Dispatcher Queue Model

A dispatcher decides where work should run; this example models dispatching as a deterministic queue of labels.
dispatcher A dispatcher chooses an execution lane. This page models lanes as plain strings so replay stays deterministic.
                            lane
                            lane = "main" (default)lane = "io"lane = "default"
                        

                            DispatcherQueueModel.kt
                        
Replay: real traced execution (multi-file project)

                            import kotlin.coroutines.Continuation
import kotlin.coroutines.EmptyCoroutineContext
import kotlin.coroutines.startCoroutine

suspend fun dispatch(lane: String, task: String): String {
    return "$lane:$task"
}

fun main() {
    val lane = "main"
    val queue = mutableListOf("parse", "render", "publish")
    val handled = mutableListOf<String>()

    val work: suspend () -> String = {
        for (task in queue) {
            handled.add(dispatch(lane, task))
        }
        handled.joinToString(",")
    }

    work.startCoroutine(object : Continuation<String> {
        override val context = EmptyCoroutineContext

        override fun resumeWith(result: Result<String>) {
            handled.add("complete")
        }
    })

    println("lane=$lane")
    println("handled=" + handled.joinToString(","))
}
import kotlin.coroutines.Continuation
import kotlin.coroutines.EmptyCoroutineContext
import kotlin.coroutines.startCoroutine

suspend fun dispatch(lane: String, task: String): String {
    return "$lane:$task"
}

fun main() {
    val lane = "io"
    val queue = mutableListOf("parse", "render", "publish")
    val handled = mutableListOf<String>()

    val work: suspend () -> String = {
        for (task in queue) {
            handled.add(dispatch(lane, task))
        }
        handled.joinToString(",")
    }

    work.startCoroutine(object : Continuation<String> {
        override val context = EmptyCoroutineContext

        override fun resumeWith(result: Result<String>) {
            handled.add("complete")
        }
    })

    println("lane=$lane")
    println("handled=" + handled.joinToString(","))
}
import kotlin.coroutines.Continuation
import kotlin.coroutines.EmptyCoroutineContext
import kotlin.coroutines.startCoroutine

suspend fun dispatch(lane: String, task: String): String {
    return "$lane:$task"
}

fun main() {
    val lane = "default"
    val queue = mutableListOf("parse", "render", "publish")
    val handled = mutableListOf<String>()

    val work: suspend () -> String = {
        for (task in queue) {
            handled.add(dispatch(lane, task))
        }
        handled.joinToString(",")
    }

    work.startCoroutine(object : Continuation<String> {
        override val context = EmptyCoroutineContext

        override fun resumeWith(result: Result<String>) {
            handled.add("complete")
        }
    })

