What are peoples goto solution for confining number of paral

Question

What are peoples goto solution for confining number of parallel coroutines If I use a dispatcher with e g 20 threads I guess I can still executon infinite number of coroutines to execute on these threads

gotoOla · Answer

does there exist any such support or do you have to implement something else to keep track of this via channels references to jobs deffered values

elizarov · Answer

What exactly are you trying to do

gotoOla · Answer

< elizarov> so I have something that reads from a queue so I want to pick up a message gt fire off business logic non blocking

gotoOla · Answer

so that the next message can be picked up without having to wait for the first message to be fully processed however I want max 100 messages to be processed at one time

elizarov · Answer

There are two approaches 1 Use worker pool pattern create 25 coroutines and a channel ahead of time Have all coroutines receive from the channel fan out and execute task send work to the channel when needed 2 Just launch a new coroutine for each new piece of work but use use semaphore to limit concurrency acquire permit from semaphore before launching a coroutine

gotoOla · Answer

Ah ok I see I guess the worker pool pattern would make more sense to me just because I am familiar with that behavior before slightly smiling face And the overhead of 25 in memory coroutines is not that much of a trade off Thank you

gotoOla · Answer

HI < elizarov> I had to leave but I finally sat down again and did a little test what I have now is this ``` suspend fun main val channel = Channel lt Job gt 5 GlobalScope launch while true channel send doJob System currentTimeMillis for job in channel job join private fun doJob time Long Job return GlobalScope launch println starting a job and waiting delay 5000 ``` But I see the logs come in bursts of 7 even though the capacity is 5 Did I missunderstand something here

elizarov · Answer

Burst size is always capacity + 2

elizarov · Answer

i had it explained somewhere

gotoOla · Answer

Okok I might have to sit down and watch your talk from the latest KotlinConf again watched it when it was released but we haven t worked with channels until now

gotoOla · Answer

Anyway I think this would work as a quite nice fan out strategy when reading our messages thanks for the pointers