Helm Templates and Values: Building the Dynamic Cluster

In the previous lesson, we learned that Helm is a "Recipe Book." But to be a master chef, you need to be able to write the recipes yourself.

A Helm Chart isn't just a static folder of YAML files. It's a dynamic program. It uses the Go Templating Language to decide exactly what the final YAML should look like based on the input from your values.yaml file.

Why is this powerful?

• You want an Ingress only in production? Use an if statement.
• You want to spin up 5 sidecar containers for 5 different AI metrics? Use a range loop.
• You want to standardize your labels across 50 different microservices? Use a Named Template.

In this lesson, we will master the Go Templates Syntax, learn the power of Built-in Objects, and build a professional-grade Helm chart from scratch for your AI agents.

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1. The Core Syntax: Double Curlies {{ }}

In Helm, any text inside {{ }} is treated as code.

A. Accessing Values

The most common operation is pulling data from values.yaml. replicas: {{ .Values.replicaCount }}

B. The Dot .

The dot represents the "Scope." In most cases, it refers to the "Root" of the chart.

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2. Built-in Objects: The Magic Variables

Helm gives you several "Searchable" objects that provide data about the environment.

• {{ .Release.Name }}: The name you gave the installation (e.g. my-app-v1).
• {{ .Release.Namespace }}: Where the chart is being installed.
• {{ .Chart.Version }}: The version of the chart itself.
• {{ .Capabilities.KubeVersion }}: The version of Kubernetes running in the cluster.

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3. Conditional Logic: The if Statement

This allows you to create optional resources.

{{- if .Values.ingress.enabled }}
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: {{ .Release.Name }}-ingress
spec:
  rules:
    - host: {{ .Values.ingress.host }}
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: {{ .Release.Name }}-service
                port:
                  number: 80
{{- end }}

Pro Tip: The dash in {{- removes the empty line that the code would otherwise generate, keeping your final YAML clean and readable.

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4. Loops: The range Command

If you have a list of environment variables in your values.yaml, you don't want to type env: 50 times. Use a loop!

In values.yaml:

envVars:
  - name: DB_URL
    value: "localhost:5432"
  - name: MODEL_NAME
    value: "gpt-4"

In Deployment Template:

env:
{{- range .Values.envVars }}
- name: {{ .name }}
  value: {{ .value | quote }}
{{- end }}

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5. Visualizing the Template Engine

graph LR
    V["values.yaml (Configuration)"] -- "Inputs" --> T["Engine (Go Templates)"]
    D["deployment.yaml (Blueprint)"] -- "Inputs" --> T
    
    subgraph "The Transformation"
        T -- "Replace [.Values.x]" --> C["Cleaning whitespace"]
        C -- "Check [if/else]" --> Logic["Final YAML Generation"]
    end
    
    Logic -- "kubectl apply" --> K8s["K8s Control Plane"]

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6. Practical Example: The Global Labels Template

In a large company, every resource must have standard labels (owner, cost-center, env). Instead of repeating this in 50 files, we use a Named Template in _helpers.tpl.

In _helpers.tpl:

{{- define "mychart.labels" -}}
app.kubernetes.io/name: {{ .Chart.Name }}
app.kubernetes.io/instance: {{ .Release.Name }}
owner: ai-team
{{- end }}

In any other template:

metadata:
  labels:
    {{- include "mychart.labels" . | nindent 4 }}

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7. AI Implementation: Templating "Inference Profiles"

When deploying AI models, the resource requirements vary wildly based on the model type.

The Flexible Chart Strategy:

In your values.yaml, define different profiles:

profiles:
  light:
    cpu: 1
    memory: 2Gi
  heavy:
    cpu: 8
    memory: 32Gi
    gpu: 1

In your deployment template:

resources:
  limits:
    cpu: {{ index .Values.profiles .Values.activeProfile "cpu" }}
    memory: {{ index .Values.profiles .Values.activeProfile "memory" }}

This allows you to change a single word in your values (activeProfile: heavy) and your entire deployment architecture shifts to support a massive GPU model.

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8. Summary and Key Takeaways

• Templates: The skeletal structure of your application.
• Values: The flesh and parameters that change per environment.
• Go Templating: USes syntax like if, range, and include.
• Helpers: Store reusable patterns to keep your code DRY (Don't Repeat Yourself).
• Quotes & Indentation: Use functions like quote and nindent to ensure your final YAML is valid.
• Dynamic Power: Build one chart that can be deployed as 1 replica in Dev and 100 replicas in Prod with different identities.

In the next lesson, we will learn how to automate the deployment of these charts using GitHub Actions.

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9. SEO Metadata & Keywords

Focus Keywords: Helm templates tutorial K8s, how to use helm values.yaml, Go templating for Kubernetes, Helm if statement and range loop, writing reusable Helm charts, helm nindent and quote functions.

Meta Description: Go beyond basic YAML. Learn how to master the Helm templating engine to create dynamic, reusable, and intelligent Kubernetes blueprints. Discover how to use logic, loops, and named templates to manage your AI and web services professionally.