    println("lane=$lane")
    println("handled=" + handled.joinToString(","))
}

                        
1lane ← main, queue ← [parse, render, publish], handled ← [], work ← () -> kotlin.String⋯9fun main() {10    val lane→ main = "main" //@lane="io", "default"11    val queue→ [parse, render, publish] = mutableListOf("parse", "render", "publish")12    val handled→ [] = mutableListOf<String>()1314    val work→ () -> kotlin.String: suspend () -> String = {15        for (task in queue) {16            handled.add(dispatch(lane, task))17        }18        handled.joinToString(",")19    }2021    work() -> kotlin.String.startCoroutine(object : Continuation<String> {22        override val context = EmptyCoroutineContext2324        override fun resumeWith(result: Result<String>) {25            handled.add("complete")26        }27    })⋯
2suspend fun dispatch(lane: String, task: String): Stringpass 1 of 3⋯5suspend fun dispatch(lanemain: String, taskparse: String): String {6    return "$lanemain:$taskparse"7}⋯All 3 passes — pass 1 is the card abovepasstask
1parse
2render
3publish
3handled.add(dispatch(lane, task))⋯15for (task in queue) {16    handled.add(dispatch(lane, task))17}⋯
4handled.add(dispatch(lane, task))⋯15for (task in queue) {16    handled.add(dispatch(lane, task))17}⋯
5handled.add(dispatch(lane, task))⋯15for (task in queue) {16    handled.add(dispatch(lane, task))17}⋯
6override fun resumeWith(result: Result<String>)⋯21work() -> kotlin.String.startCoroutine(object : Continuation<String> {22    override val context = EmptyCoroutineContext2324    override fun resumeWith(resultSuccess(main:parse,main:render,main:publish): Result<String>) {25        handled[main:parse, main:render, main:publish].add("complete")26    }27})⋯
7println("lane=$lane")⋯29    println("lane=$lanemain")30    println("handled=" + handled[main:parse, main:render, main:publish, complete].joinToString(","))31}⋯outputlane=main
handled=main:parse,main:render,main:publish,complete
1lane ← io, queue ← [parse, render, publish], handled ← [], work ← () -> kotlin.String⋯9fun main() {10    val lane→ io = "io"11    val queue→ [parse, render, publish] = mutableListOf("parse", "render", "publish")12    val handled→ [] = mutableListOf<String>()1314    val work→ () -> kotlin.String: suspend () -> String = {15        for (task in queue) {16            handled.add(dispatch(lane, task))17        }18        handled.joinToString(",")19    }2021    work() -> kotlin.String.startCoroutine(object : Continuation<String> {22        override val context = EmptyCoroutineContext2324        override fun resumeWith(result: Result<String>) {25            handled.add("complete")26        }27    })⋯
2suspend fun dispatch(lane: String, task: String): Stringpass 1 of 3⋯5suspend fun dispatch(laneio: String, taskparse: String): String {6    return "$laneio:$taskparse"7}⋯All 3 passes — pass 1 is the card abovepasstask
1parse
2render
3publish
3handled.add(dispatch(lane, task))⋯15for (task in queue) {16    handled.add(dispatch(lane, task))17}⋯
4handled.add(dispatch(lane, task))⋯15for (task in queue) {16    handled.add(dispatch(lane, task))17}⋯
5handled.add(dispatch(lane, task))⋯15for (task in queue) {16    handled.add(dispatch(lane, task))17}⋯
6override fun resumeWith(result: Result<String>)⋯21work() -> kotlin.String.startCoroutine(object : Continuation<String> {22    override val context = EmptyCoroutineContext2324    override fun resumeWith(resultSuccess(io:parse,io:render,io:publish): Result<String>) {25        handled[io:parse, io:render, io:publish].add("complete")26    }27})⋯
7println("lane=$lane")⋯29    println("lane=$laneio")30    println("handled=" + handled[io:parse, io:render, io:publish, complete].joinToString(","))31}⋯outputlane=io
handled=io:parse,io:render,io:publish,complete
1lane ← default, queue ← [parse, render, publish], handled ← []⋯9fun main() {10    val lane→ default = "default"11    val queue→ [parse, render, publish] = mutableListOf("parse", "render", "publish")12    val handled→ [] = mutableListOf<String>()1314    val work→ () -> kotlin.String: suspend () -> String = {15        for (task in queue) {16            handled.add(dispatch(lane, task))17        }18        handled.joinToString(",")19    }2021    work() -> kotlin.String.startCoroutine(object : Continuation<String> {22        override val context = EmptyCoroutineContext2324        override fun resumeWith(result: Result<String>) {25            handled.add("complete")26        }27    })⋯
2suspend fun dispatch(lane: String, task: String): Stringpass 1 of 3⋯5suspend fun dispatch(lanedefault: String, taskparse: String): String {6    return "$lanedefault:$taskparse"7}⋯All 3 passes — pass 1 is the card abovepasstask
1parse
2render
3publish
3handled.add(dispatch(lane, task))⋯15for (task in queue) {16    handled.add(dispatch(lane, task))17}⋯
4handled.add(dispatch(lane, task))⋯15for (task in queue) {16    handled.add(dispatch(lane, task))17}⋯
5handled.add(dispatch(lane, task))⋯15for (task in queue) {16    handled.add(dispatch(lane, task))17}⋯
6override fun resumeWith(result: Result<String>)⋯21work() -> kotlin.String.startCoroutine(object : Continuation<String> {22    override val context = EmptyCoroutineContext2324    override fun resumeWith(resultSuccess(default:parse,default:render,default:publish): Result<String>) {25        handled[default:parse, default:render, default:publish].add("complete")26    }27})⋯
7println("lane=$lane")⋯29    println("lane=$lanedefault")30    println("handled=" + handled[default:parse, default:render, default:publish, complete].joinToString(","))31}⋯outputlane=default
handled=default:parse,default:render,default:publish,complete
All 3 passes — pass 1 is the card above
pass	`task`
1	parse
2	render
3	publish
All 3 passes — pass 1 is the card above
pass	`task`
1	parse
2	render
3	publish
All 3 passes — pass 1 is the card above
pass	`task`
1	parse
2	render
3	publish