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From Joe Witt <>
Subject Re: Open / Close Gate examples?
Date Fri, 17 May 2019 16:33:28 GMT

Using Wait/Notify would ensure you only have one message in flight at a
time (or it can/should).  But the message will be ack'd before processed.

For Kafka and some of these message queue mechanisms if we want to offer a
'do not ack until the whole flow is done' behavior we should update the
processors to allow for that and actually this is a great use case for the
nifi-fn/stateless work that SamH in the community has been talking about.


On Fri, May 17, 2019 at 12:30 PM David Gallagher <> wrote:

> Hi – I have a requirement to read one message off RabbitMQ and fully
> process that message before I take another message off the queue. I found
> some great guidance to setting up a ‘traffic light’ pattern here (
> but it won’t work for my process because the Notify will get triggered by
> the GenerateFlowFile before the long-running process triggers, which will
> put two or more messages into the process at once. The documentation for
> Notify makes reference to using a 0 value in Signal Counter Delta to
> simulate ‘open-close-gate’ flow control, which sounds like what I’m looking
> for. Can someone point me in the right direction?
> Thanks,
> Dave

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