feat: Add Rollout replicas metrics (#507)

[d-kuro]

close #507

I've added two controller metrics.

• rollout_info_replicas_available
• rollout_info_replicas_unavailable

Rollout is a custom resource and therefore no metrics are provided by kube-state-metrics.
I think the replicas metrics are useful and well used.
I would be happy to provide replicas metrics in the Rollout controller.

[d-kuro]

CI fails...
In my local machine, the test has been a success.

make test
./test/kustomize/test.sh
go test -failfast -covermode=count -coverprofile=coverage.out ./...
ok      github.com/argoproj/argo-rollouts/analysis      2.320s  coverage: 82.6% of statements
?       github.com/argoproj/argo-rollouts/cmd/kubectl-argo-rollouts     [no test files]
?       github.com/argoproj/argo-rollouts/cmd/rollouts-controller       [no test files]
?       github.com/argoproj/argo-rollouts/controller    [no test files]
ok      github.com/argoproj/argo-rollouts/controller/metrics    1.061s  coverage: 91.9% of statements
ok      github.com/argoproj/argo-rollouts/experiments   5.348s  coverage: 88.4% of statements
?       github.com/argoproj/argo-rollouts/hack/gen-crd-spec     [no test files]
?       github.com/argoproj/argo-rollouts/hack/gen-plugin-docs  [no test files]
ok      github.com/argoproj/argo-rollouts/ingress       1.731s  coverage: 81.4% of statements
?       github.com/argoproj/argo-rollouts/metricproviders       [no test files]
ok      github.com/argoproj/argo-rollouts/metricproviders/job   1.835s  coverage: 90.7% of statements
ok      github.com/argoproj/argo-rollouts/metricproviders/kayenta       0.422s  coverage: 91.3% of statements
?       github.com/argoproj/argo-rollouts/metricproviders/mocks [no test files]
ok      github.com/argoproj/argo-rollouts/metricproviders/prometheus    0.651s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/metricproviders/wavefront     0.866s  coverage: 91.2% of statements
ok      github.com/argoproj/argo-rollouts/metricproviders/webmetric     0.870s  coverage: 73.6% of statements
?       github.com/argoproj/argo-rollouts/pkg/apis/rollouts     [no test files]
ok      github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1    0.655s  coverage: 1.5% of statements
ok      github.com/argoproj/argo-rollouts/pkg/apis/rollouts/validation  1.122s  coverage: 94.9% of statements
?       github.com/argoproj/argo-rollouts/pkg/client/clientset/versioned        [no test files]
?       github.com/argoproj/argo-rollouts/pkg/client/clientset/versioned/fake   [no test files]
?       github.com/argoproj/argo-rollouts/pkg/client/clientset/versioned/scheme [no test files]
?       github.com/argoproj/argo-rollouts/pkg/client/clientset/versioned/typed/rollouts/v1alpha1        [no test files]
?       github.com/argoproj/argo-rollouts/pkg/client/clientset/versioned/typed/rollouts/v1alpha1/fake   [no test files]
?       github.com/argoproj/argo-rollouts/pkg/client/informers/externalversions [no test files]
?       github.com/argoproj/argo-rollouts/pkg/client/informers/externalversions/internalinterfaces      [no test files]
?       github.com/argoproj/argo-rollouts/pkg/client/informers/externalversions/rollouts        [no test files]
?       github.com/argoproj/argo-rollouts/pkg/client/informers/externalversions/rollouts/v1alpha1       [no test files]
?       github.com/argoproj/argo-rollouts/pkg/client/listers/rollouts/v1alpha1  [no test files]
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd 2.310s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/abort   1.217s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/create  2.741s  coverage: 80.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/get     4.230s  coverage: 77.7% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/list    8.963s  coverage: 92.7% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/pause   3.326s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/promote 3.248s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/restart 3.567s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/retry   3.764s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/set     3.965s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/terminate       3.375s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/cmd/version 3.342s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/info        3.470s  coverage: 81.2% of statements
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/options     3.577s  coverage: 76.6% of statements
?       github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/options/fake        [no test files]
ok      github.com/argoproj/argo-rollouts/pkg/kubectl-argo-rollouts/viewcontroller      5.410s  coverage: 82.9% of statements
?       github.com/argoproj/argo-rollouts/pkg/signals   [no test files]
ok      github.com/argoproj/argo-rollouts/rollout       16.705s coverage: 88.6% of statements
ok      github.com/argoproj/argo-rollouts/rollout/trafficrouting/alb    3.113s  coverage: 97.7% of statements
ok      github.com/argoproj/argo-rollouts/rollout/trafficrouting/istio  3.268s  coverage: 96.5% of statements
ok      github.com/argoproj/argo-rollouts/rollout/trafficrouting/nginx  2.387s  coverage: 89.7% of statements
ok      github.com/argoproj/argo-rollouts/rollout/trafficrouting/smi    2.505s  coverage: 95.2% of statements
ok      github.com/argoproj/argo-rollouts/service       2.593s  coverage: 72.1% of statements
ok      github.com/argoproj/argo-rollouts/utils/analysis        2.573s  coverage: 98.6% of statements
ok      github.com/argoproj/argo-rollouts/utils/annotations     2.730s  coverage: 97.5% of statements
ok      github.com/argoproj/argo-rollouts/utils/conditions      3.047s  coverage: 95.2% of statements
ok      github.com/argoproj/argo-rollouts/utils/controller      9.014s  coverage: 89.0% of statements
ok      github.com/argoproj/argo-rollouts/utils/defaults        2.496s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/utils/diff    2.415s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/utils/evaluate        3.079s  coverage: 97.6% of statements
ok      github.com/argoproj/argo-rollouts/utils/experiment      3.111s  coverage: 97.4% of statements
ok      github.com/argoproj/argo-rollouts/utils/ingress 3.077s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/utils/json    2.998s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/utils/kubeclientmetrics       2.574s  coverage: 91.6% of statements
ok      github.com/argoproj/argo-rollouts/utils/log     2.394s  coverage: 92.3% of statements
ok      github.com/argoproj/argo-rollouts/utils/metric  2.652s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/utils/replicaset      2.478s  coverage: 89.2% of statements
ok      github.com/argoproj/argo-rollouts/utils/service 2.533s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/utils/template        2.613s  coverage: 100.0% of statements
ok      github.com/argoproj/argo-rollouts/utils/unstructured    2.460s  coverage: 100.0% of statements
?       github.com/argoproj/argo-rollouts/utils/version [no test files]

[mclarke47]

CI failure is probably related to #579

[dthomson25]

LGTM! Thanks for your contribution!