How to properly initialize such kind of patterns Currently d

Question

How to properly initialize such kind of patterns Currently depending on the state of the device and load the repeat call can trigger creation of tons of threads even if there s no tasks yet Generating a lot of unecessary load at init time ``` class XXX CoroutineScope override val coroutineContext = <http Dispatchers IO|Dispatchers IO> + SupervisorJob internal val tasks = Channel lt Task gt UNLIMITED fun startWorkers repeat 150 launch for task in tasks executeTask task ```

Zach Klippenstein (he/him) [MOD] · Answer

What if you use the `Default` dispatcher smaller fixed size thread pool so you re not gonna create a bunch of threads then inside each of the workers you wait to switch to the `IO` dispatcher until you have the first task ``` launch Unconfined var initialTask = tasks receive withContext IO executeTask initialTask for task in tasks executeTask task ```

Zach Klippenstein (he/him) [MOD] · Answer

I think you could even use `Unconfined` to launch them since the only work they d be doing initially would be registering to receive from the channel

Tolriq · Answer

The problem is that your solution loose the parallelism configuration At some point I need to start at max X for loops 150 in the posted sample for example

Tolriq · Answer

Maybe < elizarov> have an official pattern for that I suppose I could wrap the repeat in a coroutine and add a small delay after each launch as a workaround

Zach Klippenstein (he/him) [MOD] · Answer

You only lose parallelism while waiting for the first emission from the channel but that doesn t matter the coroutines aren t doing any work then anyway they re just waiting As soon as you switch to the IO dispatcher you get the full parallelism of the IO dispatcher back

Tolriq · Answer

I m talking about the parallelism in active running tasks the repeat ensure the number of simultaneous tasks Without 1 launch + for loop you only have 1 running task And if I do the launch in the for loop then I loose control over max running tasks too

Zach Klippenstein (he/him) [MOD] · Answer

oh sorry i meant you d still have the repeat i was just referring to the code inside it So ``` fun startWorkers repeat 150 startWorker private fun startWorker launch Unconfined var initialTask = tasks receive withContext IO executeTask initialTask for task in tasks executeTask task ```

Tolriq · Answer

Ho yes I m stupid slightly smiling face Thanks this should work nicely

Tolriq · Answer

For the record tasks receive throw on channel closing unlike the for loop So call require try catch ClosedReceiveChannelException And it seems there s maybe a side effect of using Unconfined leading to withContext not always switching Will investigate more on that last one

Zach Klippenstein (he/him) [MOD] · Answer

Oh yikes that seems bad Is there an issue

Zach Klippenstein (he/him) [MOD] · Answer

Anyway you can use `Default` too for that initial dispatcher

Tolriq · Answer

That issue was due to me being too tired and inheriting the wrong coroutineContext With Unconfined there s strange difference in the number of launch but I did not investigate that much and use my global background dispatcher that fit the needs and solve my issue

Tolriq · Answer

``` repeat maxConcurrentTasks launch Dispatchers Unconfined Log e AAAA Launch $ Thread currentThread name val initialTask = try tasks receive catch e Exception return launch withContext this OkHttpWorkerPool coroutineContext Log e AAAA Run $ Thread currentThread name executeTask initialTask for task in tasks executeTask task ``` Will only log 4 Launch main thread

Tolriq · Answer

Using Dispatchers Default or IO will properly log 1 Launch per repeat