/**
* 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.ByteArrayInputStream;
import java.io.IOException;
import java.net.InetSocketAddress;
import org.apache.jute.BinaryInputArchive;
import org.apache.jute.Record;
import org.apache.zookeeper.server.util.SerializeUtils;
import org.apache.zookeeper.txn.TxnHeader;
/**
* This class has the control logic for the Follower.
*/
public class Follower extends Learner{
private long lastQueued;
// This is the same object as this.zk, but we cache the downcast op
final FollowerZooKeeperServer fzk;
Follower(QuorumPeer self,FollowerZooKeeperServer zk) {
this.self = self;
this.zk=zk;
this.fzk = zk;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("Follower ").append(sock);
sb.append(" lastQueuedZxid:").append(lastQueued);
sb.append(" pendingRevalidationCount:")
.append(pendingRevalidations.size());
return sb.toString();
}
/**
* the main method called by the follower to follow the leader
*
* @throws InterruptedException
*/
void followLeader() throws InterruptedException {
fzk.registerJMX(new FollowerBean(this, zk), self.jmxLocalPeerBean);
try {
InetSocketAddress addr = findLeader();
try {
connectToLeader(addr);
long newLeaderZxid = registerWithLeader(Leader.FOLLOWERINFO);
//check to see if the leader zxid is lower than ours
//this should never happen but is just a safety check
long lastLoggedZxid = self.getLastLoggedZxid();
if ((newLeaderZxid >> 32L) < (lastLoggedZxid >> 32L)) {
LOG.fatal("Leader epoch " + Long.toHexString(newLeaderZxid >> 32L)
+ " is less than our epoch " + Long.toHexString(lastLoggedZxid >> 32L));
throw new IOException("Error: Epoch of leader is lower");
}
syncWithLeader(newLeaderZxid);
QuorumPacket qp = new QuorumPacket();
while (self.isRunning()) {
readPacket(qp);
processPacket(qp);
}
} catch (IOException e) {
LOG.warn("Exception when following the leader", e);
try {
sock.close();
} catch (IOException e1) {
e1.printStackTrace();
}
synchronized (pendingRevalidations) {
// clear pending revalidations
pendingRevalidations.clear();
pendingRevalidations.notifyAll();
}
}
} finally {
zk.unregisterJMX((Learner)this);
}
}
/**
* Examine the packet received in qp and dispatch based on its contents.
* @param qp
* @throws IOException
*/
protected void processPacket(QuorumPacket qp) throws IOException{
switch (qp.getType()) {
case Leader.PING:
ping(qp);
break;
case Leader.PROPOSAL:
TxnHeader hdr = new TxnHeader();
BinaryInputArchive ia = BinaryInputArchive
.getArchive(new ByteArrayInputStream(qp.getData()));
Record txn = SerializeUtils.deserializeTxn(ia, hdr);
if (hdr.getZxid() != lastQueued + 1) {
LOG.warn("Got zxid 0x"
+ Long.toHexString(hdr.getZxid())
+ " expected 0x"
+ Long.toHexString(lastQueued + 1));
}
lastQueued = hdr.getZxid();
fzk.logRequest(hdr, txn);
break;
case Leader.COMMIT:
fzk.commit(qp.getZxid());
break;
case Leader.UPTODATE:
fzk.takeSnapshot();
self.cnxnFactory.setZooKeeperServer(fzk);
break;
case Leader.REVALIDATE:
revalidate(qp);
break;
case Leader.SYNC:
fzk.sync();
break;
}
}
/**
* The zxid of the last operation seen
* @return zxid
*/
public long getZxid() {
try {
synchronized (fzk) {
return fzk.getZxid();
}
} catch (NullPointerException e) {
LOG.warn("error getting zxid", e);
}
return -1;
}
/**
* The zxid of the last operation queued
* @return zxid
*/
protected long getLastQueued() {
return lastQueued;
}
@Override
public void shutdown() {
LOG.info("shutdown called", new Exception("shutdown Follower"));
super.shutdown();
}
}