/**
* 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.test;
import java.io.File;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.concurrent.Semaphore;
import junit.framework.TestCase;
import org.apache.log4j.Logger;
import org.apache.zookeeper.server.quorum.FastLeaderElection;
import org.apache.zookeeper.server.quorum.QuorumCnxManager;
import org.apache.zookeeper.server.quorum.QuorumPeer;
import org.apache.zookeeper.server.quorum.Vote;
import org.apache.zookeeper.server.quorum.QuorumPeer.QuorumServer;
import org.apache.zookeeper.server.quorum.QuorumPeer.ServerState;
import org.junit.Test;
/**
* This test uses a mock server to interact with a ZooKeeper peer and
* reproduces a specific sequence of messages that can cause FLE to fail.
* In particular, it reproduces the following scenario:
*
* 1- We have an ensemble of 3 servers, but only two start;
* 2- Process 0 elects 1, but 1 fails to receive the message from 0
* stating that it changed its vote to 1;
* 3- The next from 0 that 1 receives is a notification that 0 is
* following 1. However, because 1 does not receive a notification
* from 0 while 0 is following, it may end up not becoming leader
* with old code.
*
* This test checks that this sequence of messages does not lead to a
* deadlock. In practice, even if this situation occurs in a run, it would
* have to occur continuously to prevent a leader from being elected
* forever. This happens with low probability.
*
*/
public class FLELostMessageTest extends TestCase {
protected static final Logger LOG = Logger.getLogger(FLELostMessageTest.class);
int baseport;
int baseLEport;
int count;
HashMap<Long,QuorumServer> peers;
File tmpdir[];
int port[];
QuorumCnxManager cnxManager;
@Override
public void setUp() throws Exception {
this.baseport= 33003;
this.baseLEport = 43003;
count = 3;
peers = new HashMap<Long,QuorumServer>(count);
tmpdir = new File[count];
port = new int[count];
LOG.info("SetUp " + getName());
}
@Override
public void tearDown() throws Exception {
cnxManager.halt();
LOG.info("FINISHED " + getName());
}
class LEThread extends Thread {
int i;
QuorumPeer peer;
LEThread(QuorumPeer peer, int i) {
this.i = i;
this.peer = peer;
LOG.info("Constructor: " + getName());
}
public void run(){
boolean flag = true;
try{
Vote v = null;
peer.setPeerState(ServerState.LOOKING);
LOG.info("Going to call leader election: " + i);
v = peer.getElectionAlg().lookForLeader();
if (v == null){
fail("Thread " + i + " got a null vote");
}
/*
* A real zookeeper would take care of setting the current vote. Here
* we do it manually.
*/
peer.setCurrentVote(v);
LOG.info("Finished election: " + i + ", " + v.id);
assertTrue("State is not leading.", peer.getPeerState() == ServerState.LEADING);
} catch (Exception e) {
e.printStackTrace();
}
LOG.info("Joining");
}
}
@Test
public void testLostMessage() throws Exception {
FastLeaderElection le[] = new FastLeaderElection[count];
LOG.info("TestLE: " + getName()+ ", " + count);
for(int i = 0; i < count; i++) {
peers.put(Long.valueOf(i),
new QuorumServer(i,
new InetSocketAddress(baseport + i),
new InetSocketAddress(baseLEport + i)));
tmpdir[i] = ClientBase.createTmpDir();
port[i] = baseport + i;
}
/*
* Start server 0
*/
QuorumPeer peer = new QuorumPeer(peers, tmpdir[1], tmpdir[1], port[1], 3, 1, 2, 2, 2);
peer.startLeaderElection();
LEThread thread = new LEThread(peer, 1);
thread.start();
/*
* Start mock server 1
*/
mockServer();
thread.join(5000);
if (thread.isAlive()) {
fail("Threads didn't join");
}
}
ByteBuffer createMsg(int state, long leader, long zxid, long epoch){
byte requestBytes[] = new byte[28];
ByteBuffer requestBuffer = ByteBuffer.wrap(requestBytes);
/*
* Building notification packet to send
*/
requestBuffer.clear();
requestBuffer.putInt(state);
requestBuffer.putLong(leader);
requestBuffer.putLong(zxid);
requestBuffer.putLong(epoch);
return requestBuffer;
}
void mockServer() throws InterruptedException, IOException {
/*
* Create an instance of the connection manager
*/
QuorumPeer peer = new QuorumPeer(peers, tmpdir[0], tmpdir[0], port[0], 3, 0, 2, 2, 2);
cnxManager = new QuorumCnxManager(peer);
QuorumCnxManager.Listener listener = cnxManager.listener;
if(listener != null){
listener.start();
} else {
LOG.error("Null listener when initializing cnx manager");
}
cnxManager.toSend(new Long(1), createMsg(ServerState.LOOKING.ordinal(), 0, -1, 1));
cnxManager.recvQueue.take();
cnxManager.toSend(new Long(1), createMsg(ServerState.FOLLOWING.ordinal(), 1, -1, 1));
}
}