NIFIREG-232 Introducing flow persistence provider migrator and toolkit

[brosander]

No description provided.

[bbende]

@brosander this looks interesting, will definitely take a closer look soon

[brosander]

I probably need to add a readme section if this pr looks good to you @bbende

Usage:

1. Shutdown registry
2. Copy providers.xml -> providers-to.xml, edit to reflect what you'd like to migrate to (e.g. git)
3. In registry home as working dir, run persistence-toolkit.sh -t providers-to.xml

I tested it by converting filesystem provider to git provider, then back to filesystem provider and diffing original, roundtrip directory.

Also by using it on a registry and verifying that everything looked right after conversion (could still get old versions of things, sync w/ nifi, etc)

[bbende]

Tested this out and was able to migrate back and forth, definitely cool!

Besides the two minor comments, we probably need to document the usage somewhere. I guess we can add a "NiFi Registry Toolkit" section to the admin guide with a sub-section for each tool, currently just the persistence migrator.

Was thinking about it more, and maybe instead of the admin guide we can do something less formal and just add a README to the root of nifi-registry-toolkit module.

[brosander]

I can add to the admin guide and update the doc around changing flow persistence providers as well.

[bbende]

Thanks for addressing the feedback. For the documentation, we can probably just have a README in the nifi-registry-toolkit module, and then if we end up adding more tools and have a significant amount of content, we can promote it to a nifi registry toolkit guide like we did in NiFi.

[brosander]

@bbende I think I've addressed your feedback, please let me know if more changes are needed

[bbende]

@brosander looks good, thanks! Going to merge