Because of the architectural changes in OpenShift v3, a number of core terms used in OpenShift v2 have changed to better reflect the new model. The following sections highlight some of these important changes. See the Core Concepts topics for more detailed information on the concepts and objects in the new model.
A specific application term or concept no longer exists in OpenShift v3. See the Applications topic for a more in-depth look at this change.
Cartridge vs Image
The easiest replacement term for cartridge in OpenShift v3 is image. An image does more than a cartridge from a packaging perspective, providing better encapsulation and flexibility. But the cartridge concept also included logic for building, deploying, and routing which do not exist in images. In OpenShift v3, these additional needs are met by Source-to-Image (S2I) and templated configuration.
See the Cartridges vs Images topic for more detailed information on these changes.
Project vs Domain
Project is essentially a rename of domain from OpenShift v2. Projects do have several features that are not a part of domains in OpenShift v2.
Gear vs Container
The gear and container terms are interchangeable. Containers have a cleaner mapping of being one-to-one with images, whereas many cartridges could be added to a single gear. With containers, the collocation concept is satisfied by pods.
Master vs Broker
Masters in OpenShift v3 do the job of the broker layer in OpenShift v2. However, the MongoDB and ActiveMQ layers used by the broker in OpenShift v2 are no longer necessary because the key-value store etcd is typically installed with each master.