HBASE API操作问题总结

org.apache.hadoop.hbase.MasterNotRunningException

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在centos中查看，发现没有HMaster进程

解决方法：

1.启动hadoop后，需要等一段时间，再开启hbase

2、启动hadoop后，去掉hadoop的安全模式，然后启动hbase

hadoop dfsadmin -safemode leave

org.apache.hadoop.hbase.client.HTablePool$PooledHTable cannot be cast to org.apache.hadoop.hbase.client.HTable

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  HTablePool pool = new HTablePool(cfg, 1000); 
  HTable table = (HTable) pool.getTable(tableName);

原因：现在使用的api版本中pool.getTable返回的类型是HTableInterface ，无法强转为HTable

解决方法：不用转为HTable直接调用其put方法即可：

 HTablePool pool = new HTablePool(cfg, 1000); 

 pool.getTable(tableName).put(put); 

 HMaster aborted（出现后消失）

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 已关闭安全模式，配置等正确，查看日志如下：

2014-05-26 10:59:41,887 ERROR org.apache.hadoop.security.UserGroupInformation: PriviledgedActionException as:root cause:java.io.IOException: File /usr/local/hadoop/tmp/mapred/system/jobtracker.info could only be replicated to 0 nodes, instead of 1
2014-05-26 10:59:41,887 INFO org.apache.hadoop.ipc.Server: IPC Server handler 3 on 9000, call addBlock(/usr/local/hadoop/tmp/mapred/system/jobtracker.info, DFSClient_NONMAPREDUCE_985848864_1, null) from 192.168.1.95:48016: error: java.io.IOException: File /usr/local/hadoop/tmp/mapred/system/jobtracker.info could only be replicated to 0 nodes, instead of 1
java.io.IOException: File /usr/local/hadoop/tmp/mapred/system/jobtracker.info could only be replicated to 0 nodes, instead of 1
    at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:1639)
    at org.apache.hadoop.hdfs.server.namenode.NameNode.addBlock(NameNode.java:736)
    at sun.reflect.GeneratedMethodAccessor6.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:578)
    at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1393)
    at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1389)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:396)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149)
    at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1387)

因为namenode多次格式化造成的

每次namenode format 会重新创建一个namenodeId，而dfs.data.dir 参数配置的目录中包含的是上次format 创建的id，和dfs.name.dir 参数配置的目录中的id 不一致。namenode format 清空了namenode 下的数据，但是没有清空datanode 下的数据，导致启动时失败

解决方法：fotmat 前，清空dfs.data.dir 参数配置的目录，重新格式化hdfs的命令。