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Does Kotlin delay use a dispatcher internally to unblock the caller thread?
In Kotlin, is it possible to change delegation at Runtime?Difference between thread and coroutine in KotlinHow does the delay function in Kotlin internally work?Kotlin coroutine async with delayWhen should I make my normal function suspending function?How do Kotlin coroutines work internally?Coroutines: runBlocking vs coroutineScopeIs NetworkOnMainThreadException valid for a network call in a coroutine?How to achieve non blocking with CoroutinesBasic coroutine network call in a library
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This is some test code I am using to learn kotlin coroutines. The code works as expected and takes about 1 Second to print the sum, but now If I replace delay(1000) by a blocking call like a network request, then the code takes about 10 seconds to print the sum ( each call takes around 1 second), but if I wrap the network call in a withContext and use the IO dispatcher it takes 1 second to print the sum, because it is run on a different thread. Does the delay function use some kind of a dispatcher to unblock the thread?
suspend fun asyncDoubleFn(num: Int): Int
delay(1000)
return num * 2
fun main() = runBlocking
launch
val tt = measureTimeMillis
val results = mutableListOf<Deferred<Int>>()
for (num in 0..10)
val result = async asyncDoubleFn(num + 1)
results.add(result)
val sum = results.map it.await() .reduce acc, i -> acc + i
println("[SUM]: $sum")
println("[TT]: $tt")
launch
println("Another coroutine")
println("Main Code")
kotlin kotlin-coroutines
asked Mar 23 at 6:07
Shubhang BShubhang B
3213
add a comment |
This is some test code I am using to learn kotlin coroutines. The code works as expected and takes about 1 Second to print the sum, but now If I replace delay(1000) by a blocking call like a network request, then the code takes about 10 seconds to print the sum ( each call takes around 1 second), but if I wrap the network call in a withContext and use the IO dispatcher it takes 1 second to print the sum, because it is run on a different thread. Does the delay function use some kind of a dispatcher to unblock the thread?
suspend fun asyncDoubleFn(num: Int): Int
delay(1000)
return num * 2
fun main() = runBlocking
launch
val tt = measureTimeMillis
val results = mutableListOf<Deferred<Int>>()
for (num in 0..10)
val result = async asyncDoubleFn(num + 1)
results.add(result)
val sum = results.map it.await() .reduce acc, i -> acc + i
println("[SUM]: $sum")
println("[TT]: $tt")
launch
println("Another coroutine")
println("Main Code")
kotlin kotlin-coroutines
asked Mar 23 at 6:07
Shubhang BShubhang B
3213
Source: github.com/Kotlin/kotlinx.coroutines/blob/master/common/…
– Moira
Mar 23 at 8:32
Thanks! I was looking for a little detailed explanation , since I am new to this concept, but am familiar with JS async await(Mostly do front-end JS). I mainly want to understand if we can take a blocking API like java.net.URL and run it in suspend mode.
– Shubhang B
Mar 23 at 9:28
You can, take a look atsuspendCoroutine. I'm not familiar enough with the details to fully explain how it works, but there was a good talk on this at KotlinConf.
– Moira
Mar 23 at 9:31
add a comment |
This is some test code I am using to learn kotlin coroutines. The code works as expected and takes about 1 Second to print the sum, but now If I replace delay(1000) by a blocking call like a network request, then the code takes about 10 seconds to print the sum ( each call takes around 1 second), but if I wrap the network call in a withContext and use the IO dispatcher it takes 1 second to print the sum, because it is run on a different thread. Does the delay function use some kind of a dispatcher to unblock the thread?
suspend fun asyncDoubleFn(num: Int): Int
delay(1000)
return num * 2
fun main() = runBlocking
launch
val tt = measureTimeMillis
val results = mutableListOf<Deferred<Int>>()
for (num in 0..10)
val result = async asyncDoubleFn(num + 1)
results.add(result)
val sum = results.map it.await() .reduce acc, i -> acc + i
println("[SUM]: $sum")
println("[TT]: $tt")
launch
println("Another coroutine")
println("Main Code")
kotlin kotlin-coroutines
asked Mar 23 at 6:07
Shubhang BShubhang B
3213
This is some test code I am using to learn kotlin coroutines. The code works as expected and takes about 1 Second to print the sum, but now If I replace delay(1000) by a blocking call like a network request, then the code takes about 10 seconds to print the sum ( each call takes around 1 second), but if I wrap the network call in a withContext and use the IO dispatcher it takes 1 second to print the sum, because it is run on a different thread. Does the delay function use some kind of a dispatcher to unblock the thread?
