Hadoop学习笔记

Hadoop学习笔记-HA验证

集群规划

HOST	NN	NN	JNN	DN	ZKFC	ZK
node01	*		*		*
node02		*	*	*	*	*
node03			*	*	*	*
node04				*		*

配置文件

hdfs-site.xml

• 由于是多个NameNode节点，所以不能单独直接配置NameNode对应的地址，相应的要配置一个映射集

• dfs.nameservices - the logical name for this new nameservice (相当与自己给集合取的名称)

  例如

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

• dfs.ha.namenodes.[nameservice ID] - unique identifiers for each NameNode in the nameservic (对应的NameNode有哪些)，例如

  <property>
    <name>dfs.ha.namenodes.mycluster</name>
    <value>nn1,nn2, nn3</value>
  </property>
  

  表明有三个NameNode节点，其分别为nn1,nn2,nn3 (官方说数量为2-5，推荐为3)

• dfs.namenode.rpc-address.[nameservice ID].[name node ID] - the fully-qualified RPC address for each NameNode to listen on (每台NameNode所对应的监听RPC地址和端口号)

  例如

  <property>
    <name>dfs.namenode.rpc-address.mycluster.nn1</name>
    <value>node01:8020</value>
  </property>
  <property>
    <name>dfs.namenode.rpc-address.mycluster.nn2</name>
    <value>node02:8020</value>
  </property>
  

• dfs.namenode.http-address.[nameservice ID].[name node ID] - the fully-qualified HTTP address for each NameNode to listen on (Web地址以及端口号)

  <property>
    <name>dfs.namenode.http-address.mycluster.nn1</name>
    <value>node01:9870</value>
  </property>
  <property>
    <name>dfs.namenode.http-address.mycluster.nn2</name>
    <value>node02:9870</value>
  </property>
  

• dfs.namenode.shared.edits.dir - the URI which identifies the group of JNs where the NameNodes will write/read edits (NameNode读写JN组的uri。配置JournalNode)

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

  其中 /mycluster 在JournalNode上写入的目录，当以后搭建新的集群时，可以与当前集群共用一组JourNalNode，但是为了避免元数据覆盖，其后面的这一串要设定成不相同的目录

• dfs.journalnode.edits.dir - the path where the JournalNode daemon will store its local state (JournalNode中文件的绝对路径)

  <property>
    <name>dfs.journalnode.edits.dir</name>
    <value>/var/bigdata/hadoop/ha/dfs/jn</value>
  </property>
  

• dfs.client.failover.proxy.provider.[nameservice ID] - the Java class that HDFS clients use to contact the Active NameNode

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

• dfs.ha.fencing.methods - a list of scripts or Java classes which will be used to fence the Active NameNode during a failover (免密方式以及秘钥路径)

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

• ZKFC配置 (automatic failover 自动失效转移)

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

core-site.xml

• fs.defaultFS - the default path prefix used by the Hadoop FS client when none is given

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

• Configuring automatic failover (ZooKeeper 节点)

   <property>
     <name>ha.zookeeper.quorum</name>
     <value>node02:2181,node03:2181,znode04:2181</value>
   </property>
  

初始化准备

1. ssh免密

   • 启动start-dfs.sh的机器要将自己的公钥分发给其他的节点
   • 在HA模式下，每一个NameNode会启动ZKFC，ZKFC会用免密的ssh控制自己和其他NameNode节点的NameNode状态

2. 先启动JN：hadoop-daemon.sh start journalnode

3. 选择一个NN做格式化： hdfs namenode -format

4. 启动这个格式化的NN，以备另一台同步：hadoop-daemon.sh start namenode

5. 在另外一台机器中：hdfs namenode -bootstrapStandby

6. 格式化Zookeeper：hdfs zkfc -formatZK

7. start-dfs.sh