Service Update Pattern

Labels are used to determine which Pods should receive traffic from a service. As we have learned, labels can be dynamically updated for an object, which may affect which Pods continue to connect to a service.

The default update pattern is for a rolling deployment, where new Pods are added, with different versions of an application, and due to automatic load balancing, receive traffic along with previous versions of the application.

Should there be a difference in applications deployed, such that clients would have issues communicating with different versions, you may consider a more specific label for the deployment, which includes a version number. When the deployment creates a new replication controller for the update, the label would not match. Once the new Pods have been created, and perhaps allowed to fully initialize, we would edit the labels for which the Service connects. Traffic would shift to the new and ready version, minimizing client version confusion.