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flink: replace a lot of dataflow in job manager with internal events

This commit is contained in:
Sam Caldwell 2020-02-21 15:49:46 -05:00
parent 220d112393
commit 5d5b827535
1 changed files with 69 additions and 45 deletions
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114
racket/syndicate/examples/actor/flink.rkt
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@ -282,30 +282,70 @@ The JobManager then performs the job and, when finished, asserts
;; ---------------------------------------------------------------------------------------------------
;; JobManager
;; assertions used for internal slot-management protocol
(assertion-struct slots (v))
(assertion-struct slot-assignment (who mngr))
;; tid is the TaskID, rid is a unique symbol to a particular request for a slot
(struct request-id (tid rid) #:prefab)
(define (spawn-job-manager)
(spawn
(assert (job-manager-alive))
(log "Job Manager Up")
;; keep track of task managers, how many slots they say are open, and how many tasks we have assigned.
(define/query-hash task-managers (task-manager $id $slots) id slots
#:on-add (log "JM learns that ~a has ~v slots" id slots))
(on-start
(react
;; (Hashof TaskManagerID Nat)
;; to better understand the supply of slots for each task manager, keep track of the number
;; of requested tasks that we have yet to hear back about
(field [requests-in-flight (hash)])
(define (slots-available)
(for/sum ([(id v) (in-hash (task-managers))])
(max 0 (- v (hash-ref (requests-in-flight) id 0)))))
;; ID -> Void
;; mark that we have requested the given task manager to perform a task
(define (take-slot! id)
(requests-in-flight (hash-update (requests-in-flight) id add1 0)))
;; ID -> Void
;; mark that we have heard back from the given manager about a requested task
(define (received-answer! id)
(requests-in-flight (hash-update (requests-in-flight) id sub1)))
;; keep track of task managers, how many slots they say are open, and how many tasks we have assigned.
;; (Hashof TaskManagerID Nat)
(define/query-hash task-managers (task-manager $id $slots) id slots
#:on-add (begin (log "JM learns that ~a has ~v slots" id slots)
#;(requests-in-flight (hash-set (requests-in-flight) id 0))))
(field [waiting-tasks '()] ;; (Listof ID)
[requests-in-flight (hash)] ;; (Hashof ID Nat)
[assignments (hash)]) ;; (Hashof ID ID) request ID to manager ID
;; to better understand the supply of slots for each task manager, keep track of the number
;; of requested tasks that we have yet to hear back about
(define (slots-available)
(for/sum ([(id v) (in-hash (task-managers))])
(max 0 (- v (hash-ref (requests-in-flight) id 0)))))
;; ID -> (U #f ID)
(define (try-take-slot! me)
(define mngr
(for/first ([(id slots) (in-hash (task-managers))]
#:when (positive? (- slots (hash-ref (requests-in-flight) id 0))))
id))
(when mngr
(assignments (hash-set (assignments) me mngr))
(requests-in-flight (hash-update (requests-in-flight) mngr add1 0)))
mngr)
(know (slots (slots-available)))
(during (know (observe (slot-assignment (request-id $tid $who) _)))
(on-start
(react
;; what if one manager gains a slot but another loses one, so n stays the same?
(on (know (slots $n))
#;(log "Dispatcher request ~a learns there are ~a slots" tid n)
(unless (or (zero? n) (hash-has-key? (assignments) who))
(define mngr (try-take-slot! who))
(when mngr
(stop-current-facet
(log "Dispatcher assigns task ~a to ~a" tid mngr)
(react (know (slot-assignment (request-id tid who) mngr)))
(react
(define waiting-for-answer (current-facet-id))
(on (asserted (observe (task-performance mngr (task tid $x) _)))
(react (on (asserted (task-performance mngr (task tid x) _))
(log "Dispatcher sees answer for ~a" tid)
(stop-facet waiting-for-answer))))
(on-stop
(requests-in-flight (hash-update (requests-in-flight) mngr sub1))))))))))
(on-stop (assignments (hash-remove (assignments) who))))))
(during (observe (job-completion $job-id $tasks _))
(log "JM receives job ~a" job-id)
@ -315,14 +355,10 @@ The JobManager then performs the job and, when finished, asserts
[tasks-in-progress 0])
(begin/dataflow
(define slots (slots-available))
(define-values (ts readys)
(split-at/lenient (ready-tasks) slots))
(for ([t ts])
(perform-task t push-results))
(unless (empty? ts)
;; the empty? check may be necessary to avoid a dataflow loop
(ready-tasks readys)))
(unless (empty? (ready-tasks))
(for ([t (ready-tasks)])
(perform-task t push-results))
(ready-tasks '())))
;; Task -> Void
(define (add-ready-task! t)
@ -340,35 +376,23 @@ The JobManager then performs the job and, when finished, asserts
(match-define (task this-id desc) t)
(log "JM begins on task ~a" this-id)
(define (select-a-task-manager)
(react
(field [selection #f])
(begin/dataflow
(unless (selection)
(define mngr
(for/first ([(id slots) (in-hash (task-managers))]
#:when (positive? (- slots (hash-ref (requests-in-flight) id 0))))
id))
(when mngr
(selection mngr)
(take-slot! mngr)
(log "JM assigns task ~a to ~a" this-id mngr)
(stop-current-facet (assign-task mngr)))))))
(define req-id (gensym 'perform-task))
(on (know (slot-assignment (request-id this-id req-id) $mngr))
(assign-task mngr))))
;; ID -> ...
(define (assign-task mngr)
(define this-facet (current-facet-id))
(react
(define this-facet (current-facet-id))
#;(define this-facet (current-facet-id))
(on (retracted (task-manager mngr _))
;; our task manager has crashed
(stop-current-facet (select-a-task-manager)))
(on-start
;; N.B. when this line was here, and not after `(when mngr ...)` above,
;; things didn't work. I think that due to script scheduling, all ready
;; tasks were being assigned to the manager
#;(take-slot! mngr)
(react (stop-when (asserted (task-performance mngr t _))
(received-answer! mngr)))
(log "JM assigns task ~a to manager ~a" this-id mngr)
(task-assigner t mngr
(lambda ()
;; need to find a new task manager