How are frameworks in Mesos notified when tasks scheduled by them finish?

Question

My question is a combination of this and this question on stackoverflow, however, answers there don't help me. I want to know that when in a Mesos cluster a task corresponding to a framework finishes how is the framework scheduler informed of this. The more details (like who initiates the communication, is there a lag?, what all information is included in the message etc..) you can provide better it will be for me. I was not able to find my answer even in the Mesos docs.

Answer 1

Frameworks are notified about tasks with Update event

Update Sent by the master whenever there is a status update that is generated by the executor, agent or master. Status updates should be used by executors to reliably communicate the status of the tasks that they manage. It is crucial that a terminal update (e.g., TASK_FINISHED, TASK_KILLED, TASK_FAILED) is sent by the executor as soon as the task terminates, in order for Mesos to release the resources allocated to the task. It is also the responsibility of the scheduler to explicitly acknowledge the receipt of status updates that are reliably retried. See ACKNOWLEDGE in the Calls section above for the semantics. Note that uuid and data are raw bytes encoded in Base64.

All communication (in V1 API) is imitated by a framework. Framework is calling subscribe method and keep connection open to revive updates. Basically when task is done communication looks like this: Task → Executor → Agent → Master → Framework