I'm a fan of Bryan's last suggestion. For dynamic/automatic retry
(such as database connection retries), I recommend putting the
connection logic in the onTrigger() method. If you can check
connectivity, then your onTrigger() would know whether it needs to try
to reconnect before it does any work. If it tries to reconnect and is
unsuccessful, you can yield the processor if you want, so as not to
hammer the DB with connection attempts. The CaptureChangeMySQL
processor does this, it has a retry loop for trying various nodes in a
MySQL cluster, but once it's connected, it goes on about its work, and
if a connection fails, it will retry the connection loop before it
does any more work. It only uses onTrigger and none of the scheduling
stuff.

Regards,
Matt

On Fri, Aug 11, 2017 at 11:06 AM, Bryan Bende <bbe...@gmail.com> wrote:
> Ben,
>
> I apologize if I am not understanding the situation, but...
>
> In the case where your OnScheduled code is in a retry loop, if someone
> stops the processor it will call your OnUnscheduled code which will
> set the flag to bounce out of the loop. This sounds like what you
> want, right?
>
> In the case where OnScheduled times out, the framework is calling
> OnUnscheduled which would call your code to set the flag, but wouldn't
> that not matter at this point because you aren't looping anymore
> anyway?
>
> If the framework calls OnScheduled again, your code should set the
> flag back to whatever it needs to be to start looping again right?
>
> An alternative that might avoid some of this would be to lazily
> initialize the connection in the onTrigger method of the processor.
>
> -Bryan
>
>
> On Fri, Aug 11, 2017 at 9:16 AM, 尹文才 <batman...@gmail.com> wrote:
>> thanks Pierre, my case is that I need to implement a database connection
>> retry logic inside my OnScheduled method, when the database is not
>> available I will retry until the connection is back online.
>> The problem is when the database is offline it will throw timed out
>> execution exception inside OnScheduled and then call OnUnscheduled. But
>> when I manually stop the processor the OnUnsheduled
>> will also get called. I know my logic sounds a little weird but I need to
>> set some flag in the OnUnscheduled method to stop the retry logic inside
>> OnScheduled in order to be able to stop the processor,
>> otherwise the processor is not able to be stopped unless I restart the
>> whole NIFI.
>>
>> Regards,
>> Ben
>>
>> 2017-08-11 17:18 GMT+08:00 Pierre Villard <pierre.villard...@gmail.com>:
>>
>>> Oh OK, get it now!
>>>
>>> Not sure what's your use case, but I don't think you can do that unless you
>>> set some information when the process actually executes onTrigger for the
>>> first time and you then check this value in your OnUnscheduled annotated
>>> method.
>>>
>>> Pierre
>>>
>>> 2017-08-11 10:11 GMT+02:00 尹文才 <batman...@gmail.com>:
>>>
>>> > Hi Pierre, I've checked the developer guide before I sent the email and
>>> > according to the developer guide, the method annotated with OnUnScheduled
>>> > will be called in 2 cases according to my understanding, please correct
>>> me
>>> > if I'm wrong:
>>> > 1. when user tries to stop the processor in the NIFI UI, thus the
>>> processor
>>> > is no longer scheduled to run in this case, and the method will be
>>> called.
>>> > 2. when method annotated with OnScheduled throws exceptions, for example
>>> > time out execution exception, the OnUnScheduled method will also be
>>> called.
>>> >
>>> > My question is how to tell the first scenario from the second one?
>>> Thanks.
>>> >
>>> > Regards,
>>> > Ben
>>> >
>>> > 2017-08-11 15:51 GMT+08:00 Pierre Villard <pierre.villard...@gmail.com>:
>>> >
>>> > > Hi Ben,
>>> > >
>>> > > You might want to have a look here:
>>> > > https://nifi.apache.org/docs/nifi-docs/html/developer-
>>> > > guide.html#component-lifecycle
>>> > >
>>> > > Pierre
>>> > >
>>> > > 2017-08-11 9:06 GMT+02:00 尹文才 <batman...@gmail.com>:
>>> > >
>>> > > > Hi guys, I'm trying to execute some code in my processor when the
>>> > > processor
>>> > > > is asked to stop in the NIFI UI by the user, I checked the developer
>>> > > guide
>>> > > > and only find OnUnscheduled will be called when the processor is no
>>> > long
>>> > > > scheduled to run. I've tested this OnUnscheduled, it will also be
>>> > called
>>> > > > after timed out executing OnScheduled task. So is there a way to
>>> > execute
>>> > > > some code only when the processor is stopping?
>>> > > >
>>> > > > Regards,
>>> > > > Ben
>>> > > >
>>> > >
>>> >
>>>

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