#ApplicationSet

#Introduction

ApplicationSet controller is a Kubernetes controller that adds support for an ApplicationSet CustomResourceDefinition (CRD). This controller/CRD enables both automation and greater flexibility managing Argo CD Applications across a large number of clusters and within monorepos, plus it makes self-service usage possible on multitenant Kubernetes clusters.

#Use Cases for ApplicationSet

• Deploying multiple similar applications: When you need to deploy multiple applications with similar configurations, you can use ApplicationSet to reduce redundant configurations. For example, you could use ApplicationSet to deploy multiple microservices that utilize the same template, but have different service names and port numbers.
• Multi - cluster deployments: When you need to deploy the same application across multiple Kubernetes clusters, you can use ApplicationSet to simplify configuration. For instance, you could define an application with ApplicationSet and deploy it across multiple clusters, each using different parameters.
• Dynamically generating applications: When you need to dynamically generate applications based on certain conditions, ApplicationSet can be utilized. For example, you could dynamically generate different application instances based on branches or tags in a Git repository.

#ApplicationSet Example

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: guestbook
spec:
  goTemplate: true
  goTemplateOptions: ["missingkey=error"]
  generators:
  - list:
      elements:
      - cluster: engineering-dev
        url: https://1.2.3.4
      - cluster: engineering-prod
        url: https://2.4.6.8
      - cluster: finance-preprod
        url: https://9.8.7.6
  template:
    metadata:
      name: '{{.cluster}}-guestbook'
    spec:
      project: my-project
      source:
        repoURL: https://github.com/infra-team/cluster-deployments.git
        targetRevision: HEAD
        path: guestbook/{{.cluster}}
      destination:
        server: '{{.url}}'
        namespace: guestbook

#References

• Argo CD ApplicationSet Documentation