Harness follows standard Kubernetes behavior during rollback. See kubectl rollout undo.
Scaling and Rollback
Each time Harness deploys, the deployment gets new replicas that get scaled up and the old replicas are scaled down.
By default, Kubernetes keeps the last 10 revisions as ReplicaSets.
When Harness performs rollback it identifies which revision number to use (
rollback-to). Harness identifies that last successful ReplicaSet, and selects it to be scaled up.
Rollback and Artifacts
The artifact(s) used for the replicas that are scaled up as part of rollback are simply the artifact(s) from the time that version was deployed.
In the case of Blue/Green, the resources are not versioned because a Blue/Green deployment uses rapid rollback: network traffic is simply routed back to the original instances.
You do not need to redeploy previous versions of the service/artifact and the instances that comprised their environment.
You can add a Rollback Deployment command to the Rollback Steps in your Workflow to roll back the workloads deployed by the Rollout Deployment step.
Simply add this command to the Rollback Steps in a Workflow where you want to initiate a rollback. Note that this command applies to the deployments of the Rollout Deployment command, and not the Apply Step command.