Use --ephemeral by default

Ref https://github.com/actions-runner-controller/actions-runner-controller/issues/1189

controllers/runner_controller.go

@@ -50,10 +50,12 @@ const (
 	// This is an annotation internal to actions-runner-controller and can change in backward-incompatible ways
 	annotationKeyRegistrationOnly = "actions-runner-controller/registration-only"
 
-	EnvVarOrg        = "RUNNER_ORG"
-	EnvVarRepo       = "RUNNER_REPO"
-	EnvVarEnterprise = "RUNNER_ENTERPRISE"
-	EnvVarEphemeral  = "RUNNER_EPHEMERAL"
+	EnvVarOrg                        = "RUNNER_ORG"
+	EnvVarRepo                       = "RUNNER_REPO"
+	EnvVarEnterprise                 = "RUNNER_ENTERPRISE"
+	EnvVarEphemeral                  = "RUNNER_EPHEMERAL"
+	EnvVarRunnerFeatureFlagEphemeral = "RUNNER_FEATURE_FLAG_EPHEMERAL"
+	EnvVarTrue                       = "true"
 )
 
 // RunnerReconciler reconciles a Runner object
@@ -812,6 +814,12 @@ func newRunnerPod(runnerName string, template corev1.Pod, runnerSpec v1alpha1.Ru
 		}
 	}
 
+	// TODO Remove this once we remove RUNNER_FEATURE_FLAG_EPHEMERAL from runner's entrypoint.sh
+	// and make --ephemeral the default option.
+	if getRunnerEnv(pod, EnvVarRunnerFeatureFlagEphemeral) == "" {
+		setRunnerEnv(pod, EnvVarRunnerFeatureFlagEphemeral, EnvVarTrue)
+	}
+
 	return *pod, nil
 }
 

controllers/runner_graceful_stop.go

@@ -283,6 +283,21 @@ func getRunnerEnv(pod *corev1.Pod, key string) string {
 	return ""
 }
 
+func setRunnerEnv(pod *corev1.Pod, key, value string) {
+	for i := range pod.Spec.Containers {
+		c := pod.Spec.Containers[i]
+		if c.Name == containerName {
+			for j, env := range c.Env {
+				if env.Name == key {
+					pod.Spec.Containers[i].Env[j].Value = value
+					return
+				}
+			}
+			pod.Spec.Containers[i].Env = append(c.Env, corev1.EnvVar{Name: key, Value: value})
+		}
+	}
+}
+
 // unregisterRunner unregisters the runner from GitHub Actions by name.
 //
 // This function returns: