Preliminary Support for Deploying Helm Charts from .tgz URLs

This PR introduces preliminary support for deploying Helm charts directly from URLs pointing to .tgz files, addressing issue #775. While the core functionality is implemented, this PR is still a work in progress and is not ready for merge.

Current Status

Core Features Implemented

• URL Field Addition: A new url field has been added to the HelmChartConfig structure to support .tgz Helm charts sourced from URLs.
• Integration of URL-based Downloads: The Helm chart handling logic has been updated to integrate URL-based chart downloads, allowing users to specify a direct link to a .tgz file.
• Extraction and Caching: Implemented proper extraction and caching mechanisms for .tgz charts to ensure efficient deployment.
• Partial Integration: The new URL feature has been partially integrated with existing Helm deployment workflows, allowing for seamless usage alongside traditional chart sources.

Modified Files

• pkg/helm/chart.go: Added logic to handle URL-based charts, including download and extraction functionality.
• pkg/helm/helm_release.go: Updated release handling to accommodate charts sourced from URLs.
• pkg/helm/pulled_chart.go: Enhanced support for pulling charts from URL sources, ensuring proper validation and error handling.
• pkg/types/helm_chart.go: Introduced the url field and validation logic to ensure that only valid URLs are accepted.
• pkg/utils/tar.go: Added utility functions to handle .tgz files, including extraction and validation.

Checklist

Type of Change

• New feature (non-breaking change that adds functionality)

PR Status

• Corresponding issue exists ([Feature] Ability to handle tgz helm targets #775)
• Motivation and explanation of changes added
• Contribution guidelines followed (needs review)
• Code self-review performed
• Added meaningful comments in code
• Tests added (needs review)
• All tests passing locally (needs review)
• Documentation added (needs review)

Implementation Details

What’s Done

• Support for URL-based .tgz Helm Charts: Users can now specify a URL to a .tgz file directly in their Helm chart configuration.
• Validation Logic:
  • Ensures that only one source (repo, path, git, or url) is specified.
  • Validates that the URL points to a valid .tgz file.
  • Requires a ChartName to be provided when using a URL.
• Core Logic:
  • Implemented download functionality in chart.go to fetch and cache the .tgz files.
  • Integrated .tgz extraction via utils/tar.go to handle the downloaded files properly.

Work in Progress

• Tests: Basic tests have been implemented but are currently failing. Coverage is insufficient for edge cases, and further testing is needed.
• Documentation: The URL feature needs detailed documentation, including configuration examples and usage guidelines.

TODO Before Merge

1. Fix failing tests and ensure 100% coverage for the new functionality.
2. Add examples and documentation for the URL feature.

Testing Summary for PR:

To ensure the functionality of the changes made in this PR, I conducted a comprehensive testing process that involved the following steps:

1. Configuration Validation:

   • Verified the .kluctl.yaml configuration file, which is crucial for defining the deployment targets and their respective environments. The configuration is as follows:

     discriminator: kluctl-examples-simple-helm-{{ target.name }}
     
     targets:
     - name: simple-helm
       args:
         environment: simple-helm
       context: minikube
     
     args:
     - name: environment

   • In this configuration:
     • The discriminator is set to create unique identifiers for the Helm deployments based on the target name.
     • The targets section defines a target named simple-helm, which specifies the environment as simple-helm and uses minikube as the context for deployment.

2. Deployment Configuration:

   • The main deployment configuration is defined in deployment.yml:

     deployments:
     - include: deployment

   • This file includes the deployment configurations from the deployment directory, allowing for modular organization of deployment files.

3. Specific Deployment Details:

   • The deployment/deployment.yml file specifies the details of the NGINX deployment:

     deployments:
     - path: nginx
     
     overrideNamespace: "nginx"

   • Here, the deployment path is set to nginx, and the namespace is overridden to ensure that all resources are created within the nginx namespace.

4. Helm Chart Configuration:

   • The nginx/helm-chart.yml file defines helm chart to be downloaded either from repo or url:

     helmChart:
      # repo: https://charts.bitnami.com/bitnami
      chartName: nginx
      chartVersion: 17.3.2
      skipUpdate: false
      skipPrePull: true
      releaseName: nginx-proxy
      namespace: nginx
      output: helm-rendered.yml #
   
      # This is what we're testing - direct URL support
      tarUrl: https://charts.bitnami.com/bitnami/nginx-15.1.1.tgz

   • This configuration ensures that the NGINX service is of type ClusterIP, and it sets resource limits to manage resource allocation effectively.

5. Helm Values Configuration:

   • The nginx/helm-values.yml file defines resource limits and requests for the NGINX deployment:

     resources:
       limits:
         cpu: 100m
         memory: 128Mi
       requests:
         cpu: 100m
         memory: 128Mi
     
     service:
       type: ClusterIP

   • This configuration ensures that the NGINX service is of type ClusterIP, and it sets resource limits to manage resource allocation effectively.

6. Kustomization Configuration:

   • The nginx/kustomization.yml file is responsible for managing the resources for the NGINX deployment:

     apiVersion: kustomize.config.k8s.io/v1beta1
     kind: Kustomization
     
     resources:
     - namespace.yml
     - helm-rendered.yml # this file is auto-generated at deploy time

   • This file includes the namespace.yml and a placeholder for helm-rendered.yml, which is generated during the deployment process.

7. Namespace Definition:

   • The nginx/namespace.yml file defines the namespace for the NGINX deployment:

     apiVersion: v1
     kind: Namespace
     metadata:
       name: "nginx"

   • This ensures that all resources related to the NGINX deployment are created within the specified namespace.