Hadoop Oozie学习笔记(五) E0720: Fork/join mismatch, node [join_node_name]异常解决
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? ? Oozie是个针对Hadoop的工作流,有些自己的语法. 这两天碰到一个异常,查看源码才明白Oozie的join只允许承接fork下来的任务,否则会报以下错误.整个异常如下:
??WARN CallableQueueService$CallableWrapper:528 - USER[-] GROUP[-] TOKEN[-] APP[-] JOB[-] ACTION[-] exception callable [signal], E0720: Fork/join mismatch, node [join_node_name]
org.apache.oozie.command.CommandException: E0720: Fork/join mismatch, node [tianqi_sawlog_transformation_done]
at org.apache.oozie.command.wf.SignalCommand.call(SignalCommand.java:213)
at org.apache.oozie.command.wf.SignalCommand.execute(SignalCommand.java:305)
at org.apache.oozie.command.wf.SignalCommand.execute(SignalCommand.java:59)
at org.apache.oozie.command.Command.call(Command.java:202)
at org.apache.oozie.service.CallableQueueService$CallableWrapper.run(CallableQueueService.java:128)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Caused by: org.apache.oozie.workflow.WorkflowException: E0720: Fork/join mismatch, node [tianqi_sawlog_transformation_done]
at org.apache.oozie.workflow.lite.JoinNodeDef$JoinNodeHandler.loopDetection(JoinNodeDef.java:44)
at org.apache.oozie.workflow.lite.LiteWorkflowInstance.signal(LiteWorkflowInstance.java:203)
at org.apache.oozie.workflow.lite.LiteWorkflowInstance.signal(LiteWorkflowInstance.java:284)
at org.apache.oozie.command.wf.SignalCommand.call(SignalCommand.java:120)
... 7 more
? ? 源码来自org.apache.oozie.workflow.lite.JoinNodeDef,检测这个语法的代码如下:
?? ? 可以发现这个两个方法都会通过String forkCount = context.getVar(ForkNodeDef.FORK_COUNT_PREFIX + parentExecutionPath);去获取当前节点
的所有父节点是Fork的个数.如果为空,则通过这行代码throw new WorkflowException(ErrorCode.E0720, context.getNodeDef().getName());抛出这个异常
? ? 所以我们今年在使用join节点的时候,一定要承接来自fork或者join本身的节点.下面举几个例子:
? ? 1.错误的例子,由于join并没有承接fork或者join,所以会报以上的错误
?? ? 2.正确的例子,join承接了fork(join1承接了fork1过来的action1和action2)
?? ?3.正确的例子,join承接了join(join2承接了join1)
?? 4.正确的例子,join承接了fork下来的所有节点
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? ?这里只是大概玩了下Oozie,希望能起抛砖引玉...
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