Flagger is a Kubernetes operator that automates the promotion of canary deployments using Istio routing for traffic shifting and Prometheus metrics for canary analysis.

Flagger implements a control loop that gradually shifts traffic to the canary while measuring key performance indicators like HTTP requests success rate, requests average duration and pods health. Based on the KPIs analysis a canary is promoted or aborted and the analysis result is published to Slack.

Flagger takes a Kubernetes deployment and creates a series of objects (Kubernetes deployments, ClusterIP services and Istio virtual services) to drive the canary analysis and promotion.