govuk-helm-charts: Adding an App
It has been decided to use Helm v3 to package GOV.UK apps for our Kubernetes platform.
All Helm charts for the apps are located under the helm directory.
Creating an App
After installing Helm v3, it is
typical to use helm create <app_name> to create a template app that is then
customized for a given GOV.UK app.
For a typical non-internet facing app, the helm directory structure is:
├── Chart.yaml
├── templates
│ ├── deployment.yaml
│ ├── service.yaml
│ ├── \_helpers.tpl
│ ├── NOTES.txt
└── values.yaml
For an internet facing app, there will be an additional ingress.yaml template
file to configure the AWS load balancer that will direct traffic to that app.
Operations
After creating an app, the following operations can be done
(note that you need to have AWS credentials loaded e.g.
eval $(gds aws govuk-test-admin)):
- test the config that Helm will generate for Kubernetes:
<chart_directory>$ helm template .
- validate the Helm chart Kubernetes files against the Kubernetes schemas using a plugin such as kubeval:
helm plugin install https://github.com/instrumenta/helm-kubeval
<chart_directory>$ helm kubeval .
If kubeval is using a default Kubernetes schema repository that is [not updated] (https://github.com/instrumenta/kubeval/issues/301) promptly, you can use another repo:
<chart_directory>$ helm kubeval -v 1.20.0 -s \
https://raw.githubusercontent.com/yannh/kubernetes-json-schema/master .
- install the app in the Kubernetes cluster:
<chart_directory>$ helm install <app_name> . -namespace <namespace_to_deploy_to>
- check that the status of the app in the Kubernetes cluster:
helm list --namespace <namespace_where_app_deployed>
- upgrade an existing deployed app:
<chart_directory>$ helm upgrade <app_name> . -namespace <namespace_to_deploy_to>
In the future, the charts will be hosted on a HTTP repository and Helm will retrieve the charts from there.