GitOps - CD for cloud native apps

SG

Scott Griffiths / July 08, 2020

3 min read •

GitOps

Tldr;#

  • GitOps is a pull based model that uses Git as the source of truth for application and Infra code. State (Actual vs Desired) is managed via an operator that runs in your kubernetes cluster

What Is It#

GitOps is a paradigm for kubernetes cluster management that uses Git as the source of trust for declarative applications and infrastructure

How Is It Different#

Gitops Is a Pull-Based Model

  • The majority of CI/CD tools available today use a push-based model. A push-based pipeline means that code starts with the CI system and then continues its path through a series of encoded scripts to push changes to the Kubernetes cluster

  • Pull relates to the Operator installed to the cluster that watches the image repository for new updates

Why Use This Approach#

  • GitOps takes full advantage of the move towards immutable infrastructure and declarative container orchestration
  • The approach helps to prevent configuration drift

What Does This Look like#

In a pull pipeline, a Kubernetes Operator reads new images from the image repository from inside of the cluster.

At the centre of the GitOps pattern is the Operator/Agent. It monitors the single source of truth (a config repo) that contains deployment manifest and the actual state in the cluster

GitOps Flow The Operator constantly monitors the Actual State in the cluster, and the Desired State defined in the Repo

Separation of Concerns#

The pipelines can only communicate by Git updates:

  • Whenever Git is updated, the Operator is notified.
  • Whenever the Operator detects drifts, monitoring and alerting tooling are notified

Benefits#

  • Consistency
    • -> Prod states matches your test env’s
  • Reliability
    • -> With Git’s capability to revert/rollback and fork, you gain stable and reproducible rollbacks
  • Developer Experience
    • -> Focus on dev code rather than kubernetes exp (faster onboarding)
  • Standards and Consistency
    • -> One model for apps, Infra and kubernetes changes
  • Enhanced security
    • -> reduced potential to expose credentials outside of your cluster

Gitops 3 Initialisms#

3 initialisms

Argocd in 5 Mins (Example)#

Prerequisites#

To be installed and running

  • Docker / Kubernetes
  • Git
  • Kubectl

Set Alias#

alias k=kubectl

Create Namespace and Install Argocd in Your Local Cluster#

- k create namespace argocd
- git clone https://github.com/marcel-dempers/docker-development-youtube-series.git
- cd docker-development-youtube-series/argo/
- k -n argocd apply -f argo-cd/install.yaml

View Running Pods#

k -n argocd get pods

Set Port Forwarding#

k port-forward svc/argocd-server -n argocd 8080:443

Login to the UI#

Access

k get pods -n argocd -l app.kubernetes.io/name=argocd-server -o name | cut -d'/' -f 2
username: admin
password: (result of query)

Deploy Sample App and View in the UI#

k apply -n argocd -f argo-cd/app.yaml

Delete / Cleanup#

- k -n argocd delete -f install.yaml
- k delete -n argocd -f app.yaml
- k delete namespace argocd

Useful Tools#

References#

@ Discuss on Twitter