.initLimit);
s.setTcpNoDelay(nodelay);
LearnerHandler fh = new LearnerHandler(s, Leader.this);
fh.start();
} catch (SocketException e) {
if (stop) {
LOG.info("exception while shutting down acceptor: "
+ e);
// When Leader.shutdown() calls ss.close(),
// the call to accept throws an exception.
// We catch and set stop to true.
stop = true;
} else {
throw e;
}
}
}
} catch (Exception e) {
LOG.warn("Exception while accepting follower", e.getMessage());
handleException(this.getName(), e);
}
}
public void halt() {
stop = true;
}
}
StateSummary leaderStateSummary;
long epoch = -1;
boolean waitingForNewEpoch = true;
// when a reconfig occurs where the leader is removed or becomes an observer,
// it does not commit ops after committing the reconfig
boolean allowedToCommit = true;
/**
* This method is main function that is called to lead
*
* @throws IOException
* @throws InterruptedException
*/
void lead() throws IOException, InterruptedException {
self.end_fle = Time.currentElapsedTime();
long electionTimeTaken = self.end_fle - self.start_fle;
self.setElectionTimeTaken(electionTimeTaken);
LOG.info("LEADING - LEADER ELECTION TOOK - {} {}", electionTimeTaken,
QuorumPeer.FLE_TIME_UNIT);
self.start_fle = 0;
self.end_fle = 0;
zk.registerJMX(new LeaderBean(this, zk), self.jmxLocalPeerBean);
try {
self.tick.set(0);
zk.loadData();
leaderStateSummary = new StateSummary(self.getCurrentEpoch(), zk.getLastProcessedZxid());
// Start thread that waits for connection requests from
// new followers.
cnxAcceptor = new LearnerCnxAcceptor();
cnxAcceptor.start();
long epoch = getEpochToPropose(self.getId(), self.getAcceptedEpoch());
zk.setZxid(ZxidUtils.makeZxid(epoch, 0));
synchronized(this){
lastProposed = zk.getZxid();
}
newLeaderProposal.packet = new QuorumPacket(NEWLEADER, zk.getZxid(),
null, null);
if ((newLeaderProposal.packet.getZxid() & 0xffffffffL) != 0) {
LOG.info("NEWLEADER proposal has Zxid of "
+ Long.toHexString(newLeaderProposal.packet.getZxid()));
}
QuorumVerifier lastSeenQV = self.getLastSeenQuorumVerifier();
QuorumVerifier curQV = self.getQuorumVerifier();
if (curQV.getVersion() == 0 && curQV.getVersion() == lastSeenQV.getVersion()) {
// This was added in ZOOKEEPER-1783. The initial config has version 0 (not explicitly
// specified by the user; the lack of version in a config file is interpreted as version=0).
// As soon as a config is established we would like to increase its version so that it
// takes presedence over other initial configs that were not established (such as a config
// of a server trying to join the ensemble, which may be a partial view of the system, not the full config).
// We chose to set the new version to the one of the NEWLEADER message. However, before we can do that
// there must be agreement on the new version, so we can only change the version when sending/receiving UPTODATE,
// not when sending/receiving NEWLEADER. In other words, we can't change curQV here since its the committed quorum verifier,
// and there's still no agreement on the new version that we'd like to use. Instead, we use
// lastSeenQuorumVerifier which is being sent with NEWLEADER message
// so its a good way to let followers know about the new version. (The original reason for sending
// lastSeenQuorumVerifier with NEWLEADER is so that the leader completes any potentially uncommitted reconfigs
// that it finds before starting to propose operations. Here we're reusing the same code path for
// reaching consensus on the new version number.)
