ZooKeeper是一個分布式開源框架，提供了協(xié)調分布式應用的基本服務，它向外部應用暴露一組通用服務——分布式同步（Distributed Synchronization）、命名服務（Naming Service）、集群維護（Group Maintenance）等，簡化分布式應用協(xié)調及其管理的難度，提供高性能的分布式服務。ZooKeeper本身可以以Standalone模式安裝運行，不過它的長處在于通過分布式ZooKeeper集群（一個Leader，多個Follower），基于一定的策略來保證ZooKeeper集群的穩(wěn)定性和可用性，從而實現(xiàn)分布式應用的可靠性。

有關ZooKeeper的介紹，網(wǎng)上很多，也可以參考文章后面，我整理的一些相關鏈接。

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下面，我們簡單說明一下ZooKeeper的配置。

ZooKeeper Standalone模式

從Apache網(wǎng)站上（zookeeper.apache.org）下載ZooKeeper軟件包，我選擇了3.3.4版本的（zookeeper-3.3.4.tar.gz），在一臺Linux機器上安裝非常容易，只需要解壓縮后，簡單配置一下即可以啟動ZooKeeper服務器進程。

將zookeeper-3.3.4/conf目錄下面的 zoo_sample.cfg修改為zoo.cfg，配置文件內容如下所示：

tickTime=2000 dataDir=/home/hadoop/storage/zookeeper clientPort=2181 initLimit=5 syncLimit=2

上面各個配置參數(shù)的含義也非常簡單，引用如下所示：

1.tickTime —— the basic time unit in milliseconds used by ZooKeeper.
　It is used to do heartbeats and the minimum session timeout will be twice the tickTime. 2.dataDir —— the location to store the in-memory database snapshots and, unless specified otherwise, the transaction log of updates to the database. 3.clientPort —— the port to listen for client connections

