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Do not delay min/maxReplicas propagation from HRA to RD due to caching
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As part of #282, I have introduced some caching mechanism to avoid excessive GitHub API calls due to the autoscaling calculation involving GitHub API calls is executed on each Webhook event.

Apparently, it was saving the wrong value in the cache- The value was one after applying `HRA.Spec.{Max,Min}Replicas` so manual changes to {Max,Min}Replicas doesn't affect RunnerDeployment.Spec.Replicas until the cache expires. This isn't what I had wanted.

This patch fixes that, by changing the value being cached to one before applying {Min,Max}Replicas.

Follow-up for #282
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@mumoshu
mumoshu committed Mar 19, 2021
1 parent d874a5c commit 92fdda9
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Showing 3 changed files with 122 additions and 102 deletions.
57 changes: 13 additions & 44 deletions controllers/autoscaling.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ func getValueAvailableAt(now time.Time, from, to *time.Time, reservedValue int)
return &reservedValue
}

func (r *HorizontalRunnerAutoscalerReconciler) getDesiredReplicasFromCache(hra v1alpha1.HorizontalRunnerAutoscaler) *int {
func (r *HorizontalRunnerAutoscalerReconciler) fetchSuggestedReplicasFromCache(hra v1alpha1.HorizontalRunnerAutoscaler) *int {
var entry *v1alpha1.CacheEntry

for i := range hra.Status.CacheEntries {
Expand Down Expand Up @@ -63,7 +63,7 @@ func (r *HorizontalRunnerAutoscalerReconciler) getDesiredReplicasFromCache(hra v
return nil
}

func (r *HorizontalRunnerAutoscalerReconciler) determineDesiredReplicas(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
func (r *HorizontalRunnerAutoscalerReconciler) suggestDesiredReplicas(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
if hra.Spec.MinReplicas == nil {
return nil, fmt.Errorf("horizontalrunnerautoscaler %s/%s is missing minReplicas", hra.Namespace, hra.Name)
} else if hra.Spec.MaxReplicas == nil {
Expand All @@ -73,20 +73,20 @@ func (r *HorizontalRunnerAutoscalerReconciler) determineDesiredReplicas(rd v1alp
metrics := hra.Spec.Metrics
if len(metrics) == 0 {
if len(hra.Spec.ScaleUpTriggers) == 0 {
return r.calculateReplicasByQueuedAndInProgressWorkflowRuns(rd, hra)
return r.suggestReplicasByQueuedAndInProgressWorkflowRuns(rd, hra)
}

return hra.Spec.MinReplicas, nil
return nil, nil
} else if metrics[0].Type == v1alpha1.AutoscalingMetricTypeTotalNumberOfQueuedAndInProgressWorkflowRuns {
return r.calculateReplicasByQueuedAndInProgressWorkflowRuns(rd, hra)
return r.suggestReplicasByQueuedAndInProgressWorkflowRuns(rd, hra)
} else if metrics[0].Type == v1alpha1.AutoscalingMetricTypePercentageRunnersBusy {
return r.calculateReplicasByPercentageRunnersBusy(rd, hra)
return r.suggestReplicasByPercentageRunnersBusy(rd, hra)
} else {
return nil, fmt.Errorf("validting autoscaling metrics: unsupported metric type %q", metrics[0].Type)
}
}

func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByQueuedAndInProgressWorkflowRuns(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
func (r *HorizontalRunnerAutoscalerReconciler) suggestReplicasByQueuedAndInProgressWorkflowRuns(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {

var repos [][]string
metrics := hra.Spec.Metrics
Expand All @@ -101,7 +101,7 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByQueuedAndInPro
// we assume that the desired replicas should always be `minReplicas + capacityReservedThroughWebhook`.
// See https://github.com/summerwind/actions-runner-controller/issues/377#issuecomment-793372693
if len(metrics) == 0 {
return hra.Spec.MinReplicas, nil
return nil, nil
}

if len(metrics[0].RepositoryNames) == 0 {
Expand Down Expand Up @@ -178,28 +178,10 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByQueuedAndInPro
}
}

minReplicas := *hra.Spec.MinReplicas
maxReplicas := *hra.Spec.MaxReplicas
necessaryReplicas := queued + inProgress

var desiredReplicas int

if necessaryReplicas < minReplicas {
desiredReplicas = minReplicas
} else if necessaryReplicas > maxReplicas {
desiredReplicas = maxReplicas
} else {
desiredReplicas = necessaryReplicas
}