// It is important that this is done before the leader executes waitForEpochAck,
// so before LearnerHandlers return from their waitForEpochAck
// hence before they construct the NEWLEADER message containing
// the last-seen-quorumverifier of the leader, which we change below
try {
QuorumVerifier newQV = self.configFromString(curQV.toString());
newQV.setVersion(zk.getZxid());
self.setLastSeenQuorumVerifier(newQV, true);
} catch (Exception e) {
throw new IOException(e);
}
}
newLeaderProposal.addQuorumVerifier(self.getQuorumVerifier());
if (self.getLastSeenQuorumVerifier().getVersion() > self.getQuorumVerifier().getVersion()){
newLeaderProposal.addQuorumVerifier(self.getLastSeenQuorumVerifier());
}
// We have to get at least a majority of servers in sync with
// us. We do this by waiting for the NEWLEADER packet to get
// acknowledged
waitForEpochAck(self.getId(), leaderStateSummary);
self.setCurrentEpoch(epoch);
try {
waitForNewLeaderAck(self.getId(), zk.getZxid(), LearnerType.PARTICIPANT);
} catch (InterruptedException e) {
shutdown("Waiting for a quorum of followers, only synced with sids: [ "
+ newLeaderProposal.ackSetsToString() + " ]");
HashSet<Long> followerSet = new HashSet<Long>();
for(LearnerHandler f : getLearners()) {
if (self.getQuorumVerifier().getVotingMembers().containsKey(f.getSid())){
followerSet.add(f.getSid());
}
}
boolean initTicksShouldBeIncreased = true;
for (Proposal.QuorumVerifierAcksetPair qvAckset:newLeaderProposal.qvAcksetPairs) {
if (!qvAckset.getQuorumVerifier().containsQuorum(followerSet)) {
initTicksShouldBeIncreased = false;
break;
}
}
if (initTicksShouldBeIncreased) {
LOG.warn("Enough followers present. "+
"Perhaps the initTicks need to be increased.");
}
return;
}
startZkServer();
/**
* WARNING: do not use this for anything other than QA testing
* on a real cluster. Specifically to enable verification that quorum
* can handle the lower 32bit roll-over issue identified in
* ZOOKEEPER-1277. Without this option it would take a very long
* time (on order of a month say) to see the 4 billion writes
* necessary to cause the roll-over to occur.
*
* This field allows you to override the zxid of the server. Typically
* you'll want to set it to something like 0xfffffff0 and then
* start the quorum, run some operations and see the re-election.
*/
String initialZxid = System.getProperty("zookeeper.testingonly.initialZxid");
if (initialZxid != null) {
long zxid = Long.parseLong(initialZxid);
zk.setZxid((zk.getZxid() & 0xffffffff00000000L) | zxid);
}
if (!System.getProperty("zookeeper.leaderServes", "yes").equals("no")) {
self.setZooKeeperServer(zk);
}
self.adminServer.setZooKeeperServer(zk);
// Everything is a go, simply start counting the ticks
// WARNING: I couldn't find any wait statement on a synchronized
// block that would be notified by this notifyAll() call, so
// I commented it out
//synchronized (this) {
// notifyAll();
//}
// We ping twice a tick, so we only update the tick every other
// iteration
boolean tickSkip = true;
// If not null then shutdown this leader
String shutdownMessage = null;
while (true) {
synchronized (this) {
long start = Time.currentElapsedTime();
long cur = start;
long end = start + self.tickTime / 2;
while (cur < end) {
wait(end - cur);
cur = Time.currentElapsedTime();
}
if (!tickSkip) {
self.tick.incrementAndGet();
}
// We use an instance of SyncedLearnerTracker to
// track synced learners to make sure we still have a
// quorum of current (and potentially next pending) view.
