vitess-mixin: add structure & first 2 dashboards

[guidoiaquinti]

Description

First draft of the vitess-mixin: a set of Grafana dashboards, Prometheus rules and alerts, packaged together in a reuseable and extensible bundle.

Why

Following the same path as other monitoring mixins. This mixin was heavily inspired by the kubernetes-mixin.

Disclaimer

This bundle is still a WIP:

• It only generates Grafana dashboards
• Prometheus rules and alerts are still missing
• there's quite a bit of code duplication that could be refactored

I just rushed to push something out before 🎄Christmas to get a first feedback from the community.

Feedback are welcome, thanks and happy holidays!

[dkhenry]

This looks like it might be a better fit in https://github.com/vitessio/contrib

[guidoiaquinti]

👋@dkhenry thanks for your comment. I thought about it but I ended up pushing it here as this allow us to make changes to metrics and directly reflect those to Grafana dashboards, Prometheus rules and alerts at the same time without breaking anything. What do you think about it? Thanks!

[deepthi]

This looks like it might be a better fit in https://github.com/vitessio/contrib

@dkhenry can you articulate why you don't think this should be in the main repo?

[sougou]

If you're willing to keep this up-to-date, then it's a good idea to make this part of the main repo. And I do trust that you will, since you're running this in production :).