Lab11

k8s/HELM.md

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+# Lab 10: Helm Package Manager
+
+**Student**: Selivanov George  
+**Date**: April 2, 2026  
+**Workspace**: DevOps-Core-Course
+
+## 1. Overview
+
+This lab converts Kubernetes manifests from Lab 9 into reusable Helm charts with:
+
+- full templating and centralized values
+- dev/prod environment override files
+- lifecycle hooks (pre-install and post-install)
+- bonus implementation with library chart reuse across two app charts
+
+The implementation is aligned with existing application behavior:
+
+- app container port remains `5000`
+- service port remains `80`
+- readiness/liveness probes remain enabled and use `GET /health`
+- rollout strategy remains rolling update (`maxSurge: 1`, `maxUnavailable: 0`)
+
+## 2. Task-by-Task Solution
+
+### 2.1 Task 1 - Helm Fundamentals (Implemented + execution steps provided)
+
+Helm concepts applied in this lab:
+
+- **Chart**: Package with templates and defaults (`k8s/devops-python-app`)
+- **Release**: Runtime installation instance (example: `myapp-dev`)
+- **Repository**: Dependency source, including local file dependency (`file://../common-lib`)
+- **Values**: Centralized configuration in `values.yaml` and override files
+
+Environment note:
+
+- Helm CLI is not installed in this agent environment, so command execution evidence is prepared as a step-by-step algorithm with highlighted placeholders for your local run outputs.
+
+### 2.2 Task 2 - Create Helm Chart (Implemented)
+
+Primary chart created:
+
+- `k8s/devops-python-app`
+
+Implemented files:
+
+- `Chart.yaml` with metadata and dependency on `common-lib`
+- `values.yaml` with image, replicas, resources, probes, service, env vars
+- `templates/deployment.yaml` converted from `k8s/deployment.yml`
+- `templates/service.yaml` converted from `k8s/service.yml`
+- `templates/_helpers.tpl` (wrapper helpers)
+
+Templated elements:
+
+- image repo/tag/pullPolicy
+- replica count
+- service type/port/targetPort/nodePort
+- resource requests/limits
+- readiness/liveness probes (kept active, configurable)
+- labels/selectors via helper templates
+
+### 2.3 Task 3 - Multi-Environment Support (Implemented)
+
+Environment override files created in primary chart:
+
+- `k8s/devops-python-app/values-dev.yaml`
+- `k8s/devops-python-app/values-prod.yaml`
+
+Differences implemented:
+
+- **Dev**: 1 replica, lower resources, NodePort usage
+- **Prod**: 3 replicas, stronger resources, LoadBalancer type, fixed image tag
+
+### 2.4 Task 4 - Chart Hooks (Implemented)
+
+Hook templates added:
+
+- `k8s/devops-python-app/templates/hooks/pre-install-job.yaml`
+- `k8s/devops-python-app/templates/hooks/post-install-job.yaml`
+
+Hook configuration:
+
+- `pre-install` with weight `-5`
+- `post-install` with weight `5`
+- deletion policy: `hook-succeeded,before-hook-creation`
+- hook commands and image configurable from values (`hooks.*`)
+
+### 2.5 Task 5 - Documentation (This file)
+
+This document includes:
+
+- chart overview and file structure
+- configuration guide
+- hook design and behavior
+- installation, validation, operations commands
+- evidence placeholders to paste your local outputs
+
+### 2.6 Bonus Task - Library Charts (Implemented)
+
+Library chart created:
+
+- `k8s/common-lib`
+
+Second app chart created:
+
+- `k8s/devops-python-app-v2`
+
+Shared templates implemented in library chart:
+
+- `common.name`
+- `common.fullname`
+- `common.chart`
+- `common.selectorLabels`
+- `common.labels`
+
+Both app charts depend on and reference the library chart using:
+
+```yaml
+dependencies:
+  - name: common-lib
+    version: 0.1.0
+    repository: file://../common-lib
+```
+
+## 3. Chart Structure
+
+```text
+k8s/
+  common-lib/
+    Chart.yaml
+    values.yaml
+    templates/
+      _helpers.tpl
+
+  devops-python-app/
+    Chart.yaml
+    values.yaml
+    values-dev.yaml
+    values-prod.yaml
+    templates/
+      _helpers.tpl
+      deployment.yaml
+      service.yaml
+      NOTES.txt
+      hooks/
+        pre-install-job.yaml
+        post-install-job.yaml
+
+  devops-python-app-v2/
+    Chart.yaml
+    values.yaml
+    templates/
+      _helpers.tpl
+      deployment.yaml
+      service.yaml
+```
+
+## 4. Configuration Guide
+
+### 4.1 Important values (primary chart)
+
