In the context of Helm and Kubernetes, a Helm release refers to a specific instance of a Helm chart deployed in your Kubernetes cluster. Think of it as the running and configured version of a packaged application within your cluster, created from a blueprint defined by the Helm chart.
1. Breakdown of what a Helm release entails
Deployed Resources: It consists of all Kubernetes resources (Deployments, Services, ConfigMaps, Secrets, etc.) created by installing the Helm chart. These resources are customized with the specific configuration values used for that particular release.
Unique Identity: Each release has a unique name within the namespace it's deployed to, differentiating it from other instances of the same chart. This allows you to manage multiple versions of the application side-by-side.
Version Tracking: Each release also has a revision number, indicating its specific version within the chart's history. This allows you to track changes and roll back to previous versions if needed.
State Management: The release tracks the state of the deployed resources, including their running status and configuration. This allows Helm to perform operations on the release, like upgrades or rollbacks.
2. Key points to remember about Helm releases
One Chart, Many Releases: You can install the same Helm chart multiple times in your cluster, creating different releases with distinct configurations and versions.
Independent Deployments: Each release operates independently, managing its own resources and configuration without affecting other releases in the cluster.
Upgrade and Rollback: You can easily upgrade a release to a newer version of the chart or even roll back to a previous version if something goes wrong.
Management Commands: Helm provides various commands like helm list, helm upgrade, and helm uninstall to manage your releases effectively.
Release name: Choose a descriptive name to easily identify different instances of the same chart.
Configuration customization: Use the values.yaml file to tailor the deployed resources to your specific needs.
3. Release vs. Deployment Chart
It's important to distinguish between a release and a deployment chart:
Deployment chart: The blueprint or template containing the resources and configuration options for an application.
Release: The actual running instance of the deployment chart in your cluster with specific configuration applied.
Think of the chart as the recipe and the release as the cooked dish on your table. You can have multiple dishes (releases) from the same recipe (chart) with different ingredients or variations.
Understanding Helm releases is crucial for effectively deploying and managing applications within your Kubernetes cluster using Helm. By leveraging the concept of releases, you gain flexibility, version control, and ease of management for your deployed applications.