suspend fun asyncDoubleFn(num: Int): Int
delay(1000)
return num * 2
fun main() = runBlocking
launch
val tt = measureTimeMillis
val results = mutableListOf<Deferred<Int>>()
for (num in 0..10)
val result = async asyncDoubleFn(num + 1)
results.add(result)
val sum = results.map it.await() .reduce acc, i -> acc + i
println("[SUM]: $sum")
println("[TT]: $tt")
launch
println("Another coroutine")
println("Main Code")
kotlin kotlin-coroutines
kotlin kotlin-coroutines
asked Mar 23 at 6:07
Shubhang BShubhang B
3213
asked Mar 23 at 6:07
Shubhang BShubhang B
3213
asked Mar 23 at 6:07
Shubhang BShubhang B
3213
asked Mar 23 at 6:07
Shubhang BShubhang B
3213
asked Mar 23 at 6:07
Shubhang BShubhang B
3213
3213
Source: github.com/Kotlin/kotlinx.coroutines/blob/master/common/…
– Moira
Mar 23 at 8:32
Thanks! I was looking for a little detailed explanation , since I am new to this concept, but am familiar with JS async await(Mostly do front-end JS). I mainly want to understand if we can take a blocking API like java.net.URL and run it in suspend mode.
– Shubhang B
Mar 23 at 9:28
You can, take a look atsuspendCoroutine. I'm not familiar enough with the details to fully explain how it works, but there was a good talk on this at KotlinConf.
– Moira
Mar 23 at 9:31
add a comment |
Source: github.com/Kotlin/kotlinx.coroutines/blob/master/common/…
– Moira
Mar 23 at 8:32
Thanks! I was looking for a little detailed explanation , since I am new to this concept, but am familiar with JS async await(Mostly do front-end JS). I mainly want to understand if we can take a blocking API like java.net.URL and run it in suspend mode.
– Shubhang B
Mar 23 at 9:28
You can, take a look atsuspendCoroutine. I'm not familiar enough with the details to fully explain how it works, but there was a good talk on this at KotlinConf.
– Moira
Mar 23 at 9:31
Source: github.com/Kotlin/kotlinx.coroutines/blob/master/common/…
– Moira
Mar 23 at 8:32
Source: github.com/Kotlin/kotlinx.coroutines/blob/master/common/…
– Moira
Mar 23 at 8:32
Thanks! I was looking for a little detailed explanation , since I am new to this concept, but am familiar with JS async await(Mostly do front-end JS). I mainly want to understand if we can take a blocking API like java.net.URL and run it in suspend mode.
– Shubhang B
Mar 23 at 9:28
Thanks! I was looking for a little detailed explanation , since I am new to this concept, but am familiar with JS async await(Mostly do front-end JS). I mainly want to understand if we can take a blocking API like java.net.URL and run it in suspend mode.
– Shubhang B
Mar 23 at 9:28
You can, take a look at
suspendCoroutine. I'm not familiar enough with the details to fully explain how it works, but there was a good talk on this at KotlinConf.– Moira
Mar 23 at 9:31
You can, take a look at
suspendCoroutine. I'm not familiar enough with the details to fully explain how it works, but there was a good talk on this at KotlinConf.– Moira
Mar 23 at 9:31
add a comment |
1 Answer
1
active
oldest
votes
Does the delay function use some kind of a dispatcher to unblock the thread?
Not just delay. All suspendable functions interact with the dispatcher.
The question you should ask is: "Which dispatcher is in charge here?"
And the answer is: runBlocking installs its own dispatcher that dispatches to the thread it is called on. Both launch and async in your code inherit it.
With this in mind:
If I replace delay(1000) by a blocking call like a network request, then the code takes about 10 seconds to print the sum (each call takes around 1 second)
Each blocking call will hold on to the single thread of the dispatcher. It won't be able to do any other work while being blocked.
but if I wrap the network call in a
withContextand use theIOdispatcher it takes 1 second to print the sum, because it is run on a different thread
Yes, this changes the dispatcher, problem solved.
