Helm vs Kustomize

Introduction: Kubernetes has revolutionized the way we manage containerized applications, but the complexity of managing configurations can be daunting. Helm and Kustomize are two popular tools in the Kubernetes ecosystem that aim to simplify configuration management. In this blog, we will explore the concepts, use cases, and pros and cons of Helm and Kustomize, along with detailed code examples to demonstrate their functionalities.

What is Helm vs Kustomize?

Helm:

Helm is a package manager for Kubernetes that allows you to define, share, and deploy applications as charts. A Helm chart is a collection of pre-configured Kubernetes manifests, which can include deployments, services, ingress rules, and more. Helm provides templating capabilities, allowing you to dynamically generate manifest files based on configuration values. Let's dive into an example to understand Helm better.

Example: Deploying an Nginx Application using Helm

1. Install Helm: Before using Helm, make sure you have Helm installed on your machine. You can find installation instructions in the Helm documentation.

2. Create a Helm Chart: Create a new Helm chart for deploying an Nginx application by running the following command:

helm create nginx-app

This will generate a directory structure for the Helm chart.

3. Customize the Chart: Edit the values.yaml file in the nginx-app directory to define configuration values for the Nginx deployment. For example, you can set the replica count, image repository, and service type.

4. Install the Chart: Use the following command to install the chart:

helm install nginx nginx-app

This will deploy the Nginx application using the default configuration values specified in the chart. You can customize the installation by providing values through the --set flag.

Kustomize:

Kustomize is a native Kubernetes configuration management tool that allows you to customize and manage Kubernetes manifests using overlays. With Kustomize, you define a base configuration and then apply patches or overlays to customize it for different environments or deployments. Kustomize integrates seamlessly with kubectl, making it a lightweight and straightforward option for managing configurations. Let's explore an example to illustrate the usage of Kustomize.

Example: Customizing Nginx Deployment using Kustomize

1. Create Base Configuration: Create a directory called base and create a deployment.yaml file inside it with the base configuration for the Nginx deployment.

apiVersion: apps/v1

kind: Deployment

metadata:

  name: nginx-deployment

spec:

  replicas: 3

  selector:

    matchLabels:

      app: nginx

  template:

    metadata:

      labels:

        app: nginx

    spec:

      containers:

        - name: nginx

          image: nginx:1.19.4

          ports:

            - containerPort: 80

2. Create Overlays: Create an overlay directory, such as dev, and create a kustomization.yaml file inside it.

apiVersion: kustomize.config.k8s.io/v1beta1

kind: Kustomization

bases:

  - ../../base

patches:

  - deployment-patch.yaml

3. Apply Patches: Create a deployment-patch.yaml file inside the overlay directory to define the customization you want to apply. For example, you can modify the replica count.

apiVersion: apps/v1

kind: Deployment

metadata:

  name: nginx-deployment

spec:

  replicas: 5

4. Apply Customization: Use the following command to apply the customization:

kubectl apply -k dev

This will apply the overlay on top of the base configuration, resulting in a customized deployment with five replicas.

Why Use Helm vs Kustomize?

Helm:

Helm provides several advantages that make it a preferred choice for certain use cases:

1. Package Management: Helm acts as a package manager, allowing you to bundle multiple Kubernetes resources into a single chart. This simplifies the deployment process and enables easy sharing and reusability of charts.

2. Templating: Helm's templating feature enables dynamic generation of Kubernetes manifests. You can use Go templates to customize and parameterize your charts based on configuration values, making them highly flexible.

3. Extensive Ecosystem: Helm has a vibrant and active community, with a vast library of Helm charts available for popular applications. This ecosystem makes it easy to find and deploy applications using Helm, saving valuable time and effort.

Example: Deploying a WordPress Application using Helm

Let's say you want to deploy a WordPress application using Helm. With Helm, you can find a pre-packaged chart for WordPress that includes the necessary resources. Simply run the following command to install the WordPress chart:

helm install wordpress bitnami/wordpress

This will deploy WordPress with all its dependencies, such as a MariaDB database and a service, with default configuration values. You can customize the deployment by providing additional values using the --set flag.

Kustomize:

Kustomize offers its own set of advantages that make it a suitable choice for specific scenarios:

1. Declarative Approach: Kustomize follows a declarative approach to configuration management. You define overlays that specify the differences between the base configuration and the desired customization. This approach makes it easier to manage and maintain configuration changes.

