Chapter 8. Cartridge Events

OpenShift Enterprise provides a publish and subscribe system that enables a cartridge to act when a developer adds or removes another cartridge in an application.
The Publishes and Subscribes elements in the $cartridge_name/metadata/manifest.yml file detail support for cartridge events.

8.1. Cartridge Event Publishing

When OpenShift Enterprise adds a cartridge to an application, it uses entries in the Publishes section of the $cartridge_name/metadata/manifest.yml file to construct events sent to other cartridges in the application. Define publish events in the manifest.yml file using the following format: 
Publishes:
  <event_name>:
    Type: "<event type>"

Example 8.1. PHP Cartridge Publishes Entry

Publishes:
  get-php-ini:
    Type: "FILESYSTEM:php-ini"
  publish-http-url:
    Type: "NET_TCP:httpd-proxy-info"
  publish-gear-endpoint:
    Type: "NET_TCP:gear-endpoint-info"
For each Publishes entry, OpenShift Enterprise runs a script named $cartridge_name/hooks/$event_name.
OpenShift Enterprise joins lines of output that the hooks/$event_name script writes to stdout with single spaces, then inputs the result to subscriber scripts in other cartridges that match the Type of the publish event. The input to matching subscriber scripts is prefaced with hooks/<event_name> <gear_name> <namespace> <gear_uuid>.