A Dispatcher Limited to a Single Thread
Learn the approaches to use for dispatchers that are limited to a single thread.
We'll cover the following...
We saw a dispatcher with parallelism limited to a single thread in the “Dispatchers” chapter. This is the easiest solution for most problems with shared states.
package kotlinx.coroutines.app
import kotlinx.coroutines.*
import java.util.concurrent.Executors
val dispatcher = Dispatchers.IO
.limitedParallelism(1)
var counter = 0
fun main() = runBlocking {
massiveRun {
withContext(dispatcher) {
counter++
}
}
println(counter) // 1000000
}
suspend fun massiveRun(action: suspend () -> Unit) =
withContext(Dispatchers.Default) {
repeat(1000) {
launch {
repeat(1000) { action() }
}
}
}
Problem of concurrent use
In practice, we can use this approach in two ways.
Coarse-grained thread confinement
The first approach is known as coarse-grained thread confinement. This is a straightforward approach where we wrap the whole function with withContext, with a dispatcher limited to a single thread. This solution is easy and eliminates conflicts, but the problem ...