HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}

场景

在Hadoop3.13的YARN上运行MapReduce

报错信息

终端界面提示
FAILED: Execution Error, return code 2 from org.apache.hadoop.hive.ql.exec.mr.MapRedTask

再查YARN历史
Error: Could not find or load main class org.apache.hadoop.mapreduce.v2.app.MRAppMaster

Please check whether your etc/hadoop/mapred-site.xml contains the below configuration:
<property>
<name>yarn.app.mapreduce.am.env</name>
<value>HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}</value>
</property>
<property>
<name>mapreduce.map.env</name>
<value>HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}</value>
</property>
<property>
<name>mapreduce.reduce.env</name>
<value>HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}</value>
</property>

解决方案

vi $HADOOP_HOME/etc/hadoop/yarn-site.xml

<property>
    <name>yarn.nodemanager.env-whitelistname>
    <value>JAVA_HOME,HADOOP_COMMON_HOME,HADOOP_HDFS_HOME,HADOOP_CONF_DIR,CLASSPATH_PREPEND_DISTCACHE,HADOOP_YARN_HOME,HADOOP_MAPRED_HOMEvalue>
property>

修改值 和 默认值 的区别

• 修改值：
  JAVA_HOME,HADOOP_COMMON_HOME,HADOOP_HDFS_HOME,
  HADOOP_CONF_DIR,CLASSPATH_PREPEND_DISTCACHE,HADOOP_YARN_HOME,
  HADOOP_MAPRED_HOME
• 默认值：
  JAVA_HOME,HADOOP_COMMON_HOME,HADOOP_HDFS_HOME,
  HADOOP_CONF_DIR,CLASSPATH_PREPEND_DISTCACHE,HADOOP_YARN_HOME,
  HADOOP_HOME,PATH,LANG,TZ

参数详解

• MapReducer执行时，会在NodeManager上创建Container，在Container上执行Task（JAVA程序），该程序需要环境变量（如：JDK、HADOOP_MAPRED_HOME…）
• 该参数就是 设置Container的能继承NodeManager的哪些环境变量