I was just about to suggest the same. Run-once would be a bit counter intuitive to the flow processing as a concept. Basically think of it this way; Flow or parts of it have only two states - RUNNING or STOPPED. In the RUNNING state it processes the data as it arrives (every second, every minute or every day etc). Indeed there may be a concern that the processor will do a lot of 'dry’ spins if no data is available but fortunately NiFi allows you to limit the impact of that by configuring “yield duration’. By default it is set to 1 sec, but for your case you may wan to set it to 1 hour or so essentially controlling the scheduling of such processor between ‘dry’ spins.
That said and just to entertain the idea of Run Once, what do you think should be the processor state if it did ran once? Let’s assume it did and somehow was stopped. . . then what? The data arrived on the incoming queue, but nothing is processed until someone manually goes and re-starts the processor. Right? I mean from the general workflow standpoint the concern is very valid, but from flow processing the fact that NiFi does not support it is actually more of a feature rather then lack of functionality. Thoughts? Cheers Oleg > On Jan 12, 2017, at 1:02 PM, Joe Witt <[email protected]> wrote: > > Naz, > > Why not just leave all the processes running? If the data only > arrives periodically that is ok, right? > > Thanks > Joe > > On Thu, Jan 12, 2017 at 10:54 AM, Irizarry Jr., Nazario <[email protected]> > wrote: >> On a project that I am on we have been looking at using NiFi for >> orchestrations that are invoked infrequently. For example, once a month a >> new data input product becomes available and then one wants to run it >> through a set of processing steps that can be nicely implemented using NiFi >> processors. However, using the interval or cron scheduling for this purpose >> begins to get cumbersome after a while with the need to start and manually >> stop these occasional flows. >> >> It would be fairly easy to add an additional scheduling option - “Run Once” >> for this use case. The behavior would be that when a processor is set to >> run once it automatically stops after it has successfully processed one >> input. >> >> What do people think? We are willing to implement this small enhancement. >> >> Cheers, >> >> Naz Irizarry >> MITRE Corp. >> 617-893-0074 >> >> >> >
