Allow preprepared CoreDNS image to be used

[aaronjwood]

What type of PR is this?
/kind bug
/area conformance-machinery

What this PR does / why we need it:
For folks that are pulling images from Docker's public registry in an unauthenticated way rate limits are an immediate problem. This PR fixes three things:

1. Explicitly sets the pull policy for CoreDNS to be IfNotPresent, allowing for a cluster with an already-prepared CoreDNS image to be used
2. Moves away from Docker's public registry to registry.k8s.io/coredns/coredns
3. Fixes getContentsFromPathOrURL to correctly handle multiple fs.FS. If this was already supported client code could've easily done something like this to work around the issue:

virtFS := fstest.MapFS{...} // Imagine this to hold an override for the manifest with issues.
suite.ConformanceOptions{
...
    ManifestFS:               []fs.FS{&conformance.Manifests, &virtFS},
...
}

Does this PR introduce a user-facing change?:

NONE

[k8s-ci-robot]

@aaronjwood: The label(s) kind/conformance-machinery cannot be applied, because the repository doesn't have them.

Details

In response to this:

What type of PR is this?
/kind bug
/kind conformance-machinery

What this PR does / why we need it:
For folks that are pulling images from Docker's public registry in an unauthenticated way rate limits are an immediate problem. This PR fixes two things:

1. Explicitly sets the pull policy for CoreDNS to be IfNotPresent, allowing for a cluster with an already-prepared CoreDNS image to be used
2. Fixes getContentsFromPathOrURL to correctly handle multiple fs.FS. If this was already supported client code could've easily done something like this to work around the issue:

virtFS := fstest.MapFS{...} // Imagine this to hold an override for the manifest with issues.
suite.ConformanceOptions{
...
   ManifestFS:               []fs.FS{&conformance.Manifests, &virtFS},
...
}

Does this PR introduce a user-facing change?:

NONE

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[k8s-ci-robot]

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[k8s-ci-robot]

Hi @aaronjwood. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[aaronjwood]

/area conformance-machinery

[mikemorris]

/ok-to-test

[aaronjwood]

The failing test looks like some kind of flake...? Is it known to anybody?

[aaronjwood]

/retest

[mikemorris]

I missed which test was failing, looks like everything is in good shape now.

Tagging conformance leads for review @candita @sunjayBhatia @arkodg @LiorLieberman

[aaronjwood]

Wanted to follow up on this and see if we can get it merged. Thanks!

[rikatz]

and what if using registry.k8s.io/coredns/coredns:v1.12.0 instead, and pulling directly from our own repo?

[rikatz]

we can probably also pull directly from registry.k8s.io/coredns/coredns:v1.12.0 and while the imagePullPolicy is great, we avoid any sort of rate limiting at all

[aaronjwood]

I'd prefer this too, I didn't realize the image existed here. When I poked around in the past I didn't see anything that referenced CoreDNS having an image here.

I'll update the URI.

[aaronjwood]

Since there's no latest in this registry are folks ok moving to pinning a specific version here? Someone/something will need to keep it moving going forward.

[rikatz]

I am ok with keeping it pinned (tho it is good to have some second opinion), and tbh I prefer it :) IMHO latest can bring some undesired behavior and as this is used for test, we may want consistency.

Also, usually the CoreDNS version is bumped together with Kubernetes version (eg.: kubernetes/kubernetes#131151)

[aaronjwood]

Sounds good, I've seen the arguments for pinning vs not pinning go both ways. I'll update this and see if we can reach a consensus.

[robscott]

+1 to keep it pinned so we have a point in time test manifest that can be reproducible - would hate for a new version of coredns to affect an old version of our conformance tests.

[aaronjwood]

Any interest in merging this?

[robscott]

Thanks @aaronjwood!

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aaronjwood, robscott

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Details

Needs approval from an approver in each of these files:

• conformance/OWNERS [robscott]

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