下面啟動ZooKeeper服務器進程：

cd zookeeper-3.3.4/ bin/zkServer.sh start

通過jps命令可以查看ZooKeeper服務器進程，名稱為QuorumPeerMain。

在客戶端連接ZooKeeper服務器，執(zhí)行如下命令：

bin/zkCli.sh -server dynamic:2181

上面dynamic是我的主機名，如果在本機執(zhí)行，則執(zhí)行如下命令即可：

bin/zkCli.sh

客戶端連接信息如下所示：

hadoop@master:~/installation/zookeeper-3.3.4$ bin/zkCli.sh -server dynamic:2181 Connecting to dynamic:2181 2012-01-08 21:30:06,178 - INFO [main:Environment@97] - Client environment:zookeeper.version=3.3.3-1203054, built on 11/17/2011 05:47 GMT 2012-01-08 21:30:06,188 - INFO [main:Environment@97] - Client environment:host.name=master 2012-01-08 21:30:06,191 - INFO [main:Environment@97] - Client environment:java.version=1.6.0_30 2012-01-08 21:30:06,194 - INFO [main:Environment@97] - Client environment:java.vendor=Sun Microsystems Inc. 2012-01-08 21:30:06,200 - INFO [main:Environment@97] - Client environment:java.home=/home/hadoop/installation/jdk1.6.0_30/jre 2012-01-08 21:30:06,203 - INFO [main:Environment@97] - Client environment:java.class.path=/home/hadoop/installation/zookeeper-3.3.4/bin/../build/
classes:/home/hadoop/installation/zookeeper-3.3.4/bin/../build/lib/*.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../zookeeper-3.3.4.jar:
/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/log4j-1.2.15.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/jline-0.9.94.jar:
/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/commons-lang-2.4.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/
commons-collections-3.2.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/commons-cli-1.1.jar:/home/hadoop/installation/zookeeper-3.3.4/bin
/../lib/apache-rat-tasks-0.6.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/apache-rat-core-0.6.jar:/home/hadoop/installation/
zookeeper-3.3.4/bin/../src/java/lib/*.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../conf:/home/hadoop/installation/jdk1.6.0_30/lib/*.jar:
/home/hadoop/installation/jdk1.6.0_30/jre/lib/*.jar 2012-01-08 21:30:06,206 - INFO [main:Environment@97] - Client environment:java.library.path=/home/hadoop/installation/jdk1.6.0_30/
jre/lib/i386/client:/home/hadoop/installation/jdk1.6.0_30/jre/lib/i386:/home/hadoop/installation/jdk1.6.0_30/jre/../lib/i386:
/usr/java/packages/lib/i386:/lib:/usr/lib 2012-01-08 21:30:06,213 - INFO [main:Environment@97] - Client environment:java.io.tmpdir=/tmp 2012-01-08 21:30:06,216 - INFO [main:Environment@97] - Client environment:java.compiler=<NA> 2012-01-08 21:30:06,235 - INFO [main:Environment@97] - Client environment:os.name=Linux 2012-01-08 21:30:06,244 - INFO [main:Environment@97] - Client environment:os.arch=i386 2012-01-08 21:30:06,246 - INFO [main:Environment@97] - Client environment:os.version=3.0.0-14-generic 2012-01-08 21:30:06,251 - INFO [main:Environment@97] - Client environment:user.name=hadoop 2012-01-08 21:30:06,254 - INFO [main:Environment@97] - Client environment:user.home=/home/hadoop 2012-01-08 21:30:06,255 - INFO [main:Environment@97] - Client environment:user.dir=/home/hadoop/installation/zookeeper-3.3.4 2012-01-08 21:30:06,264 - INFO [main:ZooKeeper@379] - Initiating client connection, connectString=dynamic:2181 sessionTimeout=30000
watcher=org.apache.zookeeper.ZooKeeperMain$MyWatcher@bf32c 2012-01-08 21:30:06,339 - INFO [main-SendThread():ClientCnxn$SendThread@1061] - Opening socket connection to server dynamic/192.168.0.107:2181 Welcome to ZooKeeper! 2012-01-08 21:30:06,397 - INFO [main-SendThread(dynamic:2181):ClientCnxn$SendThread@950] -
Socket connection established to dynamic/192.168.0.107:2181, initiating session JLine support is enabled 2012-01-08 21:30:06,492 - INFO [main-SendThread(dynamic:2181):ClientCnxn$SendThread@739] -
Session establishment complete on server dynamic/192.168.0.107:2181, sessionid = 0x134b9b714f9000c, negotiated timeout = 30000 WATCHER:: WatchedEvent state:SyncConnected type:None path:null [zk: dynamic:2181(CONNECTED) 0]

接著，可以使用help查看Zookeeper客戶端可以使用的基本操作命令。

ZooKeeper Distributed模式

ZooKeeper分布式模式安裝（ZooKeeper集群）也比較容易，這里說明一下基本要點。

首先要明確的是，ZooKeeper集群是一個獨立的分布式協(xié)調服務集群，“獨立”的含義就是說，如果想使用ZooKeeper實現(xiàn)分布式應用的協(xié)調與管理，簡化協(xié)調與管理，任何分布式應用都可以使用，這就要歸功于Zookeeper的數(shù)據(jù)模型（Data Model）和層次命名空間（Hierarchical Namespace）結構，詳細可以參考http://zookeeper.apache.org/doc/trunk/zookeeperOver.html。在設計你的分布式應用協(xié)調服務時，首要的就是考慮如何組織層次命名空間。

下面說明分布式模式的安裝配置，過程如下所示：

第一步：主機名稱到IP地址映射配置

ZooKeeper集群中具有兩個關鍵的角色：Leader和Follower。集群中所有的結點作為一個整體對分布式應用提供服務，集群中每個結點之間都互相連接，所以，在配置的ZooKeeper集群的時候，每一個結點的host到IP地址的映射都要配置上集群中其它結點的映射信息。

