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Is delay() In Kotlin Coroutine a non-blocking function?

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-2

The comment in example code says delay() is non-blocking. Should it be suspending ?

https://kotlinlang.org/docs/reference/coroutines/basics.html

fun main() 
 GlobalScope.launch // launch new coroutine in background and continue
 delay(1000L) // non-blocking delay for 1 second (default time unit is ms)
 println("World!") // print after delay
 
 println("Hello,") // main thread continues while coroutine is delayed
 Thread.sleep(2000L) // block main thread for 2 seconds to keep JVM alive

kotlin kotlin-coroutines

share|improve this question

asked Mar 24 at 18:57

user1443721user1443721

2141518

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It is a correct description because it does not block any thread, it just suspends the current coroutine.
  
  – Moira
  Mar 24 at 19:15
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  non-blocking is a well defined term in Computer Science. The println("World!") would be run immediately, instead of waiting for 1 second, based on the definition. Don't use this term if your meaning is different.
  
  – user1443721
  Mar 25 at 4:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  My meaning is definitely not different, I don't see what you're trying to say. Delay is not a blocking call, as I just explained.
  
  – Moira
  Mar 25 at 5:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Moira: delay is suspending and non-blocking. Joffrey has answered it. it is not "non-blocking" only.
  
  – user1443721
  Mar 25 at 23:05
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Moira: as you said, "it just suspends the current coroutine". Why does the comment for the delay call not say so? Instead, the comment is "non-blocking". Is it not misleading?
  
  – user1443721
  Mar 26 at 4:34
  

  
  
  
  

 | 
show 1 more comment

-2

The comment in example code says delay() is non-blocking. Should it be suspending ?

https://kotlinlang.org/docs/reference/coroutines/basics.html

fun main() 
 GlobalScope.launch // launch new coroutine in background and continue
 delay(1000L) // non-blocking delay for 1 second (default time unit is ms)
 println("World!") // print after delay
 
 println("Hello,") // main thread continues while coroutine is delayed
 Thread.sleep(2000L) // block main thread for 2 seconds to keep JVM alive

kotlin kotlin-coroutines

share|improve this question

asked Mar 24 at 18:57

user1443721user1443721

2141518

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It is a correct description because it does not block any thread, it just suspends the current coroutine.
  
  – Moira
  Mar 24 at 19:15
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  non-blocking is a well defined term in Computer Science. The println("World!") would be run immediately, instead of waiting for 1 second, based on the definition. Don't use this term if your meaning is different.
  
  – user1443721
  Mar 25 at 4:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  My meaning is definitely not different, I don't see what you're trying to say. Delay is not a blocking call, as I just explained.
  
  – Moira
  Mar 25 at 5:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Moira: delay is suspending and non-blocking. Joffrey has answered it. it is not "non-blocking" only.
  
  – user1443721
  Mar 25 at 23:05
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Moira: as you said, "it just suspends the current coroutine". Why does the comment for the delay call not say so? Instead, the comment is "non-blocking". Is it not misleading?
  
  – user1443721
  Mar 26 at 4:34
  

  
  
  
  

 | 
show 1 more comment

The comment in example code says delay() is non-blocking. Should it be suspending ?

https://kotlinlang.org/docs/reference/coroutines/basics.html

fun main() 
 GlobalScope.launch // launch new coroutine in background and continue
 delay(1000L) // non-blocking delay for 1 second (default time unit is ms)
 println("World!") // print after delay
 
 println("Hello,") // main thread continues while coroutine is delayed
 Thread.sleep(2000L) // block main thread for 2 seconds to keep JVM alive

kotlin kotlin-coroutines

share|improve this question

asked Mar 24 at 18:57

user1443721user1443721

2141518

fun main() 
 GlobalScope.launch // launch new coroutine in background and continue
 delay(1000L) // non-blocking delay for 1 second (default time unit is ms)
 println("World!") // print after delay
 
 println("Hello,") // main thread continues while coroutine is delayed
 Thread.sleep(2000L) // block main thread for 2 seconds to keep JVM alive

share|improve this question

asked Mar 24 at 18:57

user1443721user1443721

2141518

share|improve this question

asked Mar 24 at 18:57

user1443721user1443721

2141518

asked Mar 24 at 18:57

user1443721user1443721

2141518

asked Mar 24 at 18:57

user1443721user1443721

2141518

1 Answer
1

active

oldest

votes

4

The Kotlin documentation often says "non-blocking" for suspending functions to make it clear that they don't block the current thread, but simply suspend the current coroutine.

So yes, delay is suspending and non-blocking.

It may be misleading sometimes because "non-blocking" places the emphasis on the fact that nothing is blocked, while it should still be made clear that suspending functions do suspend the current coroutine (so at least something is kinda blocked, even if the thread itself carries on).

The fact that they suspend the current coroutine make these functions appear synchronous from the point of view of the current coroutine, because the coroutine needs to wait for these functions to complete before executing the rest of the code. However, they don't actually block the current thread because their implementation uses asynchronous mechanisms under the cover.

share|improve this answer

edited Mar 24 at 19:29

answered Mar 24 at 19:24

JoffreyJoffrey

7,73312953

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks! Your answer is reasonable. "non-blocking" here is really misleading. The formal document should not use this well defined term for something else. Coroutine is a new feature. It is worth to define a new set of terms to explain the features.
  
  – user1443721
  Mar 25 at 4:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @user1443721 FWIW this terminology is not new to asynchronous programming at all; see the C# docs for example.
  
