Channel

fs2.concurrent.Channel
See theChannel companion object
sealed trait Channel[F[_], A]

Stream aware, multiple producer, single consumer closeable channel.

Attributes

Companion
object
Source
Channel.scala
Graph
Supertypes
class Object
trait Matchable
class Any

Members list

Value members

Abstract methods

def close: F[Either[Closed, Unit]]

This method achieves graceful shutdown: when the channel gets closed, stream will terminate naturally after consuming all currently enqueued elements, including the ones by producers blocked on a bound.

This method achieves graceful shutdown: when the channel gets closed, stream will terminate naturally after consuming all currently enqueued elements, including the ones by producers blocked on a bound.

"Termination" here means that stream will no longer wait for new elements on the channel, and not that it will be interrupted while performing another action: if you want to interrupt stream immediately, without first processing enqueued elements, you should use interruptWhen on it instead.

After a call to close, any further calls to send or close 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 stream is executing.

In other words, if close is called while stream is executing, blocked producers will eventually become unblocked, before stream terminates and further send calls become no-ops. However, if close is called after stream has terminated (e.g because it was interrupted, or had a .take(n)), then blocked producers will stay blocked unless they get explicitly unblocked, either by a further call to stream to drain the channel, or by a a race with closed.

Attributes

Source
Channel.scala

Gracefully closes this channel with a final element.

Gracefully closes this channel with a final element. This method will never block.

No-op if the channel is closed, see close for further info.

Attributes

Source
Channel.scala
def closed: F[Unit]

Semantically blocks until the channel gets closed.

Semantically blocks until the channel gets closed.

Attributes

Source
Channel.scala
def isClosed: F[Boolean]

Returns true if this channel is closed

Returns true if this channel is closed

Attributes

Source
Channel.scala
def send(a: A): F[Either[Closed, Unit]]

Sends an element through this channel.

Sends an element through this channel.

It can be called concurrently by multiple producers, and it may semantically block if the channel is bounded or synchronous.

No-op if the channel is closed, see close for further info.

Attributes

Source
Channel.scala
def sendAll: (F, A) => Nothing

Sends all the elements of the input stream through this channel, and closes it after.

Sends all the elements of the input stream through this channel, and closes it after. Especially useful if the channel is single producer.

Attributes

Source
Channel.scala
def stream: Stream[F, A]

The stream of elements sent through this channel.

The stream of elements sent through this channel. It terminates if close is called and all elements in the channel have been emitted (see close for futher info).

This method CANNOT be called concurrently by multiple consumers, if you do so, one of the consumers might become permanently deadlocked.

It is possible to call stream again once the previous one has terminated, but be aware that some element might get lost in the process, e.g if the first call to stream got 5 elements off the channel, and terminated after emitting 2, when the second call to stream starts it won't see those 3 elements.

Every time stream is pulled, it will serve all the elements that are queued up in a single chunk, including those from producers that might be semantically blocked on a bounded channel, which will then become unblocked. That is, a bound on a channel represents the maximum number of elements that can be queued up before a producer blocks, and not the maximum number of elements that will be received by stream at once.

Attributes

Source
Channel.scala
def trySend(a: A): F[Either[Closed, Boolean]]

Attempts to send an element through this channel, and indicates if it succeeded (true) or not (false).

Attempts to send an element through this channel, and indicates if it succeeded (true) or not (false).

It can be called concurrently by multiple producers, and it may not succeed if the channel is bounded or synchronous. It will never semantically block.

No-op if the channel is closed, see close for further info.

Attributes

Source
Channel.scala