hive执行sql后一直处在ACCEPTED: waiting for AM container to be allocated, launched and register with RM.状态

hive执行sql后一直处在ACCEPTED: waiting for AM container to be allocated, launched and register with RM.状态，并且报错返回FAILED: Execution Error, return code 2 from org.apache.hadoop.hive.ql.exec.mr.MapRedTask

查看hadoop的8088端口网页时可以看到错误日志是在datanode里打印出来的，并且是

java.net.ConnectException: Call From localhost/127.0.0.1 to localhost:56908 failed on connection exceptjava.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at org.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:791)
	at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:731)
	at org.apache.hadoop.ipc.Client.call(Client.java:1473)
	at org.apache.hadoop.ipc.Client.call(Client.java:1400)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:232)
	at com.sun.proxy.$Proxy14.sendHeartbeat(Unknown Source)
	at org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolClientSideTranslatorPB.sendHeartbeat(DatanodeProtocolClientSideTranslatorPB.java:139)
	at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.sendHeartBeat(BPServiceActor.java:617)
	at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.offerService(BPServiceActor.java:715)
	at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:889)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.ConnectException: Connection refused
	at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
	at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:739)
	at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
	at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:530)
	at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:494)
	at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:608)
	at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:706)
	at org.apache.hadoop.ipc.Client$Connection.access$2800(Client.java:369)
	at org.apache.hadoop.ipc.Client.getConnection(Client.java:1522)
	at org.apache.hadoop.ipc.Client.call(Client.java:1439)
	... 8 more

这种情况可能是配置的hostname在/etc/hosts里找不到对应的ip

但是另外一种情况就是在执行hive sql的机器上没有启动datanode，这时候任务找的还是localhost:9000服务对应的hdfs,找不到就会报错，但是任务却一直在等待。

之所以能找到这个问题是看了hadoop-root-datanode-localhost.log这个日志里的内容。

直接在http://s1:8088/logs/hadoop-root-datanode-localhost.log这个路径下就可以看，很方便。s1是你部署hive或hadoop namenode的服务器所在地址