SyncedLearnerTracker syncedAckSet = new SyncedLearnerTracker();
syncedAckSet.addQuorumVerifier(self.getQuorumVerifier());
if (self.getLastSeenQuorumVerifier() != null
&& self.getLastSeenQuorumVerifier().getVersion() > self
.getQuorumVerifier().getVersion()) {
syncedAckSet.addQuorumVerifier(self
.getLastSeenQuorumVerifier());
}
syncedAckSet.addAck(self.getId());
for (LearnerHandler f : getLearners()) {
if (f.synced()) {
syncedAckSet.addAck(f.getSid());
}
}
// check leader running status
if (!this.isRunning()) {
// set shutdown flag
shutdownMessage = "Unexpected internal error";
break;
}
if (!tickSkip && !syncedAckSet.hasAllQuorums()) {
// Lost quorum of last committed and/or last proposed
// config, set shutdown flag
shutdownMessage = "Not sufficient followers synced, only synced with sids: [ "
+ syncedAckSet.ackSetsToString() + " ]";
break;
}
tickSkip = !tickSkip;
}
for (LearnerHandler f : getLearners()) {
f.ping();
}
}
if (shutdownMessage != null) {
shutdown(shutdownMessage);
// leader goes in looking state
}
} finally {
zk.unregisterJMX(this);
}
}
boolean isShutdown;
/**
* Close down all the LearnerHandlers
*/
void shutdown(String reason) {
LOG.info("Shutting down");
if (isShutdown) {
return;
}
LOG.info("Shutdown called",
new Exception("shutdown Leader! reason: " + reason));
if (cnxAcceptor != null) {
cnxAcceptor.halt();
}
// NIO should not accept conenctions
self.setZooKeeperServer(null);
self.adminServer.setZooKeeperServer(null);
try {
ss.close();
} catch (IOException e) {
LOG.warn("Ignoring unexpected exception during close",e);
}
self.closeAllConnections();
// shutdown the previous zk
if (zk != null) {
zk.shutdown();
}
synchronized (learners) {
for (Iterator<LearnerHandler> it = learners.iterator(); it
.hasNext();) {
LearnerHandler f = it.next();
it.remove();
f.shutdown();
}
}
isShutdown = true;
}
/** In a reconfig operation, this method attempts to find the best leader for next configuration.
* If the current leader is a voter in the next configuartion, then it remains the leader.
* Otherwise, choose one of the new voters that acked the reconfiguartion, such that it is as
* up-to-date as possible, i.e., acked as many outstanding proposals as possible.
*
* @param reconfigProposal
* @param zxid of the reconfigProposal
* @return server if of the designated leader
*/
private long getDesignatedLeader(Proposal reconfigProposal, long zxid) {
//new configuration
Proposal.QuorumVerifierAcksetPair newQVAcksetPair = reconfigProposal.qvAcksetPairs.get(reconfigProposal.qvAcksetPairs.size()-1);
//check if I'm in the new configuration with the same quorum address -
// if so, I'll remain the leader
if (newQVAcksetPair.getQuorumVerifier().getVotingMembers().containsKey(self.getId()) &&
newQVAcksetPair.getQuorumVerifier().getVotingMembers().get(self.getId()).addr.equals(self.getQuorumAddress())){
return self.getId();
}
// start with an initial set of candidates that are voters from new config that
// acknowledged the reconfig op (there must be a quorum). Choose one of them as
// current leader candidate
HashSet<Long> candidates = new HashSet<Long>(newQVAcksetPair.getAckset());
candidates.remove(self.getId()); // if we're here, I shouldn't be the leader
long curCandidate = candidates.iterator().next();
//go over outstanding ops in order, and try to find a candidate that acked the most ops.
//this way it will be the most up-to-date and we'll minimize the number of ops that get dropped
long curZxid = zxid + 1;
Proposal p = outstandingProposals.get(curZxid);
while (p!=null && !candidates.isEmpty()) {
for (Proposal.QuorumVerifierAcksetPair qvAckset: p.qvAcksetPairs){
//reduce the set of candidates to those that acknowledged p
candidates.retainAll(qvAckset.getAckset());
//no candidate acked p, return the best candidate found so far
if (candidates.isEmpty()) return curCandidate;
//update the current candidate, and if it is the only one remaining, return it
curCandidate = candidates.iterator().next();
if (candidates.size() == 1) return curCandidate;
}
curZxid++;
p = outstandingProposals.get(curZxid);
}
return curCandidate;
}
/**
* @return True if committed, otherwise false.
