Simplify rock testing with containerd

[sed-i]

Currently, the rock testing workflow depends on microk8s registry, skopeo copying the rock to the microk8s local registry, and using kgoss.
Recently we started seeing timeout failures.

observability/.github/workflows/rock-pull-request.yaml

Line 43 in 78f655b

sudo concierge prepare -p microk8s --extra-snaps rockcraft,just,kubectl

However,

• We now use "k8s" rather than "microk8s", so testing this locally means deploying a dedicated VM with conierge prepare -p microk8s instead of -p dev.
• The current approach has many dependencies which are fragmented across this repo and the rock's justfile.
• Use of kgoss with the microk8s registry is yet another level of indirection which complicates things.

We can accomplish the same with a single dependency - containerd - regardless of which k8s is installed, for example:

sudo ctr image import --base-name grafana/agent grafana-agent_0.44.6_amd64.rock
sudo ctr run --net-host -d grafana/agent:0.44.6 ga

# Run regular goss here
curl localhost:12345/agent/api/v1/targets

sudo ctr task kill ga
sudo ctr container rm ga

[sed-i]

The CI step would then look like this:

      - name: Install dependencies
        run: |
          sudo snap install concierge --classic
          # We need the kubectl (classic) snap because `kgoss` needs access to the /tmp directory
          sudo concierge prepare -p crafts --extra-snaps just
          # FIXME: install via the goss snap when available
          goss_base_url="https://github.com/goss-org/goss/releases/latest/download"
          curl -L ${goss_base_url}/goss-linux-amd64 -o /usr/local/bin/goss
          chmod +rx /usr/local/bin/goss
          sudo apt install containerd

          # If we also want nerdctl:
          sudo sh -c 'curl -fsSL https://github.com/containerd/nerdctl/releases/download/v2.2.0/nerdctl-2.2.0-linux-amd64.tar.gz | tar xz -C /usr/bin nerdctl'
          sudo mkdir -p /opt/cni/bin
          sudo sh -c 'curl -fsSL https://github.com/containernetworking/plugins/releases/download/v1.9.0/cni-plugins-linux-amd64-v1.9.0.tgz | tar xz -C /opt/cni/bin'

And in the justfile, the "push ro registry recipe" changes to:

push-to-registry version:
  echo "Pushing $rock_name $version to local registry"
  sudo ctr image import --base-name local/gagent ${version}/${rock_name}_${version}_amd64.rock

The run recipe:

run version=latest_version: (push-to-registry version)
  sudo ctr run --rm -t local/gagent:${version} ga bash

And the test recipe:

test version=latest_version: (push-to-registry version)
  sudo ctr run --net-host -d local/gagent:${version} ga
  goss validate
  sudo ctr task kill ga
  sudo ctr container rm ga

[sed-i]

NOTE: Both of these pass when run locally:

sudo ctr run --net-host -d local/gagent:${version} ga

  sudo nerdctl run -p 12345:12345 -d --name ga local/gagent:${version}

but both fail on the GH runner:

FFF.
Failures/Skipped:
HTTP: healthy: http://127.0.0.1:12345/-/healthy: status:
Error
    Get "http://127.0.0.1:12345/-/healthy": dial tcp 127.0.0.1:12345: connect: connection refused
HTTP: instances: http://127.0.0.1:12345/agent/api/v1/metrics/instances: status:
Error
    Get "http://127.0.0.1:12345/agent/api/v1/metrics/instances": dial tcp 127.0.0.1:12345: connect: connection refused
HTTP: ready: http://127.0.0.1:12345/-/ready: status:
Error
    Get "http://127.0.0.1:12345/-/ready": dial tcp 127.0.0.1:12345: connect: connection refused