Define the lifetime of the system and a component in the system

[oubiwann]

Plan can be iterated in comments ...

[oubiwann]

Registry actions

• Add a system to the registry (supply key)
• Add one or more components to the registry (requires system key; supply component keys)
• Get a system from the registry
• Get all the components of a system from the registry
• Get one component of a system from the registry (requires system key, component key)

The registry is an in-memory database only; it doesn't know how a system should be run, when components should be started, etc.

System lifecycle

• Get system dependencies (topological sort on all system components)
• Startup a system
     * get all the components for the system
     * sort them in reverse topological order
     * iterate, getting their references from the registry
     * set each component's status to "starting"
     * iterate again, calling the component's start method and
     * setting each component's status to "running"
• Shutdown a system (which will stop all the components in reverse start-order)
     * get all the components for the system
     * sort them in topological order
     * iterate, getting their references from the registry
     * set each component's status to "stopping"
     * iterate again, calling the component's stop method and
     * setting each component's status to "terminated"
• Health check of a system
     * check the status of each component
     * for a component whose health check fails, set status to "failing"
     * for a component that has no retry strategy configured, set status to "failed"
     * for a component that does have a retry strategy configured, set status to "retrying"
     * perform strategy
     * if successful, set status to "recovering"
     * if unsuccessful, set status to "failed"
     * if health check passes and current status isn't "running" set to "running"

Also, offer registry wrapping methods:* register component* get all components* get one component

Component lifecycle

• start a component
• stop a component
• set the status of a component
• provide a status on the health of a component