feat: add configurable PodDisruptionBudget for core deployment (#953)

Author: ppawlowski

helm/flowfuse/README.md

@@ -67,6 +67,9 @@ For other values please refer to the documentation below.
  - `forge.revisionHistoryLimit` global default for number of old ReplicaSets/ControllerRevisions to retain for rollback across all Deployments and StatefulSets managed by this chart (default `10`). Can be overridden per component.
  - `forge.tolerations` allows to configure [tolerations](https://kubernetes.io/docs/concepts/scheduling-eviction/taint-and-toleration/) for the core application deployment (default `[]`)
  - `forge.priorityClassName` allows to set [priorityClassName](https://kubernetes.io/docs/concepts/configuration/pod-priority-preemption/) for all deployments created by this Helm chart (default not set)
+ - `forge.podDisruptionBudget.enabled` enables a [PodDisruptionBudget](https://kubernetes.io/docs/tasks/run-application/configure-pdb/) for the core application deployment (default `false`)
+ - `forge.podDisruptionBudget.minAvailable` minimum number/percentage of pods that must remain available during voluntary disruption (default `1`). Mutually exclusive with `maxUnavailable`.
+ - `forge.podDisruptionBudget.maxUnavailable` maximum number/percentage of pods unavailable during voluntary disruption (default not set). Mutually exclusive with `minAvailable`.
  - `forge.service.type` allows to set the service type for the core application service (default `ClusterIP`)
  - `forge.service.nodePort` allows to set custom nodePort value when `forge.service.type` value is set to `NodePort` (default not set)
  - `forge.logging.level` sets logging level for the Forge app (default: `info` from "info", "error", "debug", "warn", "trace", "fatal")

helm/flowfuse/templates/pdb.yaml

@@ -0,0 +1,22 @@
+{{- if .Values.forge.podDisruptionBudget.enabled }}
+apiVersion: policy/v1
+kind: PodDisruptionBudget
+metadata:
+  name: flowfuse
+  namespace: {{ .Release.Namespace }}
+  labels:
+    {{- include "forge.labels" . | nindent 4 }}
+    {{- with .Values.forge.labels }}
+    {{- toYaml . | nindent 4 }}
+    {{- end }}
+spec:
+  {{- if .Values.forge.podDisruptionBudget.minAvailable }}
+  minAvailable: {{ .Values.forge.podDisruptionBudget.minAvailable }}
+  {{- end }}
+  {{- if .Values.forge.podDisruptionBudget.maxUnavailable }}
+  maxUnavailable: {{ .Values.forge.podDisruptionBudget.maxUnavailable }}
+  {{- end }}
+  selector:
+    matchLabels:
+      {{- include "forge.forgeSelectorLabels" . | nindent 6 }}
+{{- end }}

helm/flowfuse/tests/pdb_test.yaml

@@ -0,0 +1,42 @@
+# yaml-language-server: $schema=https://raw.githubusercontent.com/helm-unittest/helm-unittest/main/schema/helm-testsuite.json
+suite: test forge PodDisruptionBudget
+templates:
+  - pdb.yaml
+set:
+  forge.domain: "chart-unit-tests.com"
+tests:
+  - it: should not render PDB by default
+    asserts:
+      - hasDocuments:
+          count: 0
+
+  - it: should render PDB when enabled with minAvailable
+    set:
+      forge.podDisruptionBudget.enabled: true
+    asserts:
+      - isKind:
+          of: PodDisruptionBudget
+      - equal:
+          path: metadata.name
+          value: flowfuse
+      - equal:
+          path: spec.minAvailable
+          value: 1
+      - notExists:
+          path: spec.maxUnavailable
+      - equal:
+          path: spec.selector.matchLabels.app
+          value: flowforge
+
+  - it: should render maxUnavailable when set
+    set:
+      forge.podDisruptionBudget:
+        enabled: true
+        minAvailable: null
+        maxUnavailable: 1
+    asserts:
+      - equal:
+          path: spec.maxUnavailable
+          value: 1
+      - notExists:
+          path: spec.minAvailable

helm/flowfuse/values.schema.json

@@ -839,6 +839,20 @@
                 "tolerations": {
                     "type": "array"
                 },
+                "podDisruptionBudget": {
+                    "type": "object",
+                    "properties": {
+                        "enabled": {
+                            "type": "boolean"
+                        },
+                        "minAvailable": {
+                            "type": ["integer", "string"]
+                        },
+                        "maxUnavailable": {
+                            "type": ["integer", "string"]
+                        }
+                    }
+                },
                 "logPassthrough": {
                     "type": "boolean"
                 },

helm/flowfuse/values.yaml

@@ -135,6 +135,11 @@ forge:
 
   priorityClassName: ""
 
+  podDisruptionBudget:
+    enabled: false
+    minAvailable: 1
+    # maxUnavailable: 1   # set instead of minAvailable (mutually exclusive)
+
   logPassthrough: false
   customHostname:
     enabled: false