NIFI-4200 - Initial commit for a ControlNiFi processor

[pvillard31]

Thank you for submitting a contribution to Apache NiFi.

In order to streamline the review of the contribution we ask you
to ensure the following steps have been taken:

For all changes:

• Is there a JIRA ticket associated with this PR? Is it referenced
  in the commit message?

• Does your PR title start with NIFI-XXXX where XXXX is the JIRA number you are trying to resolve? Pay particular attention to the hyphen "-" character.

• Has your PR been rebased against the latest commit within the target branch (typically master)?

• Is your initial contribution a single, squashed commit?

For code changes:

• Have you ensured that the full suite of tests is executed via mvn -Pcontrib-check clean install at the root nifi folder?
• Have you written or updated unit tests to verify your changes?
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
• If applicable, have you updated the LICENSE file, including the main LICENSE file under nifi-assembly?
• If applicable, have you updated the NOTICE file, including the main NOTICE file found under nifi-assembly?
• If adding new Properties, have you added .displayName in addition to .name (programmatic access) for each of the new properties?

For documentation related changes:

• Have you ensured that format looks appropriate for the output in which it is rendered?

Note:

Please ensure that once the PR is submitted, you check travis-ci for build issues and submit an update to your PR as soon as possible.

[trixpan]

@pvillard31 - I assume the processor should be able to control nifi components only. Should we rename it to make this explicit?

[pvillard31]

Hey @trixpan. Just pushed a new commit with the following modifications:

• Renamed the processor to ControlNiFiComponent
• Allow the user to control processor, process group, controller service, reporting task
• Allow the user to defined dynamic properties (with EL allowed) that will be used to update the configuration of the target component

This would, for instance, allow a user to define a web service to download files with something like:
HandleHttpRequest -> ControlNiFiComponent -failure-> HandleHttpResponse
GetHDFS -> HandleHttpResponse
This way, a user could send a HTTP request with the path of the file to download, the ControlNiFiComponent is used to start/stop the GetHDFS processor with the path to set in the processor, and the file is sent back to the user.

I believe this would cover NIFI-890.

[patricker]

@pvillard31 I was reviewing this today, but wanted to make sure you still wanted to move forward. No reason not to that I can see, it's just been dormant a long time.

[pvillard31]

Hey @patricker - I'd need to revisit the PR to add some minor things like EL scope and similar things. Regarding the processor itself, I believe it adds some interesting possibilities and still think it could be an interesting addition. However, I want to be sure the concerns raised in the JIRA are addressed before moving on. If people are interested by this feature, feel free to drop a comment on the JIRA: https://issues.apache.org/jira/browse/NIFI-4200

[joewitt]

closing due to inactivity