Kubernetes # helm

What is Helm?

• Helm is considered a package manager for Kubernetes.

• Helm automates the maintenance of the YAML manifest file for the Kubernetes object.

• Helm keeps track of the version history of every chart installation.

• It helps developers and operators to package, configure and deploy applications and services onto the Kubernetes cluster easily.

• We can deploy versions of the chart.

                                                                                                                                                                                            

 

Why do we need Helm?

• At some point, writing a manifest YAML file for any application in Kubernetes would result in complexity since that application would have a config YAML file, pod YAML file, service YAML file, and many more.

• Helm helps us in managing these tedious time-consuming tasks by allowing us to create charts where we define the Kubernetes objects as packages.

• In short, every Kubernetes object would need a separate YAML file and if we want to make any changes or upgrade our applications we would result up opening each manifest file and making those changes which is a time-consuming task.

                                                                               

                                                                                                          

What are Helm charts?

• A Helm chart can be considered an instruction manual. 

• Charts can be considered as a collection of files.

• Concept of Helm chart:

1. Charts: Template of Kubernetes resources. 
2. Release: A chart deployed to a Kubernetes cluster.
3. Repository: Storage for Helm chart.

                                                                                                   

Difference between Helm2 and Helm3?

Helm 2:

• An extra component (Tiller) was installed in the Kubernetes cluster while using helm2.

• Any action to be performed by the helm, it had to communicate with Tiller and that would communicate with the Kubernetes cluster.

• Rollback to older change: Helm2 compares the current revision(chart) with the previous version(chart) and if the current revision is a manual change, helm2 won't find any revision and its lacks in rollback to older changes.

Helm 3:

• Any user who had tiller access, could perform any action in cluster, which lead to security concerns hence it was removed.

• Roll back to older change: Helm3 uses 3-way strategic merge patch to get the changes and revert back.

Folder Structure:

•  Chart.yaml - All the information about the chart that we are packaging will be added to chart.yaml file

• values.yaml - These files are like the input files where configurable values are stored..helmignore: This is similar to .gitignore file that we use in git.

• Templates: Here we place our manifest files such as deployment.yaml, service.yaml,config.yaml.

• Charts: Here we store other charts.

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