* @param a proposal p
**/
synchronized public boolean tryToCommit(Proposal p, long zxid, SocketAddress followerAddr) {
// make sure that ops are committed in order. With reconfigurations it is now possible
// that different operations wait for different sets of acks, and we still want to enforce
// that they are committed in order. Currently we only permit one outstanding reconfiguration
// such that the reconfiguration and subsequent outstanding ops proposed while the reconfig is
// pending all wait for a quorum of old and new config, so it's not possible to get enough acks
// for an operation without getting enough acks for preceding ops. But in the future if multiple
// concurrent reconfigs are allowed, this can happen.
if (outstandingProposals.containsKey(zxid - 1)) return false;
// in order to be committed, a proposal must be accepted by a quorum.
//
// getting a quorum from all necessary configurations.
if (!p.hasAllQuorums()) {
return false;
}
// commit proposals in order
if (zxid != lastCommitted+1) {
LOG.warn("Commiting zxid 0x" + Long.toHexString(zxid)
+ " from " + followerAddr + " not first!");
LOG.warn("First is "
+ (lastCommitted+1));
}
outstandingProposals.remove(zxid);
if (p.request != null) {
toBeApplied.add(p);
}
if (p.request == null) {
LOG.warn("Going to commmit null: " + p);
} else if (p.request.getHdr().getType() == OpCode.reconfig) {
LOG.debug("Committing a reconfiguration! " + outstandingProposals.size());
//if this server is voter in new config with the same quorum address,
//then it will remain the leader
//otherwise an up-to-date follower will be designated as leader. This saves
//leader election time, unless the designated leader fails
Long designatedLeader = getDesignatedLeader(p, zxid);
//LOG.warn("designated leader is: " + designatedLeader);
QuorumVerifier newQV = p.qvAcksetPairs.get(p.qvAcksetPairs.size()-1).getQuorumVerifier();
self.processReconfig(newQV, designatedLeader, zk.getZxid(), true);
if (designatedLeader != self.getId()) {
allowedToCommit = false;
}
// we're sending the designated leader, and if the leader is changing the followers are
// responsible for closing the connection - this way we are sure that at least a majority of them
// receive the commit message.
commitAndActivate(zxid, designatedLeader);
informAndActivate(p, designatedLeader);
//turnOffFollowers();
} else {
commit(zxid);
inform(p);
}
zk.commitProcessor.commit(p.request);
if(pendingSyncs.containsKey(zxid)){
for(LearnerSyncRequest r: pendingSyncs.remove(zxid)) {
sendSync(r);
}
}
return true;
}
/**
* Keep a count of acks that are received by the leader for a particular
* proposal
*
* @param zxid, the zxid of the proposal sent out
* @param sid, the id of the server that sent the ack
* @param followerAddr
*/
synchronized public void processAck(long sid, long zxid, SocketAddress followerAddr) {
if (!allowedToCommit) return; // last op committed was a leader change - from now on
// the new leader should commit
if (LOG.isTraceEnabled()) {
LOG.trace("Ack zxid: 0x{}", Long.toHexString(zxid));
for (Proposal p : outstandingProposals.values()) {
long packetZxid = p.packet.getZxid();
LOG.trace("outstanding proposal: 0x{}",
Long.toHexString(packetZxid));
}
LOG.trace("outstanding proposals all");
}
if ((zxid & 0xffffffffL) == 0) {
/*
* We no longer process NEWLEADER ack with this method. However,
* the learner sends an ack back to the leader after it gets
* UPTODATE, so we just ignore the message.
*/
return;
}
if (outstandingProposals.size() == 0) {
if (LOG.isDebugEnabled()) {
LOG.debug("outstanding is 0");
}
return;
}
if (lastCommitted >= zxid) {
if (LOG.isDebugEnabled()) {
LOG.debug("proposal has already been committed, pzxid: 0x{} zxid: 0x{}",
Long.toHexString(lastCommitted), Long.toHexString(zxid));
}
// The proposal has already been committed
return;
}
Proposal p = outstandingProposals.get(zxid);
if (p == null) {
LOG.warn("Trying to commit future proposal: zxid 0x{} from {}",
Long.toHexString(zxid), followerAddr);
return;
}
p.addAck(sid);
/*if (LOG.isDebugEnabled()) {
LOG.debug("Count for zxid: 0x{} is {}",
Long.toHexString(zxid), p.ackSet.size());
}*/
boolean hasCommitted = tryToCommit(p, zxid, followerAddr);
// If p is a reconfiguration, multiple other operations may be ready to be committed,
// since operations wait for different sets of acks.
