Rollout

When Rollout and Autoscle traits are attached to the same service, they two will fight over the number of instances during rollout. Thus, it’s by design that will take over replicas control (specified by .replicas field) during rollout.

Rollout trait implements progressive release process to rollout your app following Canary strategy.

In detail, controller will create a canary of your app , and then gradually shift traffic to the canary while measuring key performance indicators like HTTP requests success rate at the same time.

In this sample, for every 10s, 5% traffic will be shifted to canary from the primary, until the traffic on canary reached 50%. At the mean time, the instance number of canary will automatically scale to replicas: 2 per configured in Appfile.

Based on analysis result of the KPIs during this traffic shifting, a canary will be promoted or aborted if analysis is failed. If promoting, the primary will be upgraded from v1 to v2, and traffic will be fully shifted back to the primary instances. So as result, canary instances will be deleted after the promotion finished.

Note: KubeVela’s Rollout trait is implemented with operator.