Decrease first bucket size

[dmitrii-sisutech]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Decreased first bucket size, so min recommended target is decreased as well and can go now under 10m.

Which issue(s) this PR fixes:

Fixes #6415

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: dmitrii-sisutech / name: Dmitrii Bobrovskii (1150875)

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[voelzmo]

Hey @dmitrii-sisutech thanks for immediately jumping to do the PR fort that issue! Unfortunately, it isn't this simple, as the line right above your change hints at

When parameters below are changed SupportedCheckpointVersion has to be bumped.

We cannot simply change the buckets of the Checkpoints, as they get written to VPA objects and the recommender reads them when restarting. I didn't do an update of the CheckpointVersion before, but I'll try to find people with more experience on that topic today. We will hopefully be able to get a more comprehensive list of the necessary steps.

[voelzmo]

ping @mwielgus: we talked about this in the SIG meeting and you wanted to provide some context on reducing the minimum recommendation size for VPA.

[mwielgus]

This is a potentially breaking change - updating VPA may require cleaning the whole cluster history as the buckets will be different. If this is really needed, this should be behind a flag, with the old value as the default and a warning about consequences of changing it.

[dmitrii-sisutech]

Thanks @mwielgus for the details.
I'm working at the moment on something different and for now we solved the problem by creating our own image of VPA recommender. I'll get back to that PR with proper solution probably somewhere in summer.

[mwielgus]

Ok, closing this one for now. Feel free to reopen once needed.