Flagger vs Knative

Flagger is a self-hosted Kubernetes operator that automates progressive delivery for applications running on Kubernetes. It gradually shifts traffic to a new version while checking measures such as HTTP or gRPC request success and latency. Deployment approaches include canary releases, A/B testing, and blue/green deployments, routed through an ingress controller or a service mesh compatible with the Kubernetes Gateway API. Built-in checks cover HTTP request success rate and duration; teams can add custom metrics and webhooks for acceptance tests, load tests, or other validation. Release analysis can query systems including Prometheus, Datadog, CloudWatch, New Relic, Graphite, Dynatrace, InfluxDB, and Google Cloud Monitoring. If SLO analysis detects a performance drop, Flagger rolls back the release automatically. Manual controls allow approval, pausing, or resuming deployments, and notifications can go to Slack, Microsoft Teams, Discord, or Rocket. It is configured through Kubernetes custom resources, works with Kubernetes-compatible CI/CD solutions, and can be used with Flux for GitOps canary pipelines. Flagger is Apache 2.0 licensed and free.

Knative is open-source Kubernetes middleware for building, deploying, and managing serverless workloads. Knative Serving handles stateless HTTP services, including deployment, routing, and automatic scaling. Services can scale from zero when idle and rise again with incoming traffic. Serving also supports blue-green deployments, canary releases, and traffic splitting between revisions. Knative Eventing routes asynchronous events through CloudEvents over HTTP. Knative Functions provides a framework for packaging stateless functions as containers. Installation can use a local quickstart or a production setup on an existing Kubernetes cluster with YAML or the Knative Operator. The project runs on Kubernetes across cloud providers and on-premises environments, with Linux, macOS, and Windows listed for installation. Integrations include Istio, Contour, Gateway API, Kafka, RabbitMQ, and NATS. The open-source plan is free, with self-managed Kubernetes deployment.