Platform & DevOps·Traffic into and inside the cluster
the instance is taken out of rotation but its open connections are allowed to finish, instead of being cut mid-response.
Connection draining
Also calledderegistration delay, graceful removal
Stopping new connections to a backend being removed while letting existing ones complete, up to a timeout. It is the load balancer's half of a clean shutdown, and it must overlap with the workload's own grace period or requests are dropped in the gap. Long-lived connections — websockets, streaming, gRPC — are where a drain timeout tuned for short requests visibly fails.