abstract class Topic[F[_], A] extends AnyRef
Topic allows you to distribute A
s published by an arbitrary
number of publishers to an arbitrary number of subscribers.
Topic has built-in back-pressure support implemented as the maximum
number of elements (maxQueued
) that a subscriber is allowed to enqueue.
Once that bound is hit, any publishing action will semantically block until the lagging subscriber consumes some of its queued elements.
- Self Type
- Topic[F, A]
- Source
- Topic.scala
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- new Topic()
Abstract Value Members
- abstract def close: F[Either[Closed, Unit]]
This method achieves graceful shutdown: when the topics gets closed, its subscribers will terminate naturally after consuming all currently enqueued elements.
This method achieves graceful shutdown: when the topics gets closed, its subscribers will terminate naturally after consuming all currently enqueued elements.
"Termination" here means that subscribers no longer wait for new elements on the topic, and not that they will be interrupted while performing another action: if you want to interrupt a subscriber, without first processing enqueued elements, you should use
interruptWhen
on it instead.After a call to
close
, any further calls topublish1
orclose
will be no-ops.Note that
close
does not automatically unblock producers which might be blocked on a bound, they will only become unblocked if/when subscribers naturally finish to consume the respective elements. You canrace
the publish withclose
to interrupt them immediately. - abstract def closed: F[Unit]
Semantically blocks until the topic gets closed.
- abstract def isClosed: F[Boolean]
Returns true if this topic is closed
- abstract def publish: Pipe[F, A, Nothing]
Publishes elements from source of
A
to this topic.Publishes elements from source of
A
to this topic. Pipe equivalent ofpublish1
. Closes the topic when the input stream terminates. Especially useful when the topic has a single producer. - abstract def publish1(a: A): F[Either[Closed, Unit]]
Publishes one
A
to topic.Publishes one
A
to topic. No-op if the channel is closed, see close for further info.This operation does not complete until after the given element has been enqued on all subscribers, which means that if any subscriber is at its
maxQueued
limit,publish1
will semantically block until that subscriber consumes an element.A semantically blocked publication can be interrupted, but there is no guarantee of atomicity, and it could result in the
A
being received by some subscribers only.Note: if
publish1
is called concurrently by multiple producers, different subscribers may receive messages from different producers in a different order. - abstract def subscribe(maxQueued: Int): Stream[F, A]
Subscribes for
A
values that are published to this topic.Subscribes for
A
values that are published to this topic.Pulling on the returned stream opens a "subscription", which allows up to
maxQueued
elements to be enqueued as a result of publication.If at any point, the queue backing the subscription has
maxQueued
elements in it, any further publications semantically block until elements are dequeued from the subscription queue.- maxQueued
maximum number of elements to enqueue to the subscription queue before blocking publishers
- abstract def subscribeAwait(maxQueued: Int): Resource[F, Stream[F, A]]
Like
subscribe
, but represents the subscription explicitly as aResource
which returns after the subscriber is subscribed, but before it has started pulling elements. - abstract def subscribers: Stream[F, Int]
Signal of current active subscribers.
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- final def !=(arg0: Any): Boolean
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- def imap[B](f: (A) => B)(g: (B) => A): Topic[F, B]
Returns an alternate view of this
Topic
where its elements are of typeB
, given two functions,A => B
andB => A
. - final def isInstanceOf[T0]: Boolean
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Deprecated Value Members
- def finalize(): Unit
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- Deprecated