在map或者reduce函数中使用System.out.println打印的信息沾满查看呢?
步骤1:启动history server
/usr/local/hadoop-2.6.0/sbin/mr-jobhistory-daemon.sh start historyserver
步骤2:使用http://hadoop26:19888/jobhistory来查看作业log
意外情况:
如果在查看日志的时候,发生了下面的情况
在yarn-default.xml中有这样的一个配置
<property>
<description>Whether to enable log aggregation. Log aggregation collects
each container‘s logs and moves these logs onto a file-system, for e.g.
HDFS, after the application completes. Users can configure the
"yarn.nodemanager.remote-app-log-dir" and
"yarn.nodemanager.remote-app-log-dir-suffix" properties to determine
where these logs are moved to. Users can access the logs via the
Application Timeline Server.
</description>
<name>yarn.log-aggregation-enable</name>
<value>false</value>
</property>
我们需要把这个值改为true,也就是在yarn-site.xml中再配置一遍
配置完成后重启historyserver即可。
现在来看看logs的输出吧: