helm: add helm chart

[roobre]

This PR adds a basic helm chart, which allows easy deployment of scrutiny in Kubernetes.

This is a pretty rough first iteration, but is as far as I can tell funcitonal and allows certain degree of customization.

There are some rough edges I've left as review comments, just to doublecheck what I'm doing makes sense.

Please let me know what you think!

[roobre]

From what I can tell, the collector writes stuff in /opt/scrutiny.
Good K8s hygiene mandates the root of the container to be read-only, and all locations where temporary files are written to be specific EmptyDir mount points. Is there any other location where this docker image writes to?

[uhthomas]

I tried to make it use a read only file system, but it really freaks out. It want to write for entrypoints and cron job stuff. I think the collector would need significant changes to facilitate this.

[AnalogJ]

woah, this is great, thanks! 🥳
I should be able to give you a detailed review this weekend.

[AnalogJ]

I'd love to use Kubernetes's built in cron-scheduling, instead of my kludgy cron-in-docker solution if we can.
I've used https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/ in the past, but I'm not sure if it has the capabilities to force a container on every node. Is that something you're familiar with?

[roobre]

I completely agree, I do not particularly like the cron-in-docker thing. Unfortunately as far as I know, there is no reliable way to run a CronJob on all nodes :(
I've seen hacks here and there, like forcing a number of replicas == number of nodes and setting antiaffinity rules, but I don't think that's very reliable.

An alternative to the cron in docker could be a simpler image that just does:

#!/bin/sh
while [ true ]; do
    /opt/scrutiny/bin/something something
    sleep 6h
done

This script is simple enough to inline in the K8s manifest. WDYT?

[roobre]

Thanks for the in-depth review @AnalogJ!
On my side:

• Get rid of the autoscaling functionality
• Rewrite default tags to use appVersion

What I'd like to confirm:

• Wether we need to mount /run/udev
• If you're ok with maintaining appVersion in sync
• If you like the idea of replacing the cron-in-docker with the custom script inline in the manifest (no changes required to the docker image)

[AnalogJ]

Hey @roobre

• Wether we need to mount /run/udev
  • Yes, I think this is still required with --privileged
• If you're ok with maintaining appVersion in sync
  • Yes, I'll tweak my packagr tooling to support multiple files - https://github.com/PackagrIO/docs
• If you like the idea of replacing the cron-in-docker with the custom script inline in the manifest (no changes required to the docker image)
  • Unfortunately I don't think we can use a simple custom script like you mentioned, some of our users definitely depend on the customization of the cron schedule.

I hope that answers all your questions!

[roobre]

@AnalogJ
We could expose an entry in values.yaml and use it to feed the script. For example:

collector:
  period: 6h

And then:

while [ true ]; do
    /opt/scrutiny/bin/something something
    sleep {{ .Values.period }}
done

It is definitely not the same as cron, but might fill the gap and be more idiomatic than the cron.
Otherwise, we can just keep the cron in place.

[AnalogJ]

Hey @roobre I promise I'm not ignoring your hard work, I just got a bit distracted with some other projects -- https://www.reddit.com/r/selfhosted/comments/xj9rx7/introducing_fasten_a_selfhosted_personal/

I need to make some tweaks to my "bumpr" tool (to keep the versions in the helm manifest in sync with the scrutiny version) but this is looking pretty good.

[Starttoaster]

Just wanted to say thanks @AnalogJ for the update, and @roobre for the hard work. Wanted to chime in as an interested 3rd party waiting for this to merge before I run scrutiny, personally.

[issmirnov]

Hey folks,

Sorry to necromance old PR's, but I too am interested in deploying scrutiny. Is this helm chart in a good enough state to be used?

P.S. Fasten looks amazing, looking forward to running it on my k8s cluster too!

[roobre]

Hey @issmirnov,

I'm using this chart for my NAS and while some things UX-wise can definitely be improved it should work well for the most part.

[uhthomas]

I am not sure this can be a deployment. My understanding is that there is a sqlite database somewhere in /opt/scrutiny/config which is required. Issues occur if it's lost.

This should probably be a stateful set with one replica, or at least /opt/scrutiny/config should have persistence.

[AnalogJ]

correct, https://github.com/AnalogJ/scrutiny/blob/master/webapp/backend/pkg/config/config.go#L37 must be persisted

[uhthomas]

SYS_ADMIN is also required for nvme

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 31.91%. Comparing base (0febe3f) to head (1d527c9).
Report is 84 commits behind head on master.

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@@            Coverage Diff             @@
##           master     #363      +/-   ##
==========================================
- Coverage   32.54%   31.91%   -0.64%     
==========================================
  Files          54       30      -24     
  Lines        3045     2717     -328     
  Branches       66        0      -66     
==========================================
- Hits          991      867     -124     
+ Misses       2018     1811     -207     
- Partials       36       39       +3     

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[adepssimius]

This looks cool and would be awesome to have in my cluster. I've been using scrutiny for years on a homelab server and I hope I can continue to use it now that that I'm migrating to k8s.