Handle offline runners gracefully (#341)

* if a runner pod starts up with an invalid token, it will go in an 
infinite retry loop, appearing as RUNNING from the outside
* normally, this error situation is detected because no corresponding 
runner objects exists in GitHub and the pod will get removed after 
registration timeout
* if the GitHub runner object already existed before - e.g. because a 
finalizer was not properly run as part of a partial Kubernetes crash, 
the runner will always stay in a running mode, even updating the 
registration token will not kill the problematic pod
* introducing RunnerOffline exception that can be handled in runner 
controller and replicaset controller
* as runners are offline when a pod is completed and marked for restart, 
only do additional restart checks if no restart was already decided, 
making code a bit cleaner and saving GitHub API calls after each job 
completion

controllers/runner_controller.go

@@ -244,15 +244,25 @@ func (r *RunnerReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) {
 			return ctrl.Result{}, err
 		}
 
+		// all checks done below only decide whether a restart is needed
+		// if a restart was already decided before, there is no need for the checks
+		// saving API calls and scary log messages
+		if !restart {
+
 			notRegistered := false
+			offline := false
 
 			runnerBusy, err := r.GitHubClient.IsRunnerBusy(ctx, runner.Spec.Enterprise, runner.Spec.Organization, runner.Spec.Repository, runner.Name)
 			if err != nil {
-			var e *github.RunnerNotFound
+				var notFoundException *github.RunnerNotFound
-			if errors.As(err, &e) {
+				var offlineException *github.RunnerOffline
+				if errors.As(err, &notFoundException) {
 					log.V(1).Info("Failed to check if runner is busy. Either this runner has never been successfully registered to GitHub or it still needs more time.", "runnerName", runner.Name)
 
 					notRegistered = true
+				} else if errors.As(err, &offlineException) {
+					log.V(1).Info("GitHub runner appears to be offline, waiting for runner to get online ...", "runnerName", runner.Name)
+					offline = true
 				} else {
 					var e *gogithub.RateLimitError
 					if errors.As(err, &e) {
@@ -300,6 +310,21 @@ func (r *RunnerReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) {
 				restart = true
 			}
 
+			if offline && registrationDidTimeout {
+				log.Info(
+					"Already existing GitHub runner still appears offline . "+
+						"Recreating the pod to see if it resolves the issue. "+
+						"CAUTION: If you see this a lot, you should investigate the root cause. ",
+					"podCreationTimestamp", pod.CreationTimestamp,
+					"currentTime", currentTime,
+					"configuredRegistrationTimeout", registrationTimeout,
+				)
+
+				restart = true
+			}
+
+		}
+
 		// Don't do anything if there's no need to restart the runner
 		if !restart {
 			return ctrl.Result{}, nil

controllers/runnerreplicaset_controller.go

@@ -109,11 +109,15 @@ func (r *RunnerReplicaSetReconciler) Reconcile(req ctrl.Request) (ctrl.Result, e
 			busy, err := r.GitHubClient.IsRunnerBusy(ctx, runner.Spec.Enterprise, runner.Spec.Organization, runner.Spec.Repository, runner.Name)
 			if err != nil {
 				notRegistered := false
+				offline := false
 
-				var e *github.RunnerNotFound
+				var notFoundException *github.RunnerNotFound
-				if errors.As(err, &e) {
+				var offlineException *github.RunnerOffline
-					log.V(1).Info("Failed to check if runner is busy. Either this runner has never been successfully registered to GitHub or has not managed yet to, and therefore we prioritize it for deletion", "runnerName", runner.Name)
+				if errors.As(err, &notFoundException) {
+					log.V(1).Info("Failed to check if runner is busy. Either this runner has never been successfully registered to GitHub or it still needs more time.", "runnerName", runner.Name)
 					notRegistered = true
+				} else if errors.As(err, &offlineException) {
+					offline = true
 				} else {
 					var e *gogithub.RateLimitError
 					if errors.As(err, &e) {
@@ -140,7 +144,7 @@ func (r *RunnerReplicaSetReconciler) Reconcile(req ctrl.Request) (ctrl.Result, e
 				if notRegistered && registrationDidTimeout {
 					log.Info(
 						"Runner failed to register itself to GitHub in timely manner. "+
-							"Recreating the pod to see if it resolves the issue. "+
+							"Marking the runner for scale down. "+
 							"CAUTION: If you see this a lot, you should investigate the root cause. "+
 							"See https://github.com/summerwind/actions-runner-controller/issues/288",
 						"runnerCreationTimestamp", runner.CreationTimestamp,
@@ -150,6 +154,12 @@ func (r *RunnerReplicaSetReconciler) Reconcile(req ctrl.Request) (ctrl.Result, e
 
 					notBusy = append(notBusy, runner)
 				}
+
+				// offline runners should always be a great target for scale down
+				if offline {
+					notBusy = append(notBusy, runner)
+				}
+
 			} else if !busy {
 				notBusy = append(notBusy, runner)
 			}

github/github.go

@@ -310,6 +310,14 @@ func (e *RunnerNotFound) Error() string {
 	return fmt.Sprintf("runner %q not found", e.runnerName)
 }
 
+type RunnerOffline struct {
+	runnerName string
+}
+
+func (e *RunnerOffline) Error() string {
+	return fmt.Sprintf("runner %q offline", e.runnerName)
+}
+
 func (r *Client) IsRunnerBusy(ctx context.Context, enterprise, org, repo, name string) (bool, error) {
 	runners, err := r.ListRunners(ctx, enterprise, org, repo)
 	if err != nil {
@@ -318,6 +326,9 @@ func (r *Client) IsRunnerBusy(ctx context.Context, enterprise, org, repo, name s
 
 	for _, runner := range runners {
 		if runner.GetName() == name {
+			if runner.GetStatus() == "offline" {
+				return false, &RunnerOffline{runnerName: name}
+			}
 			return runner.GetBusy(), nil
 		}
 	}