RFC: Isolate the Rules DSL and package it as a bundle

[5iver]

As we transition to the NGRE, we will need the ability to choose which engine is installed on a system. I will begin researching this, but wanted to quickly throw this out here to pull in others that would like to help and/or discuss.

[kaikreuzer]

This should be really fairly simple - we already have dedicated Karaf features for the DSL rules, so those could be simply made optional, once we do not want to package the "old" rule engine by default anymore.

[5iver]

That info probably saved me a couple hours! Is there a way to turn a Karaf feature into a bundle, so that someone could choose to install/uninstall through Paper UI?

[kaikreuzer]

Sounds as if you still have to learn a bit about Karaf features 😎 - they cannot be "turned into a bundle", they are simply a set of bundles (roughly speaking).
And they are the entities that you can install+deinstall in Karaf/openHAB.

Features with a specific naming (openhab-<addontype>-name, e..g. openhab-misc-ruleengine) are automatically shown in the Paper UI.

[5iver]

Sounds as if you still have to learn a bit about Karaf features sunglasses -

Yes... this is definitely an area I'm not familiar with! 🙂 I'd like to make this change locally to test (and learn!), but I'm not sure I understand the mechanism for toggling optional/required.

I see an /etc/org.apache.karaf.features.cfg with featuresBoot in my local install, but I can't find this file in the repo. I'm also not sure which line in featureBoot installs openhab-core-model-rule. But if it is removed from features.xml, this should prevent it from installing by default.

Then, move org.openhab.core.model.rule into openhab2-addons? Although, it seems strange to currently have it in openhab2-core, so why not move it now, after the smoke settles from the ESH migration?

A rule engine is at the heart of an HA system, but shouldn't it be optional, for people who DIY their own (e.g. node-RED)? I'm not saying to make it an optional feature now, but maybe in OH3 make them both optional?

[Misiu]

@openhab-5iver I'm relatively new to openHAB but I like the direction it is taking.
I really like Node-RED and I support Your idea.
The idea to have an option to install/uninstall default rule engine and install Node-RED as a replacement would be awesome 🚀
@kaikreuzer maybe this could be considered for OH3?
There also should be tighter integration with non-default rule engines, for example if user will install Node-RED he should see Node-RED instead of Rules here:

[5iver]

@kaikreuzer,

1. Should the old rule engine be removed completely in OH 3.0 or just made to be optional?
2. As stated above, IMO the new rule engine should stay optional. WDYT?

I'd be happy to submit the PRs for these!

[kaikreuzer]

Should the old rule engine be removed completely in OH 3.0 or just made to be optional?

Depends on whether we can make existing rules work on the new rule engine with merely small adaptations. As long as we don't have an answer to this, it should be optionally available.

As stated above, IMO the new rule engine should stay optional. WDYT?

It should be technically an independent component, but any standard openHAB setup must have it included. Just like @ghys' new Default UI.