Flink on Yarn 的模式下,TaskManager的日志会存储到所在的 DataNode 上,当 Flink 任务发生异常，产生异常日志时，需要第一时间感知任务已经出现异常，避免影响业务。因此需要将Flink任务的日志实时收集起来，任务出现异常日志立刻报警，做的真正意义上的实时报警，，而不是等Flink任务掉线了再发出报警。收集任务日志的好处除了任务掉线方便我们通过日志定位问题，还可以支持日志实时报警，搜索，展示等功能的实现。
Flink-1.7.2/1.101、修改$Flink_HOME/conf/log4j.properties配置文件如下
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