Hi Alain, Having applied some step by step debugging the issue I can see is actually a deadlock in the async worker pool - we call asyncMap with a parallelism of 2, but we use the default executor from the push stream, which has only one thread.
If the timing is wrong then we end up with the final debounce window timing out and trying to complete while the one pushing thread is blocking waiting for the timeout to be sent. I’ll dig a little further, but the probable answer is just that one of the thread pools needs an extra thread (or possibly that the inline executor needs to be changed). Best Regards, Tim > On 6 Feb 2019, at 14:36, Alain Picard <pic...@castortech.com> wrote: > > Jurgen, > > Thanks for the clarifications. I also did about the same change to match our > standard stream implementation, and didn't get the issue, but I was too much > in the dark to make any meaningful conclusions. > > I was looking to modify the test to verify various scenarios. So I guess I'll > make those changes and proceed from there. > > Thanks > Alain > > > On Wed, Feb 6, 2019 at 9:21 AM Jürgen Albert <j.alb...@data-in-motion.biz > <mailto:j.alb...@data-in-motion.biz>> wrote: > Creating the PushStream with an exclusive Executor fixes the Problem. > > Promise<List<Collection<Integer>>> result = psp.buildStream(sps) > .withBuffer(new ArrayBlockingQueue<PushEvent<? extends > Integer>>(32)) > .withExecutor(Executors.newCachedThreadPool()).build() > .asyncMap(5, 0, new StreamDebouncer<Integer>( > new PromiseFactory(PromiseFactory.inlineExecutor()), > 10, Duration.ofSeconds(1))) > .filter(c -> !c.isEmpty()) > .collect(Collectors.toList()); > > Am 06/02/2019 um 15:14 schrieb Jürgen Albert: >> Hi Alain, >> >> the issue has a couple of reasons: >> >> The Pushstream and eventsource have by default 2 queues with a size of 32 >> each. The default pushback policy is linear. This means, that when 10 events >> are in the buffer a pushback of 10 ms will be given to the eventsource. This >> means, that the eventsource will wait this time, before it sends the next >> event downstream. This default behaviour can cause long processing times, >> especially when a lot of events are written in a for loop. This means that >> the queues fill up very quick even if the actual processing time of the code >> of yours is close to 0. Use e.g. the ON_FULL_FIXED policy to get ride of >> this problem. >> >> As far as I understand the bouncer, it waits a second, before it returns a >> list, if no new events are coming. Thus a sleep time of less then a second >> or even 1,5 (together with the pushback thing I described before) will keep >> the stream busy longer then your sleep time for a batch. Thus all the >> batches return when hitting the max size, except the last one. This waits >> and for some threading reasons, the last deferred is blocked from resolving, >> which in turn blocks eventsource close. If you add a small wait before the >> close is called everything is fine. >> >> The blocking issue is interesting non the less, but my experience is that >> these kind of tests are often harsher then reality. >> >> Regards, >> >> Jürgen. >> >> Am 05/02/2019 um 23:58 schrieb Alain Picard: >>> Tim, >>> >>> Finally got around to this debouncer, and I tested to change the sleep >>> time. When I set it to like 800 to 1500, it never completes after shoing >>> "Closing the Generator". At 500, I get a Queue full that I can understand. >>> So why the hang? >>> >>> Alain >>> >>> >>> >>> On Mon, Jan 7, 2019 at 8:11 AM Tim Ward <tim.w...@paremus.com >>> <mailto:tim.w...@paremus.com>> wrote: >>> This use case is effectively a “debouncing” behaviour, which is possible to >>> implement with a little thought. >>> >>> There are a couple of ways to attempt it. This one uses the asyncMap >>> operation to asynchronously gather the events until it either times out the >>> promise or it hits the maximum stream size. Note that you have to filter >>> out the “empty” lists that are used to resolve the promises which are being >>> aggregated into the window. The result of this is a window which starts on >>> the first event arrival and then buffers the events for a while. The next >>> window isn’t started until the next event >>> >>> >>> Best Regards, >>> >>> Tim >>> >>> >>> @Test >>> public void testWindow2() throws InvocationTargetException, >>> InterruptedException { >>> >>> PushStreamProvider psp = new PushStreamProvider(); >>> >>> SimplePushEventSource<Integer> sps = >>> psp.createSimpleEventSource(Integer.class); >>> >>> Promise<List<Collection<Integer>>> result = >>> psp.createStream(sps) >>> .asyncMap(2, 0, new StreamDebouncer<Integer>( >>> new >>> PromiseFactory(PromiseFactory.inlineExecutor()), >>> 10, Duration.ofSeconds(1))) >>> .filter(c -> !c.isEmpty()) >>> .collect(Collectors.toList()); >>> >>> new Thread(() -> { >>> >>> for (int i = 0; i < 200;) { >>> >>> for (int j = 0; j < 23; j++) { >>> sps.publish(i++); >>> } >>> >>> try { >>> System.out.println("Burst finished, now >>> at " + i); >>> Thread.sleep(2000); >>> } catch (InterruptedException e) { >>> sps.error(e); >>> break; >>> } >>> } >>> >>> System.out.println("Closing generator"); >>> sps.close(); >>> >>> }).start(); >>> >>> System.out.println(result.getValue().toString()); >>> >>> } >>> >>> public static class StreamDebouncer<T> implements Function<T, Promise<? >>> extends Collection<T>>> { >>> >>> private final PromiseFactory promiseFactory; >>> private final int maxSize; >>> private final Duration maxTime; >>> >>> private final Object lock = new Object(); >>> >>> private List<T> currentWindow; >>> private Deferred<Collection<T>> currentDeferred; >>> >>> public StreamDebouncer(PromiseFactory promiseFactory, int >>> maxSize, Duration maxTime) { >>> this.promiseFactory = promiseFactory; >>> this.maxSize = maxSize; >>> this.maxTime = maxTime; >>> } >>> >>> @Override >>> public Promise<Collection<T>> apply(T t) throws Exception { >>> >>> Deferred<Collection<T>> deferred = null; >>> Collection<T> list = null; >>> boolean hitMaxSize = false; >>> synchronized (lock) { >>> if(currentWindow == null) { >>> currentWindow = new >>> ArrayList<>(maxSize); >>> currentDeferred = >>> promiseFactory.deferred(); >>> deferred = currentDeferred; >>> list = currentWindow; >>> } >>> currentWindow.add(t); >>> if(currentWindow.size() == maxSize) { >>> hitMaxSize = true; >>> deferred = currentDeferred; >>> currentDeferred = null; >>> list = currentWindow; >>> currentWindow = null; >>> } >>> } >>> >>> if(deferred != null) { >>> if(hitMaxSize) { >>> // We must resolve this way round to >>> avoid racing >>> // the timeout and ending up with empty >>> lists in >>> // all the promises >>> >>> deferred.resolve(Collections.emptyList()); >>> return promiseFactory.resolved(list); >>> } else { >>> final Collection<T> finalList = list; >>> return deferred.getPromise() >>> >>> .timeout(maxTime.toMillis()) >>> .recover(x -> { >>> synchronized >>> (lock) { >>> >>> if(currentWindow == finalList) { >>> >>> currentWindow = null; >>> >>> currentDeferred = null; >>> >>> return finalList; >>> } >>> } >>> return >>> Collections.emptyList(); >>> }); >>> } >>> } else { >>> return >>> promiseFactory.resolved(Collections.emptyList()); >>> } >>> } >>> >>> } >>> >>> >>> >>>> On 7 Jan 2019, at 11:25, Alain Picard via osgi-dev <osgi-dev@mail.osgi.org >>>> <mailto:osgi-dev@mail.osgi.org>> wrote: >>>> >>>> Thanks Jürgen, >>>> >>>> As I said that is what I went with and it is very satisfying right now. As >>>> for pushback, I'm out of luck since the producer is fully "disjoint" with >>>> a whiteboard pattern, but we have configured ourselves with appropriated >>>> buffering But I'll keep this code in mind, as we will surely have other >>>> patterns to support as we use push streams more and more. >>>> >>>> Alain >>>> >>>> >>>> On Mon, Jan 7, 2019 at 5:55 AM Jürgen Albert via osgi-dev >>>> <osgi-dev@mail.osgi.org <mailto:osgi-dev@mail.osgi.org>> wrote: >>>> Hi Alain, >>>> >>>> windowing would be your goto method. AFAIK there is not way to extend a >>>> window, if you expect more messages to arrive. Thus you would need to live >>>> with multiple batches, in case of a prolonged burst. back pressure however >>>> is possible, even if you use a buffer and/or windowing. The solution >>>> would look like this: >>>> >>>> psp.createPushStreamBuilder() >>>> .withPushbackPolicy( q -> { >>>> return Math.max(0, q.size() - 650); >>>> }) >>>> .withQueuePolicy(QueuePolicyOption.BLOCK) >>>> .withBuffer(new ArrayBlockingQueue<PushEvent<? >>>> extends EObject>>(1200)) >>>> .build(); >>>> >>>> This PuschbackPolicy looks at the queue size and gradually increases the >>>> pushback starting with one on the 651st element. >>>> >>>> The grouping is another