Helm vs Kustomize: What are the differences?

Introduction Helm and Kustomize are both tools used in Kubernetes for managing and deploying applications. While they have similar goals, there are key differences between them that make them suitable for different use cases.

1. Package Management: Helm is primarily a package manager for Kubernetes, providing a way to manage and deploy complete applications, including multiple resources such as deployments, services, and config maps. It allows users to define and share packages called charts, which can be version controlled and easily installed using Helm commands. On the other hand, Kustomize focuses on managing configurations for Kubernetes resources. It allows users to customize and modify existing resources without needing to create a separate package. Kustomize uses overlays to apply configuration changes to base resources, making it a more flexible option for configuration management.

2. Component Architecture: Helm uses a component-based architecture, where the applications are divided into multiple components or sub-charts. These components can be arranged and composed into a single chart, providing modularity and reusability. This allows for easy management of complex applications with multiple dependencies. In contrast, Kustomize follows a more flat structure, without the concept of components or sub-charts. Users can directly modify and customize the base resources without having to deal with separate components, providing a simpler approach for managing smaller applications or single resources.

3. Upgradability and Rollbacks: Helm provides built-in support for upgrading and rolling back application releases. It tracks the release history, allowing users to easily upgrade to newer versions of the package or roll back to a previous known working state. This makes it convenient for managing application lifecycle in a production environment. On the other hand, Kustomize does not offer native support for upgrades and rollbacks. Users need to manually update the configuration files and apply the changes, making it more suitable for development or testing stages where frequent changes are expected.

4. Templating and Variables: Helm uses a templating language called Go templates to generate Kubernetes manifests based on user-defined values. It supports conditionals, loops, and variables, allowing for dynamic and flexible templating. Helm charts can be easily customized by providing values files or using command-line arguments. Kustomize, on the other hand, does not provide a templating language. It relies on Kubernetes' native JSON patches and YAML anchors to apply configuration changes. While this provides a more declarative approach, it lacks the versatility and extensibility offered by Helm's templating system.

5. Community and Ecosystem: Helm has a larger and more mature community compared to Kustomize, with a wide range of available charts and support from various organizations. It has been widely adopted and has an extensive ecosystem of tools and plugins. Kustomize, being a relatively newer tool, has a smaller community but is steadily gaining traction. It is part of the Kubernetes project and benefits from its growing popularity and support.

6. Ease of Use and Learning Curve: Helm is known for its ease of use and convenient command-line interface, making it quick to learn and get started with. It provides intuitive commands for package management and deployment. Kustomize, on the other hand, has a steeper learning curve due to its more nuanced approach to configuration management. It requires familiarity with Kubernetes resources and YAML syntax to effectively use overlays and customization features.

In summary, Helm is a comprehensive package manager for Kubernetes, providing features such as package management, upgrades, and rollbacks, while Kustomize focuses on configuration management with a more flexible and simpler approach. Helm is suitable for managing complex applications with multiple dependencies, while Kustomize is ideal for smaller applications or customizing individual resources.