What are Helm Hooks and how to use them?

Question

Accepted Answer

**Helm Hooks** — events in the release lifecycle (install, upgrade, delete).

**Hook types:**
- **pre-install** — before installation.
- **post-install** — after installation.
- **pre-delete** — before deletion.
- **pre-upgrade** — before upgrade.
- **post-upgrade** — after upgrade.
- **test** — during `helm test`.

**DB Migration hook:**
```yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: {{ .Release.Name }}-migrate
  annotations:
    "helm.sh/hook": pre-upgrade,pre-install
    "helm.sh/hook-weight": "0"
    "helm.sh/hook-delete-policy": hook-succeeded,hook-failed
spec:
  template:
    spec:
      containers:
        - name: migrate
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          command: ["python", "migrate.py"]
          env:
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: {{ .Release.Name }}-db
                  key: url
      restartPolicy: Never
  backoffLimit: 1
```

**Helm Test hook:**
```yaml
apiVersion: v1
kind: Pod
metadata:
  name: {{ .Release.Name }}-test
  annotations:
    "helm.sh/hook": test
spec:
  containers:
    - name: test
      image: curlimages/curl:latest
      command: ["curl", "-f", "http://{{ .Release.Name }}:{{ .Values.service.port }}/health"]
  restartPolicy: Never
```
```bash
helm test my-release
```

**hook-weight:** controls execution order (-1 → 0 → 1).

**hook-delete-policy:** hook-succeeded (delete after success), hook-failed (delete after failure), before-hook-creation (delete before creating new).

DevOps: What are Helm Hooks and how to use them?