What is Helm

Kubernetes is good a managing complex structures.
Humans struggle with complexity.
A simple Wordpress site needs the following:
- Deployment for pods.
- A Persistent Volume to store the database.
- A Persistent Volume Claim.
- A Service to expose the web server running in a pod.
- A Secret to store credentials.
- Other items if you want periodic backups etc.
  - We would need a separate yaml file for every object in the above example.
  - Need to run kubectl apply on each yaml file to create each object.
  - You would need to open each yaml file and change each to your needs.
    - Then need to upgrade parts of the application, therefore editing more yaml files.
  - One solution is writing all object declarations in a single yaml file.
    - Makes it difficult to find certain object arguments to change.
Kubernetes doesn’t care about the application being ran.
- All Kubernetes knows is that we declared various objects and try to make each exist in the cluster.
- It looks at all of the little pieces instead.
Helm however takes into consideration the Application, as well as the little pieces. It is known as a package manager for Kubernetes.
- In the previous example with Wordpress, Helm looks at all of those objects and sees them as one big package as a group.
- We don’t tell Helm which objects we want it to touch, just which application to act on.
- Based on the package name, it knows which objects to change and how.
- Imagine downloading each file of a game separately. This is bad. An installer helps to put the files into the right locations.
  - Helm does the same thing for the yaml files and Kubernetes objects as part of the application.
  - Example: helm install wordpress
  - Can customise settings by setting the right values at install time.
    - Don’t need to change values in every yaml file - have a single location where we can state every custom setting. An example is values.yaml.
    - Can upgrade the application with a single command: helm upgrade wordpress - Helm knows what individual objects need changing.
      - Due to Helm keeping track of all of the changes, this allows us to rollback versions by using helm rollback wordpress.
      - To remove the app , we use helm uninstall wordpress.
        
        Removes all objects.
Allows us to treat Kubernetes Applications as apps and don’t need to micromanage each object.