例如，我的ZooKeeper集群中每個結點的配置，以slave-01為例，/etc/hosts內容如下所示：

192.168.0.179 slave-01 192.168.0.178 slave-02 192.168.0.177 slave-03

ZooKeeper采用一種稱為Leader election的選舉算法。在整個集群運行過程中，只有一個Leader，其他的都是Follower，如果ZooKeeper集群在運行過程中Leader出了問題，系統(tǒng)會采用該算法重新選出一個Leader。因此，各個結點之間要能夠保證互相連接，必須配置上述映射。

ZooKeeper集群啟動的時候，會首先選出一個Leader，在Leader election過程中，某一個滿足選舉算的結點就能成為Leader。整個集群的架構可以參考http://zookeeper.apache.org/doc/trunk/zookeeperOver.html#sc_designGoals。

第二步：修改ZooKeeper配置文件

在其中一臺機器（slave-01）上，解壓縮zookeeper-3.3.4.tar.gz，修改配置文件conf/zoo.cfg，內容如下所示：

tickTime=2000 dataDir=/home/hadoop/storage/zookeeper clientPort=2181 initLimit=5 syncLimit=2 server.1=slave-01:2888:3888 server.2=slave-02:2888:3888 server.3=slave-03:2888:3888

上述配置內容說明，可以參考http://zookeeper.apache.org/doc/trunk/zookeeperStarted.html#sc_RunningReplicatedZooKeeper。

第三步：遠程復制分發(fā)安裝文件

上面已經(jīng)在一臺機器slave-01上配置完成ZooKeeper，現(xiàn)在可以將該配置好的安裝文件遠程拷貝到集群中的各個結點對應的目錄下：

cd /home/hadoop/installation/ scp -r zookeeper-3.3.4/ hadoop@slave-02:/home/hadoop/installation/ scp -r zookeeper-3.3.4/ hadoop@slave-03:/home/hadoop/installation/

第四步：設置myid

在我們配置的dataDir指定的目錄下面，創(chuàng)建一個myid文件，里面內容為一個數(shù)字，用來標識當前主機，conf/zoo.cfg文件中配置的server.X中X為什么數(shù)字，則myid文件中就輸入這個數(shù)字，例如：

hadoop@slave-01:~/installation/zookeeper-3.3.4$ echo "1" > /home/hadoop/storage/zookeeper/myid hadoop@slave-02:~/installation/zookeeper-3.3.4$ echo "2" > /home/hadoop/storage/zookeeper/myid hadoop@slave-03:~/installation/zookeeper-3.3.4$ echo "3" > /home/hadoop/storage/zookeeper/myid

按照上述進行配置即可。

第五步：啟動ZooKeeper集群

在ZooKeeper集群的每個結點上，執(zhí)行啟動ZooKeeper服務的腳本，如下所示：

hadoop@slave-01:~/installation/zookeeper-3.3.4$ bin/zkServer.sh start hadoop@slave-02:~/installation/zookeeper-3.3.4$ bin/zkServer.sh start hadoop@slave-03:~/installation/zookeeper-3.3.4$ bin/zkServer.sh start