// Currently we only permit one outstanding reconfiguration at a time
// such that the reconfiguration and subsequent outstanding ops proposed while the reconfig is
// pending all wait for a quorum of old and new config, so its not possible to get enough acks
// for an operation without getting enough acks for preceding ops. But in the future if multiple
// concurrent reconfigs are allowed, this can happen and then we need to check whether some pending
// ops may already have enough acks and can be committed, which is what this code does.
if (hasCommitted && p.request!=null && p.request.getHdr().getType() == OpCode.reconfig){
long curZxid = zxid;
while (allowedToCommit && hasCommitted && p!=null){
curZxid++;
p = outstandingProposals.get(curZxid);
if (p !=null) hasCommitted = tryToCommit(p, curZxid, null);
}
}
}
static class ToBeAppliedRequestProcessor implements RequestProcessor {
private final RequestProcessor next;
private final Leader leader;
/**
* This request processor simply maintains the toBeApplied list. For
* this to work next must be a FinalRequestProcessor and
* FinalRequestProcessor.processRequest MUST process the request
* synchronously!
*
* @param next
* a reference to the FinalRequestProcessor
*/
ToBeAppliedRequestProcessor(RequestProcessor next, Leader leader) {
if (!(next instanceof FinalRequestProcessor)) {
throw new RuntimeException(ToBeAppliedRequestProcessor.class
.getName()
+ " must be connected to "
+ FinalRequestProcessor.class.getName()
+ " not "
+ next.getClass().getName());
}
this.leader = leader;
this.next = next;
}
/*
* (non-Javadoc)
*
* @see org.apache.zookeeper.server.RequestProcessor#processRequest(org.apache.zookeeper.server.Request)
*/
public void processRequest(Request request) throws RequestProcessorException {
next.processRequest(request);
// The only requests that should be on toBeApplied are write
// requests, for which we will have a hdr. We can't simply use
// request.zxid here because that is set on read requests to equal
// the zxid of the last write op.
if (request.getHdr() != null) {
long zxid = request.getHdr().getZxid();
Iterator<Proposal> iter = leader.toBeApplied.iterator();
if (iter.hasNext()) {
Proposal p = iter.next();
if (p.request != null && p.request.zxid == zxid) {
iter.remove();
return;
}
}
LOG.error("Committed request not found on toBeApplied: "
+ request);
}
}
/*
* (non-Javadoc)
*
* @see org.apache.zookeeper.server.RequestProcessor#shutdown()
*/
public void shutdown() {
LOG.info("Shutting down");
next.shutdown();
}
}
/**
* send a packet to all the followers ready to follow
*
* @param qp
* the packet to be sent
*/
void sendPacket(QuorumPacket qp) {
synchronized (forwardingFollowers) {
for (LearnerHandler f : forwardingFollowers) {
f.queuePacket(qp);
}
}
}
/**
* send a packet to all observers
*/
void sendObserverPacket(QuorumPacket qp) {
for (LearnerHandler f : getObservingLearners()) {
f.queuePacket(qp);
}
}
long lastCommitted = -1;
/**
* Create a commit packet and send it to all the members of the quorum
*
* @param zxid
*/
public void commit(long zxid) {
synchronized(this){
lastCommitted = zxid;
}
QuorumPacket qp = new QuorumPacket(Leader.COMMIT, zxid, null, null);
sendPacket(qp);
}
//commit and send some info
public void commitAndActivate(long zxid, long designatedLeader) {
synchronized(this){
lastCommitted = zxid;
}
byte data[] = new byte[8];
ByteBuffer buffer = ByteBuffer.wrap(data);
buffer.putLong(designatedLeader);
QuorumPacket qp = new QuorumPacket(Leader.COMMITANDACTIVATE, zxid, data, null);
sendPacket(qp);
}
/**
* Create an inform packet and send it to all observers.
