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02 - GitOps terminology

Domain 2: GitOps Terminology (20%)

The exam is literal about vocabulary, and the OpenGitOps glossary is the reference.

Core objects

Term Definition
State store The system holding desired state, satisfying versioning and immutability. Commonly Git
Desired state The declarative configuration describing what the system should be
Actual state The current running configuration of the managed system
Managed system The environment being reconciled, commonly a Kubernetes cluster but not necessarily
Agent Software running in or adjacent to the managed system that pulls and reconciles
Reconciler The component computing and applying the difference between desired and actual state

Process terms

Term Definition
Reconciliation The process of observing actual state and attempting to make it match desired state
Convergence Actual state moving toward desired state over one or more reconciliations
Divergence or drift A state where actual differs from desired
Drift detection Identifying that divergence exists
Self-healing Automatically correcting drift by reapplying desired state
Sync An agent-specific term for one reconciliation pass
Rollback Returning to a previous desired state by changing the state store

Rollback deserves emphasis. In GitOps, rollback is a change to the state store, usually a revert commit. It is not an imperative operation against the cluster, because any such operation is drift that the next reconciliation removes.

Delivery terms

Term Definition
Continuous integration Automatically building and testing changes as they are merged
Continuous delivery Keeping software in a releasable state, with release requiring a human decision
Continuous deployment Automatically releasing every change that passes the pipeline
Promotion Moving a version from one environment to the next
Environment A distinct instance of the system, such as dev, staging, or production
Release A specific version made available in an environment

GitOps is a continuous delivery approach. It does not require continuous deployment; whether production updates automatically is a policy choice expressed in the state store's approval process.

Repository terms

Term Definition
Application repository Where source code lives, and where CI builds from
Configuration repository (or environment repository) Where deployment manifests live, and what the agent reads
Monorepo One repository holding many components
Polyrepo Many repositories, typically one per component
Base Shared configuration common to all environments
Overlay Environment-specific configuration layered onto a base

Separating application and configuration repositories is the recommended pattern: different change cadence, different reviewers, and no CI loop where a pipeline commits to the repository that triggers it.

Precision the exam tests

  • A state store is not necessarily Git. The principles require versioning and immutability, which Git provides and other systems can too.
  • GitOps is not a tool. Argo CD and Flux are implementations of an approach.
  • Continuous reconciliation is not the same as self-healing. Reconciliation observes and attempts to apply; whether it corrects automatically is configurable, and legitimate designs alert instead for some resources.
  • Drift is not always a fault. It is a divergence, and sometimes the desired state is what is wrong.
  • A pull request is not part of the principles. Review is a widely used practice around GitOps, not a principle of it.

Key terms

  • State store - the versioned, immutable system of record for desired state
  • Managed system - the environment an agent reconciles toward desired state
  • Reconciler - the component computing and applying the difference between desired and actual state
  • Sync - one reconciliation pass performed by an agent
  • Self-healing - automatic correction of drift by reapplying desired state
  • Drift detection - identifying that actual state has diverged from desired state
  • Rollback - returning to a previous desired state by changing the state store rather than the running system
  • Continuous delivery - keeping software releasable, with the release decision made by a human
  • Continuous deployment - releasing every change that passes automated checks, with no human gate
  • Promotion - moving a validated version from one environment to the next
  • Application repository - the repository holding source code, built by CI
  • Configuration repository - the repository holding deployment manifests, read by the GitOps agent
  • Base and overlay - the pattern of shared configuration plus environment-specific layers