以結點slave-01為例，日志如下所示：

　 hadoop@slave-01:~/installation/zookeeper-3.3.4$ tail -500f zookeeper.out 2012-01-08 06:51:19,117 - INFO [main:QuorumPeerConfig@90] - Reading configuration from: /home/hadoop/installation/zookeeper-3.3.4/bin/../conf/zoo.cfg 2012-01-08 06:51:19,133 - INFO [main:QuorumPeerConfig@310] - Defaulting to majority quorums 2012-01-08 06:51:19,167 - INFO [main:QuorumPeerMain@119] - Starting quorum peer 2012-01-08 06:51:19,227 - INFO [main:NIOServerCnxn$Factory@143] - binding to port 0.0.0.0/0.0.0.0:2181 2012-01-08 06:51:19,277 - INFO [main:QuorumPeer@819] - tickTime set to 2000 2012-01-08 06:51:19,278 - INFO [main:QuorumPeer@830] - minSessionTimeout set to -1 2012-01-08 06:51:19,279 - INFO [main:QuorumPeer@841] - maxSessionTimeout set to -1 2012-01-08 06:51:19,281 - INFO [main:QuorumPeer@856] - initLimit set to 5 2012-01-08 06:51:19,347 - INFO [Thread-1:QuorumCnxManager$Listener@473] - My election bind port: 3888 2012-01-08 06:51:19,393 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumPeer@621] - LOOKING 2012-01-08 06:51:19,396 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:FastLeaderElection@663] - New election. My id = 1, Proposed zxid = 0 2012-01-08 06:51:19,400 - INFO [WorkerReceiver Thread:FastLeaderElection@496] - Notification: 1 (n.leader), 0 (n.zxid), 1 (n.round),
LOOKING (n.state), 1 (n.sid), LOOKING (my state) 2012-01-08 06:51:19,416 - WARN [WorkerSender Thread:QuorumCnxManager@384] - Cannot open channel to 2 at election address slave-02/192.168.0.178:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.toSend(QuorumCnxManager.java:340) at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.process(FastLeaderElection.java:360) at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.run(FastLeaderElection.java:333) at java.lang.Thread.run(Thread.java:662) 2012-01-08 06:51:19,420 - WARN [WorkerSender Thread:QuorumCnxManager@384] - Cannot open channel to 3 at election address slave-03/192.168.0.177:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.toSend(QuorumCnxManager.java:340) at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.process(FastLeaderElection.java:360) at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.run(FastLeaderElection.java:333) at java.lang.Thread.run(Thread.java:662) 2012-01-08 06:51:19,612 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] -
Cannot open channel to 2 at election address slave-02/192.168.0.178:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:51:19,615 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] -
Cannot open channel to 3 at election address slave-03/192.168.0.177:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:51:19,616 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:FastLeaderElection@697] - Notification time out: 400 2012-01-08 06:51:20,019 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] -
Cannot open channel to 2 at election address slave-02/192.168.0.178:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:51:20,021 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] -
Cannot open channel to 3 at election address slave-03/192.168.0.177:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:51:20,022 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:FastLeaderElection@697] - Notification time out: 800 2012-01-08 06:51:20,825 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] -
Cannot open channel to 2 at election address slave-02/192.168.0.178:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:51:20,827 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] -
Cannot open channel to 3 at election address slave-03/192.168.0.177:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:51:20,828 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:FastLeaderElection@697] - Notification time out: 1600 2012-01-08 06:51:22,435 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] -
Cannot open channel to 2 at election address slave-02/192.168.0.178:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:51:22,439 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] -
Cannot open channel to 3 at election address slave-03/192.168.0.177:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:51:22,441 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:FastLeaderElection@697] - Notification time out: 3200 2012-01-08 06:51:22,945 - INFO [WorkerReceiver Thread:FastLeaderElection@496] -
Notification: 2 (n.leader), 0 (n.zxid), 1 (n.round), LOOKING (n.state), 2 (n.sid), LOOKING (my state) 2012-01-08 06:51:22,946 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:FastLeaderElection@721] - Updating proposal 2012-01-08 06:51:22,949 - WARN [WorkerSender Thread:QuorumCnxManager@384] -