  – Moira
  Mar 25 at 6:31
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @user1443721 That's exactly what Kotiln did. The new terminology is "suspending" while the old terminology ("blocking") keeps the old meaning and still refers to threads.
  
  – Marko Topolnik
  Mar 25 at 7:37
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Moira: non-blocking has been well defined, even earlier than C#. check the answer to this question, stackoverflow.com/questions/10570246/…
  
  – user1443721
  Mar 26 at 3:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Marko Topolnik: "suspending" is not new terminology. It has been used to describe thread life cycle. My question is mainly on the comment for delay() function in the example.
  
  – user1443721
  Mar 26 at 4:29
  

  
  
  
  

 | 
show 8 more comments

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4

The Kotlin documentation often says "non-blocking" for suspending functions to make it clear that they don't block the current thread, but simply suspend the current coroutine.

So yes, delay is suspending and non-blocking.

It may be misleading sometimes because "non-blocking" places the emphasis on the fact that nothing is blocked, while it should still be made clear that suspending functions do suspend the current coroutine (so at least something is kinda blocked, even if the thread itself carries on).

The fact that they suspend the current coroutine make these functions appear synchronous from the point of view of the current coroutine, because the coroutine needs to wait for these functions to complete before executing the rest of the code. However, they don't actually block the current thread because their implementation uses asynchronous mechanisms under the cover.

share|improve this answer

edited Mar 24 at 19:29

answered Mar 24 at 19:24

JoffreyJoffrey

7,73312953

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks! Your answer is reasonable. "non-blocking" here is really misleading. The formal document should not use this well defined term for something else. Coroutine is a new feature. It is worth to define a new set of terms to explain the features.
  
  – user1443721
  Mar 25 at 4:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @user1443721 FWIW this terminology is not new to asynchronous programming at all; see the C# docs for example.
  
  – Moira
  Mar 25 at 6:31
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @user1443721 That's exactly what Kotiln did. The new terminology is "suspending" while the old terminology ("blocking") keeps the old meaning and still refers to threads.
  
  – Marko Topolnik
  Mar 25 at 7:37
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Moira: non-blocking has been well defined, even earlier than C#. check the answer to this question, stackoverflow.com/questions/10570246/…
  
  – user1443721
  Mar 26 at 3:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Marko Topolnik: "suspending" is not new terminology. It has been used to describe thread life cycle. My question is mainly on the comment for delay() function in the example.
  
  – user1443721
  Mar 26 at 4:29
  

  
  
  
  

 | 
show 8 more comments

4

The Kotlin documentation often says "non-blocking" for suspending functions to make it clear that they don't block the current thread, but simply suspend the current coroutine.

So yes, delay is suspending and non-blocking.

It may be misleading sometimes because "non-blocking" places the emphasis on the fact that nothing is blocked, while it should still be made clear that suspending functions do suspend the current coroutine (so at least something is kinda blocked, even if the thread itself carries on).

The fact that they suspend the current coroutine make these functions appear synchronous from the point of view of the current coroutine, because the coroutine needs to wait for these functions to complete before executing the rest of the code. However, they don't actually block the current thread because their implementation uses asynchronous mechanisms under the cover.

share|improve this answer

edited Mar 24 at 19:29

answered Mar 24 at 19:24

JoffreyJoffrey

7,73312953

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks! Your answer is reasonable. "non-blocking" here is really misleading. The formal document should not use this well defined term for something else. Coroutine is a new feature. It is worth to define a new set of terms to explain the features.
  
  – user1443721
  Mar 25 at 4:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @user1443721 FWIW this terminology is not new to asynchronous programming at all; see the C# docs for example.
  
  – Moira
  Mar 25 at 6:31
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @user1443721 That's exactly what Kotiln did. The new terminology is "suspending" while the old terminology ("blocking") keeps the old meaning and still refers to threads.
  
  – Marko Topolnik
  Mar 25 at 7:37
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Moira: non-blocking has been well defined, even earlier than C#. check the answer to this question, stackoverflow.com/questions/10570246/…
  
  – user1443721
  Mar 26 at 3:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Marko Topolnik: "suspending" is not new terminology. It has been used to describe thread life cycle. My question is mainly on the comment for delay() function in the example.
  
  – user1443721
  Mar 26 at 4:29
  

  
  
  
  

 | 
show 8 more comments

The Kotlin documentation often says "non-blocking" for suspending functions to make it clear that they don't block the current thread, but simply suspend the current coroutine.

So yes, delay is suspending and non-blocking.

It may be misleading sometimes because "non-blocking" places the emphasis on the fact that nothing is blocked, while it should still be made clear that suspending functions do suspend the current coroutine (so at least something is kinda blocked, even if the thread itself carries on).

The fact that they suspend the current coroutine make these functions appear synchronous from the point of view of the current coroutine, because the coroutine needs to wait for these functions to complete before executing the rest of the code. However, they don't actually block the current thread because their implementation uses asynchronous mechanisms under the cover.

share|improve this answer

edited Mar 24 at 19:29

answered Mar 24 at 19:24

JoffreyJoffrey

7,73312953

share|improve this answer

edited Mar 24 at 19:29

answered Mar 24 at 19:24

JoffreyJoffrey

7,73312953

answered Mar 24 at 19:24

JoffreyJoffrey

7,73312953

answered Mar 24 at 19:24

JoffreyJoffrey

7,73312953