How to clear NiFi queues?

Question

We are creating some flows in NiFi and there might be some cases where the queues are being build up but due to some reason the flow doesn't work as expected.

At the end of the day, i would like to clear the queues and somehow would like to automate it. The question is how can we delete the queues from backend? Is there any way we can achieve that?

Answer 1

In addition to the explicit "Drop Queue" function Bryan mentioned, a couple other features you may be interested are the "Back Pressure" and "FlowFile Expiration" settings on connections. These allow you to automatically control the the amount of data in any given connection. A simple explanation for each is below but for a more detail explanation I'd refer you to the Apache NiFi User Guide

Back Pressure: When a queue gets to a certain size, stop triggering the processor that feeds it.

FlowFile expiration: Once a FlowFile has spent X amount of time in the queue, it will be dropped.

Answer 2

In the Apache NiFi UI if you right-click on a queue there is an option to empty the queue. Anything you can do in the UI is backed by a REST service, so take a look at the REST API docs:

https://nifi.apache.org/docs/nifi-docs/rest-api/index.html

Specifically a POST to /flowfile-queues/{id}/drop-requests.

You can also use Chrome and open developer tools while using the application to see what calls it makes to the REST API when you perform certain actions.