Hadoop 部署之 ZooKeeper (二)

一、Zookeeper功能簡(jiǎn)介

ZooKeeper 是一個(gè)開(kāi)源的分布式協(xié)調(diào)服務(wù)，由雅虎創(chuàng)建，是 Google Chubby 的開(kāi)源實(shí)現(xiàn)。分布式應(yīng)用程序可以基于 ZooKeeper 實(shí)現(xiàn)諸如數(shù)據(jù)發(fā)布/訂閱、負(fù)載均衡、命名服務(wù)、分布式協(xié)調(diào)/通知、集群管理、Master 選舉、配置維護(hù)，名字服務(wù)、分布式同步、分布式鎖和分布式隊(duì)列等功能。

二、ZooKeeper基本概念

1、集群角色

一個(gè) ZooKeeper 集群同一時(shí)刻只會(huì)有一個(gè) Leader，其他都是 Follower 或 Observer。

ZooKeeper 配置很簡(jiǎn)單，每個(gè)節(jié)點(diǎn)的配置文件(zoo.cfg)都是一樣的，只有 myid 文件不一樣。myid 的值必須是 zoo.cfg中server.{數(shù)值} 的{數(shù)值}部分。

ZooKeeper 默認(rèn)只有 Leader 和 Follower 兩種角色，沒(méi)有 Observer 角色。為了使用 Observer 模式，在任何想變成Observer的節(jié)點(diǎn)的配置文件中加入:peerType=observer 并在所有 server 的配置文件中，配置成 observer 模式的 server 的那行配置追加 :observer

三、ZooKeeper 的安裝

1、下載安裝(在datanode節(jié)點(diǎn)安裝)

下載安裝包

wget http://mirror.bit.edu.cn/apache/zookeeper/zookeeper-3.4.10/zookeeper-3.4.10.tar.gz

解壓安裝包

tar xf zookeeper-3.4.10.tar.gz
mv zookeeper-3.4.10 /usr/local/zookeeper
mkdir -p /home/zookeeper

zk01節(jié)點(diǎn)(datanode1)配置id

echo "1">/home/zookeeper/myid

zk02節(jié)點(diǎn)(datanode2)配置id

echo "2">/home/zookeeper/myid

zk03節(jié)點(diǎn)(datanode3)配置id

echo "3">/home/zookeeper/myid

2、配置ZooKeeper環(huán)境變量

編輯文件/etc/profile.d/zookeeper.sh。

# ZOOKEEPER ENV
export ZOOKEEPER_HOME=/usr/local/zookeeper
export PATH=$PATH:$ZOOKEEPER_HOME/bin

使ZK環(huán)境變量生效。

source /etc/profile.d/zookeeper.sh

3、配置 zoo.cfg

編輯文件/usr/local/zookeeper/conf/zoo.cfg。

# The number of milliseconds of each tick
tickTime=2000
# The number of ticks that the initial 
# synchronization phase can take
initLimit=10
# The number of ticks that can pass between 
# sending a request and getting an acknowledgement
syncLimit=5
# the directory where the snapshot is stored.
# do not use /tmp for storage, /tmp here is just 
# example sakes.
dataDir=/home/zookeeper
# the port at which the clients will connect
clientPort=2181
# the maximum number of client connections.
# increase this if you need to handle more clients
#maxClientCnxns=60
#
# Be sure to read the maintenance section of the 
# administrator guide before turning on autopurge.
#
# http://zookeeper.apache.org/doc/current/zookeeperAdmin.html#sc_maintenance
#
# The number of snapshots to retain in dataDir
#autopurge.snapRetainCount=3
# Purge task interval in hours
# Set to "0" to disable auto purge feature
#autopurge.purgeInterval=1
server.1=zk01:2888:3888
server.2=zk02:2888:3888
server.3=zk03:2888:3888

比較重要的配置如下：
dataDir=/home/zookeeper
server.1=zk01:2888:3888
server.2=zk02:2888:3888
server.3=zk03:2888:3888

4、啟動(dòng)各節(jié)點(diǎn) ZK 服務(wù)

[root@datanode01 ~]# zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

[root@datanode02 ~]# zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

[root@datanode03 ~]# zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

5、查看各節(jié)點(diǎn)啟動(dòng)狀態(tài)和角色

[root@datanode01 ~]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Mode: follower

[root@datanode02 ~]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Mode: leader

[root@datanode03 ~]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Mode: follower

官方文檔：https://zookeeper.apache.org/doc/current/zookeeperStarted.html