+| Key | Purpose | Default |
+|---|---|---|
+| `replicaCount` | Number of pod replicas | `3` |
+| `image.repository` | Docker image repository | `ge0s1/devops-python-app` |
+| `image.tag` | Docker image tag | `latest` |
+| `service.type` | Service exposure type | `NodePort` |
+| `service.port` | Service port | `80` |
+| `service.targetPort` | Container target port | `5000` |
+| `service.nodePort` | Fixed node port for NodePort service | `30080` |
+| `resources.*` | CPU and memory requests/limits | from Lab 9 |
+| `readinessProbe.*` | Startup/readiness probe policy | enabled |
+| `livenessProbe.*` | Health/liveness probe policy | enabled |
+| `hooks.enabled` | Enable/disable hook jobs | `true` |
+| `hooks.preInstall.*` | Pre-install hook parameters | configured |
+| `hooks.postInstall.*` | Post-install hook parameters | configured |
+
+### 4.2 Example installs
+
+```bash
+# Build local chart dependencies first
+helm dependency update k8s/devops-python-app
+
+# Render locally
+helm template myapp k8s/devops-python-app
+
+# Install dev
+helm install myapp-dev k8s/devops-python-app -f k8s/devops-python-app/values-dev.yaml
+
+# Install prod
+helm install myapp-prod k8s/devops-python-app -f k8s/devops-python-app/values-prod.yaml
+```
+
+## 5. Hook Implementation Details
+
+Implemented hooks:
+
+1. **Pre-install hook**
+   - resource: Kubernetes Job
+   - annotation: `helm.sh/hook: pre-install`
+   - weight: `-5` (runs first)
+   - use case: preflight validation placeholder
+
+2. **Post-install hook**
+   - resource: Kubernetes Job
+   - annotation: `helm.sh/hook: post-install`
+   - weight: `5` (runs after pre-install and release resources)
+   - use case: post-install smoke-check placeholder
+
+Deletion policy behavior:
+
+- `hook-succeeded`: remove successful hook jobs
+- `before-hook-creation`: remove previous hook instance before creating a new one
+
+## 6. Execution
+
+Run these steps locally and replace placeholders with your real output.
+
+### 6.1 Install and verify Helm (Windows)
+
+```powershell
+# Option A: winget
+winget install Helm.Helm
+
+# Option B: Chocolatey
+choco install kubernetes-helm
+```
+
+### 6.2 Explore a public chart
+
+```powershell
+helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
+helm repo update
+helm show chart prometheus-community/prometheus
+```
+
+### 6.3 Validate local charts
+
+```powershell
+# Primary chart
+helm dependency update k8s/devops-python-app
+helm lint k8s/devops-python-app
+helm template devops-python-app k8s/devops-python-app
+helm install --dry-run --debug devops-python-app-test k8s/devops-python-app
+
+# Bonus second chart
+helm dependency update k8s/devops-python-app-v2
+helm lint k8s/devops-python-app-v2
+helm template devops-python-app-v2 k8s/devops-python-app-v2
+```
+
+### 6.4 Install dev environment
+
+```powershell
+helm install myapp-dev k8s/devops-python-app -f k8s/devops-python-app/values-dev.yaml
+helm list
+kubectl get all -l app.kubernetes.io/instance=myapp-dev
+kubectl get svc
+```
+
+### 6.5 Upgrade release to prod settings
+
+```powershell
+helm upgrade myapp-dev k8s/devops-python-app -f k8s/devops-python-app/values-prod.yaml
+helm get values myapp-dev
+kubectl get deploy,svc -l app.kubernetes.io/instance=myapp-dev
+```
+
+### 6.6 Verify hooks
+
+```powershell
+kubectl get jobs
+kubectl describe job myapp-dev-devops-python-app-pre-install
+kubectl describe job myapp-dev-devops-python-app-post-install
+kubectl logs job/myapp-dev-devops-python-app-pre-install
+kubectl logs job/myapp-dev-devops-python-app-post-install
+```
+
+Note: hook jobs may be auto-deleted after success due to deletion policy. If so, verify via event history and Helm release output.
+
+### 6.7 Bonus verification (library chart + second app)
+
+```powershell
+helm install myapp-v2 k8s/devops-python-app-v2
+helm list
+kubectl get all -l app.kubernetes.io/instance=myapp-v2
+```
+
+## 7. Operations Guide
+
+### 7.1 Install
+
+```bash
+helm install myapp-dev k8s/devops-python-app -f k8s/devops-python-app/values-dev.yaml
+```
+
+### 7.2 Upgrade
+
+```bash
+helm upgrade myapp-dev k8s/devops-python-app -f k8s/devops-python-app/values-prod.yaml
+```
+
+### 7.3 Rollback
+
+```bash
+helm history myapp-dev
+helm rollback myapp-dev 1
+```
+
+### 7.4 Uninstall
+
+```bash
+helm uninstall myapp-dev
+helm uninstall myapp-v2
+```