在Hadoop 中执行命令，结果卡住不动：http://www.cndba.cn/dave/article/3337

hive> select count(1) from employees;
Query ID = hadoop_20190309205753_9eac66d2-7887-475d-ac86-a7cba452e70c
Total jobs = 1
Launching Job 1 out of 1
Number of reduce tasks determined at compile time: 1
In order to change the average load for a reducer (in bytes):
  set hive.exec.reducers.bytes.per.reducer=<number>
In order to limit the maximum number of reducers:
  set hive.exec.reducers.max=<number>
In order to set a constant number of reducers:
  set mapreduce.job.reduces=<number>
2019-03-09 20:57:58,132 INFO  [6be0ea3b-ca7b-47d2-9b30-77fbe929d85a main] client.RMProxy: Connecting to ResourceManager at Master:8032
2019-03-09 20:57:58,546 INFO  [6be0ea3b-ca7b-47d2-9b30-77fbe929d85a main] client.RMProxy: Connecting to ResourceManager at Master:8032
Interrupting... Be patient, this might take some time.
Press Ctrl+C again to kill JVM
Exiting the JVM

这里是因为资源管理进程没有启动，查看进程信息：http://www.cndba.cn/dave/article/3337http://www.cndba.cn/dave/article/3337http://www.cndba.cn/dave/article/3337http://www.cndba.cn/dave/article/3337

[hadoop@hadoopMaster ~]$ jps
13970 QuorumPeerMain
21141 SecondaryNameNode
21479 Jps
20907 NameNode
[hadoop@hadoopMaster ~]$

确实没有启动，我这里是因为之前修改了主机名，而没有修改yarn-site.xml中对应的名称导致的，修改成正确的主机名后重启yarn，恢复正常：http://www.cndba.cn/dave/article/3337http://www.cndba.cn/dave/article/3337

[hadoop@hadoopMaster logs]$ pwd
/home/hadoop/hadoop/logs
[hadoop@hadoopMaster logs]$ ls
fairscheduler-statedump.log                     hadoop-hadoop-resourcemanager-hadoopMaster.out    hadoop-hadoop-secondarynamenode-hadoopMaster.out
hadoop-hadoop-namenode-hadoopMaster.log         hadoop-hadoop-resourcemanager-hadoopMaster.out.1  hadoop-hadoop-secondarynamenode-hadoopMaster.out.1
hadoop-hadoop-namenode-hadoopMaster.out    


[hadoop@hadoopMaster ~]$ jps
13970 QuorumPeerMain
23522 NameNode
24290 RunJar
23988 ResourceManager
24521 Jps
23757 SecondaryNameNode
[hadoop@hadoopMaster ~]$


hive> select count(1) from employees;
Query ID = hadoop_20190309212230_d945dafb-311b-4b04-8e0b-7e14671a71e7
Total jobs = 1
Launching Job 1 out of 1
Number of reduce tasks determined at compile time: 1
In order to change the average load for a reducer (in bytes):
  set hive.exec.reducers.bytes.per.reducer=<number>
In order to limit the maximum number of reducers:
  set hive.exec.reducers.max=<number>
In order to set a constant number of reducers:
  set mapreduce.job.reduces=<number>
2019-03-09 21:22:35,564 INFO  [11ef99e0-fe20-400e-87b6-1006d834fa31 main] client.RMProxy: Connecting to ResourceManager at hadoopMaster/192.168.56.100:8032
2019-03-09 21:22:35,917 INFO  [11ef99e0-fe20-400e-87b6-1006d834fa31 main] client.RMProxy: Connecting to ResourceManager at hadoopMaster/192.168.56.100:8032
Starting Job = job_1552137405153_0002, Tracking URL = http://hadoopMaster:8088/proxy/application_1552137405153_0002/
Kill Command = /home/hadoop/hadoop/bin/mapred job  -kill job_1552137405153_0002
Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 1
2019-03-09 21:22:47,562 Stage-1 map = 0%,  reduce = 0%
2019-03-09 21:22:53,935 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 2.27 sec
2019-03-09 21:23:01,275 Stage-1 map = 100%,  reduce = 100%, Cumulative CPU 4.6 sec
MapReduce Total cumulative CPU time: 4 seconds 600 msec
Ended Job = job_1552137405153_0002
MapReduce Jobs Launched: 
Stage-Stage-1: Map: 1  Reduce: 1   Cumulative CPU: 4.6 sec   HDFS Read: 21015 HDFS Write: 103 SUCCESS
Total MapReduce CPU Time Spent: 4 seconds 600 msec
OK
424
Time taken: 31.697 seconds, Fetched: 1 row(s)
hive>

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