/**
* 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.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Random;
import java.util.Map.Entry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.zookeeper.jmx.MBeanRegistry;
import org.apache.zookeeper.server.quorum.Vote;
import org.apache.zookeeper.server.quorum.QuorumPeer.LearnerType;
import org.apache.zookeeper.server.quorum.QuorumPeer.QuorumServer;
import org.apache.zookeeper.server.quorum.QuorumPeer.ServerState;
/**
* @deprecated This class has been deprecated as of release 3.4.0.
*/
@Deprecated
public class LeaderElection implements Election {
private static final Logger LOG = LoggerFactory.getLogger(LeaderElection.class);
protected static final Random epochGen = new Random();
protected QuorumPeer self;
public LeaderElection(QuorumPeer self) {
this.self = self;
}
protected static class ElectionResult {
public Vote vote;
public int count;
public Vote winner;
public int winningCount;
public int numValidVotes;
}
protected ElectionResult countVotes(HashMap<InetSocketAddress, Vote> votes, HashSet<Long> heardFrom) {
final ElectionResult result = new ElectionResult();
// Initialize with null vote
result.vote = new Vote(Long.MIN_VALUE, Long.MIN_VALUE);
result.winner = new Vote(Long.MIN_VALUE, Long.MIN_VALUE);
// First, filter out votes from unheard-from machines. Then
// make the views consistent. Sometimes peers will have
// different zxids for a server depending on timing.
final HashMap<InetSocketAddress, Vote> validVotes = new HashMap<InetSocketAddress, Vote>();
final Map<Long, Long> maxZxids = new HashMap<Long,Long>();
for (Map.Entry<InetSocketAddress, Vote> e : votes.entrySet()) {
// Only include votes from machines that we heard from
final Vote v = e.getValue();
if (heardFrom.contains(v.getId())) {
validVotes.put(e.getKey(), v);
Long val = maxZxids.get(v.getId());
if (val == null || val < v.getZxid()) {
maxZxids.put(v.getId(), v.getZxid());
}
}
}
// Make all zxids for a given vote id equal to the largest zxid seen for
// that id
for (Map.Entry<InetSocketAddress, Vote> e : validVotes.entrySet()) {
final Vote v = e.getValue();
Long zxid = maxZxids.get(v.getId());
if (v.getZxid() < zxid) {
// This is safe inside an iterator as per
// http://download.oracle.com/javase/1.5.0/docs/api/java/util/Map.Entry.html
e.setValue(new Vote(v.getId(), zxid, v.getElectionEpoch(), v.getPeerEpoch(), v.getState()));
}
}
result.numValidVotes = validVotes.size();
final HashMap<Vote, Integer> countTable = new HashMap<Vote, Integer>();
// Now do the tally
for (Vote v : validVotes.values()) {
Integer count = countTable.get(v);
if (count == null) {
count = 0;
}
countTable.put(v, count + 1);
if (v.getId() == result.vote.getId()) {
result.count++;
} else if (v.getZxid() > result.vote.getZxid()
|| (v.getZxid() == result.vote.getZxid() && v.getId() > result.vote.getId())) {
result.vote = v;
result.count = 1;
}
}
result.winningCount = 0;
LOG.info("Election tally: ");
for (Entry<Vote, Integer> entry : countTable.entrySet()) {
if (entry.getValue() > result.winningCount) {
result.winningCount = entry.getValue();
result.winner = entry.getKey();
}
LOG.info(entry.getKey().getId() + "\t-> " + entry.getValue());
}
return result;
}
/**
* There is nothing to shutdown in this implementation of
* leader election, so we simply have an empty method.
*/
public void shutdown(){}
/**
* Invoked in QuorumPeer to find or elect a new leader.
