What is Helm?
Helm is a package manager for Kubernetes, often referred to as the "Kubernetes package manager." Just as package managers like apt or yum are used in Linux to manage software packages, Helm manages Kubernetes applications. It simplifies the process of defining, installing, and upgrading even the most complex Kubernetes applications.
Helm uses a packaging format called charts, which are collections of files that describe a related set of Kubernetes resources. This allows developers and operators to package applications along with their dependencies, configuration, and even documentation, making it easier to deploy and manage applications across different environments.
What are Helm Charts?
A Helm Chart is a structured collection of files that describe a set of Kubernetes resources. Charts are used to define, install, and upgrade Kubernetes applications. They contain all the resource definitions necessary to run an application, tool, or service inside a Kubernetes cluster.
Components of a Helm Chart
Chart.yaml: This file contains metadata about the chart, such as the name, version, and description.
Values.yaml: This file allows users to specify default values for the chart's configurable parameters.
Templates: This directory contains the Kubernetes manifest templates that Helm uses to generate the final YAML files for Kubernetes resources.
Charts: This directory can contain dependencies (other charts) required by the chart.
README.md: A readme file that provides an overview and usage instructions for the chart.
Example Chart Structure
mychart/
Chart.yaml
values.yaml
charts/
templates/
README.md
Why is Helm Needed?
Simplified Application Deployment
Helm charts simplify the deployment process by packaging all Kubernetes resources and configuration files into a single chart. This means that deploying an application can be as simple as running a single helm install command. This reduces the complexity and potential for errors that can occur when manually configuring and deploying multiple resources.
Consistency Across Environments
Using Helm ensures that applications are deployed consistently across different environments, such as development, testing, and production. This consistency is achieved by using the same chart for all deployments, with environment-specific values provided through the values.yaml file or command-line overrides.
Version Control and Rollbacks
Helm supports versioning of charts, allowing you to track and manage different versions of your applications. This is particularly useful for rolling back to previous versions in case of issues with a new deployment. Helm makes it easy to revert to a previous version of a chart with a simple helm rollback command.
Dependency Management
Complex applications often have dependencies on other services or applications. Helm charts can specify these dependencies, ensuring that all required components are deployed and configured correctly. Helm handles the installation and management of these dependencies automatically, simplifying the deployment process.
Reusable Templates
Helm charts use Go templating to create reusable templates for Kubernetes manifests. This allows for dynamic configuration of Kubernetes resources based on the values provided in the values.yaml file or through command-line overrides. Templating reduces duplication and makes it easier to manage complex configurations.
Parameterization and Customization
Helm allows you to define default values for your application's parameters in the values.yaml file. These parameters can be easily overridden during deployment, providing flexibility and customization without modifying the chart itself. This makes it easier to adapt applications to different environments and requirements.
Simplified Upgrades
Upgrading an application deployed with Helm is straightforward. You can use the helm upgrade command to apply changes to your application, whether it's updating an image version, modifying configurations, or adding new resources. Helm ensures that these changes are applied consistently and with minimal disruption to the running application.
Helm Use Cases
Application Deployment
Helm is widely used for deploying applications on Kubernetes. It simplifies the process of packaging, deploying, and managing applications, making it easier for developers and operators to work together. Popular applications like Jenkins, Prometheus, and Grafana have official Helm charts, enabling quick and easy deployment on Kubernetes.
Continuous Integration and Continuous Deployment (CI/CD)
Helm plays a crucial role in CI/CD pipelines by automating the deployment and management of applications. CI/CD pipelines can use Helm to package applications, deploy them to different environments, and manage upgrades and rollbacks. This automation reduces the risk of human error and speeds up the deployment process.
Infrastructure as Code (IaC)
Helm charts can be used as part of an Infrastructure as Code (IaC) strategy. By defining Kubernetes resources in Helm charts, you can version control your infrastructure and manage it using the same tools and processes as your application code. This promotes consistency, reproducibility, and automation in your infrastructure management.
Multi-Tenant Environments
In multi-tenant Kubernetes environments, managing resources and configurations for different tenants can be challenging. Helm charts can be used to package and deploy applications with tenant-specific configurations, ensuring isolation and consistency across tenants. This simplifies the management of multi-tenant environments and reduces the risk of configuration drift.
Helm in Action: A Practical Example
To illustrate the power and simplicity of Helm, let's walk through a practical example of deploying a simple web application using a Helm chart.
Step 1: Create a Helm Chart
First, create a new Helm chart for your application:
helm create mywebapp
This command generates a basic chart structure with default templates and configuration files.
Step 2: Define Application Resources
Next, define the Kubernetes resources required by your application in the templates directory. For example, you might create a deployment.yaml file for your application's deployment:
apiVersion: apps/v1
kind: Deployment
metadata:
name: {{ .Values.name }}
spec:
replicas: {{ .Values.replicas }}
selector:
matchLabels:
app: {{ .Values.name }}
template:
metadata:
labels:
app: {{ .Values.name }}
spec:
containers:
- name: {{ .Values.name }}
image: {{ .Values.image }}
ports:
- containerPort: 80
Step 3: Customize Values
Customize the default values in the values.yaml file:
name: mywebapp
replicas: 2
image: mywebapp:latest
Step 4: Deploy the Application
Deploy the application using the Helm chart:
helm install mywebapp ./mywebapp
Helm will use the templates and values to generate the final Kubernetes manifests and apply them to the cluster.
Step 5: Upgrade the Application
To upgrade the application, modify the values in the values.yaml file or override them with command-line arguments, and then run:
helm upgrade mywebapp ./mywebapp
Helm will apply the changes, ensuring a smooth and consistent upgrade process.
Step 6: Rollback if Needed
If something goes wrong with the upgrade, you can easily rollback to the previous version:
helm rollback mywebapp 1
Helm will revert the changes and restore the application to its previous state.
Best Practices for Using Helm
Organize Charts by Application
Organize your Helm charts by application or service. This makes it easier to manage and maintain your charts, especially in large and complex environments.
Use Version Control
Version control your Helm charts and configuration files. This allows you to track changes, collaborate with team members, and revert to previous versions if needed.
Automate Deployments
Integrate Helm into your CI/CD pipelines to automate the deployment and management of your applications. This reduces the risk of human error and speeds up the deployment process.
Leverage Helm Repositories
Use Helm repositories to share and distribute your charts. This makes it easier to manage dependencies, share charts with your team, and use charts from the community.
Follow Kubernetes Best Practices
Follow Kubernetes best practices when creating Helm charts. This includes using resource limits, defining health checks, and following security best practices.
Conclusion
Helm and Helm charts are essential tools for managing Kubernetes applications. They simplify the deployment process, ensure consistency across environments, and provide powerful features for versioning, rollbacks, and dependency management. By using Helm, you can streamline your Kubernetes operations, reduce complexity, and improve the overall reliability and maintainability of your applications.
In future blogs I will elaborate on how to setup argo CD and helm charts for GitOps deployment strategy.