From aef554340ff52643c9fbd67afd14fdfa3a0a8b3e Mon Sep 17 00:00:00 2001
From: Anton Gilgur <4970083+agilgur5@users.noreply.github.com>
Date: Mon, 24 Apr 2023 01:47:18 -0400
Subject: [PATCH] feat(argo-workflows): add optional HPA to Server (#1974)

---
 charts/argo-workflows/Chart.yaml              |  4 +-
 charts/argo-workflows/README.md               |  6 +++
 .../server/server-deployment-hpa.yaml         | 45 +++++++++++++++++++
 .../templates/server/server-deployment.yaml   |  2 +
 charts/argo-workflows/values.yaml             | 26 +++++++++++
 5 files changed, 81 insertions(+), 2 deletions(-)
 create mode 100644 charts/argo-workflows/templates/server/server-deployment-hpa.yaml

diff --git a/charts/argo-workflows/Chart.yaml b/charts/argo-workflows/Chart.yaml
index 616f3cc4..fe52da19 100644
--- a/charts/argo-workflows/Chart.yaml
+++ b/charts/argo-workflows/Chart.yaml
@@ -3,7 +3,7 @@ appVersion: v3.4.7
 name: argo-workflows
 description: A Helm chart for Argo Workflows
 type: application
-version: 0.24.1
+version: 0.25.0
 icon: https://raw.githubusercontent.com/argoproj/argo-workflows/master/docs/assets/argo.png
 home: https://github.com/argoproj/argo-helm
 sources:
@@ -14,4 +14,4 @@ maintainers:
 annotations:
   artifacthub.io/changes: |
     - kind: added
-      description: Add option for workflow controller to read all secrets.
+      description: Add optional HPA for Argo Server
diff --git a/charts/argo-workflows/README.md b/charts/argo-workflows/README.md
index 463fa485..50bc7ce9 100644
--- a/charts/argo-workflows/README.md
+++ b/charts/argo-workflows/README.md
@@ -237,6 +237,12 @@ Fields to note:
 | Key | Type | Default | Description |
 |-----|------|---------|-------------|
 | server.affinity | object | `{}` | Assign custom [affinity] rules |
+| server.autoscaling.behavior | object | `{}` | Configures the scaling behavior of the target in both Up and Down directions. This is only available on HPA apiVersion `autoscaling/v2beta2` and newer |
+| server.autoscaling.enabled | bool | `false` | Enable Horizontal Pod Autoscaler ([HPA]) for the Argo Server |
+| server.autoscaling.maxReplicas | int | `5` | Maximum number of replicas for the Argo Server [HPA] |
+| server.autoscaling.minReplicas | int | `1` | Minimum number of replicas for the Argo Server [HPA] |
+| server.autoscaling.targetCPUUtilizationPercentage | int | `50` | Average CPU utilization percentage for the Argo Server [HPA] |
+| server.autoscaling.targetMemoryUtilizationPercentage | int | `50` | Average memory utilization percentage for the Argo Server [HPA] |
 | server.baseHref | string | `"/"` | Value for base href in index.html. Used if the server is running behind reverse proxy under subpath different from /. |
 | server.clusterWorkflowTemplates.enableEditing | bool | `true` | Give the server permissions to edit ClusterWorkflowTemplates. |
 | server.clusterWorkflowTemplates.enabled | bool | `true` | Create a ClusterRole and CRB for the server to access ClusterWorkflowTemplates. |
diff --git a/charts/argo-workflows/templates/server/server-deployment-hpa.yaml b/charts/argo-workflows/templates/server/server-deployment-hpa.yaml
new file mode 100644
index 00000000..ebc45925
--- /dev/null
+++ b/charts/argo-workflows/templates/server/server-deployment-hpa.yaml
@@ -0,0 +1,45 @@
+{{- if and .Values.server.enabled .Values.server.autoscaling.enabled }}
+apiVersion: autoscaling/v2beta1
+kind: HorizontalPodAutoscaler
+metadata:
+  name: {{ template "argo-workflows.server.fullname" . }}