Cannot open channel to 3 at election address slave-03/192.168.0.177:3888 java.net.ConnectException: Connection refused at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567) at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:100) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.toSend(QuorumCnxManager.java:340) at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.process(FastLeaderElection.java:360) at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.run(FastLeaderElection.java:333) at java.lang.Thread.run(Thread.java:662) 2012-01-08 06:51:22,951 - INFO [WorkerReceiver Thread:FastLeaderElection@496] -
Notification: 2 (n.leader), 0 (n.zxid), 1 (n.round), LOOKING (n.state), 1 (n.sid), LOOKING (my state) 2012-01-08 06:51:23,156 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumPeer@643] - FOLLOWING 2012-01-08 06:51:23,170 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Learner@80] - TCP NoDelay set to: true 2012-01-08 06:51:23,206 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] -
Server environment:zookeeper.version=3.3.3-1203054, built on 11/17/2011 05:47 GMT 2012-01-08 06:51:23,207 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:host.name=slave-01 2012-01-08 06:51:23,207 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:java.version=1.6.0_30 2012-01-08 06:51:23,208 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:java.vendor=Sun Microsystems Inc. 2012-01-08 06:51:23,208 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] -
Server environment:java.home=/home/hadoop/installation/jdk1.6.0_30/jre 2012-01-08 06:51:23,209 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] -
Server environment:java.class.path=/home/hadoop/installation/zookeeper-3.3.4/bin/../build/classes:/home/hadoop/installation/
zookeeper-3.3.4/bin/../build/lib/*.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../zookeeper-3.3.4.jar:/home/hadoop/installation/
zookeeper-3.3.4/bin/../lib/log4j-1.2.15.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/jline-0.9.94.jar:/home/hadoop/installation/
zookeeper-3.3.4/bin/../lib/commons-lang-2.4.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/commons-collections-3.2.jar:/home/hadoop/
installation/zookeeper-3.3.4/bin/../lib/commons-cli-1.1.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/apache-rat-tasks-0.6.jar:/home/
hadoop/installation/zookeeper-3.3.4/bin/../lib/apache-rat-core-0.6.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../src/java/lib/*.jar:
/home/hadoop/installation/zookeeper-3.3.4/bin/../conf:/home/hadoop/installation/jdk1.6.0_30/lib/*.jar:/home/hadoop/installation/jdk1.6.0_30/
jre/lib/*.jar 2012-01-08 06:51:23,210 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:java.library.path=
/home/hadoop/installation/jdk1.6.0_30/jre/lib/i386/client:/home/hadoop/installation/jdk1.6.0_30/jre/lib/i386:
/home/hadoop/installation/jdk1.6.0_30/jre/../lib/i386:/usr/java/packages/lib/i386:/lib:/usr/lib 2012-01-08 06:51:23,210 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:java.io.tmpdir=/tmp 2012-01-08 06:51:23,212 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:java.compiler=<NA> 2012-01-08 06:51:23,212 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:os.name=Linux 2012-01-08 06:51:23,212 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:os.arch=i386 2012-01-08 06:51:23,213 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:os.version=3.0.0-14-generic 2012-01-08 06:51:23,213 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:user.name=hadoop 2012-01-08 06:51:23,214 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:user.home=/home/hadoop 2012-01-08 06:51:23,214 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Environment@97] - Server environment:user.dir=/home/hadoop/
installation/zookeeper-3.3.4 2012-01-08 06:51:23,223 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:ZooKeeperServer@151] -
Created server with tickTime 2000 minSessionTimeout 4000 maxSessionTimeout 40000 datadir /home/hadoop/storage/zookeeper/version-2 snapdir
/home/hadoop/storage/zookeeper/version-2 2012-01-08 06:51:23,339 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Learner@294] - Getting a snapshot from leader 2012-01-08 06:51:23,358 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:Learner@325] - Setting leader epoch 1 2012-01-08 06:51:23,358 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:FileTxnSnapLog@254] - Snapshotting: 0 2012-01-08 06:51:25,511 - INFO [WorkerReceiver Thread:FastLeaderElection@496] - Notification: 3 (n.leader), 0 (n.zxid), 1 (n.round),
LOOKING (n.state), 3 (n.sid), FOLLOWING (my state) 2012-01-08 06:51:42,584 - INFO [WorkerReceiver Thread:FastLeaderElection@496] - Notification: 3 (n.leader), 0 (n.zxid), 2 (n.round),
LOOKING (n.state), 3 (n.sid), FOLLOWING (my state)

