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Onechart concepts

"One chart to rule them all"

A generic Helm chart for your application deployments. Because no one can remember the Kubernetes yaml syntax.

The Yaml

Kubernetes has a powerful deployment manifest, or "the yaml" as people often call it.

It allows for great flexibility with its many options and knobs, but that also means that it requires extensive boilerplate to get started.

The bigger issue is that it's not easy to piece together the needed Kubernetes Deployment, Service and Ingress objects, as there is no go-to place besides the Kubernetes documentation.

How to get started with Kubernetes yamls

Most people copy it from somewhere.

If they need to extend it with new features, they search and copy that snippet too. When they start a new project, they copy their proven yamls.

At some point, they want to make it more clever, support variables, apply pieces conditionally, they come up with some templating solution.

This scales to a certain point, but there has to be a better way.

And you keep hearing about Helm, don't you?

What is Helm

If you want to deploy well known infrastructure components, like Redis, the community has a solution for you: it's called Helm, and it is a package manager.

There are prepackaged deployment manifests, called Helm Charts, that can get you started with installation and configuration.

Helm charts allow you to progress from a simple two liner that installs a default Redis:

helm repo add bitnami
helm install my-redis bitnami/redis

to more tailored setups:

helm repo add bitnami
helm install my-redis bitnami/redis -f values.yaml

# values.yaml
size: 10Gi

While most infrastructure software have a Helm Chart today, there is no go-to chart to use for your own applications.

You can try writing your own, but that it is even a larger endeavour than piecing your yamls together from blog posts.

Most companies have an internal best practice and reference implementation on how to deploy to Kubernetes. That usually includes a Helm Chart, or a corresponding internal tool.

But if you don't work for a company like that, you can use Gimlet's OneChart Helm Chart for your application.

Use OneChart to deploy your application

OneChart is a generic Helm Chart for web applications. The idea is that most Kubernetes manifest look alike, only very few parts actually change.

The example below deploys your application image, sets environment variables and configures the Kubernetes Ingress domain name:

helm repo add onechart
helm template my-release onechart/onechart -f values.yaml

# values.yaml
repository: my-app
tag: fd803fc
VAR_1: "value 1"
VAR_2: "value 2"
annotations: nginx

Getting started

Add the Onechart Helm repository:

helm repo add onechart

Set your image name and version, the boilerplate is generated.

helm template my-release onechart/onechart \
  --set image.repository=nginx \
  --set image.tag=1.19.3

Deploy with Helm:

helm install my-release onechart/onechart \
  --set image.repository=nginx \
  --set image.tag=1.19.3

Next steps