5.3 Jsonnet (Optional)
This lab explains how to use jsonnet as manifest format together with Argo CD.
Jsonnet
Jsonnet is a templating language which adds the possibility to programmatically work with the underlying data. It basically is a simple extension of JSON .
Let’s have a look at an example first. The following jsonnet file
{
application1: {
name: "jsonnet-application1",
basepath: "/application/test",
path: self.basepath + "/" + self.name,
},
application2: self.application1 { name: "jsonnet-application2" },
}
will render into:
{
"application1": {
"basepath": "/application/test",
"name": "jsonnet-application1",
"path": "/application/test/jsonnet-application1"
},
"application2": {
"basepath": "/application/test",
"name": "jsonnet-application2",
"path": "/application/test/jsonnet-application2"
}
}
Among many other features, Jsonnet can help to reduce duplications.
Further Docs
Read more about the jsonnet integration in the official documentation
Task 5.3.1: Deploy the simple-example with jsonnet
Let’s first explore the files in your local repository under jsonnet.
Similar to helm, jsonnet allows us to extract parameters into a separate file. In our example we extracted all values to the params.libsonnet file:
{
containerPort: 5000,
image: "quay.io/acend/example-web-go",
name: "argo-jsonnet-example-<username>",
replicas: 1,
servicePort: 5000,
type: "ClusterIP",
}
And the actual template file, containing the kubernetes service and deployment definitions, simple-application.jsonnet file:
local params = import 'params.libsonnet';
[
{
"apiVersion": "v1",
"kind": "Service",
"metadata": {
"name": params.name
},
"spec": {
"ports": [
{
"port": params.servicePort,
"protocol": "TCP",
"targetPort": params.containerPort
}
],
"selector": {
"app": params.name
},
"type": params.type
}
},
{
"apiVersion": "apps/v1",
"kind": "Deployment",
"metadata": {
"name": params.name
},
"spec": {
"replicas": params.replicas,
"revisionHistoryLimit": 3,
"selector": {
"matchLabels": {
"app": params.name
},
},
"template": {
"metadata": {
"labels": {
"app": params.name
}
},
"spec": {
"containers": [
{
"image": params.image,
"name": params.name,
"ports": [
{
"containerPort": params.containerPort
}
]
}
]
}
}
}
}
]
Note the first line, where we tell jsonnet where to get params from.
Ok now replace the <username> placeholder in the params.libsonnet file with your username.
Commit and push the changes to your repository.
Hint
git add jsonnet/params.libsonnet
git commit -m "Change Username"
git push
Create the new Argo CD application.
argocd app create argo-jsonnet-$USER --repo https://gitea.training.cluster.acend.ch/$USER/argocd-training-examples.git --path 'jsonnet' --dest-server https://kubernetes.default.svc --dest-namespace $USER
Sync the application
Hint
To sync (deploy) the resources you can simply click sync in the web UI or execute the following command:
argocd app sync argo-jsonnet-$USER
And verify whether your jsonnet Application definition has be successfully synced.
Task 5.3.2: Autosync and scale up
Tell the application to sync automatically, to enable self-healing and auto-prune
Hint
argocd app set argo-jsonnet-$USER --sync-policy automated
argocd app set argo-jsonnet-$USER --self-heal
argocd app set argo-jsonnet-$USER --auto-prune
Now let’s change the replicacount of the deployment and scale to 2 pods.
Change the replica param in your params.libsonnet to 2
{
containerPort: 5000,
image: "quay.io/acend/example-web-go",
name: "argo-jsonnet-example-<username>",
replicas: 2,
servicePort: 5000,
type: "ClusterIP",
}
Commit and push the changes to your repository.
Hint
git add jsonnet/params.libsonnet
git commit -m "Scale Jsonnet to two"
git push
And verify the result in the ArgoCD Ui or by using the following command, this might take a little while to happen, depending on how many trainees are currently working on the labs. Hint: hit refresh to speed up the process.
kubectl get pod --namespace $USER --watch
Task 5.3.4: Delete the Applications
Delete the applications after you’ve explored the Argo CD Resources and the managed Kubernetes resources.
Hint
argocd app delete argo-jsonnet-$USER