topic. The split method can do your grouping, if >>>> you know what groups to expect. It essentially returns an array of >>>> pushstreams correlating to each predicate you give it. For everything >>>> else, you would need to do the grouping for every batch you get with the >>>> usual stream methods. >>>> >>>> Regards, >>>> >>>> Jürgen. >>>> >>>> Am 05/01/2019 um 19:47 schrieb Alain Picard via osgi-dev: >>>>> For now I went with my simple solution of using a window with just >>>>> duration, and that is working fine, even if it might not be the most >>>>> optimal or streamlined approach. >>>>> >>>>> Alain >>>>> >>>>> >>>>> On Sat, Jan 5, 2019 at 5:27 AM Alain Picard <pic...@castortech.com >>>>> <mailto:pic...@castortech.com>> wrote: >>>>> Hi, >>>>> >>>>> We are using push streams to process post-commit events. Those events >>>>> originate from different data sources. At the moment we are processing >>>>> those individually, but the overhead of having a transaction for each is >>>>> too much. Quite often those events come in bursts following an upstream >>>>> transaction/ change set. >>>>> >>>>> The goal is to group events by data source and batch them, i.e. wait a >>>>> bit when an event arrives to see if others are also coming. If they keep >>>>> coming, keep collecting a bit longer, o/w move on. >>>>> >>>>> I see that the PushStream has methods coalesce and window. Window seems a >>>>> bit more appropriate here, as it offers both duration and maxEvents. But >>>>> it seems to operate all the time, and not start a batch upon receiving an >>>>> event, which doesn't sound optimal in this case. More concerning to me is >>>>> the comment regarding back-pressure. We can't use back pressure (no >>>>> control on producer which is implemented via whiteboard. So here the >>>>> maxEvents is more a way to limit the batch and not to indicate need for >>>>> back pressure. >>>>> >>>>> Still, that doesn't address grouping. See that there is a fork, but that >>>>> is made to deal with a fixed number of child streams. >>>>> >>>>> Would I just be best to use a window with just duration, collect a number >>>>> of events, then move on and use a regular stream to group them and if >>>>> necessary batch them in smaller groups? >>>>> >>>>> Cheers, >>>>> >>>>> Alain >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> OSGi Developer Mail List >>>>> osgi-dev@mail.osgi.org <mailto:osgi-dev@mail.osgi.org> >>>>> https://mail.osgi.org/mailman/listinfo/osgi-dev >>>>> <https://mail.osgi.org/mailman/listinfo/osgi-dev> >>>> -- >>>> Jürgen Albert >>>> Geschäftsführer >>>> >>>> Data In Motion Consulting GmbH >>>> >>>> Kahlaische Str. 4 >>>> 07745 Jena >>>> >>>> Mobil: 0157-72521634 >>>> E-Mail: j.alb...@datainmotion.de <mailto:j.alb...@datainmotion.de> >>>> Web: www.datainmotion.de <http://www.datainmotion.de/> >>>> >>>> XING: https://www.xing.com/profile/Juergen_Albert5 >>>> <https://www.xing.com/profile/Juergen_Albert5> >>>> >>>> Rechtliches >>>> >>>> Jena HBR 513025 >>>> _______________________________________________ >>>> OSGi Developer Mail List >>>> osgi-dev@mail.osgi.org <mailto:osgi-dev@mail.osgi.org> >>>> https://mail.osgi.org/mailman/listinfo/osgi-dev >>>> <https://mail.osgi.org/mailman/listinfo/osgi-dev>_______________________________________________ >>>> OSGi Developer Mail List >>>> osgi-dev@mail.osgi.org <mailto:osgi-dev@mail.osgi.org> >>>> https://mail.osgi.org/mailman/listinfo/osgi-dev >>>> <https://mail.osgi.org/mailman/listinfo/osgi-dev> >> >> -- >> Jürgen Albert >> Geschäftsführer >> >> Data In Motion Consulting GmbH >> >> Kahlaische Str. 4 >> 07745 Jena >> >> Mobil: 0157-72521634 >> E-Mail: j.alb...@datainmotion.de <mailto:j.alb...@datainmotion.de> >> Web: www.datainmotion.de <http://www.datainmotion.de/> >> >> XING: https://www.xing.com/profile/Juergen_Albert5 >> <https://www.xing.com/profile/Juergen_Albert5> >> >> Rechtliches >> >> Jena HBR 513025 > > -- > Jürgen Albert > Geschäftsführer > > Data In Motion Consulting GmbH > > Kahlaische Str. 4 > 07745 Jena > > Mobil: 0157-72521634 > E-Mail: j.alb...@datainmotion.de <mailto:j.alb...@datainmotion.de> > Web: www.datainmotion.de <http://www.datainmotion.de/> > > XING: https://www.xing.com/profile/Juergen_Albert5 > <https://www.xing.com/profile/Juergen_Albert5> > > Rechtliches > > Jena HBR 513025
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