Global services

Plural natively supports a concept of global services, e.g. a service that's replicated across a subset of your fleet. This is particular for low level kubernetes system add-ons like ingress controllers, service meshes, cert manager, etc. To define a global service, you first need to define a service that will serve as a source, then use the GlobalService CRD:

apiVersion: deployments.plural.sh/v1alpha1
kind: GlobalService
metadata:
  name: system-upgrade
  namespace: infra
spec:
  tags:
    fabric: edge
  template:
    namespace: system-upgrade
    helm:
      version: '0.1.1'
      chart: system-upgrade-controller
      repository:
        namespace: infra
        name: console

In this specific case, we set up the k3s system upgrade controller on a single cluster, then replicate it using the GlobalService CR to all clusters with the edge: fabric tags. You can also target on kubernetes distribution (eg EKS, AKS, GKE, K3s, etc) or cluster api provider, and we're welcome to other targeting/organization mechanisms as well if those are not sufficient.

Templating within Global Services

A very common problem you'll face when redeploying apps across your fleet is there's cluster-specific data you'll need for each instance of it. Plural supports that through its templating capabilities in the deployment agent on a cluster.

Take an example of setting up external-dns fleet wide. You'll likely need to configure a different domain and iam arn for each cluster. You can leverage the cluster resources built-in metadata field alongside templating to accomplish that easily, like so:

The ideal way to provide metadata is via terraform, since very often that is the source of truth for the initial values. This would be done via code like this:

resource "plural_cluster" "this" {
  name = "eks-prod"

  metadata = jsonencode({
    externaldnsRoleArn = "arn:..."
    domain = "my.domain.com"
    ...
  })
}

That said, you can also do it in yaml using a Cluster custom resource, like what's presented below:

apiVersion: deployments.plural.sh/v1alpha1
kind: Cluster
metadata:
  name: eks-prod
  namespace: infra
spec:
  handle: eks-prod
  tags:
    fabric: eks # add eks tag
  metadata:
    externaldnsRoleArn: arn:...//externaldns
    domain: my.domain.com # can add any nested map structure as metadata