Allow mounting of NFS volumes instead of using st2packs for pack management

[valentintorikian]

This should close #18

This will allow the end users to mount NFS volumes to manage their custom packs. To be noted: when using an NFS mount, the lifecycle management of the packs (installing/updating/registering) is deferred back to the stackstorm administrators.
One way to do it would be to trigger packs installation and/or registration through the API using
https://api.stackstorm.com/api/v1/packs/#/packs_controller.install.post
https://api.stackstorm.com/api/v1/packs/#/packs_controller.register.post
or directly through the st2client pod.

The st2packs method is of course still available. If both st2.packs.image.repository and st2.packs.nfs.server are set, the st2packs image will be used.

[arm4b]

@hnanchahal I think you might be interested in this story of sharing pack content via NFS mount as you did something similar.
Can you also take a look at PR and provide feedback?

[arm4b]

Great stuff! 👍

We'll need more details/instructions for users to make this NFS story more clear and easy.
Also can you provide an example about how to install/configure NFS in K8s and respective Helm values? So someone reviewing this will follow that to verify this feature/story.

[valentintorikian]

Also can you provide an example about how to install/configure NFS in K8s and respective Helm values? So someone reviewing this will follow that to verify this feature/story.

Isn't that a bit out of scope ?

[arm4b]

Having the full example is out of scope for the README, but it'll be good to have this kind of info in this issue to help someone test and try it end to end.

[arm4b]

Overall with NFS like distributing pack content we provide a story/solution for the user.
For instance, custom st2packs has
https://docs.stackstorm.com/install/k8s_ha.html#custom-st2-packs
https://github.com/stackstorm/stackstorm-ha#install-custom-st2-packs-in-the-cluster
https://github.com/StackStorm/st2packs-dockerfiles/
as a helpers to guide users about preparing custom packs in K8s environment.
Alternative solution with NFS shouldn't have less information about how to use it and overall what steps to follow.

[chris3081]

I would love to see a deployment engine in front of this like a Jenkins lite (API / UI) which has write on the volume.. It would offer a clean deployment solution and might allow us to have something in the runners, st2api, st2client etc to install pack OS dependencies, tho I'm not 100% sure how it would work at the moment, but maybe the actionrunner could be commanded by the deployment engine to install OS packs (would need to account for the st2api which runs as stanley)

[ericreeves]

Greetings! This PR needs a rebase given the big upstream changes from master, which I have been unsuccessful at so far. Anybody else have any luck? :)

[cognifloyd]

Thanks for this PR! I used some of the ideas here in building #199 . I need flexVolume + ceph-rook, you need NFS, and others will need who knows which storage solution, so I tried to make something that was both generic and simple. What do you think of #199? Will that work for you?

[cognifloyd]

@angrydeveloper could you review #199? Is there anything missing from #199 that you included in this PR, or that you think would be better a different way?

[cognifloyd]

If #199 is satisfactory for you, then I think we could close this PR. What do you think?