Require prometheus storage to init history and add option to explicitly not use history storage

[Evedel]

What type of PR is this?

/kind bug

What this PR does / why we need it:

It will allow to run VPA explicitly without history initialisation, but also will make it compulsory to initialise history if prometheus is a provider.

Which issue(s) this PR fixes:

Fixes #6050

Special notes for your reviewer:

Please see the bug/issue description detailed in #6050

Does this PR introduce a user-facing change?

No

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

No

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Evedel / name: Biriukov Sergei (8d1573a, c5d307e, dc3ee8c, 8d2cbf3, c837778, e90294c, 6be45f6, 6fc960d, a301cc7, 0e0dc53, 17a0efe, 7d3747a, be1bcd6)

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[sophieliu15]

LGTM.

[Evedel]

This potentially could also be an error/restart, but some (valid?) cases are possible, so leaving with a warning for now.

As for the error cases, at the moment --metric-for-pod-labels=up{job=\"kubernetes-pods\"}, if prom is not configured to have a given pair of job/metric, the query will not return any results, so history will not be used (and users won't be notified about the misconfiguration either)

[sophieliu15]

This case does not seem to be treated differently (e.g., issue warning logs) before this PR. Is anything changed in this PR that make this case special? Or you just hope to add a log for this case?

[Evedel]

Yes, this behaviour is preexisting to PR. (also it can be a valid behaviour, say when a user specified the metric filter to target a subset of pods, but no such pods existed in the required history window).

Adding warning here just in case when this behaviour is not intentional, so it is easier to uncover a misconfiguration, for example when it could have been handy please see #6221 and #5031 (comment).

[sophieliu15]

@kwiesmueller Could you do a final round of review and approve if it looks good to you?
cc: @laoj2

[kwiesmueller]

Just a few nits.

[ben-bertrands-hs]

Hi, Can this be merged in?

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/lifecycle stale

[Evedel]

/remove-lifecycle stale

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Evedel
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[Evedel]

Any chance someone can have a look please?

@jbartosik
@kgolab
@mwielgus
@kwiesmueller
@sophieliu15

[k8s-ci-robot]

PR needs rebase.

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