Glassthought

example

1 min read

With Dispatchers.IO

With Dispatchers.IO

Simple dispatcher IO

Simple usage of CoRoutines with IO Dispatcher

About

Here we show example of simple usage of dispatcher io.

We can see that different OS threads are being used.

Code

package gt.sandbox
 
import gt.sandbox.internal.output.Out
import kotlinx.coroutines.*
 
val out = Out.standard()
 
suspend fun fetchData(s: String) {
    out.println("Fetching data... $s")
    delay(1000) // This suspends the coroutine for 1 second without blocking the thread
    out.println("Data fetched $s")
}
 
fun main(): Unit = runBlocking {
    launch(Dispatchers.IO) {
        fetchData("a-1")
        fetchData("a-2")
    }
    launch(Dispatchers.IO) {
        fetchData("b")
    }
    launch(Dispatchers.IO) {
        fetchData("c")
    }
}

Command to reproduce:

gt.sandbox.checkout.commit 1fc85e0 \
&& cd "${GT_SANDBOX_REPO}" \
&& cmd.run.announce "./gradlew run"

Recorded output of command:

> Task :app:checkKotlinGradlePluginConfigurationErrors SKIPPED
> Task :app:processResources NO-SOURCE
> Task :app:compileKotlin
> Task :app:compileJava NO-SOURCE
> Task :app:classes UP-TO-DATE
 
> Task :app:run
[2024-06-09T04:18:21.291646Z][ms-elapsed-since-start:   50][tname:DefaultDispatcher-worker-2/tid:22] Fetching data... c
[2024-06-09T04:18:21.291456Z][ms-elapsed-since-start:   50][tname:DefaultDispatcher-worker-1/tid:21] Fetching data... a-1
[2024-06-09T04:18:21.291454Z][ms-elapsed-since-start:   50][tname:DefaultDispatcher-worker-3/tid:23] Fetching data... b
[2024-06-09T04:18:22.323347Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-2/tid:22] Data fetched c
[2024-06-09T04:18:22.323736Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-3/tid:23] Data fetched a-1
[2024-06-09T04:18:22.323347Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-1/tid:21] Data fetched b
[2024-06-09T04:18:22.324494Z][ms-elapsed-since-start: 1072][tname:DefaultDispatcher-worker-3/tid:23] Fetching data... a-2
[2024-06-09T04:18:23.325568Z][ms-elapsed-since-start: 2073][tname:DefaultDispatcher-worker-3/tid:23] Data fetched a-2
 
BUILD SUCCESSFUL in 2s
2 actionable tasks: 2 executed
Link to original

Increasing beyond double number of cores

beyond-number-of-cores

About

In this exame we illustrate the Dispatchers.IO re-using the same OS thread for 2 different executions.

This is illustrated in these lines of output:

 
[2024-06-09T04:23:29.653692Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-21/tid:41] Fetching data... task 19
[2024-06-09T04:23:29.653867Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-21/tid:41] Fetching data... task 22

Code

package gt.sandbox
 
import gt.sandbox.internal.output.Out
import kotlinx.coroutines.*
 
val out = Out.standard()
 
suspend fun fetchData(s: String) {
    out.println("Fetching data... $s")
    delay(1000) // This suspends the coroutine for 1 second without blocking the thread
    out.println("Data fetched $s")
}
 
fun main(): Unit = runBlocking {
    val availableCores = Runtime.getRuntime().availableProcessors()
    out.println("Number of available cores: $availableCores")
 
    for (i in 1..(availableCores* 2) + 2) {
        launch(Dispatchers.IO) {
            fetchData("task $i")
        }
    }
}

Command to reproduce:

gt.sandbox.checkout.commit 95c0ae2 \
&& cd "${GT_SANDBOX_REPO}" \
&& cmd.run.announce "./gradlew run"

Recorded output of command:

> Task :app:checkKotlinGradlePluginConfigurationErrors SKIPPED
> Task :app:processResources NO-SOURCE
> Task :app:compileKotlin
> Task :app:compileJava NO-SOURCE
> Task :app:classes UP-TO-DATE
 