* @param zxid
* @param proposal
*/
public void inform(Proposal proposal) {
QuorumPacket qp = new QuorumPacket(Leader.INFORM, proposal.request.zxid,
proposal.packet.getData(), null);
sendObserverPacket(qp);
}
/**
* Create an inform&activate packet and send it to all observers.
* @param zxid
* @param proposal
*/
public void informAndActivate(Proposal proposal, long designatedLeader) {
byte[] proposalData = proposal.packet.getData();
byte[] data = new byte[proposalData.length + 8];
ByteBuffer buffer = ByteBuffer.wrap(data);
buffer.putLong(designatedLeader);
buffer.put(proposalData);
QuorumPacket qp = new QuorumPacket(Leader.INFORMANDACTIVATE, proposal.request.zxid, data, null);
sendObserverPacket(qp);
}
long lastProposed;
/**
* Returns the current epoch of the leader.
*
* @return
*/
public long getEpoch(){
return ZxidUtils.getEpochFromZxid(lastProposed);
}
@SuppressWarnings("serial")
public static class XidRolloverException extends Exception {
public XidRolloverException(String message) {
super(message);
}
}
/**
* create a proposal and send it out to all the members
*
* @param request
* @return the proposal that is queued to send to all the members
*/
public Proposal propose(Request request) throws XidRolloverException {
/**
* Address the rollover issue. All lower 32bits set indicate a new leader
* election. Force a re-election instead. See ZOOKEEPER-1277
*/
if ((request.zxid & 0xffffffffL) == 0xffffffffL) {
String msg =
"zxid lower 32 bits have rolled over, forcing re-election, and therefore new epoch start";
shutdown(msg);
throw new XidRolloverException(msg);
}
ByteArrayOutputStream baos = new ByteArrayOutputStream();
BinaryOutputArchive boa = BinaryOutputArchive.getArchive(baos);
try {
request.getHdr().serialize(boa, "hdr");
if (request.getTxn() != null) {
request.getTxn().serialize(boa, "txn");
}
baos.close();
} catch (IOException e) {
LOG.warn("This really should be impossible", e);
}
QuorumPacket pp = new QuorumPacket(Leader.PROPOSAL, request.zxid,
baos.toByteArray(), null);
Proposal p = new Proposal();
p.packet = pp;
p.request = request;
synchronized(this) {
p.addQuorumVerifier(self.getQuorumVerifier());
if (request.getHdr().getType() == OpCode.reconfig){
self.setLastSeenQuorumVerifier(request.qv, true);
}
if (self.getQuorumVerifier().getVersion()<self.getLastSeenQuorumVerifier().getVersion()) {
p.addQuorumVerifier(self.getLastSeenQuorumVerifier());
}
if (LOG.isDebugEnabled()) {
LOG.debug("Proposing:: " + request);
}
lastProposed = p.packet.getZxid();
outstandingProposals.put(lastProposed, p);
sendPacket(pp);
}
return p;
}
public LearnerSnapshotThrottler getLearnerSnapshotThrottler() {
return learnerSnapshotThrottler;
}
/**
* Process sync requests
*
* @param r the request
*/
synchronized public void processSync(LearnerSyncRequest r){
if(outstandingProposals.isEmpty()){
sendSync(r);
} else {
List<LearnerSyncRequest> l = pendingSyncs.get(lastProposed);
if (l == null) {
l = new ArrayList<LearnerSyncRequest>();
}
l.add(r);
pendingSyncs.put(lastProposed, l);
}
}
/**
* Sends a sync message to the appropriate server
*
* @param f
* @param r
*/
public void sendSync(LearnerSyncRequest r){
QuorumPacket qp = new QuorumPacket(Leader.SYNC, 0, null, null);
r.fh.queuePacket(qp);
}
/**
* lets the leader know that a follower is capable of following and is done
* syncing
*
* @param handler handler of the follower
* @return last proposed zxid
* @throws InterruptedException
*/
synchronized public long startForwarding(LearnerHandler handler,
long lastSeenZxid) {
// Queue up any outstanding requests enabling the receipt of
// new requests
if (lastProposed > lastSeenZxid) {
for (Proposal p : toBeApplied) {
if (p.packet.getZxid() <= lastSeenZxid) {
continue;
}
handler.queuePacket(p.packet);
// Since the proposal has been committed we need to send the
