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trait ConsumerF[F[_], E, A] extends Serializable

A simple interface that models the consumer side of a producer-consumer communication channel.

Currently exposed by ConcurrentChannel.consume.

F

is effect type used for processing tasks asynchronously

E

is the type for the completion event

A

is the type for the stream of events being consumed

Source
ConsumerF.scala
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Abstract Value Members

  1. abstract def pull: F[Either[E, A]]

    Pulls one message from the communication channel, when it becomes available.

    Pulls one message from the communication channel, when it becomes available.

    Example:

    import cats.implicits._
    import cats.effect.Async
    
    def sum[F[_]](channel: ConsumerF[F, Int, Int], acc: Long = 0)
      (implicit F: Async[F]): F[Long] = {
    
      channel.pull.flatMap {
        case Left(e) => F.pure(acc + e)
        case Right(i) => sum(channel, acc + i)
      }
    }
    returns

    either Left(e), if the channel was closed with a final e completion event, or Right(a), representing a message that was pulled from the channel

  2. abstract def pullMany(minLength: Int, maxLength: Int): F[Either[E, Seq[A]]]

    Pulls a whole batch of messages from the channel, at least one, the returned sequence being no larger than the specified maxLength.

    Pulls a whole batch of messages from the channel, at least one, the returned sequence being no larger than the specified maxLength.

    import cats.implicits._
    import cats.effect.Async
    
    def sum[F[_]](channel: ConsumerF[F, Int, Int], acc: Long = 0)
      (implicit F: Async[F]): F[Long] = {
    
      channel.pullMany(1, 16).flatMap {
        case Left(e) => F.pure(acc + e)
        case Right(seq) => sum(channel, acc + seq.sum)
      }
    }
    minLength

    is the minimum size of the returned sequence; for as long as the channel isn't halted, the returned task will back-pressure until the required number of events have been collected

    maxLength

    is the maximum size of the returned sequence; for fairness purposes (e.g. multiple workers consuming from the same ConsumerF), a smaller value is recommended, or otherwise Int.MaxValue can be used

    returns

    either Left(e), if the channel was closed with a final e completion event, or Right(seq), representing a non-empty sequence of messages pulled from the channel, but that is no larger than maxLength

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  18. final def wait(): Unit
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  1. def finalize(): Unit
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