12_03 Helm Chart Exploration - Retail UI¶

Step-01: Goals & Prerequisites¶

Goals * How to pull an OCI chart and explore its source. * How values.yaml feeds into templates/ (and how to trace it). * How to lint and render charts locally before deploying. * Confidence to read any Helm chart like source code, not a black box.

Prerequisites - Helm v3.8+ (OCI support) - (Optional) tree or find, and grep (or rg/ripgrep if you have it) - Your custom values from earlier demos (e.g., values-ui.yaml)

Step-02: Pull & Unpack the Chart (OCI → Local Folder)¶

# Create a workspace and enter it
mkdir -p charts && cd charts

# Pull the UI chart from ECR Public (OCI) and unpack it
helm pull oci://public.ecr.aws/aws-containers/retail-store-sample-ui-chart \
  --version 1.3.0 \
  --untar

# Inspect what got created
ls -la

# Optional: install 'tree' if not present
# Amazon Linux
sudo dnf install tree -y
# macOS
brew install tree

# If you have 'tree':
tree -a || true
````

**Folder Structure (after --untar):**

. └── retail-store-sample-ui-chart ├── .helmignore ├── Chart.yaml ├── README.md ├── templates │ ├── _helpers.tpl │ ├── configmap.yml │ ├── deployment.yaml │ ├── hpa.yaml │ ├── ingress.yaml │ ├── istio-gateway.yml │ ├── istio-virtualservice.yml │ ├── NOTES.txt │ ├── pdb.yaml │ ├── service.yaml │ ├── serviceaccount.yaml │ └── tests │ └── test-connection.yaml └── values.yaml

> If you’re not using **Istio**, the `istio-*.yml` templates typically remain disabled by default.

**Rename for brevity (so we use `ui/` everywhere next):**

```bash
mv retail-store-sample-ui-chart ui

Renaming isn’t required, but it keeps paths short for the rest of this demo.

Step-03: Quick Tour — What Each File Does¶

Typical Helm chart layout (names may vary slightly by publisher):

Chart.yaml – Chart metadata: name, description, type, version (chart), appVersion (app).
values.yaml – Default values shipped with the chart (what gets used when you don’t override).
.helmignore – Files/paths excluded when packaging.
templates/ – Where the K8s YAML templates live:
deployment.yaml – Pod/ReplicaSet spec; references many .Values.* keys.
service.yaml – ClusterIP/LoadBalancer spec and ports.
ingress.yaml – Ingress rules and annotations (if supported).
configmap.yml (or similarly named) – App configuration rendered from values.
_helpers.tpl – Helper templates for names/labels (used across templates).
NOTES.txt – Post-install notes printed by Helm.
Optional: hpa.yaml, serviceaccount.yaml, tests/* (Helm test hooks), istio-*.yml.

Tip: Open values.yaml next to templates/. As you skim templates, note every .Values.* usage and where it maps in values.yaml.

Step-04: Discover the Available Knobs (Chart Defaults)¶

# See the chart’s default values directly from the registry (handy reference)
helm show values oci://public.ecr.aws/aws-containers/retail-store-sample-ui-chart \
  --version 1.3.0 | less

# Also inspect the local copy you just pulled:
cat ui/values.yaml

# (Optional) extra discovery
helm show chart  oci://public.ecr.aws/aws-containers/retail-store-sample-ui-chart --version 1.3.0
helm show readme oci://public.ecr.aws/aws-containers/retail-store-sample-ui-chart --version 1.3.0

Step-05: Lint & Render (No Cluster Needed)¶

If you’re not already in the charts/ folder, run:
cd 12-03-Helm-Chart-Explore/charts

# Lint the chart templates
helm lint ui

# Render the chart locally (defaults)
helm template ui ./ui | less

# Render with your custom values (adjust path if your repo differs)
helm template ui ./ui -f ../retailstore-apps/values-ui.yaml | less

# With custom values + extra debug
helm template ui ./ui -f ../retailstore-apps/values-ui.yaml --debug | less

Goal: See the final K8s YAML that Helm will apply, and verify that custom values are reflected.

Step-06: (Optional) Install Locally From the Unpacked Chart¶

If you want to run this chart from source (not from OCI) to test changes:

# If needed, enter the charts directory
cd 12-03-Helm-Chart-Explore/charts

# Install with a different release name to avoid clobbering your previous demo
helm install ui-local ./ui -f ../retailstore-apps/values-ui.yaml

# Check what got created
helm status ui-local --show-resources
kubectl get pods,svc,ing

Step-07: Quick Value Change (Theme → orange)¶

We’ll make a small change in values-ui.yaml and see it reflected in the rendered manifests (and optionally in a running release).

A) Edit the value¶

app:
  theme: orange

(Edit ../retailstore-apps/values-ui.yaml to the above.)

B) Re-render locally (no cluster needed)¶

helm template ui ./ui -f ../retailstore-apps/values-ui.yaml | less
# See where theme appears
helm template ui ./ui -f ../retailstore-apps/values-ui.yaml | grep -ni theme

C) (Optional) Apply to a running release from the local chart¶

# Install/upgrade a local test release
helm upgrade --install ui-local ./ui -f ../retailstore-apps/values-ui.yaml

# Verify the effective values
helm get values ui-local --all
helm get values ui-local --all | grep theme

# List pods
kubectl get pods

If pods don’t restart automatically (some charts put theme into a ConfigMap/env without changing the pod template), do a quick restart:

# Restart pods reliably via release label (works across naming templates)
kubectl rollout restart deploy -l app.kubernetes.io/instance=ui-local

# Verify
kubectl get pods

Step-08: Helm Tests (If the Chart Ships Them)¶

Some charts include test hooks under templates/tests/*.
In our chart, we have templates/tests/test-connection.yaml.

# Helm test
helm test ui-local

Note: helm test runs after a release is installed and ready.

Step-09: Uninstall ui-local Helm Release¶

# Uninstall
helm uninstall ui-local

Step-10: Handy Reference Commands (Cheat-Sheet)¶

# Pull (OCI) + unpack
helm pull oci://public.ecr.aws/aws-containers/retail-store-sample-ui-chart --version 1.3.0 --untar

# Show chart metadata & defaults from registry
helm show chart  oci://public.ecr.aws/aws-containers/retail-store-sample-ui-chart --version 1.3.0
helm show values oci://public.ecr.aws/aws-containers/retail-store-sample-ui-chart --version 1.3.0
helm show readme oci://public.ecr.aws/aws-containers/retail-store-sample-ui-chart --version 1.3.0

# Lint + render from local source
helm lint ui
helm template ui ./ui -f ../retailstore-apps/values-ui.yaml --debug

# Install from local source (separate release name)
helm install ui-local ./ui -f ../retailstore-apps/values-ui.yaml
helm status ui-local --show-resources