Package org.glassfish.jersey.internal.jsr166

Interface SubmittableFlowPublisher<T>

Type Parameters:
T - the published item type
All Superinterfaces:
AutoCloseable, Flow.Publisher<T>
All Known Implementing Classes:
SubmissionPublisher
public interface SubmittableFlowPublisher<T> extends Flow.Publisher<T>, AutoCloseable
A Flow.Publisher that asynchronously issues submitted (non-null) items to current subscribers until it is closed. Each current subscriber receives newly submitted items in the same order unless drops or exceptions are encountered. Using a SubmittableFlowPublisher allows item generators to act as compliant reactive-streams Publishers relying on drop handling and/or blocking for flow control.

An implementation of SubmittableFlowPublisher uses the Executor supplied in its constructor for delivery to subscribers. The best choice of Executor depends on expected usage. If the generator(s) of submitted items run in separate threads, and the number of subscribers can be estimated, consider using a Executors.newFixedThreadPool(int). Otherwise consider using the default, normally the ForkJoinPool.commonPool().

Buffering allows producers and consumers to transiently operate at different rates. Each subscriber uses an independent buffer. Buffers are created upon first use and expanded as needed up to the given maximum. (The enforced capacity may be rounded up to the nearest power of two and/or bounded by the largest value supported by this implementation.) Invocations of request do not directly result in buffer expansion, but risk saturation if unfilled requests exceed the maximum capacity. The default value of Flow.defaultBufferSize() may provide a useful starting point for choosing a capacity based on expected rates, resources, and usages.

Publication methods support different policies about what to do when buffers are saturated. Method submit blocks until resources are available. This is simplest, but least responsive. The offer methods may drop items (either immediately or with bounded timeout), but provide an opportunity to interpose a handler and then retry.

If any Subscriber method throws an exception, its subscription is cancelled. If a handler is supplied as a constructor argument, it is invoked before cancellation upon an exception in method onNext, but exceptions in methods onSubscribe, onError and onComplete are not recorded or handled before cancellation. If the supplied Executor throws RejectedExecutionException (or any other RuntimeException or Error) when attempting to execute a task, or a drop handler throws an exception when processing a dropped item, then the exception is rethrown. In these cases, not all subscribers will have been issued the published item. It is usually good practice to closeExceptionally in these cases.

Method consume(Consumer) simplifies support for a common case in which the only action of a subscriber is to request and process all items using a supplied function.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    close()
    Unless already closed, issues onComplete signals to current subscribers, and disallows subsequent attempts to publish.
    void
    closeExceptionally(Throwable error)
    Unless already closed, issues onError signals to current subscribers with the given error, and disallows subsequent attempts to publish.
    CompletableFuture<Void>
    consume(Consumer<? super T> consumer)
    Processes all published items using the given Consumer function.
    int
    estimateMaximumLag()
    Returns an estimate of the maximum number of items produced but not yet consumed among all current subscribers.
    long
    estimateMinimumDemand()
    Returns an estimate of the minimum number of items requested (via request) but not yet produced, among all current subscribers.
    Throwable
    getClosedException()
    Returns the exception associated with closeExceptionally, or null if not closed or if closed normally.
    int
    getMaxBufferCapacity()
    Returns the maximum per-subscriber buffer capacity.
    int
    offer(T item, long timeout, TimeUnit unit, BiPredicate<Flow.Subscriber<? super T>,? super T> onDrop)
    Publishes the given item, if possible, to each current subscriber by asynchronously invoking its onNext method, blocking while resources for any subscription are unavailable, up to the specified timeout or until the caller thread is interrupted, at which point the given handler (if non-null) is invoked, and if it returns true, retried once.
    int
    offer(T item, BiPredicate<Flow.Subscriber<? super T>,? super T> onDrop)
    Publishes the given item, if possible, to each current subscriber by asynchronously invoking its onNext method.
    int
    submit(T item)
    Publishes the given item to each current subscriber by asynchronously invoking its onNext method, blocking uninterruptibly while resources for any subscriber are unavailable.
    void
    subscribe(Flow.Subscriber<? super T> subscriber)
    Adds the given Subscriber unless already subscribed.

  • Method Details

    • consume

      CompletableFuture<Void> consume(Consumer<? super T> consumer)
      Processes all published items using the given Consumer function. Returns a CompletableFuture that is completed normally when this publisher signals onComplete, or completed exceptionally upon any error, or an exception is thrown by the Consumer, or the returned CompletableFuture is cancelled, in which case no further items are processed.
      Parameters:
      consumer - the function applied to each onNext item
      Returns:
      a CompletableFuture that is completed normally when the publisher signals onComplete, and exceptionally upon any error or cancellation
      Throws:
      NullPointerException - if consumer is null

    • close

      void close()
      Unless already closed, issues onComplete signals to current subscribers, and disallows subsequent attempts to publish. Upon return, this method does NOT guarantee that all subscribers have yet completed.
      Specified by:
      close in interface AutoCloseable

    • closeExceptionally

      void closeExceptionally(Throwable error)
      Unless already closed, issues onError signals to current subscribers with the given error, and disallows subsequent attempts to publish. Future subscribers also receive the given error. Upon return, this method does NOT guarantee that all subscribers have yet completed.
      Parameters:
      error - the onError argument sent to subscribers
      Throws:
      NullPointerException - if error is null

    • estimateMinimumDemand

      long estimateMinimumDemand()
      Returns an estimate of the minimum number of items requested (via request) but not yet produced, among all current subscribers.
      Returns:
      the estimate, or zero if no subscribers

