hadoop有哪些常見錯誤

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1.Got too many exceptions to achieve quorum size 2/3. 3 exceptions thrown:

2016-01-05 23:03:32,967 FATAL org.apache.hadoop.hdfs.server.namenode.FSEditLog: Error: recoverUnfinalizedSegments failed for required journal (JournalAndStream(mgr=QJM to [192.168.10.31:8485, 192.168.10.32:8485, 192.168.10.33:8485], stream=null))
org.apache.hadoop.hdfs.qjournal.client.QuorumException: Got too many exceptions to achieve quorum size 2/3. 3 exceptions thrown:
192.168.10.31:8485: Call From bdata4/192.168.10.34 to bdata1:8485 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
192.168.10.33:8485: Call From bdata4/192.168.10.34 to bdata3:8485 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
192.168.10.32:8485: Call From bdata4/192.168.10.34 to bdata2:8485 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
        at org.apache.hadoop.hdfs.qjournal.client.QuorumException.create(QuorumException.java:81)
        at org.apache.hadoop.hdfs.qjournal.client.QuorumCall.rethrowException(QuorumCall.java:223)
        at org.apache.hadoop.hdfs.qjournal.client.AsyncLoggerSet.waitForWriteQuorum(AsyncLoggerSet.java:142)
        at org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager.createNewUniqueEpoch(QuorumJournalManager.java:182)
        at org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager.recoverUnfinalizedSegments(QuorumJournalManager.java:436)
        at org.apache.hadoop.hdfs.server.namenode.JournalSet$8.apply(JournalSet.java:624)
        at org.apache.hadoop.hdfs.server.namenode.JournalSet.mapJournalsAndReportErrors(JournalSet.java:393)
        at org.apache.hadoop.hdfs.server.namenode.JournalSet.recoverUnfinalizedSegments(JournalSet.java:621)
        at org.apache.hadoop.hdfs.server.namenode.FSEditLog.recoverUnclosedStreams(FSEditLog.java:1394)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startActiveServices(FSNamesystem.java:1151)
        at org.apache.hadoop.hdfs.server.namenode.NameNode$NameNodeHAContext.startActiveServices(NameNode.java:1658)
        at org.apache.hadoop.hdfs.server.namenode.ha.ActiveState.enterState(ActiveState.java:61)
        at org.apache.hadoop.hdfs.server.namenode.ha.HAState.setStateInternal(HAState.java:63)
        at org.apache.hadoop.hdfs.server.namenode.ha.StandbyState.setState(StandbyState.java:49)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.transitionToActive(NameNode.java:1536)
        at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.transitionToActive(NameNodeRpcServer.java:1335)
        at org.apache.hadoop.ha.protocolPB.HAServiceProtocolServerSideTranslatorPB.transitionToActive(HAServiceProtocolServerSideTranslatorPB.java:107)
        at org.apache.hadoop.ha.proto.HAServiceProtocolProtos$HAServiceProtocolService$2.callBlockingMethod(HAServiceProtocolProtos.java:4460)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:619)
        at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:962)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2040)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2036)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:415)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1656)
        at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2034)

2016-01-05 23:03:32,968 INFO org.apache.hadoop.util.ExitUtil: Exiting with status 1

錯誤原因：

我們在執行start-dfs.sh的時候，默認啟動順序是namenode>datanode>journalnode>zkfc，如果journalnode和namenode不在一臺機器啟動的話，很容易因為網絡延遲問題導致NN無法連接JN，無法實現選舉，最后導致剛剛啟動的namenode會突然掛掉一個主的，留下一個standy的，雖然有NN啟動時有重試機制等待JN的啟動，但是由于重試次數限制，可能網絡情況不好，導致重試次數用完了，也沒有啟動成功，

A:此時需要手動啟動主的那個namenode，避免了網絡延遲等待journalnode的步驟，一旦兩個namenode連入journalnode，實現了選舉，則不會出現失敗情況，

B:先啟動JournalNode然后再運行start-dfs.sh，

C:把nn對jn的容錯次數或時間調成更大的值，保證能夠對正常的啟動延遲、網絡延遲能容錯

在hdfs-site.xml中加入，nn對jn檢測的重試次數，默認為10次，每次1000ms，故網絡情況差需要增加，這里設置為30次

    <property>
         <name>ipc.client.connect.max.retries</name>
         <value>30</value>

    </property>

2、org.apache.hadoop.security.AccessControlException: Permission denied

在master節點上修改hdfs-site.xml加上以下內容 

<property> 

<name>dfs.permissions</name> 

<value>false</value> 

</property> 

旨在取消權限檢查，原因是為了解決我在windows機器上配置eclipse連接hadoop服務器時，配置map/reduce連接后報錯

3、運行報：[org.apache.hadoop.security.ShellBasedUnixGroupsMapping]-[WARN] got exception trying to get groups for user bdata

在master節點上修改hdfs-site.xml加上以下內容

<property>
<name>dfs.web.ugi</name>
<value>bdata,supergroup</value>
</property>

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