typed flink data definitions

racket/typed/examples/roles/flink.rkt

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+#lang typed/syndicate/roles
+
+;; ---------------------------------------------------------------------------------------------------
+;; Protocol
+
+#|
+Conversations in the flink dataspace primarily concern two topics: presence and
+task execution.
+
+Presence Protocol
+-----------------
+
+The JobManager (JM) asserts its presence with (job-manager-alive). The operation
+of each TaskManager (TM) is contingent on the presence of a job manager.
+|#
+(assertion-struct job-manager-alive : JobManagerAlive ())
+#|
+In turn, TaskManagers advertise their presence with (task-manager ID slots),
+where ID is a unique id, and slots is a natural number. The number of slots
+dictates how many tasks the TM can take on. To reduce contention, the JM
+should only assign a task to a TM if the TM actually has the resources to
+perform a task.
+|#
+(assertion-struct task-manager : TaskManager (id slots))
+;; an ID is a symbol
+#|
+The resources available to a TM are its associated TaskRunners (TRs). TaskRunners
+assert their presence with (task-runner ID Status), where Status is one of
+  - IDLE, when the TR is not executing a task
+  - (executing ID), when the TR is executing the task with the given ID
+  - OVERLOAD, when the TR has been asked to perform a task before it has
+    finished its previous assignment. For the purposes of this model, it indicates a
+    failure in the protocol; like the exchange between the JM and the TM, a TR
+    should only receive tasks when it is IDLE.
+|#
+(assertion-struct task-runner : TaskRunner (id status))
+(define IDLE 'idle)
+(define OVERLOAD 'overload)
+(define-constructor* (executing : Executing id))
+
+#|
+Task Delegation Protocol
+-----------------------
+
+Task Delegation has two roles, TaskAssigner (TA) and TaskPerformer (TP).
+
+A TaskAssigner asserts the association of a Task with a particular TaskPerformer
+through
+    (task-assignment ID ID Task)
+where the first ID identifies the TP and the second identifies the job.
+|#
+(assertion-struct task-assignment : TaskAssignment (assignee job-id task))
+#|
+A Task is a (task TaskID Work), where Work is one of
+  - (map-work String)
+  - (reduce-work (U TaskID TaskResult) (U TaskID TaskResult)), referring to either the
+    ID of the dependent task or its results. A reduce-work is ready to be executed
+    when it has both results.
+
+A TaskID is a natural number
+
+A TaskResult is a (Hashof String Natural), counting the occurrences of words
+|#
+(define-constructor* (task : Task id desc))
+(define-constructor* (map-work : MapWork data))
+(define-constructor* (reduce-work : ReduceWork left right))
+
+#|
+The TaskPerformer responds to a task-assignment by describing its state with respect
+to that task,
+    (task-state ID ID ID TaskStateDesc)
+where the first ID is that of the TP, the second is that of the job,
+and the third that of the task.
+
+A TaskStateDesc is one of
+  - ACCEPTED, when the TP has the resources to perform the task. (TODO - not sure if this is ever visible, currently)
+  - OVERLOAD, when the TP does not have the resources to perform the task.
+  - RUNNING, indicating that the task is being performed
+  - (finished TaskResult), describing the results
+|#
+(assertion-struct task-state : TaskState (assignee job-id task-id desc))
+(define-constructor* (finished : Finished data))
+(define ACCEPTED 'accepted)
+(define RUNNING 'running)
+#|
+Two instances of the Task Delegation Protocol take place: one between the
+JobManager and the TaskManager, and one between the TaskManager and its
+TaskRunners.
+|#
+
+#|
+Job Submission Protocol
+-----------------------
+
+Finally, Clients submit their jobs to the JobManager by asserting a Job, which is a (job ID (Listof Task)).
+The JobManager then performs the job and, when finished, asserts (job-finished ID TaskResult)
+|#
+(assertion-struct job : Job (id tasks))
+(assertion-struct job-finished : JobFinished (id data))