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Extrapolate stage and expand redoc #23804

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mikolak-net 2018-03-27 10:39:25 +02:00 • committed by Johan Andrén
parent 26f0f86088
commit 00068e2d1d
13 changed files with 670 additions and 82 deletions
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70
akka-stream/src/main/scala/akka/stream/javadsl/SubSource.scala
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@ -1103,7 +1103,7 @@ class SubSource[Out, Mat](delegate: scaladsl.SubFlow[Out, Mat, scaladsl.Source[O
new SubSource(delegate.batchWeighted(max, costFn.apply, seed.apply)(aggregate.apply))
/**
* Allows a faster downstream to progress independently of a slower publisher by extrapolating elements from an older
* Allows a faster downstream to progress independently of a slower upstream by extrapolating elements from an older
* element until new element comes from the upstream. For example an expand step might repeat the last element for
* the subscriber until it receives an update from upstream.
*
@ -1112,7 +1112,9 @@ class SubSource[Out, Mat](delegate: scaladsl.SubFlow[Out, Mat, scaladsl.Source[O
* subscriber.
*
* Expand does not support [[akka.stream.Supervision#restart]] and [[akka.stream.Supervision#resume]].
* Exceptions from the `seed` or `extrapolate` functions will complete the stream with failure.
* Exceptions from the `expander` function will complete the stream with failure.
*
* See also [[#extrapolate]] for a version that always preserves the original element and allows for an initial "startup" element.
*
* '''Emits when''' downstream stops backpressuring
*
@ -1122,11 +1124,67 @@ class SubSource[Out, Mat](delegate: scaladsl.SubFlow[Out, Mat, scaladsl.Source[O
*
* '''Cancels when''' downstream cancels
*
* @param extrapolate Takes the current extrapolation state to produce an output element and the next extrapolation
* state.
* @param expander Takes the current extrapolation state to produce an output element and the next extrapolation
* state.
* @see [[#extrapolate]]
*/
def expand[U](extrapolate: function.Function[Out, java.util.Iterator[U]]): SubSource[U, Mat] =
new SubSource(delegate.expand(in ⇒ extrapolate(in).asScala))
def expand[U](expander: function.Function[Out, java.util.Iterator[U]]): SubSource[U, Mat] =
new SubSource(delegate.expand(in ⇒ expander(in).asScala))
/**
* Allows a faster downstream to progress independent of a slower upstream.
*
* This is achieved by introducing "extrapolated" elements - based on those from upstream - whenever downstream
* signals demand.
*
* Extrapolate does not support [[akka.stream.Supervision#restart]] and [[akka.stream.Supervision#resume]].
* Exceptions from the `extrapolate` function will complete the stream with failure.
*
* See also [[#expand]] for a version that can overwrite the original element.
*
* '''Emits when''' downstream stops backpressuring, AND EITHER upstream emits OR initial element is present OR
* `extrapolate` is non-empty and applicable
*
* '''Backpressures when''' downstream backpressures or current `extrapolate` runs empty
*
* '''Completes when''' upstream completes and current `extrapolate` runs empty
*
* '''Cancels when''' downstream cancels
*
* @param extrapolator takes the current upstream element and provides a sequence of "extrapolated" elements based
* on the original, to be emitted in case downstream signals demand.
* @see [[#expand]]
*/
def extrapolate(extrapolator: function.Function[Out @uncheckedVariance, java.util.Iterator[Out @uncheckedVariance]]): SubSource[Out, Mat] =
new SubSource(delegate.extrapolate(in ⇒ extrapolator(in).asScala))
/**
* Allows a faster downstream to progress independent of a slower upstream.
*
* This is achieved by introducing "extrapolated" elements - based on those from upstream - whenever downstream
* signals demand.
*
* Extrapolate does not support [[akka.stream.Supervision#restart]] and [[akka.stream.Supervision#resume]].
* Exceptions from the `extrapolate` function will complete the stream with failure.
*
* See also [[#expand]] for a version that can overwrite the original element.
*
* '''Emits when''' downstream stops backpressuring, AND EITHER upstream emits OR initial element is present OR
* `extrapolate` is non-empty and applicable
*
* '''Backpressures when''' downstream backpressures or current `extrapolate` runs empty
*
* '''Completes when''' upstream completes and current `extrapolate` runs empty
*
* '''Cancels when''' downstream cancels
*
* @param extrapolator takes the current upstream element and provides a sequence of "extrapolated" elements based
* on the original, to be emitted in case downstream signals demand.
* @param initial the initial element to be emitted, in case upstream is able to stall the entire stream.
* @see [[#expand]]
*/
def extrapolate(extrapolator: function.Function[Out @uncheckedVariance, java.util.Iterator[Out @uncheckedVariance]], initial: Out @uncheckedVariance): SubSource[Out, Mat] =
new SubSource(delegate.extrapolate(in ⇒ extrapolator(in).asScala, Some(initial)))
/**
* Adds a fixed size buffer in the flow that allows to store elements from a faster upstream until it becomes full.