Upgrading containers
In Kubernetes, applications are very easily updated. For this, Kubernetes uses rolling updates, which means that traffic to a container is first drained before the container is replaced. During an upgrade of the application, Kubernetes will deploy an additional Pod and run it through some specified probes.
A probe is a diagnostic that is periodically performed on a Pod to check its status. During the upgrading or creation of a Pod, Kubernetes brings up the additional Pod and makes sure that it passes the liveness and readiness probes.
If the newly created Pod succeeds with both probes, the traffic to a single, old Pod is terminated and traffic to the new Pod is opened. For this termination, Kubernetes uses a termination grace period. During this period, the connection to the load balancer is stopped and active connections are processed successfully, and new traffic is routed to a running Pod. During the 30-second default grace period, the Pod is in a termination...
