How could I know what the number of threads is used by specific coroutines dispatcher?

Question

How could I know what the number of threads Dispatchers.IO is currently using ?

Answer 1

As you can read here Dispatchers.IO doesn't have own pool of threads, it uses a shared pool. Dispatchers.Default uses the same pool of threads. There no simple way to get active threads currently used by Dispatchers.IO. But you can try get thread count inside shared pool of threads. The common pool of threads is creating inside CommonPool.kt. It can create own pool or use ForkJoinPool. All threads created in pool have a specific name. So you can find all active thread of shared pool by name.

val threads = Thread.getAllStackTraces().keys.filter {
    it.name.startsWith("CommonPool") || it.name.startsWith("ForkJoinPool")
}
threads.size