Michael, Hello. First, thanks for your interest in NiFi! I'm very happy to see that you're already starting to dig in pretty deep here!
I admit that the wording here can be a little confusing. Let me try to explain what's going on here and how yielding works. When you are developing a Processor in NiFi, especially if reaching out to some external resource, a common occurrence is to realize that there is no work that can really be done at this point in time (for example, because the remote resource is not accessible). In that case, the processor can call ProcessContext.yield() and as a result, the framework will stop scheduling that processor to run for the configured amount of time, so that we aren't wasting resources when we know there is nothing that we can accomplish. This is where the configured Yield Duration comes in. There is, however, a concept of "administratively yielding" a processor. The idea here is that the Processor throws some unexpected exception. Since the Exception was not of type ProcessException, the framework considers this a bug and will perform an administrative yield to avoid continually triggering a processor that may be in a bad state. Perhaps using the term "administratively yielding" was a bad idea, as it can clearly lead to confusion. If you feel that something is not behaving properly, though, or you believe that the user experience can be improved in some way, please do let us know, as we strive to continually improve the user experience. Thanks -Mark > On Nov 17, 2015, at 10:34 AM, Michael De Courci <[email protected]> wrote: > > FYI > >> Begin forwarded message: >> >> From: Michael De Courci <[email protected]> >> Date: 16 November 2015 at 15:41:27 GMT >> To: [email protected], [email protected], Kefah Issa >> <[email protected]> >> Subject: NiFI Custom Plugin - Yield Duration Ignored >> >> I wrote a NAR custom plugin to verify NoFi Exception handling. - version; >> nifi-0.3.0 >> >> The plugin was written to always through a RunTimeException for any >> exception including ProcessException. >> >> I created a simple flow; GetFile->MyPlugin->PutFile >> >> and set the Yield duration to 60 seconds. >> >> The log shows that the yield duration is always 1 sec >> >> I debugged the NiFi framework code and see that the yield duration always >> defaults to 1 sec; >> See; >> org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent >> >> Setting the duration updates the class >> org.apache.nifi.controller.StandardProcessorNode >> but this does not communicate the change to TimerDrivenSchedulingAgent >> >> Evidence from log; >> >> 80eb-552a-471c-8ffd-f2509d71fd2e] failed to process session due to >> java.lang.RuntimeException: java.lang.RuntimeException >> >> 2015-11-15 16:17:58,417 WARN [Timer-Driven Process Thread-7] >> c.b.n.p.SampleErrorHandlerProcessor >> SampleErrorHandlerProcessor[id=8e8f80eb-552a-471c-8ffd-f2509d71fd2e] >> Processor Administratively Yielded for 1 sec due to processing failure >> >> 2015-11-15 16:17:58,417 WARN [Timer-Driven Process Thread-7] >> o.a.n.c.t.ContinuallyRunProcessorTask Administratively Yielding >> SampleErrorHandlerProcessor[id=8e8f80eb-552a-471c-8ffd-f2509d71fd2e] due to >> uncaught Exception: java.lang.RuntimeException >> >> 2015-11-15 16:17:58,419 WARN [Timer-Driven Process Thread-7] >> o.a.n.c.t.ContinuallyRunProcessorTask >> >> java.lang.RuntimeException: null >> >> at >> com.barclays.nifi.processor.SampleErrorHandlerProcessor.onTrigger(SampleErrorHandlerProcessor.scala:103) >> ~[na:na] >> >> >> >> With Kind Regards >> Michael de Courci >