// commit message also
QuorumPacket qp = new QuorumPacket(Leader.COMMIT, p.packet
.getZxid(), null, null);
handler.queuePacket(qp);
}
// Only participant need to get outstanding proposals
if (handler.getLearnerType() == LearnerType.PARTICIPANT) {
List<Long>zxids = new ArrayList<Long>(outstandingProposals.keySet());
Collections.sort(zxids);
for (Long zxid: zxids) {
if (zxid <= lastSeenZxid) {
continue;
}
handler.queuePacket(outstandingProposals.get(zxid).packet);
}
}
}
if (handler.getLearnerType() == LearnerType.PARTICIPANT) {
addForwardingFollower(handler);
} else {
addObserverLearnerHandler(handler);
}
return lastProposed;
}
private final HashSet<Long> connectingFollowers = new HashSet<Long>();
public long getEpochToPropose(long sid, long lastAcceptedEpoch) throws InterruptedException, IOException {
synchronized(connectingFollowers) {
if (!waitingForNewEpoch) {
return epoch;
}
if (lastAcceptedEpoch >= epoch) {
epoch = lastAcceptedEpoch+1;
}
connectingFollowers.add(sid);
QuorumVerifier verifier = self.getQuorumVerifier();
if (connectingFollowers.contains(self.getId()) &&
verifier.containsQuorum(connectingFollowers)) {
waitingForNewEpoch = false;
self.setAcceptedEpoch(epoch);
connectingFollowers.notifyAll();
} else {
long start = Time.currentElapsedTime();
long cur = start;
long end = start + self.getInitLimit()*self.getTickTime();
while(waitingForNewEpoch && cur < end) {
connectingFollowers.wait(end - cur);
cur = Time.currentElapsedTime();
}
if (waitingForNewEpoch) {
throw new InterruptedException("Timeout while waiting for epoch from quorum");
}
}
return epoch;
}
}
private final HashSet<Long> electingFollowers = new HashSet<Long>();
private boolean electionFinished = false;
public void waitForEpochAck(long id, StateSummary ss) throws IOException, InterruptedException {
synchronized(electingFollowers) {
if (electionFinished) {
return;
}
if (ss.getCurrentEpoch() != -1) {
if (ss.isMoreRecentThan(leaderStateSummary)) {
throw new IOException("Follower is ahead of the leader, leader summary: "
+ leaderStateSummary.getCurrentEpoch()
+ " (current epoch), "
+ leaderStateSummary.getLastZxid()
+ " (last zxid)");
}
if (ss.getLastZxid() != -1) {
electingFollowers.add(id);
}
}
QuorumVerifier verifier = self.getQuorumVerifier();
if (electingFollowers.contains(self.getId()) && verifier.containsQuorum(electingFollowers)) {
electionFinished = true;
electingFollowers.notifyAll();
} else {
long start = Time.currentElapsedTime();
long cur = start;
long end = start + self.getInitLimit()*self.getTickTime();
while(!electionFinished && cur < end) {
electingFollowers.wait(end - cur);
cur = Time.currentElapsedTime();
}
if (!electionFinished) {
throw new InterruptedException("Timeout while waiting for epoch to be acked by quorum");
}
}
}
}
/**
* Return a list of sid in set as string
*/
private String getSidSetString(Set<Long> sidSet) {
StringBuilder sids = new StringBuilder();
Iterator<Long> iter = sidSet.iterator();
while (iter.hasNext()) {
sids.append(iter.next());
if (!iter.hasNext()) {
break;
}
sids.append(",");
}
return sids.toString();
}
/**
* Start up Leader ZooKeeper server and initialize zxid to the new epoch
*/
private synchronized void startZkServer() {
// Update lastCommitted and Db's zxid to a value representing the new epoch
lastCommitted = zk.getZxid();
LOG.info("Have quorum of supporters, sids: [ "
+ newLeaderProposal.ackSetsToString()
+ " ]; starting up and setting last processed zxid: 0x{}",
Long.toHexString(zk.getZxid()));
/*
* ZOOKEEPER-1324. the leader sends the new config it must complete
* to others inside a NEWLEADER message (see LearnerHandler where
* the NEWLEADER message is constructed), and once it has enough
* acks we must execute the following code so that it applies the
* config to itself.
