cloudnative wiki

README

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Argo CD

Architecture:

Live example: https://cd.apps.argoproj.io/applications

Below are some of the concepts that are specific to Argo CD.

  • Application A group of Kubernetes resources as defined by a manifest. This is a Custom Resource Definition (CRD).
  • Application source type Which Tool is used to build the application.
  • Target state The desired state of an application, as represented by files in a Git repository.
  • Live state The live state of that application. What pods etc are deployed.
  • Sync status Whether or not the live state matches the target state. Is the deployed application the same as Git says it should be?
  • Sync The process of making an application move to its target state. E.g. by applying changes to a Kubernetes cluster.
  • Sync operation status Whether or not a sync succeeded.
  • Refresh Compare the latest code in Git with the live state. Figure out what is different.
  • Health The health of the application, is it running correctly? Can it serve requests?
  • Tool A tool to create manifests from a directory of files. E.g. Kustomize. See Application Source Type.
  • Configuration management tool See Tool.
  • Configuration management plugin A custom tool.

Gotchas:

  • Argo CD project follows the same support scheme as Kubernetes but for N, N-1 while Kubernetes supports N, N-1, N-2 versions.
  • Argo CD applications, projects and settings can be defined declaratively using Kubernetes manifests. These can be updated using kubectl apply, without needing to touch the argocd command-line tool.
    • Be sure to annotate your ConfigMap resources using the label app.kubernetes.io/part-of: argocd, otherwise Argo CD will not be able to use them.
  • By default, deleting an application will not perform a cascade delete, which would delete its resources. You must add the finalizer if you want this behaviour - which you may well not want.
  • You can create an app that creates other apps, which in turn can create other apps. This allows you to declaratively manage a group of apps that can be deployed and configured in concert.
  • Resources can be excluded from discovery and sync so that Argo CD is unaware of them. For example, events.k8s.io and metrics.k8s.io are always excluded. Use cases:
    • You have temporal issues and you want to exclude problematic resources.
    • There are many of a kind of resources that impacts Argo CD’s performance.
    • Restrict Argo CD’s access to certain kinds of resources, e.g. secrets.

“https://www.youtube.com/watch?v=fQ9846hRiFo”

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