Trove Heartbeats

Trobe has an api, a taskmanager, a conductor, and a guestagent

The task manager that orchestrates tasks, both tasks related to prvisioning infra as well as tasks to be executed on the instance

Agent Communication
Trove agent runs within the guest instance, and listens to message bus (MQ)
GuestAgent runs on every DB instance, and a dedicated MQ topic is used (identified as the instance's id).
It works as RPC, so the task name to execute is passed over the queue to the agent, and the agent runs the appropiate function (basically sounds like they implemented celery like functionality with oslo.rpc, which has been replaced with oslo.messaging)

Heartbeats

The results of heartbeats are stored in the DB https://github.com/openstack/trove/blob/master/trove/guestagent/models.py
The heartbeat model provides a method for determining if an agent is active based on the heartbeat: https://github.com/openstack/trove/blob/master/trove/guestagent/models.py#L90-92

The trove-conducter contains tasks for receiving an incoming service_status message, and saving it as a heatbeat: https://github.com/openstack/trove/blob/master/trove/conductor/manager.py
There is some code for handling messages that may come in out of order, as far as heartbeats go