rd.Status.Replicas = &desiredReplicas
replicas := desiredReplicas

r.Log.V(1).Info(
"Calculated desired replicas",
"computed_replicas_desired", desiredReplicas,
"spec_replicas_min", minReplicas,
"spec_replicas_max", maxReplicas,
fmt.Sprintf("Suggested desired replicas of %d by TotalNumberOfQueuedAndInProgressWorkflowRuns", necessaryReplicas),
"workflow_runs_completed", completed,
"workflow_runs_in_progress", inProgress,
"workflow_runs_queued", queued,
Expand All @@ -209,13 +191,11 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByQueuedAndInPro
"horizontal_runner_autoscaler", hra.Name,
)

return &replicas, nil
return &necessaryReplicas, nil
}

func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByPercentageRunnersBusy(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
func (r *HorizontalRunnerAutoscalerReconciler) suggestReplicasByPercentageRunnersBusy(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
ctx := context.Background()
minReplicas := *hra.Spec.MinReplicas
maxReplicas := *hra.Spec.MaxReplicas
metrics := hra.Spec.Metrics[0]
scaleUpThreshold := defaultScaleUpThreshold
scaleDownThreshold := defaultScaleDownThreshold
Expand Down Expand Up @@ -363,21 +343,13 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByPercentageRunn
desiredReplicas = *rd.Spec.Replicas
}

if desiredReplicas < minReplicas {
desiredReplicas = minReplicas
} else if desiredReplicas > maxReplicas {
desiredReplicas = maxReplicas
}

// NOTES for operators:
//
// - num_runners can be as twice as large as replicas_desired_before while
// the runnerdeployment controller is replacing RunnerReplicaSet for runner update.

r.Log.V(1).Info(
"Calculated desired replicas",
"replicas_min", minReplicas,
"replicas_max", maxReplicas,
fmt.Sprintf("Suggested desired replicas of %d by PercentageRunnersBusy", desiredReplicas),
"replicas_desired_before", desiredReplicasBefore,
"replicas_desired", desiredReplicas,
"num_runners", numRunners,
Expand All @@ -391,8 +363,5 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByPercentageRunn
"repository", repository,
)

rd.Status.Replicas = &desiredReplicas
replicas := desiredReplicas

return &replicas, nil
return &desiredReplicas, nil
}
22 changes: 8 additions & 14 deletions controllers/autoscaling_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -224,7 +224,7 @@ func TestDetermineDesiredReplicas_RepositoryRunner(t *testing.T) {
},
}

got, err := h.computeReplicas(rd, hra)
got, _, _, err := h.computeReplicasWithCache(log, metav1Now.Time, rd, hra)
if err != nil {
if tc.err == "" {
t.Fatalf("unexpected error: expected none, got %v", err)
Expand All @@ -234,12 +234,8 @@ func TestDetermineDesiredReplicas_RepositoryRunner(t *testing.T) {
return
}

if got == nil {
t.Fatalf("unexpected value of rs.Spec.Replicas: nil")
}

if *got != tc.want {
t.Errorf("%d: incorrect desired replicas: want %d, got %d", i, tc.want, *got)
if got != tc.want {
t.Errorf("%d: incorrect desired replicas: want %d, got %d", i, tc.want, got)
}
})
}
Expand Down Expand Up @@ -424,6 +420,8 @@ func TestDetermineDesiredReplicas_OrganizationalRunner(t *testing.T) {
_ = v1alpha1.AddToScheme(scheme)

t.Run(fmt.Sprintf("case %d", i), func(t *testing.T) {
t.Helper()

server := fake.NewServer(
fake.WithListRepositoryWorkflowRunsResponse(200, tc.workflowRuns, tc.workflowRuns_queued, tc.workflowRuns_in_progress),
fake.WithListWorkflowJobsResponse(200, tc.workflowJobs),
Expand Down Expand Up @@ -485,7 +483,7 @@ func TestDetermineDesiredReplicas_OrganizationalRunner(t *testing.T) {
},
}

got, err := h.computeReplicas(rd, hra)
got, _, _, err := h.computeReplicasWithCache(log, metav1Now.Time, rd, hra)
if err != nil {
if tc.err == "" {
t.Fatalf("unexpected error: expected none, got %v", err)
Expand All @@ -495,12 +493,8 @@ func TestDetermineDesiredReplicas_OrganizationalRunner(t *testing.T) {
return
}

if got == nil {
t.Fatalf("unexpected value of rs.Spec.Replicas: nil, wanted %v", tc.want)
}

if *got != tc.want {
t.Errorf("%d: incorrect desired replicas: want %d, got %d", i, tc.want, *got)
if got != tc.want {
t.Errorf("%d: incorrect desired replicas: want %d, got %d", i, tc.want, got)
}
})
}
Expand Down

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