+  namespace: {{ .Release.Namespace | quote }}
+  labels:
+    {{- include "argo-workflows.labels" (dict "context" . "component" .Values.server.name "name" .Values.server.name) | nindent 4 }}
+spec:
+  scaleTargetRef:
+    apiVersion: apps/v1
+    kind: Deployment
+    name: {{ template "argo-workflows.server.fullname" . }}
+  minReplicas: {{ .Values.server.autoscaling.minReplicas }}
+  maxReplicas: {{ .Values.server.autoscaling.maxReplicas }}
+  metrics:
+  {{- with .Values.server.autoscaling.targetMemoryUtilizationPercentage }}
+    - type: Resource
+      resource:
+        name: memory
+        {{- if eq (include "argo-workflows.apiVersion.autoscaling" $) "autoscaling/v2beta1" }}
+        targetAverageUtilization: {{ . }}
+        {{- else }}
+        target:
+          averageUtilization: {{ . }}
+          type: Utilization
+        {{- end }}
+  {{- end }}
+  {{- with .Values.server.autoscaling.targetCPUUtilizationPercentage }}
+    - type: Resource
+      resource:
+        name: cpu
+        {{- if eq (include "argo-workflows.apiVersion.autoscaling" $) "autoscaling/v2beta1" }}
+        targetAverageUtilization: {{ . }}
+        {{- else }}
+        target:
+          averageUtilization: {{ . }}
+          type: Utilization
+        {{- end }}
+  {{- end }}
+  {{- with .Values.server.autoscaling.behavior }}
+  behavior:
+    {{- toYaml . | nindent 4 }}
+  {{- end }}
+{{- end }}
diff --git a/charts/argo-workflows/templates/server/server-deployment.yaml b/charts/argo-workflows/templates/server/server-deployment.yaml
index e9da0a1d..d75933ac 100644
--- a/charts/argo-workflows/templates/server/server-deployment.yaml
+++ b/charts/argo-workflows/templates/server/server-deployment.yaml
@@ -12,7 +12,9 @@ metadata:
     {{- toYaml . | nindent 4 }}
   {{- end }}
 spec:
+  {{- if not .Values.server.autoscaling.enabled }}
   replicas: {{ .Values.server.replicas }}
+  {{- end }}
   selector:
     matchLabels:
       {{- include "argo-workflows.selectorLabels" (dict "context" . "name" .Values.server.name) | nindent 6 }}
diff --git a/charts/argo-workflows/values.yaml b/charts/argo-workflows/values.yaml
index 4783e0a6..2fd166b5 100644
--- a/charts/argo-workflows/values.yaml
+++ b/charts/argo-workflows/values.yaml
@@ -431,6 +431,32 @@ server:
   resources: {}
   # -- The number of server pods to run
   replicas: 1
+  ## Argo Server Horizontal Pod Autoscaler
+  autoscaling:
+    # -- Enable Horizontal Pod Autoscaler ([HPA]) for the Argo Server
+    enabled: false
+    # -- Minimum number of replicas for the Argo Server [HPA]
+    minReplicas: 1
+    # -- Maximum number of replicas for the Argo Server [HPA]
+    maxReplicas: 5
+    # -- Average CPU utilization percentage for the Argo Server [HPA]
+    targetCPUUtilizationPercentage: 50
+    # -- Average memory utilization percentage for the Argo Server [HPA]
+    targetMemoryUtilizationPercentage: 50
+    # -- Configures the scaling behavior of the target in both Up and Down directions.
+    # This is only available on HPA apiVersion `autoscaling/v2beta2` and newer
+    behavior: {}
+      # scaleDown:
+      #  stabilizationWindowSeconds: 300
+      #  policies:
+      #   - type: Pods
+      #     value: 1
+      #     periodSeconds: 180
+      # scaleUp:
+      #   stabilizationWindowSeconds: 300
+      #   policies:
+      #   - type: Pods
+      #     value: 2
   pdb:
     # -- Configure [Pod Disruption Budget] for the server pods
     enabled: false