*/
QuorumVerifier newQV = self.getLastSeenQuorumVerifier();
Long designatedLeader = getDesignatedLeader(newLeaderProposal, zk.getZxid());
self.processReconfig(newQV, designatedLeader, zk.getZxid(), true);
if (designatedLeader != self.getId()) {
allowedToCommit = false;
}
zk.startup();
/*
* Update the election vote here to ensure that all members of the
* ensemble report the same vote to new servers that start up and
* send leader election notifications to the ensemble.
*
* @see https://issues.apache.org/jira/browse/ZOOKEEPER-1732
*/
self.updateElectionVote(getEpoch());
zk.getZKDatabase().setlastProcessedZxid(zk.getZxid());
}
/**
* Process NEWLEADER ack of a given sid and wait until the leader receives
* sufficient acks.
*
* @param sid
* @param learnerType
* @throws InterruptedException
*/
public void waitForNewLeaderAck(long sid, long zxid, LearnerType learnerType)
throws InterruptedException {
synchronized (newLeaderProposal.qvAcksetPairs) {
if (quorumFormed) {
return;
}
long currentZxid = newLeaderProposal.packet.getZxid();
if (zxid != currentZxid) {
LOG.error("NEWLEADER ACK from sid: " + sid
+ " is from a different epoch - current 0x"
+ Long.toHexString(currentZxid) + " receieved 0x"
+ Long.toHexString(zxid));
return;
}
/*
* Note that addAck already checks that the learner
* is a PARTICIPANT.
*/
newLeaderProposal.addAck(sid);
if (newLeaderProposal.hasAllQuorums()) {
quorumFormed = true;
newLeaderProposal.qvAcksetPairs.notifyAll();
} else {
long start = Time.currentElapsedTime();
long cur = start;
long end = start + self.getInitLimit() * self.getTickTime();
while (!quorumFormed && cur < end) {
newLeaderProposal.qvAcksetPairs.wait(end - cur);
cur = Time.currentElapsedTime();
}
if (!quorumFormed) {
throw new InterruptedException(
"Timeout while waiting for NEWLEADER to be acked by quorum");
}
}
}
}
/**
* Get string representation of a given packet type
* @param packetType
* @return string representing the packet type
*/
public static String getPacketType(int packetType) {
switch (packetType) {
case DIFF:
return "DIFF";
case TRUNC:
return "TRUNC";
case SNAP:
return "SNAP";
case OBSERVERINFO:
return "OBSERVERINFO";
case NEWLEADER:
return "NEWLEADER";
case FOLLOWERINFO:
return "FOLLOWERINFO";
case UPTODATE:
return "UPTODATE";
case LEADERINFO:
return "LEADERINFO";
case ACKEPOCH:
return "ACKEPOCH";
case REQUEST:
return "REQUEST";
case PROPOSAL:
return "PROPOSAL";
case ACK:
return "ACK";
case COMMIT:
return "COMMIT";
case COMMITANDACTIVATE:
return "COMMITANDACTIVATE";
case PING:
return "PING";
case REVALIDATE:
return "REVALIDATE";
case SYNC:
return "SYNC";
case INFORM:
return "INFORM";
case INFORMANDACTIVATE:
return "INFORMANDACTIVATE";
default:
return "UNKNOWN";
}
}
private boolean isRunning() {
return self.isRunning() && zk.isRunning();
}
}