feat: pre-pull Azure Stack's custom Hyperkube

[jadarsie]

Reason for Change:
Stores Azure Stack's custom Hyperkube build in the VHD image.

Issue Fixed:
Fixes #990

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

• The custom Hyperkube build are downloaded during the VHD provision process.
• For now it is just single image, will add more entries to the array in a future PR
• I added an extra optional parameter to all functions that deal with Hyperkube to slightly alter their behavior (extractHyperkube, installKubeletAndKubectl, cleanUpContainerImages)

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[jadarsie]

I just blindly created this PR. Please let me know what validations do you usually run for this set of scripts.

[codecov]

Codecov Report

Merging #1040 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1040      +/-   ##
==========================================
+ Coverage   74.33%   74.36%   +0.02%     
==========================================
  Files         131      131              
  Lines       18259    18277      +18     
==========================================
+ Hits        13573    13591      +18     
  Misses       3905     3905              
  Partials      781      781

[CecileRobertMichon]

This PR is breaking for the Ubuntu distro scenario with not-Azure-Stack env

[CecileRobertMichon]

Before this change:

/dev/sda1 30G 18G 12G 60%

After this change:

/dev/sda1 30G 19G 11G 64%

[jackfrancis]

Can't we just add 1.11.8-azs and 1.11.9-azs to the existing versions array in the VHD CI script? Then we just set the value of KUBERNETES_VERSION in pkg/engine/armvariables.go to have the proper string value if we're in an Azure Stack context.

[CecileRobertMichon]

+1 on @jackfrancis's suggestion.

This should also work with the cleanUpContainerImages function the way you wrote it right now to clean up the Azure Stack images depending on context.

[jackfrancis]

I think all of this should be outside of the if block, right? The only conditional change is to HYPERKUBE_URL, correct?

[jadarsie]

Only the hyperkube image is different, cloud-controller-manager remains the same

[jackfrancis]

The point is, this implementation doesn't actually pre-pull the image in the Azure Stack case. The if should be:

if [[ $KUBERNETES_VERSION == *"azs"* ]]; then
  HYPERKUBE_URL="msazurestackdocker/hyperkube-amd64:v${KUBERNETES_VERSION}"
else
  HYPERKUBE_URL="k8s.gcr.io/hyperkube-amd64:v${KUBERNETES_VERSION}"
fi

Unless I'm missing something.

[jadarsie]

Function extractHyperkube calls pullContainerImage $CLI_TOOL ${HYPERKUBE_URL}.

That clears your concern, right?

[CecileRobertMichon]

lgtm

[jackfrancis]

/lgtm

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