错误: 找不到或无法加载主类 org.apache.hadoop.mapreduce.v2.app.MRAppMaster

缺乏、安全感 2022-12-25 09:56 10阅读 0赞

*  yarn执行MapReduce任务时，找不到主类导致的

`[2019-12-31 20:02:59.464]Container exited with a non-zero exit code 1. Error file: prelaunch.err. 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`![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzI5MjMyOTQz_size_16_color_FFFFFF_t_70]

解决：在命令行输入：hadoop classpath

[admin@master hadoop]$ hadoop classpath
    /opt/module/hadoop/etc/hadoop:/opt/module/hadoop/share/hadoop/common/lib/*:/opt/module/hadoop/share/hadoop/common/*:/opt/module/hadoop/share/hadoop/hdfs:/opt/module/hadoop/share/hadoop/hdfs/lib/*:/opt/module/hadoop/share/hadoop/hdfs/*:/opt/module/hadoop/share/hadoop/mapreduce/lib/*:/opt/module/hadoop/share/hadoop/mapreduce/*:/opt/module/hadoop/share/hadoop/yarn:/opt/module/hadoop/share/hadoop/yarn/lib/*:/opt/module/hadoop/share/hadoop/yarn/*

*  1
 *  2

把上述输出的值添加到yarn-site.xml文件对应的属性 yarn.application.classpath下面，eg：

<property>
            <name>yarn.application.classpath</name>
            <value>/opt/module/hadoop/etc/hadoop:/opt/module/hadoop/share/hadoop/common/lib/*:/opt/module/hadoop/share/hadoop/common/*:/opt/module/hadoop/share/hadoop/hdfs:/opt/module/hadoop/share/hadoop/hdfs/lib/*:/opt/module/hadoop/share/hadoop/hdfs/*:/opt/module/hadoop/share/hadoop/mapreduce/lib/*:/opt/module/hadoop/share/hadoop/mapreduce/*:/opt/module/hadoop/share/hadoop/yarn:/opt/module/hadoop/share/hadoop/yarn/lib/*:/opt/module/hadoop/share/hadoop/yarn/*</value>
    </property>

*  1
 *  2
 *  3
 *  4

重启yarn，重新跑MapReduce任务。

yarn --daemon stop resourcemanager
    yarn --daemon stop nodemanager
    
    yarn --daemon start resourcemanager
    yarn --daemon start nodemanager

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzI5MjMyOTQz_size_16_color_FFFFFF_t_70]: /images/20221120/32bb5e6279ce4be7a7f2dc76748af6c6.png