[Scheduler] Allow modifying the schedule at runtime and recalculate heap

[Jeroeny]

Q	A
Branch?	6.4
Bug fix?	no
New feature?	yes
Deprecations?	no
Tickets	Fix #51206
License	MIT

Schedules are created statically by a ScheduleProviderInterface. This is nice if you have a small app with some predetermined scheduled actions. But if you want to schedule business logic dynamically, e.g. have admins Crud a schedule in the DB, then the schedule needs to be updateable at runtime. This also allows for the app to re-add schedules that have returned null as nextRunDate in the past (making them unscheduled) and to remove schedules.

Usage example: reading the schedule from a DB repository, adding messages based on an custom event:

class MySchedule implements ScheduleProviderInterface
{
    private ?Schedule $schedule = null;

    public function __construct(private RecurrenceRepository $repository)
    {
    }

    public function getSchedule(): Schedule
    {
        return $this->schedule ??= Schedule::with(...$this->repository->all());
    }

    #[AsEventListener(ScheduledMessageAdded::class)]
    public function onScheduleAdded(ScheduledMessageAdded $event): void
    {
        $this->schedule->add($event->getMessage());
    }
}

Or in the context of Messenger, if some periodic batch task has no more work to do, the recurring message can be removed:

class MySchedule implements ScheduleProviderInterface
{
    private ?Schedule $schedule = null;

    public function getSchedule(): Schedule
    {
        return $this->schedule ??= Schedule::with(RecurringMessage::every(60, new BatchGenerateFiles()));
    }
    
    public function clear()
    {
        $this->schedule->clear();
    }
}

class MyHandler 
{
    #[AsMessageHandler]
    public function handle(BatchGenerateFiles $message)
    {
        // <-- handle message code -->

        if ($noMoreFilesToGenerate) {
            $this->mySchedule->clear();
        }
    }
}

[kbond]

Interesting, is this a companion PR for #51542?

[Jeroeny]

@kbond they don't depend on each other. But when both of them are merged, it enables a lot of capabilities for the Scheduler.

[fabpot]

Can you add some usage example in the PR description?

[fabpot]

Suggested change

	* Allow modifying the Schedule at runtime
	* Allow modifying Schedule instances at runtime

[fabpot]

Thank you @Jeroeny.

[Sophikitis]

Hi !

Do you have any examples of use?
I'm trying to implement this, to dynamically retrieving frequencies and modifying the behavior with a custom event.
But this->schedule is always null in the listener function.
When I retrieve the instance from $this->getSchedule() I get an instance but when I try to delete a message or add one, nothing happens.

And as far as I understand, there's no documentation for this feature.
I'll try my luck here.
Thanks in advance

[Hanmac]

@fabpot I'm also looking for an example, currently i uses this Doctrine Query to build the Schedule

    public function getSchedule(): Schedule
    {
        $result = new Schedule();

        $repo = $this->manager->getRepository(Terminal::class);
        $q = $repo->createQueryBuilder('t');

        $q->where('t.status = true AND t.automatic = true');

        foreach ($q->getQuery()->getResult() as $r) {
            /**
             * @var Terminal $r
             */
            $result->add(RecurringMessage::cron(
                $r->getCronExpr(),
                new KassenschlussTask($r->getId()),
                $this->timezoneDetector->getTimezone())
            );
        }
        return $result;
    }

because each object might have its own CronExpr, each of them needs its own RecurringMessage

and how do i handle if they get disabled?

[Hanmac]

@Sophikitis while maybe not the best way, i found StopWorkersCommand

$cacheItem = $this->restartSignalCachePool->getItem(StopWorkerOnRestartSignalListener::RESTART_REQUESTED_TIMESTAMP_KEY);
$cacheItem->set(microtime(true));
$this->restartSignalCachePool->save($cacheItem);

i used [AsEntityListener] on my DB Entities, and then on Events::postRemove, Events::postUpdate, Events::postPersist i stop the messenger worker