/**
* 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.ObserverBean;
import org.apache.zookeeper.server.Request;
import org.apache.zookeeper.server.util.SerializeUtils;
import org.apache.zookeeper.txn.TxnHeader;
/**
* Observers are peers that do not take part in the atomic broadcast protocol.
* Instead, they are informed of successful proposals by the Leader. Observers
* therefore naturally act as a relay point for publishing the proposal stream
* and can relieve Followers of some of the connection load. Observers may
* submit proposals, but do not vote in their acceptance.
*
* See ZOOKEEPER-368 for a discussion of this feature.
*/
public class Observer extends Learner{
Observer(QuorumPeer self,ObserverZooKeeperServer observerZooKeeperServer) {
this.self = self;
this.zk=observerZooKeeperServer;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("Observer ").append(sock);
sb.append(" pendingRevalidationCount:")
.append(pendingRevalidations.size());
return sb.toString();
}
/**
* the main method called by the observer to observe the leader
*
* @throws InterruptedException
*/
void observeLeader() throws InterruptedException {
zk.registerJMX(new ObserverBean(this, zk), self.jmxLocalPeerBean);
try {
InetSocketAddress addr = findLeader();
LOG.info("Observing " + addr);
try {
connectToLeader(addr);
long newLeaderZxid = registerWithLeader(Leader.OBSERVERINFO);
syncWithLeader(newLeaderZxid);
QuorumPacket qp = new QuorumPacket();
while (self.isRunning()) {
readPacket(qp);
processPacket(qp);
}
} catch (IOException e) {
LOG.warn("Exception when observing the leader", e);
try {
sock.close();
} catch (IOException e1) {
e1.printStackTrace();
}
synchronized (pendingRevalidations) {
// clear pending revalidations
pendingRevalidations.clear();
pendingRevalidations.notifyAll();
}
}
} finally {
zk.unregisterJMX(this);
}
}
/**
* Controls the response of an observer to the receipt of a quorumpacket
* @param qp
* @throws IOException
*/
protected void processPacket(QuorumPacket qp) throws IOException{
switch (qp.getType()) {
case Leader.PING:
ping(qp);
break;
case Leader.PROPOSAL:
LOG.warn("Ignoring proposal");
break;
case Leader.COMMIT:
LOG.warn("Ignoring commit");
break;
case Leader.UPTODATE:
zk.takeSnapshot();
self.cnxnFactory.setZooKeeperServer(zk);
break;
case Leader.REVALIDATE:
revalidate(qp);
break;
case Leader.SYNC:
((ObserverZooKeeperServer)zk).sync();
break;
case Leader.INFORM:
TxnHeader hdr = new TxnHeader();
BinaryInputArchive ia = BinaryInputArchive
.getArchive(new ByteArrayInputStream(qp.getData()));
Record txn = SerializeUtils.deserializeTxn(ia, hdr);
Request request = new Request (null, hdr.getClientId(),
hdr.getCxid(),
hdr.getType(), null, null);
request.txn = txn;
request.hdr = hdr;
ObserverZooKeeperServer obs = (ObserverZooKeeperServer)zk;
obs.commitRequest(request);
break;
}
}
/**
* Shutdown the Observer.
*/
public void shutdown() {
LOG.info("shutdown called", new Exception("shutdown Observer"));
super.shutdown();
}
}