Chapter 13. OpenShift Cartridge Reference

OpenShift cartridges use a hierarchy so that multiple cartridges can be collocated or combined on one gear. This hierarchy consists of a single, primary cartridge, along with a combination of embedded cartridges. The primary cartridge controls the application build life cycle, responds to scaling events, and provides external network accessibility. The embedded cartridges support the primary cartridge and provide additional capabilities to applications.

A good example of this hierarchy is the relationship between the jenkins cartridge and the jenkins-client cartridge. While the jenkins cartridge provides a fully functional browser based Jenkins service, the jenkins-client cartridge is embedded in web applications to offload application builds to an existing Jenkins service. Note that the jenkins-client cartridge by itself provides no value and must be combined with an existing primary cartridge.