> Task :app:run
[2024-06-09T04:23:29.630413Z][ms-elapsed-since-start:   47][tname:main/tid:1] Number of available cores: 10
[2024-06-09T04:23:29.651359Z][ms-elapsed-since-start:   59][tname:DefaultDispatcher-worker-1/tid:21] Fetching data... task 1
[2024-06-09T04:23:29.651570Z][ms-elapsed-since-start:   59][tname:DefaultDispatcher-worker-3/tid:23] Fetching data... task 2
[2024-06-09T04:23:29.651777Z][ms-elapsed-since-start:   59][tname:DefaultDispatcher-worker-5/tid:25] Fetching data... task 3
[2024-06-09T04:23:29.651815Z][ms-elapsed-since-start:   59][tname:DefaultDispatcher-worker-2/tid:22] Fetching data... task 4
[2024-06-09T04:23:29.651846Z][ms-elapsed-since-start:   59][tname:DefaultDispatcher-worker-4/tid:24] Fetching data... task 5
[2024-06-09T04:23:29.652016Z][ms-elapsed-since-start:   60][tname:DefaultDispatcher-worker-8/tid:28] Fetching data... task 6
[2024-06-09T04:23:29.652160Z][ms-elapsed-since-start:   60][tname:DefaultDispatcher-worker-7/tid:27] Fetching data... task 7
[2024-06-09T04:23:29.652243Z][ms-elapsed-since-start:   60][tname:DefaultDispatcher-worker-6/tid:26] Fetching data... task 8
[2024-06-09T04:23:29.652418Z][ms-elapsed-since-start:   60][tname:DefaultDispatcher-worker-11/tid:31] Fetching data... task 9
[2024-06-09T04:23:29.652762Z][ms-elapsed-since-start:   60][tname:DefaultDispatcher-worker-10/tid:30] Fetching data... task 10
[2024-06-09T04:23:29.652811Z][ms-elapsed-since-start:   60][tname:DefaultDispatcher-worker-14/tid:34] Fetching data... task 11
[2024-06-09T04:23:29.652945Z][ms-elapsed-since-start:   60][tname:DefaultDispatcher-worker-13/tid:33] Fetching data... task 12
[2024-06-09T04:23:29.653149Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-18/tid:38] Fetching data... task 13
[2024-06-09T04:23:29.653555Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-9/tid:29] Fetching data... task 15
[2024-06-09T04:23:29.653556Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-21/tid:41] Fetching data... task 14
[2024-06-09T04:23:29.653623Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-7/tid:27] Fetching data... task 16
[2024-06-09T04:23:29.653651Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-9/tid:29] Fetching data... task 17
[2024-06-09T04:23:29.653676Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-13/tid:33] Fetching data... task 18
[2024-06-09T04:23:29.653717Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-7/tid:27] Fetching data... task 20
[2024-06-09T04:23:29.653692Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-21/tid:41] Fetching data... task 19
[2024-06-09T04:23:29.653867Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-21/tid:41] Fetching data... task 22
[2024-06-09T04:23:29.653732Z][ms-elapsed-since-start:   61][tname:DefaultDispatcher-worker-9/tid:29] Fetching data... task 21
[2024-06-09T04:23:30.661370Z][ms-elapsed-since-start: 1069][tname:DefaultDispatcher-worker-17/tid:37] Data fetched task 7
[2024-06-09T04:23:30.661588Z][ms-elapsed-since-start: 1069][tname:DefaultDispatcher-worker-15/tid:35] Data fetched task 4
[2024-06-09T04:23:30.662263Z][ms-elapsed-since-start: 1070][tname:DefaultDispatcher-worker-15/tid:35] Data fetched task 8
[2024-06-09T04:23:30.661870Z][ms-elapsed-since-start: 1069][tname:DefaultDispatcher-worker-19/tid:39] Data fetched task 2
[2024-06-09T04:23:30.662439Z][ms-elapsed-since-start: 1070][tname:DefaultDispatcher-worker-15/tid:35] Data fetched task 3
[2024-06-09T04:23:30.662540Z][ms-elapsed-since-start: 1070][tname:DefaultDispatcher-worker-19/tid:39] Data fetched task 6
[2024-06-09T04:23:30.662606Z][ms-elapsed-since-start: 1070][tname:DefaultDispatcher-worker-15/tid:35] Data fetched task 1
[2024-06-09T04:23:30.662685Z][ms-elapsed-since-start: 1070][tname:DefaultDispatcher-worker-19/tid:39] Data fetched task 10
[2024-06-09T04:23:30.662824Z][ms-elapsed-since-start: 1070][tname:DefaultDispatcher-worker-19/tid:39] Data fetched task 11
[2024-06-09T04:23:30.662870Z][ms-elapsed-since-start: 1070][tname:DefaultDispatcher-worker-24/tid:45] Data fetched task 13
[2024-06-09T04:23:30.662972Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-19/tid:39] Data fetched task 15
[2024-06-09T04:23:30.663027Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-24/tid:45] Data fetched task 14
[2024-06-09T04:23:30.661376Z][ms-elapsed-since-start: 1069][tname:DefaultDispatcher-worker-18/tid:38] Data fetched task 9
[2024-06-09T04:23:30.663206Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-24/tid:45] Data fetched task 17
[2024-06-09T04:23:30.663273Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-18/tid:38] Data fetched task 18
[2024-06-09T04:23:30.663533Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-6/tid:26] Data fetched task 19
[2024-06-09T04:23:30.663124Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-19/tid:39] Data fetched task 16
[2024-06-09T04:23:30.662265Z][ms-elapsed-since-start: 1070][tname:DefaultDispatcher-worker-17/tid:37] Data fetched task 5
[2024-06-09T04:23:30.662858Z][ms-elapsed-since-start: 1070][tname:DefaultDispatcher-worker-15/tid:35] Data fetched task 12
[2024-06-09T04:23:30.663355Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-24/tid:45] Data fetched task 20
[2024-06-09T04:23:30.663540Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-18/tid:38] Data fetched task 22
[2024-06-09T04:23:30.663689Z][ms-elapsed-since-start: 1071][tname:DefaultDispatcher-worker-6/tid:26] Data fetched task 21
 
BUILD SUCCESSFUL in 1s
2 actionable tasks: 2 executed
Link to original

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