我啟動的順序是slave-01>slave-02>slave-03，由于ZooKeeper集群啟動的時候，每個結點都試圖去連接集群中的其它結點，先啟動的肯定連不上后面還沒啟動的，所以上面日志前面部分的異常是可以忽略的。通過后面部分可以看到，集群在選出一個Leader后，最后穩(wěn)定了。

其他結點可能也出現(xiàn)類似問題，屬于正常。

第六步：安裝驗證

可以通過ZooKeeper的腳本來查看啟動狀態(tài)，包括集群中各個結點的角色（或是Leader，或是Follower），如下所示，是在ZooKeeper集群中的每個結點上查詢的結果：

hadoop@slave-01:~/installation/zookeeper-3.3.4$ bin/zkServer.sh status JMX enabled by default Using config: /home/hadoop/installation/zookeeper-3.3.4/bin/../conf/zoo.cfg Mode: follower hadoop@slave-02:~/installation/zookeeper-3.3.4$ bin/zkServer.sh status JMX enabled by default Using config: /home/hadoop/installation/zookeeper-3.3.4/bin/../conf/zoo.cfg Mode: leader hadoop@slave-03:~/installation/zookeeper-3.3.4$ bin/zkServer.sh status JMX enabled by default Using config: /home/hadoop/installation/zookeeper-3.3.4/bin/../conf/zoo.cfg Mode: follower

通過上面狀態(tài)查詢結果可見，slave-02是集群的Leader，其余的兩個結點是Follower。

另外，可以通過客戶端腳本，連接到ZooKeeper集群上。對于客戶端來說，ZooKeeper是一個整體（ensemble），連接到ZooKeeper集群實際上感覺在獨享整個集群的服務，所以，你可以在任何一個結點上建立到服務集群的連接，例如：