So, what does delay do? It suspends the current coroutine (the one that async launched) and returns the control to the dispatcher, which can now go on to resume your loop and start the next coroutine.
answered Mar 24 at 7:31
Marko TopolnikMarko Topolnik
149k19201332
Thank you for the detailed answer, this clears most of my confusion, you said delay suspends the current coroutine and returns control to the dispatcher, does delay use some kind of a task queue scheduling to run the code after the delay time elapses , does it work like setTimeout in JS?.
– Shubhang B
Mar 24 at 13:55
1
It works pretty much exactly like that. TherunBlockingdispatcher establishes an event queue and an event loop that drains the queue and handles the events. Just like the Android looper or the Swing event loop or the JS event loop.
– Marko Topolnik
Mar 25 at 7:34
add a comment |
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1 Answer
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oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Does the delay function use some kind of a dispatcher to unblock the thread?
Not just delay. All suspendable functions interact with the dispatcher.
The question you should ask is: "Which dispatcher is in charge here?"
And the answer is: runBlocking installs its own dispatcher that dispatches to the thread it is called on. Both launch and async in your code inherit it.
With this in mind:
If I replace delay(1000) by a blocking call like a network request, then the code takes about 10 seconds to print the sum (each call takes around 1 second)
Each blocking call will hold on to the single thread of the dispatcher. It won't be able to do any other work while being blocked.
but if I wrap the network call in a
withContextand use theIOdispatcher it takes 1 second to print the sum, because it is run on a different thread
Yes, this changes the dispatcher, problem solved.
So, what does delay do? It suspends the current coroutine (the one that async launched) and returns the control to the dispatcher, which can now go on to resume your loop and start the next coroutine.
answered Mar 24 at 7:31
Marko TopolnikMarko Topolnik
149k19201332
Thank you for the detailed answer, this clears most of my confusion, you said delay suspends the current coroutine and returns control to the dispatcher, does delay use some kind of a task queue scheduling to run the code after the delay time elapses , does it work like setTimeout in JS?.
– Shubhang B
Mar 24 at 13:55
1
It works pretty much exactly like that. TherunBlockingdispatcher establishes an event queue and an event loop that drains the queue and handles the events. Just like the Android looper or the Swing event loop or the JS event loop.
– Marko Topolnik
Mar 25 at 7:34
add a comment |
Does the delay function use some kind of a dispatcher to unblock the thread?
Not just delay. All suspendable functions interact with the dispatcher.
The question you should ask is: "Which dispatcher is in charge here?"
And the answer is: runBlocking installs its own dispatcher that dispatches to the thread it is called on. Both launch and async in your code inherit it.
With this in mind:
If I replace delay(1000) by a blocking call like a network request, then the code takes about 10 seconds to print the sum (each call takes around 1 second)
Each blocking call will hold on to the single thread of the dispatcher. It won't be able to do any other work while being blocked.
but if I wrap the network call in a
withContextand use theIOdispatcher it takes 1 second to print the sum, because it is run on a different thread
Yes, this changes the dispatcher, problem solved.
So, what does delay do? It suspends the current coroutine (the one that async launched) and returns the control to the dispatcher, which can now go on to resume your loop and start the next coroutine.
answered Mar 24 at 7:31
Marko TopolnikMarko Topolnik
149k19201332
Thank you for the detailed answer, this clears most of my confusion, you said delay suspends the current coroutine and returns control to the dispatcher, does delay use some kind of a task queue scheduling to run the code after the delay time elapses , does it work like setTimeout in JS?.
– Shubhang B
Mar 24 at 13:55
1
It works pretty much exactly like that. TherunBlockingdispatcher establishes an event queue and an event loop that drains the queue and handles the events. Just like the Android looper or the Swing event loop or the JS event loop.
– Marko Topolnik
Mar 25 at 7:34
add a comment |
Does the delay function use some kind of a dispatcher to unblock the thread?
Not just delay. All suspendable functions interact with the dispatcher.
The question you should ask is: "Which dispatcher is in charge here?"
And the answer is: runBlocking installs its own dispatcher that dispatches to the thread it is called on. Both launch and async in your code inherit it.
With this in mind:
If I replace delay(1000) by a blocking call like a network request, then the code takes about 10 seconds to print the sum (each call takes around 1 second)
Each blocking call will hold on to the single thread of the dispatcher. It won't be able to do any other work while being blocked.
but if I wrap the network call in a
withContextand use theIOdispatcher it takes 1 second to print the sum, because it is run on a different thread
Yes, this changes the dispatcher, problem solved.
