Apache Nifi的AbstractProcessor的onTrigger（）方法中的零流文件

Question

public class MyCustomProc extends AbstractProcessor {

    @Override
    public void onTrigger(final ProcessContext context, final ProcessSession session) throws ProcessException {

        List<FlowFile> flowFiles = session.get(5000);
        if (flowFiles == null || flowFiles.size() == 0) {
            return;
        }
        //...

flowfiles原来大小为零！！！我无法猜测我应该向哪个方向检查，以找出为什么会发生这种情况。有什么提示我该如何诊断吗？

编辑

斯塔克特莱斯

2019-05-02 18:08:09,456 ERROR [Timer-Driven Process Thread-10] c.c.product.module.submodule.MyCustomProcessor MyCustomProcessor[id=016a1008-8956-1dbf-bd66-993e0ce98668] MyCustomProcessor[id=016a1008-8956-1dbf-bd66-993e0ce98668] failed to process due to org.apache.nifi.processor.exception.FlowFileHandlingException: StandardFlowFileRecord[uuid=408fbb3d-7cc2-48bc-be8f-6d0afdbddaf2,claim=StandardContentClaim [resourceClaim=StandardResourceClaim[id=1556800468726-1, container=default, section=1], offset=261, length=591447],offset=0,name=188149730353200,size=591447] transfer relationship not specified; rolling back session: {}
org.apache.nifi.processor.exception.FlowFileHandlingException: StandardFlowFileRecord[uuid=408fbb3d-7cc2-48bc-be8f-6d0afdbddaf2,claim=StandardContentClaim [resourceClaim=StandardResourceClaim[id=1556800468726-1, container=default, section=1], offset=261, length=591447],offset=0,name=188149730353200,size=591447] transfer relationship not specified
    at org.apache.nifi.controller.repository.StandardProcessSession.checkpoint(StandardProcessSession.java:251)
    at org.apache.nifi.controller.repository.StandardProcessSession.commit(StandardProcessSession.java:321)
    at org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:28)
    at org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1122)
    at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:147)
    at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47)
    at org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:128)
    at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
    at java.util.concurrent.FutureTask.runAndReset(Unknown Source)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(Unknown Source)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

PS2:我在apps.log中得到以下错误，但我不确定这是否是问题的根源：

2019-05-02 18:17:32,394 ERROR [Timer-Driven Process Thread-4] o.a.nifi.groups.StandardProcessGroup Unable to synchronize StandardProcessGroup[identifier=d25747e6-719e-3ed9-c6c5-56794af6555c] with Flow Registry because Process Group was placed under Version Control using Flow Registry with identifier 80016ab0-bfab-152b-ffff-ffffc441867c but cannot find any Flow Registry with this identifier

Answer 1

有时获得零流文件是正常的行为，这就是为什么处理器会像您在开始时那样进行检查。

FlowFileHandlingException表示流文件是从会话中获得的，无论是从get还是从create中获得的，该流文件没有被转移到任何地方，也没有被删除，因此基本上是下落不明的。如果只在if语句的开头返回，就不会发生这种情况，因此处理器代码的其余部分正在执行并产生此错误。您没有提供其余的代码，所以我们看不到问题。

第二个问题是相当不言自明的。您有一个处于版本控制下的进程组，但用于启动版本控制的注册表客户端不知何故已不存在。我不知道您是如何创建此场景的，因为我相信UI/API不会允许您删除具有受版本控制的活动流的注册表客户端，但您应该能够停止对进程组的版本控制。