Perhaps we may need to start explaining ‘administrative yield” as Circuit Breaker because that ’s what it is from known pattern perspective
Question to DEV; Should we consider going as far as deprecating the name and incorporating CB in it somehow? That would definitely help to avoid the confusion Cheers Oleg > On Nov 17, 2015, at 11:19 AM, Mark Payne <[email protected]> wrote: > > 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 >> > >
