初学Hadoop（四）-HDFS HA

一、概述

  用QJM(Quorum Journal Manager)来配置 HA高可用HDFS集群概述。

 

二、用QJM实现数据共享

1. 编辑 hdfs-site.xml 文件

1.1 dfs.nameservices 新添的命名服务逻辑名称 

 

<property>  <name>dfs.nameservices</name>  <value>mycluster</value>    </property>

  1.2 dfs.ha.namenodes.[nameservice ID] NameNode的唯一标识

每个nameservice 最多2个namenodes

<property>  <name>dfs.ha.namenodes.mycluster</name>  <value>nn1,nn2</value></property>

1.3 dfs.namenode.rpc-address.[nameservice ID].[name node ID]

配置每个namenode的Rpc全路径监听地址

<property>  <name>dfs.namenode.rpc-address.mycluster.nn1</name>  <value>machine1.example.com:8020</value></property><property>  <name>dfs.namenode.rpc-address.mycluster.nn2</name>  <value>machine2.example.com:8020</value></property>

1.4 dfs.namenode.http-address.[nameservice ID].[name node ID]

配置每个namenode的http全路径监听地址

<property>  <name>dfs.namenode.http-address.mycluster.nn1</name>  <value>machine1.example.com:50070</value></property><property>  <name>dfs.namenode.http-address.mycluster.nn2</name>  <value>machine2.example.com:50070</value></property>

注意事项：Hadoop的安全特性开启时，http-address也要开启

1.5 dfs.namenode.shared.edits.dir nameNode能够读写的目录

qjournal://host1:port1;host2:port2;host3:port3/journalId

 

<property>  <name>dfs.namenode.shared.edits.dir</name>  <value>qjournal://node1.example.com:8485;node2.example.com:8485;node3.example.com:8485/mycluster</value></property>

1.6 dfs.client.failover.proxy.provider.[nameservice ID] java api 调用可用的namenode

<property>  <name>dfs.client.failover.proxy.provider.mycluster</name>  <value>org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider</value></property>

1.7 dfs.ha.fencing.methods 调用 namenode 失败后执行的脚本或是java

QJM只允许一个namdenode进行读写JournalNodes

Sshfence 必须配置 dfs.ha.fencing.ssh.private-key-files

 

<property>  <name>dfs.ha.fencing.methods</name>  <value>sshfence</value></property> <property>  <name>dfs.ha.fencing.ssh.private-key-files</name>  <value>/home/exampleuser/.ssh/id_rsa</value></property>

 

 

<property>  <name>dfs.ha.fencing.methods</name>  <value>sshfence([[username][:port]])</value></property><property>  <name>dfs.ha.fencing.ssh.connect-timeout</name>  <value>30000</value></property>

 

 

shell

 

<property>  <name>dfs.ha.fencing.methods</name>  <value>shell(/path/to/my/script.sh arg1 arg2 ...)</value></property>

 

 

<property>  <name>dfs.ha.fencing.methods</name>  <value>shell(/path/to/my/script.sh --nameservice=$target_nameserviceid $target_host:$target_port)</value></property>

$target_host	hostname of the node to be fenced
$target_port	IPC port of the node to be fenced
$target_address	the above two, combined as host:port
$target_nameserviceid	the nameservice ID of the NN to be fenced
$target_namenodeid	the namenode ID of the NN to be fenced

 

 

1.8  fs.defaultFS

core-site.xml

<property>  <name>fs.defaultFS</name>  <value>hdfs://mycluster</value></property>

1.9 dfs.journalnode.edits.dir

<property>  <name>dfs.journalnode.edits.dir</name>  <value>/path/to/journal/node/local/data</value></property>

配置自动failedOver 

hdfs-site.xml 文件

 <property>   <name>dfs.ha.automatic-failover.enabled</name>   <value>true</value> </property>

core-site.xml 文件

 <property>   <name>ha.zookeeper.quorum</name>   <value>zk1.example.com:2181,zk2.example.com:2181,zk3.example.com:2181</value> </property>

初始化HA状态在zookeeper

$ hdfs zkfc -formatZK

 

执行start-dfs.sh 后会执行ZKFC 守护进程

手动方式

$ hadoop-daemon.sh start zkfc

安全连接zookeeper core-site.xml

<property>   <name>ha.zookeeper.auth</name>   <value>@/path/to/zk-auth.txt</value> </property> <property>   <name>ha.zookeeper.acl</name>   <value>@/path/to/zk-acl.txt</value> </property>