feat: RunnerSet backed by StatefulSet (#629)

* feat: RunnerSet backed by StatefulSet

Unlike a runner deployment, a runner set can manage a set of stateful runners by combining a statefulset and an admission webhook that mutates statefulset-managed pods with required envvars and registration tokens.

Resolves #613
Ref #612

* Upgrade controller-runtime to 0.9.0

* Bump Go to 1.16.x following controller-runtime 0.9.0

* Upgrade kubebuilder to 2.3.2 for updated etcd and apiserver following local setup

* Fix startup failure due to missing LeaderElectionID

* Fix the issue that any pods become unable to start once actions-runner-controller got failed after the mutating webhook has been registered

* Allow force-updating statefulset

* Fix runner container missing work and certs-client volume mounts and DOCKER_HOST and DOCKER_TLS_VERIFY envvars when dockerdWithinRunner=false

* Fix runnerset-controller not applying statefulset.spec.template.spec changes when there were no changes in runnerset spec

* Enable running acceptance tests against arbitrary kind cluster

* RunnerSet supports non-ephemeral runners only today

* fix: docker-build from root Makefile on intel mac

* fix: arch check fixes for mac and ARM

* ci: aligning test data format and patching checks

* fix: removing namespace in test data

* chore: adding more ignores

* chore: removing leading space in shebang

* Re-add metrics to org hra testdata

* Bump cert-manager to v1.1.1 and fix deploy.sh

Co-authored-by: toast-gear <15716903+toast-gear@users.noreply.github.com>
Co-authored-by: Callum James Tait <callum.tait@photobox.com>

controllers/metrics/runnerset.go

@@ -0,0 +1,37 @@
+package metrics
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/summerwind/actions-runner-controller/api/v1alpha1"
+)
+
+const (
+	rsName      = "runnerset"
+	rsNamespace = "namespace"
+)
+
+var (
+	runnerSetMetrics = []prometheus.Collector{
+		runnerSetReplicas,
+	}
+)
+
+var (
+	runnerSetReplicas = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "runnerset_spec_replicas",
+			Help: "replicas of RunnerSet",
+		},
+		[]string{rsName, rsNamespace},
+	)
+)
+
+func SetRunnerSet(rd v1alpha1.RunnerSet) {
+	labels := prometheus.Labels{
+		rsName:      rd.Name,
+		rsNamespace: rd.Namespace,
+	}
+	if rd.Spec.Replicas != nil {
+		runnerSetReplicas.With(labels).Set(float64(*rd.Spec.Replicas))
+	}
+}