2. Kubernetes Native: Kustomize is an official Kubernetes project and integrates seamlessly with the kubectl command-line tool. This native integration makes it lightweight and avoids the need for additional dependencies.

3. Environment-Specific Configurations: Kustomize shines when it comes to managing environment-specific configurations. You can create overlays for different environments, allowing you to tailor your configuration to each specific context.

Example: Customizing ConfigMaps using Kustomize

Suppose you have a base ConfigMap configuration defined as follows:

apiVersion: v1

kind: ConfigMap

metadata:

  name: my-configmap

data:

  app.properties: |

    app.environment=dev

    app.logging.level=info

    app.timeout.seconds=30

You want to customize the app.environment value for different environments. Using Kustomize, you can create overlays for each environment. For example, create an overlay for the production environment:

apiVersion: kustomize.config.k8s.io/v1beta1

kind: Kustomization

bases:

  - ../base

patches:

  - environment-patch.yaml

Create an environment-patch.yaml file to modify the value:

apiVersion: v1

kind: ConfigMap

metadata:

  name: my-configmap

data:

  app.properties: |

    app.environment=production

By applying the customization with kubectl apply -k, you can generate a ConfigMap with the updated value specifically for the production environment.

How to Use Helm vs Kustomize?

Helm:

To use Helm, follow these steps:

1. Install Helm: Make sure you have Helm installed on your machine. Refer to the Helm documentation for installation instructions.

2. Create a Chart: Use the helm create command to create a new Helm chart skeleton:

helm create my-chart

This will create a directory structure for your chart.

3. Customize the Chart: Modify the values.yaml file in the chart directory to define configuration values for your application.

4. Install the Chart: Use the helm install command to install the chart and deploy your application:

helm install my-release my-chart

Kustomize:

To use Kustomize, follow these steps:

1. Define Base Configuration: Create a directory for your base configuration and specify the desired Kubernetes resources.

2. Create Overlays: Create separate directories for each overlay and customize the base configuration by creating patch files or adding additional resources.

3. Apply Customization: Use the kubectl apply -k command to apply the customization, specifying the path to the overlay directory.

kubectl apply -k overlays/production

When to Use Helm vs Kustomize?

Helm:

Helm is well-suited for the following scenarios:

1. Complex Application Deployments: Helm simplifies the management of large and complex applications by allowing you to package multiple Kubernetes resources into a single chart. This makes it easier to deploy and manage applications with multiple components.

2. Reusability: If you have multiple deployments that share similar components, Helm charts can be easily shared and reused across different environments. This promotes consistency and reduces duplication of effort.

Kustomize:

Kustomize is a good fit for the following situations:

1. Environment-Specific Configurations: When you need to customize your application's configuration based on different environments or deployments, Kustomize allows you to easily manage these variations. It simplifies the process of creating overlays for specific contexts.

2. Kubernetes Native Approach: If you prefer using native Kubernetes tools and want to avoid additional dependencies, Kustomize provides a lightweight and straightforward solution.

Pros and Cons of Helm and Kustomize

Helm:

Pros:

• Templating: Helm's Go templating feature enables dynamic generation of Kubernetes manifests, making it highly flexible.
• Ecosystem: Helm has a large and active community, providing a vast library of charts for popular applications. This saves time and effort in the deployment process.
• Reusability: Helm charts can be shared and reused across different deployments, promoting consistency and reducing duplication.

Cons:

• Complexity: Helm introduces additional complexity, particularly when managing dependencies and versioning.
• Tiller Dependency: Earlier versions of Helm required Tiller, the server-side component, which posed potential security risks. However, Helm v3 eliminated this dependency.

Kustomize:

Pros:

• Declarative Approach: Kustomize follows a declarative approach, making it easy to manage configuration customization using overlays.
• Kubernetes Native: Kustomize is an official Kubernetes project and integrates seamlessly with the kubectl command-line tool.
• Simplicity: Kustomize has minimal dependencies and is lightweight, making it suitable for simpler deployments.

Cons:

• Limited Templating: Kustomize lacks the advanced templating capabilities offered by Helm.
• Smaller Chart Ecosystem: Compared to Helm, Kustomize has a smaller ecosystem of available charts, which may require more manual configuration.

Conclusion: Helm and Kustomize are powerful tools for managing Kubernetes configurations. Helm's focus on package management and templating makes it ideal for complex applications, while Kustomize's declarative approach and native Kubernetes integration make it suitable for environment-specific configurations. Understanding the strengths and weaknesses of each tool allows you to choose the one that best aligns with your specific requirements and development workflow.