Dependencies & Subcharts

🔥 Vibe Prompt

"Helm chart with Postgres (subchart), Redis (subchart), and my app. Override subchart values."

Chart.yaml with Dependencies

apiVersion: v2
name: fullstack
version: 1.0.0
dependencies:
  - name: postgresql
    version: "12.x"
    repository: https://charts.bitnami.com/bitnami
    condition: postgresql.enabled
  - name: redis
    version: "18.x"
    repository: https://charts.bitnami.com/bitnami
    condition: redis.enabled

# Download dependencies
helm dependency update ./fullstack
# This creates charts/postgresql-12.x.tgz

Override Subchart Values

# values.yaml
postgresql:
  enabled: true
  auth:
    database: myapp
    username: myuser
    password: securepass
  primary:
    resources:
      limits:
        memory: "1Gi"

redis:
  enabled: true
  architecture: standalone
  auth:
    enabled: true
    password: redispass

Global Values

# Shared across all charts
global:
  environment: production
  monitoring:
    enabled: true

Structure with Subcharts

fullstack/
├── Chart.yaml        # Has dependencies
├── values.yaml       # Override subchart values
├── templates/
│   └── app.yaml
└── charts/
    ├── postgresql-12.x.tgz
    └── redis-18.x.tgz

Commands

helm dep update ./fullstack   # Download/update deps
helm dep list ./fullstack     # List dependencies
helm install full ./fullstack # Deploy everything
helm get values full          # See current values

Chapter Summary

• Understand core concepts and principles
• Master implementation methods and techniques
• Familiar with common issues and solutions
• Able to apply in real projects

Further Reading

• Official documentation and API references
• Open source examples on GitHub
• Technical books and online courses
• Community discussions and tech blogs

Implementation Example

Basic Example

# This section provides a complete implementation example

Steps

1. Setup: Configure development environment
2. Data: Prepare required data
3. Implementation: Build core functionality
4. Testing: Verify correctness
5. Optimization: Improve performance

Common Errors

| Error Type | Cause | Solution | |------------|-------|----------| | Compilation | Syntax | Check code syntax | | Runtime | Environment | Verify dependencies installed | | Logic | Algorithm | Step-by-step debugging | | Performance | Efficiency | Use profilers |

Code Example

import sys

def main():
    print("Hello, World!")

if __name__ == "__main__":
    main()

References

• Official documentation
• API reference
• Open source examples
• Community discussions

Dependency Conditions

Conditions control whether a dependency is installed based on a values field.

Condition Syntax

dependencies:
  - name: postgresql
    version: 12.x
    repository: https://charts.bitnami.com/bitnami
    condition: postgresql.enabled

This condition checks .Values.postgresql.enabled. If false, the subchart is skipped.

Values.yaml Control

# Parent chart values.yaml
postgresql:
  enabled: true        # Install PostgreSQL
  postgresqlDatabase: myapp
  postgresqlUsername: myapp
  postgresqlPassword: secret123

redis:
  enabled: false       # Skip Redis

Dependency Tags

Tags group multiple dependencies together for bulk enabling/disabling.

dependencies:
  - name: postgresql
    version: 12.x
    repository: https://charts.bitnami.com/bitnami
    tags:
      - database
  - name: mongodb
    version: 13.x
    repository: https://charts.bitnami.com/bitnami
    tags:
      - database
  - name: redis
    version: 17.x
    repository: https://charts.bitnami.com/bitnami
    tags:
      - cache

Control with Tags

# Enable all database dependencies
tags:
  database: true
  cache: false

Condition vs Tag Precedence

| Setting | Effect | |---------|--------| | condition: redis.enabled and .Values.redis.enabled: false | Subchart skipped | | tags: [cache] and .tags.cache: false | All cache-tagged subcharts skipped | | Both condition and tag | Condition takes precedence |

Parent-Child Value Passing

Values flow from parent to subcharts. Subcharts access parent values with the .global prefix.

Global Values

# Parent values.yaml
global:
  imageRegistry: my-registry.internal
  storageClass: fast-ssd

database:
  enabled: true
  size: 20Gi

Subchart accesses:

• .Values.global.imageRegistry → my-registry.internal
• .Values.size → 20Gi (subchart's own value takes precedence over parent)

Exporting Values from Subcharts

Subcharts can export values that the parent chart reads.

# Subchart values.yaml
exports:
  data:
    url: http://{{ .Release.Name }}-redis:6379
    port: 6379

# Parent chart accesses:
# {{ .Values.redis.exports.data.url }}

Dependency Update Commands

# Add dependencies after editing Chart.yaml
helm dependency update ./mychart

# List dependencies
helm dependency list ./mychart

# Build dependencies (download and lock)
helm dependency build ./mychart

# Delete dependency lock file
rm -f Chart.lock

Practical: Umbrella Chart

An umbrella chart combines multiple subcharts into one deployable unit.

Umbrella Chart Structure

umbrella-app/
  Chart.yaml
  values.yaml
  charts/          # Subcharts live here after update/build
  templates/
    _helpers.tpl
    ingress.yaml   # Shared ingress routing to subcharts
    configmap.yaml # Shared configuration

Umbrella Chart Example

# umbrella-app/Chart.yaml
apiVersion: v2
name: umbrella-app
description: Umbrella chart combining frontend, API, database
type: application
version: 1.0.0
dependencies:
  - name: frontend
    version: 0.2.0
    repository: http://my-chart-repo/
  - name: api
    version: 0.5.0
    repository: http://my-chart-repo/
  - name: postgresql
    version: 12.x
    repository: https://charts.bitnami.com/bitnami
    condition: postgresql.enabled

Summary

Chart dependencies enable composing complex applications from reusable subcharts. Use conditions and tags for fine-grained control over which subcharts deploy.

Key takeaways:

• Dependencies are declared in Chart.yaml and stored in charts/ after update |
• condition enables/disables a single subchart based on a values field |
• tags group multiple subcharts for bulk enable/disable |
• Global values propagate from parent to all subcharts |
• Subcharts can export values for parent charts to consume |
• helm dependency update downloads and locks dependency versions |
• Umbrella charts combine subcharts into single deployable units |
• Chart.lock locks dependency versions for reproducible builds |

What's Next: Hooks and Lifecycle

The next chapter covers Helm hooks and release lifecycle management.