Drop OpenShift 3 support

[astefanutti]

Camel K CRDs currently uses apiextensions.k8s.io/v1beta1, which will be removed in a future release of Kubernetes (currently planned for 1.22): kubernetes/kubernetes#82022.

Work has been done in #1514 to migrate to apiextensions.k8s.io/v1. However, OpenShift 3.11 is based on Kubernetes 1.11 that does not serve apiextensions.k8s.io/v1. It implies it won't be possible to support both Kubernetes 1.22+ and OpenShift 3.11 generally.

OpenShift 3.11 is still used in our CI, with GitHub Actions and Travis, to run integration tests on OpenShift. Before dropping support for OpenShift 3, a solution has to be found to migrate CI to run integration tests on OpenShift 4.

CRC seems the best replacement candidate to setup OpenShift 4. Unfortunately, it relies on virtualisation, and GitHub Actions Linux hosted runners do not support nested virtualisation. Yet it is supported by the macOS runner with actions/runner-images#433. After some experiments, it seems not really stable as I faced crc-org/crc#1331. It may be due to the 7GB memory limit set for the GitHub actions runners, which may be a blocker anyway whenever we'll have to run more demanding workload.

It is unfortunate DIND support has be removed from OpenShift, which is what's used to run vanilla K8s on our CI: openshift/origin#23177.

For reference, the GH Actions workflow used to experiment with CRC:

name: CRC

on:
  push:
    branches: [ master ]
  pull_request:
    branches: [ master ]

jobs:
  crc:
    runs-on: macos-latest

    steps:
      - name: Info
        run: |
          df -h
          sysctl hw.memsize
          sw_vers

      - name: Checkout code
        uses: actions/checkout@v2

      - name: Setup CRC
        env:
          PULL_SECRET: ${{ secrets.PULL_SECRET }}
        run: |
          curl -L https://mirror.openshift.com/pub/openshift-v4/clients/crc/1.11.0/crc-macos-amd64.tar.xz -o crc-macos-amd64.tar.xz
          tar xf crc-macos-amd64.tar.xz
          rm crc-macos-amd64.tar.xz
          cd crc-macos-1.11.0-amd64/

          ./crc setup

          #./crc config set memory 8192
          ./crc config view

          echo $PULL_SECRET > pull.secret
          ./crc start -p pull.secret --log-level debug
          eval $(./crc oc-env)

[tsedmik]

Please, take a look at https://github.com/openshift/release/tree/master/ci-operator. This CI should provide you with OCP 4.x environment for testing in upstream.

[tadayosi]

Should we give this a try?
https://github.com/redhat-et/microshift

[astefanutti]

Should we give this a try?
https://github.com/redhat-et/microshift

Yes, it seems worth trying. It's not very clear what are the differences / limitations compared to vanilla OCP, but the documentation mentions testing as a possible use case:

We believe these properties should also make Microshift a great tool for other use cases such as Kubernetes applications development on resource-constrained systems, scale testing, and provisioning of lightweight Kubernetes control planes.

[tadayosi]

Let me work on it a bit. Another potential option worth evaluating is:
https://github.com/code-ready/snc

[github-actions]

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[tadayosi]

Superceded by #3421