Hey Johan,
thanks for your reply!
Calling .get on a CompletableFuture blocks the thread until the future is
completed, don't do that.
That's the point. I need to call .get because otherwise the actor stops
working. I also tried to collect the stages and wait then for the Response:
CompletableFuture.allOf(stages.toArray(new CompletableFuture
<?>[stages.size()])).toCompletableFuture().get()
But also this results only in TimeoutExceptions (no matter what timeout is
given). The actors simply do nothing if I do not call .get. And that is the
point, that I do not understand.
Best regards
Simon
Am Dienstag, 12. September 2017 15:33:35 UTC+2 schrieb Akka Team:
>
> Calling .get on a CompletableFuture blocks the thread until the future is
> completed, don't do that. User.find.findPagedList also looks suspiciously
> like something blocking.
> See this section of the docs for more info:
> http://doc.akka.io/docs/akka/current/java/dispatchers.html#problem-blocking-on-default-dispatcher
>
> --
> Johan
> Akka Team
>
>
> On Fri, Sep 8, 2017 at 10:00 AM, 'Simon Jacobs' via Akka User List <
> akka...@googlegroups.com <javascript:>> wrote:
>
>> Hy there,
>>
>> I have an akka scheduler to reindex some data in the search-engine and to
>> resize the images of every user.
>>
>> It will be called directly by
>>
>> system.scheduler().scheduleOnce(FiniteDuration.create(Long.valueOf(1),
>> TimeUnit.SECONDS), reindexActor, "", system.dispatcher(), null);
>>
>> The (flatted to one method for better readability) actor:
>>
>> @Override
>> public void onReceive(Object msg) throws Exception
>> {
>> long start = System.currentTimeMillis();
>> logger.info("Start reindexing of all User");
>>
>> if (indexing) {
>> logger.info("Already reindexing. Skip");
>> return;
>> }
>>
>> try {
>> int page = 0;
>> PagedList<User> users;
>>
>> do {
>> users = User.find.findPagedList(page, COUNT_OF_ROWS);
>> List<User> active = users.getList().stream().filter(g
>> -> g.isActive()).collect(Collectors.toList());
>>
>> List<CompletionStage<Response>> stages = new
>> ArrayList<CompletionStage<Response>>(COUNT_OF_ROWS);
>> for (User user : active) {
>> ActorRef userActor = system.actorOf(Props.create(
>> DependencyInjector.class, injector, UpdateRedisActor.class));
>> userActor.tell(new UpdateRedisActor.Index(user.
>> getId()), null);
>>
>> if (user.hasProfilePicture()) {
>> /**
>> * get the image as FilePart (imitate http
>> upload)
>> */
>> File image = new File(user.getProfilePicture
>> ().getFileName());
>> FilePart<Object> filePart = new FilePart<
>> Object>("", user.getFirstname(), "image/jpg", image);
>>
>> String randomFileName = UUID.randomUUID().
>> toString();
>>
>> /**
>> * Create new actor
>> */
>> ActorRef imgActor = system.actorOf(Props.
>> create(DependencyInjector.class, injector, ImageActor.class));
>>
>> /**
>> * And ask it
>> */
>> CompletionStage<Response> stage =
>> FutureConverters
>> .toJava(ask(imgActor, new ImageActor.
>> Request(filePart, randomFileName, imageResizeOptionFactory.getValues()),
>> ImageBroker.TEN_SECONDS * 20))
>> .thenApply((response) -> ((ImageActor
>> .Response) response))
>> .exceptionally((e) -> {
>> Logger.error("Error while
>> creating picture [" + randomFileName + "]", e);
>> return new ImageActor.Response(
>> 500);
>> });
>>
>> /**
>> * Collect stages
>> */
>> stages.add(stage.toCompletableFuture().
>> thenApplyAsync(response -> {
>> user.updateAndSetProfileImage(response.
>> fileName, response.filePath);
>> user.save();
>> Logger.info("User " + user.getId() + "
>> saved with new image");
>> return response;
>> }));
>> }
>> }
>> /**
>> * Wait every iteration for the actors
>> */
>> CompletableFuture.allOf(stages.toArray(new
>> CompletableFuture<?>[stages.size()])).toCompletableFuture().get();
>> }
>> while (users.hasNext());
>> }
>> catch (Exception e) {
>> logger.error("Fatal error while reindexing: ", e);
>> }
>> finally {
>> logger.info("Finish reindexing of all user in " + (System
>> .currentTimeMillis() - start) + "ms"); //does not appear in logfile.
>> indexing = false;
>> }
>> }
>>
>> }
>>
>> My expectation was that the scheduler fire-and-forget to the redis actor
>> and then asks the image-actor. Collect the result from the image actor and
>> update the user with the new image. Of course the iteration ends before all
>> images were resized.
>>
>> What happened is that the scheduler fire-and-forget to the redis actor
>> (works!) and resizes two images (Sometimes 3 or 1 or 0, but never more and
>> in most cases two). The actor-system stops immediately every work. The
>> count of threads decreases and the cpu-loads sinks down. But (and that is
>> the most strange part): The webserver does not react anymore to any
>> request. It has to be restarted.
>>
>> All works fine if I do not collect the stages, but wait for every stage
>> (..toCompletableFuture().get()). But that seems not the way for an
>> asynchronous system.
>>
>> Has anyone an idea what my mistake is?
>>
>> Thanks and best regards
>> Simon
>>
>> --
>> >>>>>>>>>> Read the docs: http://akka.io/docs/
>> >>>>>>>>>> Check the FAQ:
>> http://doc.akka.io/docs/akka/current/additional/faq.html
>> >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
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>
>
--
>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ:
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
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