Closing Channel

Traits:

• Channel.send() will throw exception if channel is closed.
• Channel.receive() will throw exception if channel is closed.
• Receiver will get out of for loop if channel is closed.

In Action

package com.glassthought.sandbox

import com.glassthought.sandbox.util.out.impl.OutSettings
import gt.sandbox.util.output.Out
import kotlinx.coroutines.CoroutineName
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking

val out = Out.standard(OutSettings(printCoroutineName = true, printThreadInfo = false))

fun main(args: Array<String>) {
  runBlocking {
    val channel = Channel<Int>(Channel.UNLIMITED)

    val sender = launch(CoroutineName("${Emoji.LETTER}-sender")) {
      try {
        repeat(10) {
          delay(500)

          out.info("starting_to_send: $it")

          channel.send(it)

          out.info("sent: $it")
        }
      } catch (e: Exception) {
        out.infoRed("sender exception: $e")
      }
    }

    val listener = launch(CoroutineName("${Emoji.MAILBOX}-listener")) {
      try {
        for (i in channel) {
          out.info("received: $i")
        }
        out.info("Listener Done - ${Emoji.CHECKERED_FLAG}")
      } catch (e: Exception) {
        out.infoRed("listener exception: $e")
      }
    }

    delay(1700)
    out.info("Closing channel from Main")
    channel.close()

    delay(2000)
    out.info("Main completed. Exiting...")
    System.exit(0)
  }
}

class Emoji {
  companion object {
    const val LETTER = "✉\uFE0F"
    const val MAILBOX = "\uD83D\uDCEC"
    const val CHECKERED_FLAG = "\uD83C\uDFC1"
  }
}

gt.sandbox.checkout.commit 58e15651b7326dc65946 \
&& cd "${GT_SANDBOX_REPO}" \
&& cmd.run.announce "./gradlew run --quiet"

[elapsed:  559ms][coroutine:✉️-sender] starting_to_send: 0
[elapsed:  583ms][coroutine:✉️-sender] sent: 0
[elapsed:  583ms][coroutine:📬-listener] received: 0
[elapsed: 1088ms][coroutine:✉️-sender] starting_to_send: 1
[elapsed: 1089ms][coroutine:✉️-sender] sent: 1
[elapsed: 1090ms][coroutine:📬-listener] received: 1
[elapsed: 1593ms][coroutine:✉️-sender] starting_to_send: 2
[elapsed: 1594ms][coroutine:✉️-sender] sent: 2
[elapsed: 1594ms][coroutine:📬-listener] received: 2
[elapsed: 1742ms][coroutine:unnamed] Closing channel from Main
[elapsed: 1746ms][coroutine:📬-listener] Listener Done - 🏁
[elapsed: 2099ms][coroutine:✉️-sender] starting_to_send: 3
[elapsed: 2105ms][coroutine:✉️-sender] sender exception: kotlinx.coroutines.channels.ClosedSendChannelException: Channel was closed
[elapsed: 3752ms][coroutine:unnamed] Main completed. Exiting...

package com.glassthought.sandbox

import com.glassthought.sandbox.util.out.impl.OutSettings
import gt.sandbox.util.output.Out
import kotlinx.coroutines.CoroutineName
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking

val out = Out.standard(OutSettings(printCoroutineName = true, printThreadInfo = false))

fun main(args: Array<String>) {
  runBlocking {
    val channel = Channel<Int>(Channel.UNLIMITED)

    val sender = launch(CoroutineName("${Emoji.LETTER}-sender")) {
      try {
        repeat(1) {
          delay(500)

          out.info("starting_to_send: $it")

          channel.send(it)

          out.info("sent: $it")
        }
      } catch (e: Exception) {
        out.infoRed("sender exception: $e")
      }
    }

    val listener = launch(CoroutineName("${Emoji.MAILBOX}-listener")) {
      try {
        repeat(100){
          out.info("received: ${channel.receive()}")
        }
        out.info("Listener Done - ${Emoji.CHECKERED_FLAG}")
      } catch (e: Exception) {
        out.infoRed("listener exception: $e")
      }
    }

    delay(1700)
    out.info("Closing channel from Main")
    channel.close()

    delay(2000)
    out.info("Main completed. Exiting...")
    System.exit(0)
  }
}

class Emoji {
  companion object {
    const val LETTER = "✉\uFE0F"
    const val MAILBOX = "\uD83D\uDCEC"
    const val CHECKERED_FLAG = "\uD83C\uDFC1"
  }
}

gt.sandbox.checkout.commit 0a95e9908782f3bef115 \
&& cd "${GT_SANDBOX_REPO}" \
&& cmd.run.announce "./gradlew run --quiet"

[elapsed:  564ms][coroutine:✉️-sender] starting_to_send: 0
[elapsed:  588ms][coroutine:✉️-sender] sent: 0
[elapsed:  589ms][coroutine:📬-listener] received: 0
[elapsed: 1740ms][coroutine:unnamed] Closing channel from Main
[elapsed: 1746ms][coroutine:📬-listener] listener exception: kotlinx.coroutines.channels.ClosedReceiveChannelException: Channel was closed
[elapsed: 3748ms][coroutine:unnamed] Main completed. Exiting...

• Channel