So, what does delay do? It suspends the current coroutine (the one that async launched) and returns the control to the dispatcher, which can now go on to resume your loop and start the next coroutine.
answered Mar 24 at 7:31
Marko TopolnikMarko Topolnik
149k19201332
Does the delay function use some kind of a dispatcher to unblock the thread?
Not just delay. All suspendable functions interact with the dispatcher.
The question you should ask is: "Which dispatcher is in charge here?"
And the answer is: runBlocking installs its own dispatcher that dispatches to the thread it is called on. Both launch and async in your code inherit it.
With this in mind:
If I replace delay(1000) by a blocking call like a network request, then the code takes about 10 seconds to print the sum (each call takes around 1 second)
Each blocking call will hold on to the single thread of the dispatcher. It won't be able to do any other work while being blocked.
but if I wrap the network call in a
withContextand use theIOdispatcher it takes 1 second to print the sum, because it is run on a different thread
Yes, this changes the dispatcher, problem solved.
So, what does delay do? It suspends the current coroutine (the one that async launched) and returns the control to the dispatcher, which can now go on to resume your loop and start the next coroutine.
answered Mar 24 at 7:31
Marko TopolnikMarko Topolnik
149k19201332
answered Mar 24 at 7:31
Marko TopolnikMarko Topolnik
149k19201332
answered Mar 24 at 7:31
Marko TopolnikMarko Topolnik
149k19201332
answered Mar 24 at 7:31
Marko TopolnikMarko Topolnik
149k19201332
149k19201332
Thank you for the detailed answer, this clears most of my confusion, you said delay suspends the current coroutine and returns control to the dispatcher, does delay use some kind of a task queue scheduling to run the code after the delay time elapses , does it work like setTimeout in JS?.
– Shubhang B
Mar 24 at 13:55
1
It works pretty much exactly like that. TherunBlockingdispatcher establishes an event queue and an event loop that drains the queue and handles the events. Just like the Android looper or the Swing event loop or the JS event loop.
– Marko Topolnik
Mar 25 at 7:34
add a comment |
Thank you for the detailed answer, this clears most of my confusion, you said delay suspends the current coroutine and returns control to the dispatcher, does delay use some kind of a task queue scheduling to run the code after the delay time elapses , does it work like setTimeout in JS?.
– Shubhang B
Mar 24 at 13:55
1
It works pretty much exactly like that. TherunBlockingdispatcher establishes an event queue and an event loop that drains the queue and handles the events. Just like the Android looper or the Swing event loop or the JS event loop.
– Marko Topolnik
Mar 25 at 7:34
Thank you for the detailed answer, this clears most of my confusion, you said delay suspends the current coroutine and returns control to the dispatcher, does delay use some kind of a task queue scheduling to run the code after the delay time elapses , does it work like setTimeout in JS?.
– Shubhang B
Mar 24 at 13:55
Thank you for the detailed answer, this clears most of my confusion, you said delay suspends the current coroutine and returns control to the dispatcher, does delay use some kind of a task queue scheduling to run the code after the delay time elapses , does it work like setTimeout in JS?.
– Shubhang B
Mar 24 at 13:55
1
1
It works pretty much exactly like that. The
runBlocking dispatcher establishes an event queue and an event loop that drains the queue and handles the events. Just like the Android looper or the Swing event loop or the JS event loop.– Marko Topolnik
Mar 25 at 7:34
It works pretty much exactly like that. The
runBlocking dispatcher establishes an event queue and an event loop that drains the queue and handles the events. Just like the Android looper or the Swing event loop or the JS event loop.– Marko Topolnik
Mar 25 at 7:34
add a comment |
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Source: github.com/Kotlin/kotlinx.coroutines/blob/master/common/…
– Moira
Mar 23 at 8:32
Thanks! I was looking for a little detailed explanation , since I am new to this concept, but am familiar with JS async await(Mostly do front-end JS). I mainly want to understand if we can take a blocking API like java.net.URL and run it in suspend mode.
– Shubhang B
Mar 23 at 9:28
You can, take a look at
suspendCoroutine. I'm not familiar enough with the details to fully explain how it works, but there was a good talk on this at KotlinConf.– Moira
Mar 23 at 9:31