hadoop@slave-03:~/installation/zookeeper-3.3.4$ bin/zkCli.sh -server slave-01:2181 Connecting to slave-01:2181 2012-01-08 07:14:21,068 - INFO [main:Environment@97] - Client environment:zookeeper.version=3.3.3-1203054, built on 11/17/2011 05:47 GMT 2012-01-08 07:14:21,080 - INFO [main:Environment@97] - Client environment:host.name=slave-03 2012-01-08 07:14:21,085 - INFO [main:Environment@97] - Client environment:java.version=1.6.0_30 2012-01-08 07:14:21,089 - INFO [main:Environment@97] - Client environment:java.vendor=Sun Microsystems Inc. 2012-01-08 07:14:21,095 - INFO [main:Environment@97] - Client environment:java.home=/home/hadoop/installation/jdk1.6.0_30/jre 2012-01-08 07:14:21,104 - INFO [main:Environment@97] - Client environment:java.class.path=/home/hadoop/installation/zookeeper-3.3.4/bin/../
build/classes:/home/hadoop/installation/zookeeper-3.3.4/bin/../build/lib/*.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../zookeeper-3.3.4.jar:
/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/log4j-1.2.15.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/jline-0.9.94.jar:/
home/hadoop/installation/zookeeper-3.3.4/bin/../lib/commons-lang-2.4.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/
commons-collections-3.2.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/commons-cli-1.1.jar:/home/hadoop/installation/zookeeper-3.3.4/
bin/../lib/apache-rat-tasks-0.6.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../lib/apache-rat-core-0.6.jar:/home/hadoop/installation/
zookeeper-3.3.4/bin/../src/java/lib/*.jar:/home/hadoop/installation/zookeeper-3.3.4/bin/../conf:/home/hadoop/installation/jdk1.6.0_30/lib/*.jar:
/home/hadoop/installation/jdk1.6.0_30/jre/lib/*.jar 2012-01-08 07:14:21,111 - INFO [main:Environment@97] - Client environment:java.library.path=/home/hadoop/installation/jdk1.6.0_30/jre/lib/
i386/client:/home/hadoop/installation/jdk1.6.0_30/jre/lib/i386:/home/hadoop/installation/jdk1.6.0_30/jre/../lib/i386:/
usr/java/packages/lib/i386:/lib:/usr/lib 2012-01-08 07:14:21,116 - INFO [main:Environment@97] - Client environment:java.io.tmpdir=/tmp 2012-01-08 07:14:21,124 - INFO [main:Environment@97] - Client environment:java.compiler=<NA> 2012-01-08 07:14:21,169 - INFO [main:Environment@97] - Client environment:os.name=Linux 2012-01-08 07:14:21,175 - INFO [main:Environment@97] - Client environment:os.arch=i386 2012-01-08 07:14:21,177 - INFO [main:Environment@97] - Client environment:os.version=3.0.0-14-generic 2012-01-08 07:14:21,185 - INFO [main:Environment@97] - Client environment:user.name=hadoop 2012-01-08 07:14:21,188 - INFO [main:Environment@97] - Client environment:user.home=/home/hadoop 2012-01-08 07:14:21,190 - INFO [main:Environment@97] - Client environment:user.dir=/home/hadoop/installation/zookeeper-3.3.4 2012-01-08 07:14:21,197 - INFO [main:ZooKeeper@379] - Initiating client connection, connectString=slave-01:2181 sessionTimeout=30000
watcher=org.apache.zookeeper.ZooKeeperMain$MyWatcher@bf32c 2012-01-08 07:14:21,305 - INFO [main-SendThread():ClientCnxn$SendThread@1061] - Opening socket connection to server slave-01/192.168.0.179:2181 Welcome to ZooKeeper! 2012-01-08 07:14:21,376 - INFO [main-SendThread(slave-01:2181):ClientCnxn$SendThread@950] - Socket connection established to
slave-01/192.168.0.179:2181, initiating session JLine support is enabled [zk: slave-01:2181(CONNECTING) 0] 2012-01-08 07:14:21,872 - INFO [main-SendThread(slave-01:2181):ClientCnxn$SendThread@739] -
Session establishment complete on server slave-01/192.168.0.179:2181, sessionid = 0x134bdcd6b730000, negotiated timeout = 30000 WATCHER:: WatchedEvent state:SyncConnected type:None path:null [zk: slave-01:2181(CONNECTED) 0] ls / [zookeeper]

當前根路徑為/zookeeper。

總結說明

主機名與IP地址映射配置問題

啟動ZooKeeper集群時，如果ZooKeeper集群中slave-01結點的日志出現(xiàn)如下錯誤：

java.net.SocketTimeoutException at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:109) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:37:46,026 - INFO [QuorumPeer:/0:0:0:0:0:0:0:0:2181:FastLeaderElection@697] - Notification time out: 6400 2012-01-08 06:37:57,431 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] - Cannot open channel to 2 at election address
slave-02/202.106.199.35:3888 java.net.SocketTimeoutException at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:109) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:371) at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:404) at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:688) at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:622) 2012-01-08 06:38:02,442 - WARN [QuorumPeer:/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@384] - Cannot open channel to 3 at election address
slave-03/202.106.199.35:3888

很顯然，slave-01在啟動時連接集群中其他結點（slave-02、slave-03）時，主機名映射的IP與我們實際配置的不一致，所以集群中各個結點之間無法建立鏈路，整個ZooKeeper集群啟動是失敗的。

上面錯誤日志中slave-02/202.106.199.35:3888實際應該是slave-02/202.192.168.0.178:3888就對了，但是在進行域名解析的時候映射有問題，修改每個結點的/etc/hosts文件，將ZooKeeper集群中所有結點主機名到IP地址的映射配置上。

分享名稱：ZooKeeper-3.3.4集群安裝配置-創(chuàng)新互聯(lián)
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