This guide walks you through setting up a progressive delivery GitOps pipeline on a Kubernetes cluster.
What is GitOps?
GitOps is a way to do Continuous Delivery, it works by using Git as a source of truth for
declarative infrastructure and workloads. For Kubernetes this means using
git push instead
kubectl create/apply or
GitOps vs CiOps
In a traditional CI/CD pipeline, CD is an implementation extension powered by the continuous integration tooling to promote build artifacts to production. In the GitOps pipeline model, any change to production must be committed in source control (preferable via a pull request) prior to being applied on the cluster. If the entire production state is under version control and described in a single Git repository, when disaster strikes, the whole infrastructure can be quickly restored without rerunning the CI pipelines.
In order to apply the GitOps model to Kubernetes you need three things:
- a Git repository with your workloads definitions in YAML format, Helm charts and any other Kubernetes custom resource that defines your cluster desired state
- a container registry where your CI system pushes immutable images (no latest tags, use semantic versioning or git commit sha)
- a Kubernetes controller that does a two-way synchronization:
- watches for changes in the config repository and applies them to your cluster
- watches the container registry for new images and updates the workload definitions based on deployment policies
What is Progressive Delivery?
Progressive delivery is an umbrella term for advanced deployment patterns like canaries, feature flags and A/B testing. Progressive delivery techniques are used to reduce the risk of introducing a new software version in production by giving app developers and SRE teams a fine-grained control over the blast radius.
A benefit of using canary releases is the ability to do capacity testing of the new version in a production environment with a safe rollback strategy if issues are found. By slowly ramping up the load, you can monitor and capture metrics about how the new version impacts the production environment.