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;;; watchdog.scm -- Monitor fibers scheduling.
;;; Copyright © 2020 Mathieu Othacehe <othacehe@gnu.org>
;;;
;;; This file is part of Cuirass.
;;;
;;; Cuirass is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published by
;;; the Free Software Foundation, either version 3 of the License, or
;;; (at your option) any later version.
;;;
;;; Cuirass is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with Cuirass. If not, see <http://www.gnu.org/licenses/>.
(define-module (cuirass watchdog)
#:use-module (cuirass logging)
#:use-module (cuirass utils)
#:use-module (fibers)
#:use-module (fibers channels)
#:use-module (fibers internal)
#:use-module (fibers operations)
#:use-module (ice-9 match)
#:use-module (ice-9 threads)
#:export (start-watchdog))
(define* (watchdog-fiber scheduler channel
#:key
(period 1))
"Spawn a fiber running on SCHEDULER that sends over CHANNEL, every PERIOD
seconds, the scheduler name and the current time."
(spawn-fiber
(lambda ()
(while #t
(put-message channel (list (scheduler-name scheduler)
(current-time)))
(sleep period)))
scheduler))
(define* (start-watchdog #:key (timeout 5))
"Start a watchdog checking that each Fibers scheduler is not blocked for
more than TIMEOUT seconds.
The watchdog mechanism consists in spawning a dedicated fiber per running
Fiber scheduler, using the above watchdog-fiber method. Those fibers send a
ping signal periodically to a separate thread. If no signal is received from
one of the schedulers for more than TIMEOUT seconds, a warning message is
printed."
(define (check-timeouts pings last-check)
(let* ((check-period timeout)
(cur-time (current-time))
(diff-check (- cur-time last-check)))
(if (> diff-check check-period)
(begin
(for-each
(match-lambda
((scheduler . time)
(let ((diff-ping (- cur-time time)))
(when (> diff-ping timeout)
(log-message "Scheduler ~a blocked since ~a seconds."
scheduler diff-ping)))))
pings)
cur-time)
last-check)))
(let ((watchdog-channel (make-channel)))
(parameterize (((@@ (fibers internal) current-fiber) #f))
(call-with-new-thread
(lambda ()
(let loop ((pings '())
(last-check 0))
(let ((operation-timeout 10))
(match (perform-operation
(with-timeout
(get-operation watchdog-channel)
#:seconds operation-timeout
#:wrap (const 'timeout)))
((scheduler ping)
(loop (assq-set! pings scheduler ping)
(check-timeouts pings last-check)))
('timeout
(loop pings
(check-timeouts pings last-check)))))))))
(fold-all-schedulers
(lambda (name scheduler seed)
(watchdog-fiber scheduler watchdog-channel))
'())))
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