在yarn集群上面跑mapReduce的wordcount方法

hadoop jar /export/servers/hadoop3.3.5/share/hadoop/mapreduce/hadoop-mapreduce-examples-3.3.5.jar wordcount    /bigdata（要统计的文件所在的文件夹）     /test/output（输出文件夹）

出现报错

2024-12-27 19:59:33,518 INFO mapreduce.Job:  map 0% reduce 0%
2024-12-27 19:59:33,532 INFO mapreduce.Job: Job job_1735300724312_0001 failed with state FAILED to AM Container for appattempt_1735300724312_0001_000002 exited with  exitCode: 1
Failing this attempt.Diagnostics: [2024-12-27 19:59:32.704]Exception from container-launch.
Container id: container_1735300724312_0001_02_000001
Exit code: 1

[2024-12-27 19:59:32.731]Container exited with a non-zero exit code 1. Error file: prelaunch.er
Last 4096 bytes of prelaunch.err :
Last 4096 bytes of stderr :
错误: 找不到或无法加载主类 org.apache.hadoop.mapreduce.v2.app.MRAppMaster

[2024-12-27 19:59:32.732]Container exited with a non-zero exit code 1. Error file: prelaunch.er
Last 4096 bytes of prelaunch.err :
Last 4096 bytes of stderr :
错误: 找不到或无法加载主类 org.apache.hadoop.mapreduce.v2.app.MRAppMaster

解决方法

在配置文件yarn-site.xml中添加Hadoop classpath。

首先输入hadoop classpath 查看，然后把输出的这些路径全都复制上

打开yarn-site.xml添加classpath如下 （vi /../hadoop3.3.5/etc/hadoop/yarn-site.xml）

<property>
        <name>yarn.application.classpath</name>
	<value>/export/servers/hadoop3.3.5/etc/hadoop:/export/servers/hadoop3.3.5/share/hadoop/common/lib/*:/export/servers/hadoop3.3.5/share/hadoop/common/*:/export/servers/hadoop3.3.5/share/hadoop/hdfs:/export/servers/hadoop3.3.5/share/hadoop/hdfs/lib/*:/export/servers/hadoop3.3.5/share/hadoop/hdfs/*:/export/servers/hadoop3.3.5/share/hadoop/mapreduce/*:/export/servers/hadoop3.3.5/share/hadoop/yarn:/export/servers/hadoop3.3.5/share/hadoop/yarn/lib/*:/export/servers/hadoop3.3.5/share/hadoop/yarn/* </value>
   </property>