Hi I have a question on how and why to use dispatchers I hav kotlinlang #ktor

Hi, I have a question on how and why to use dispatchers. I have a ktor project in which I fetch a number of results from the database, then I need to split these results and send them to a separate service, waiting for the response. I've implemented this using Deferreds, and using awaitall() on them. My current implementation creates a

CoroutineScope(<http://Dispatchers.IO|Dispatchers.IO>)

and then uses

async

on it to create the Deferreds. My question is whether this is the correct way to do this, or if I should use the

coroutineScope

function to create the scope and call

async

from within. Unsure if this is a #ktor or #coroutines question, seems more like the former.

bdawg.io

02/25/2019, 10:56 PM

This is a #coroutines question, but I would recommend doing

Copy code

routing {
    get { // `this` is a CoroutineScope already
        // inside of your handler
        val one = async(<http://Dispatchers.IO|Dispatchers.IO>) { ... }
        val two = async(<http://Dispatchers.IO|Dispatchers.IO>) { ... }
        val three = async(<http://Dispatchers.IO|Dispatchers.IO>) { ... }
    }
}

this attaches your

async

coroutines to be part of your route’s lifecycle

alternatively you could wrap your

async

builders using

with

to reduce duplication of which dispatcher to use

Copy code

routing {
    get {
        val results = with(CoroutineScope(coroutineContext + <http://Dispatchers.IO|Dispatchers.IO>)) {
            val one = async { ... }
            val two = async { ... }
            val three = async { ... }
            listOf(one, two, three)
        }.awaitAll()
    }
}

👍 1

2 Views