Package org.infinispan.commons.reactive

Class AbstractAsyncPublisherHandler<Target,Output,InitialResponse,NextResponse>

java.lang.Object
org.infinispan.commons.reactive.AbstractAsyncPublisherHandler<Target,Output,InitialResponse,NextResponse>
All Implemented Interfaces:
io.reactivex.rxjava3.functions.Action, io.reactivex.rxjava3.functions.LongConsumer
Direct Known Subclasses:
QuerySubscription
public abstract class AbstractAsyncPublisherHandler<Target,Output,InitialResponse,NextResponse> extends Object implements io.reactivex.rxjava3.functions.LongConsumer, io.reactivex.rxjava3.functions.Action
Abstract handler that handles request and cancellation of a given non blocking resource. When additional entries are requested via Subscription.request(long) the handler will keep track of the outstanding count and invoke either sendInitialCommand(Object, int) or sendNextCommand(Object, int) depending upon if it is the first request or subsequent. This handler guarantees that there is only one outstanding request and that if the request amount is larger than the batch, it will continue to send new commands one at a time until the request amount has been satisfied.

The handler processes each target via the provided Supplier one by one, exhausting all values from the target, until there are no more targets left or the publishing has been cancelled by the subscriber.

When a command returns successfully either the handleInitialResponse(Object, Object) or handleNextResponse(Object, Object) will be invoked with the response object. The returned entries can then be emitted by invoking the onNext(Object) method for each value. Note that the return of onNext should be checked in case if the Subscriber has cancelled the publishing of values in the middle.

The publisher will continue to send requests to the initialTarget provided in the constructor. When that target no longer has any more entries to retrieve the implementation should invoke targetComplete() to signal it is complete. After this is invoked the supplier provided in the constructor will be invoked to have the next target to send to. This will repeat until the supplier returns null which is the signal to this class that there are no more entries left to retrieve.

A command may also encounter a Throwable and it is possible to customize what happens by implementing the handleThrowableInResponse(Throwable, Object) method. For example you may want to skip the given

The user is required to supply a maxBatchSize argument to the constructor. This setting will ensure that this handler will never have more than this amount of entries enqueued at once. However, we may request less than this batch size from the underlying target(s). Each request is provided a batchSize argument and the underlying resource should adhere to, failure to do so may cause an OutOfMemoryError, since entries are only emitted to the Subscriber based on the requested amount, and any additional are enqueued.

This handler also supports Subscription.cancel() by extending the sendCancel(Object) command and the underlying service must be cancelled in an asynchronous and non blocking fashion. Once cancelled this Publisher will not publish additional values or requests.

Note this handler only supports a single Subscriber for the returned Publisher from startPublisher(). Failure to do so can cause multiple requests and unexpected problems.

  • Field Details

    • log

      protected static final org.infinispan.commons.logging.Log log

    • batchSize

      protected final int batchSize

    • supplier

      protected final Supplier<Target> supplier

  • Constructor Details

    • AbstractAsyncPublisherHandler

      protected AbstractAsyncPublisherHandler(int maxBatchSize, Supplier<Target> supplier, Target firstTarget)

  • Method Details

    • startPublisher

      public org.reactivestreams.Publisher<Output> startPublisher()

    • run

      public void run()
      This is invoked when the Subscription is cancelled
      Specified by:
      run in interface io.reactivex.rxjava3.functions.Action

    • sendCancel

      protected abstract void sendCancel(Target target)

    • sendInitialCommand

      protected abstract CompletionStage<InitialResponse> sendInitialCommand(Target target, int batchSize)

    • sendNextCommand

      protected abstract CompletionStage<NextResponse> sendNextCommand(Target target, int batchSize)

    • handleInitialResponse

      protected abstract long handleInitialResponse(InitialResponse response, Target target)

    • handleNextResponse

      protected abstract long handleNextResponse(NextResponse response, Target target)

    • handleThrowableInResponse

      protected void handleThrowableInResponse(Throwable t, Target target)
      Allows any implementor to handle what happens when a Throwable is encountered. By default the returned publisher invokes Subscriber.onError(Throwable) and stops processing. It is possible to ignore the throwable and continue processing by invoking accept(long) with a value of 0. It may also be required to reset the currentTarget so it is initialized to the next supplied value.
      Parameters:
      t - throwable that was encountered
      target - the target which was invoked that caused the throwable

    • accept

      public void accept(long count)
      This method is invoked every time a new request is sent to the underlying publisher. We need to submit a request if there is not a pending one. Whenever requestedAmount is a number greater than 0, that means we must submit or there is a pending one.
      Specified by:
      accept in interface io.reactivex.rxjava3.functions.LongConsumer
      Parameters:
      count - request count

    • onNext

      protected boolean onNext(Output value)
      Method that should be called for each emitted output value. The returned boolean is whether the handler should continue publishing values or not.
      Parameters:
      value - value emit to the publisher
      Returns:
      whether to continue emitting values

    • targetComplete

      protected void targetComplete()
      Method to invoke when a given target is found to have been completed and the next target should be used

    • checkCancelled

      protected boolean checkCancelled()
      This method returns whether this subscription has been cancelled