Flagger is a progressive delivery Kubernetes operator that automates canary releases, A/B testing, and blue/green deployments by gradually shifting traffic to new application versions while measuring metrics and running conformance tests.
The tool addresses the risk of deploying new software versions to production by implementing a controlled rollout process. It works by taking a standard Kubernetes deployment and creating a series of supporting objects—including additional deployments, services, and ingress or service mesh routes—that enable gradual traffic shifting. Flagger monitors application metrics and runs conformance tests during the rollout, automatically promoting or rolling back the new version based on the results. The operator also tracks changes to ConfigMaps and Secrets referenced by deployments, triggering canary analysis when configuration changes occur alongside code updates.
Teams should adopt Flagger if they run applications on Kubernetes and want to reduce deployment risk through automated progressive delivery. It suits organizations using service meshes like Istio or Linkerd, ingress controllers such as NGINX or Contour, or cloud-native service mesh solutions like AWS App Mesh. The tool integrates with multiple monitoring platforms to analyze metrics during rollouts and supports webhook-based notifications for alerting and custom promotion logic. Flagger is part of the Flux family of GitOps tools and maintains compatibility with Flux-based deployment workflows.
The project shows sustained development activity with regular updates to support new Kubernetes versions and service mesh integrations. Maintenance includes ongoing refinement of canary analysis algorithms and metrics evaluation. The codebase receives contributions addressing edge cases in traffic shifting and integration scenarios. Documentation is actively maintained with examples covering multiple deployment strategies and integration patterns.
