Experiencing an issue with ScheduledExecutorService alongside VT

[Yuval Lombard]

Did not mention by I based the code on version 23-loom+4-102

On Sun, 21 Jul 2024 at 10:05, Yuval Lombard <yuval.l at securithings.com>
wrote:

> Hey team
>
> We are experiencing some weird halting issues when scheduling tasks with
> ScheduledExecutorService and VT.
>
> We are observing some near deadlock issues / halting of executors which we
> are not able to reproduce when using platform threads
>
> This is one example of a near deadlock situation, where for some reason
> virtual threads are starting to execute a task, and not reaching the
> finally block nor the catch Throwable block to release the acquired
> semaphore permit, reaching to drained semaphore.
>
> Are you familiar with this behavior? I hope we are doing something wrong 😅
>
> Note - The scheduler is running on a platform thread
>
> ```ScheduledFuture<?> deviceFutureTask = scheduler.scheduleAtFixedRate(()
> -> {
>
> try {
>
> logger.debug("[{}] Trying to acquire permit to schedule task [{}] for
> device. Number of available permits: [{}]",
>
> device, task, semaphore.availablePermits());
>
> if (semaphore.tryAcquire(waitingTimeout, TimeUnit.MILLISECONDS)) {
>
> logger.debug("[{}] Acquired permit to schedule [{}] task for device",
> device, task);
>
> Thread.ofVirtual().start(() -> {
>
> try {
>
> logger.debug("[{}] Scheduling [{}] task for device", device, task);
>
> // some I/O intensive work
>
> logger.debug("[{}] Finished processing [{}] task for device", device,
> task);
>
> } catch (Exception e) {
>
> logger.error("[{}] Failed to process [{}] task for device", device, task,
> e);
>
> } finally {
>
> semaphore.release();
>
> }
>
> });
>
> } else {
>
> logger.error("Timed out while waiting for permit to schedule task [{}]
> for device [{}]", task, device);
>
> }
>
> } catch (Throwable t) {
>
> logger.error("Failed to execute task [{}] for device [{}]", task,
> deviceId, t);
>
> semaphore.release();
>
> }
>
> }, (long) (entropy * schedulingInterval), schedulingInterval, TimeUnit.
> MILLISECONDS);```
>
>
> We are
> --
>
> Kind regards,
>
> *Yuval Lombard*
>
> *Lead Software Engineer*
>
> +972.50.548.0111
>
> yuval.l at securithings.com
>
> [image: logo_black.png]
>


-- 

Kind regards,

*Yuval Lombard*

*Lead Software Engineer*

+972.50.548.0111

yuval.l at securithings.com

[image: logo_black.png]
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