What is Helm for Kubernetes?
Helm is a package manager that automates several major Kubernetes operations, including the creation, packaging, configuration, and deployment of applications. It takes all information about the packaged applications and turns them into charts.
These charts consist of all the information required to run an application on the K8s clusters. These pieces of information include the configuration of the app, the resources to be used, the versions, and more.
In terms of functionality, Helm is similar to the APT packaging tool for Ubuntu Linux without parametrization capabilities. It is necessary because handling K8s operations is a complex and tedious task. This is because for different operations you need to write multiple YAML manifest files.
To avoid this, Helm is used, which provides all the information to Kubernetes in the form of charts, which represent a single package.
How does Helm Work?
Helm and Kubernetes act as client-server application, where Helm acts as the client-side and Kubernetes acts as the server side. There are three primary concepts around the functioning of Helm. These are:
● Chart: This is essentially a pre-configured package with Kubernetes resources and acts as a template. There are multiple such charts with different configurations that can be deployed on the Kubernetes cluster.
● Release: This refers to the Chart that is deployed on the Kubernetes cluster. It is one among the many instances of templates used because of its specific configuration and version that is required by the system.
● Repository: This is the history of charts that are already published and used previously in the K8 system. At any point, this repository can be made available to others and reused if necessary.
There are two versions of Helm that are popularly used - Helm V2 and Helm V3. Here’s how they work:
Helm V2 Client will retrieve the necessary chart from the repository and pass it on to the Tiller. This Tiller will then acquire the chart and advertise it to the Kubernetes API for deployment. The chart will then become a release.
However, the usage of a Tiller led to numerous security issues, and DevOps had to spend a considerable time securing it. So, in V3, the Tiller was removed. Now, Helm would take care of all aspects of package management, and the security aspect is dependent on Kubernetes itself.
Another significant purpose of the Helm is to keep track of the Kubernetes system’s chart lifecycle. This way, at any point, it can roll back to a previous state if necessary.
Structure of a Helm Chart
The Helm Chart consists of files and folders (directories) that serve a distinct purpose. Together, they all form the Helm Chart, which facilitates the operations on Kubernetes.
● chart Directory: This comprises all the charts which possess dependencies and are managed manually. The idea is to retrieve a chart whenever necessary. Without these charts, your current chart will not function properly.
● templates Directory: This directory consists of the template files written in Golang language with the configuration values from values.yaml. These together will result in various Kubernetes manifest files.
● values.yaml: This consists of the default configuration values for the chart. It is essentially all the values necessary for your templates.
● Chart.yaml: This file consists of the metadata of the chart with information such as keywords, search, version, name, and more. It is essentially all the information required when a chart is being packaged.
Besides these, there are other files such as LICENSE, README.md, and requirements.yaml. These include licenses for the chart and information for users of the chart in plain text format. Furthermore, it also enlists the various chart dependencies.
Overall, these files and folders together work as a single Helm Chart that makes Kubernetes operations simple to execute and run.
Launch and Deploy a Helm Chart with Harness
Launching and deploying a Helm Chart can be done with software known as Harness. This can be accomplished with the following steps.
Add a Helm Repository
First, one must add a Helm Repository to the Harness system. Here, details such as Type, Display Name, and Repository URL need to be added. Once the details are given, their validity can be checked and submitted.
Create a Harness Application
Next, the Harness application needs to be created. One would be required to add information such as the name of the application and description.
Create a Harness Environment
Once the application is created, the environment needs to be set up. This involves providing information such as environment name and type. After submitting these details, the infrastructure must be defined by providing the name of the cluster, cloud provider and type, and deployment type.
Create a Harness Service
Now, a service is created for deployment. Here is where the Helm Chart for the same needs to be added. So on the interface, one must share information about the manifest format, Helm repository, version, and chart name and version.
Create a Harness Workflow
The workflow brings together all the previous information, such as the name of the service, environment, and infrastructure definition. Here the type of workflow and the name is also added.
Deploy Helm Chart
With all this information in place, one can simply deploy the Helm Chart.
Benefits of Helm Charts
● Increased Productivity: Helm automates numerous processes of the Kubernetes system and enables developers to perform certain operations with a few clicks. This increases their productivity and removes the necessity to perform repetitive tasks manually.
● Minimized Redundancy: One doesn’t require to create the same manifest files or other resources repeatedly. The charts, once created, can be used whenever necessary.
● Easier Understanding of Kubernetes: Kubernetes is a complex system that takes time to learn. However, with the help of Helm Charts, the time taken is lesser, as the DevOps team needs to concern themselves with operating the charts instead of the different resources the Chart controls.
● Simple Deployment: Deployment on K8 systems is a complex process, but with Helm Charts, it becomes simpler because it automatically understands the different objects, the interdependencies, and the coupling within them. Based on this, the Helm chart can find the best way to deploy an app on the system.
Overall, this is everything you need to know about the Helm Charts and their usage with the Kubernetes system.