    • estimateMaximumLag

      int estimateMaximumLag()
      Returns an estimate of the maximum number of items produced but not yet consumed among all current subscribers.
      Returns:
      the estimate

    • getClosedException

      Throwable getClosedException()
      Returns the exception associated with closeExceptionally, or null if not closed or if closed normally.
      Returns:
      the exception, or null if none

    • getMaxBufferCapacity

      int getMaxBufferCapacity()
      Returns the maximum per-subscriber buffer capacity.
      Returns:
      the maximum per-subscriber buffer capacity

    • offer

      int offer(T item, long timeout, TimeUnit unit, BiPredicate<Flow.Subscriber<? super T>,? super T> onDrop)
      Publishes the given item, if possible, to each current subscriber by asynchronously invoking its onNext method, blocking while resources for any subscription are unavailable, up to the specified timeout or until the caller thread is interrupted, at which point the given handler (if non-null) is invoked, and if it returns true, retried once. (The drop handler may distinguish timeouts from interrupts by checking whether the current thread is interrupted.) Other calls to methods in this class by other threads are blocked while the handler is invoked. Unless recovery is assured, options are usually limited to logging the error and/or issuing an onError signal to the subscriber.

      This method returns a status indicator: If negative, it represents the (negative) number of drops (failed attempts to issue the item to a subscriber). Otherwise it is an estimate of the maximum lag (number of items submitted but not yet consumed) among all current subscribers. This value is at least one (accounting for this submitted item) if there are any subscribers, else zero.

      If the Executor for this publisher throws a RejectedExecutionException (or any other RuntimeException or Error) when attempting to asynchronously notify subscribers, or the drop handler throws an exception when processing a dropped item, then this exception is rethrown.

      Parameters:
      item - the (non-null) item to publish
      timeout - how long to wait for resources for any subscriber before giving up, in units of unit
      unit - a TimeUnit determining how to interpret the timeout parameter
      onDrop - if non-null, the handler invoked upon a drop to a subscriber, with arguments of the subscriber and item; if it returns true, an offer is re-attempted (once)
      Returns:
      if negative, the (negative) number of drops; otherwise an estimate of maximum lag
      Throws:
      IllegalStateException - if closed
      NullPointerException - if item is null
      RejectedExecutionException - if thrown by Executor

    • offer

      int offer(T item, BiPredicate<Flow.Subscriber<? super T>,? super T> onDrop)
      Publishes the given item, if possible, to each current subscriber by asynchronously invoking its onNext method. The item may be dropped by one or more subscribers if resource limits are exceeded, in which case the given handler (if non-null) is invoked, and if it returns true, retried once. Other calls to methods in this class by other threads are blocked while the handler is invoked. Unless recovery is assured, options are usually limited to logging the error and/or issuing an onError signal to the subscriber.

      This method returns a status indicator: If negative, it represents the (negative) number of drops (failed attempts to issue the item to a subscriber). Otherwise it is an estimate of the maximum lag (number of items submitted but not yet consumed) among all current subscribers. This value is at least one (accounting for this submitted item) if there are any subscribers, else zero.

      If the Executor for this publisher throws a RejectedExecutionException (or any other RuntimeException or Error) when attempting to asynchronously notify subscribers, or the drop handler throws an exception when processing a dropped item, then this exception is rethrown.

      Parameters:
      item - the (non-null) item to publish
      onDrop - if non-null, the handler invoked upon a drop to a subscriber, with arguments of the subscriber and item; if it returns true, an offer is re-attempted (once)
      Returns:
      if negative, the (negative) number of drops; otherwise an estimate of maximum lag
      Throws:
      IllegalStateException - if closed
      NullPointerException - if item is null
      RejectedExecutionException - if thrown by Executor

    • submit

      int submit(T item)
      Publishes the given item to each current subscriber by asynchronously invoking its onNext method, blocking uninterruptibly while resources for any subscriber are unavailable. This method returns an estimate of the maximum lag (number of items submitted but not yet consumed) among all current subscribers. This value is at least one (accounting for this submitted item) if there are any subscribers, else zero.

      If the Executor for this publisher throws a RejectedExecutionException (or any other RuntimeException or Error) when attempting to asynchronously notify subscribers, then this exception is rethrown, in which case not all subscribers will have been issued this item.

      Parameters:
      item - the (non-null) item to publish
      Returns:
      the estimated maximum lag among subscribers
      Throws:
      IllegalStateException - if closed
      NullPointerException - if item is null
      RejectedExecutionException - if thrown by Executor

    • subscribe

      void subscribe(Flow.Subscriber<? super T> subscriber)
      Adds the given Subscriber unless already subscribed. If already subscribed, the Subscriber's onError method is invoked on the existing subscription with an IllegalStateException. Otherwise, upon success, the Subscriber's onSubscribe method is invoked asynchronously with a new Flow.Subscription. If onSubscribe throws an exception, the subscription is cancelled. Otherwise, if this SubmittableFlowPublisher was closed exceptionally, then the subscriber's onError method is invoked with the corresponding exception, or if closed without exception, the subscriber's onComplete method is invoked. Subscribers may enable receiving items by invoking the request method of the new Subscription, and may unsubscribe by invoking its cancel method.
      Specified by:
      subscribe in interface Flow.Publisher<T>
      Parameters:
      subscriber - the subscriber
      Throws:
      NullPointerException - if subscriber is null