*
* @throws InterruptedException
*/
public Vote lookForLeader() throws InterruptedException {
try {
self.jmxLeaderElectionBean = new LeaderElectionBean();
MBeanRegistry.getInstance().register(
self.jmxLeaderElectionBean, self.jmxLocalPeerBean);
} catch (Exception e) {
LOG.warn("Failed to register with JMX", e);
self.jmxLeaderElectionBean = null;
}
try {
self.setCurrentVote(new Vote(self.getId(),
self.getLastLoggedZxid()));
// We are going to look for a leader by casting a vote for ourself
byte requestBytes[] = new byte[4];
ByteBuffer requestBuffer = ByteBuffer.wrap(requestBytes);
byte responseBytes[] = new byte[28];
ByteBuffer responseBuffer = ByteBuffer.wrap(responseBytes);
/* The current vote for the leader. Initially me! */
DatagramSocket s = null;
try {
s = new DatagramSocket();
s.setSoTimeout(200);
} catch (SocketException e1) {
LOG.error("Socket exception when creating socket for leader election", e1);
System.exit(4);
}
DatagramPacket requestPacket = new DatagramPacket(requestBytes,
requestBytes.length);
DatagramPacket responsePacket = new DatagramPacket(responseBytes,
responseBytes.length);
int xid = epochGen.nextInt();
while (self.isRunning()) {
HashMap<InetSocketAddress, Vote> votes =
new HashMap<InetSocketAddress, Vote>(self.getVotingView().size());
requestBuffer.clear();
requestBuffer.putInt(xid);
requestPacket.setLength(4);
HashSet<Long> heardFrom = new HashSet<Long>();
for (QuorumServer server : self.getVotingView().values()) {
LOG.info("Server address: " + server.addr);
try {
requestPacket.setSocketAddress(server.addr);
} catch (IllegalArgumentException e) {
// Sun doesn't include the address that causes this
// exception to be thrown, so we wrap the exception
// in order to capture this critical detail.
throw new IllegalArgumentException(
"Unable to set socket address on packet, msg:"
+ e.getMessage() + " with addr:" + server.addr,
e);
}
try {
s.send(requestPacket);
responsePacket.setLength(responseBytes.length);
s.receive(responsePacket);
if (responsePacket.getLength() != responseBytes.length) {
LOG.error("Got a short response: "
+ responsePacket.getLength());
continue;
}
responseBuffer.clear();
int recvedXid = responseBuffer.getInt();
if (recvedXid != xid) {
LOG.error("Got bad xid: expected " + xid
+ " got " + recvedXid);
continue;
}
long peerId = responseBuffer.getLong();
heardFrom.add(peerId);
//if(server.id != peerId){
Vote vote = new Vote(responseBuffer.getLong(),
responseBuffer.getLong());
InetSocketAddress addr =
(InetSocketAddress) responsePacket
.getSocketAddress();
votes.put(addr, vote);
//}
} catch (IOException e) {
LOG.warn("Ignoring exception while looking for leader",
e);
// Errors are okay, since hosts may be
// down
}
}
ElectionResult result = countVotes(votes, heardFrom);
// ZOOKEEPER-569:
// If no votes are received for live peers, reset to voting
// for ourselves as otherwise we may hang on to a vote
// for a dead peer
if (result.numValidVotes == 0) {
self.setCurrentVote(new Vote(self.getId(),
self.getLastLoggedZxid()));
} else {
if (result.winner.getId() >= 0) {
self.setCurrentVote(result.vote);
// To do: this doesn't use a quorum verifier
if (result.winningCount > (self.getVotingView().size() / 2)) {
self.setCurrentVote(result.winner);
s.close();
Vote current = self.getCurrentVote();
LOG.info("Found leader: my type is: " + self.getLearnerType());
/*
* We want to make sure we implement the state machine
* correctly. If we are a PARTICIPANT, once a leader
* is elected we can move either to LEADING or
* FOLLOWING. However if we are an OBSERVER, it is an
* error to be elected as a Leader.
*/
if (self.getLearnerType() == LearnerType.OBSERVER) {
if (current.getId() == self.getId()) {
// This should never happen!
LOG.error("OBSERVER elected as leader!");
Thread.sleep(100);
}
else {
self.setPeerState(ServerState.OBSERVING);
Thread.sleep(100);
return current;
}
} else {
self.setPeerState((current.getId() == self.getId())
? ServerState.LEADING: ServerState.FOLLOWING);
if (self.getPeerState() == ServerState.FOLLOWING) {
Thread.sleep(100);
}
return current;
}
}
}
}
Thread.sleep(1000);
}
return null;
} finally {
try {
if(self.jmxLeaderElectionBean != null){
MBeanRegistry.getInstance().unregister(
self.jmxLeaderElectionBean);
}
} catch (Exception e) {
LOG.warn("Failed to unregister with JMX", e);
}
self.jmxLeaderElectionBean = null;
}
}
}