`(DefaultDispatcher-worker-5 @coroutine#5) Subscribing 10000 listeners took 177ms` `(DefaultDispatch...

# coroutines

[SecretX]

(DefaultDispatcher-worker-5 @coroutine#5) Subscribing 10000 listeners took 177ms
(DefaultDispatcher-worker-4 @coroutine#4) Subscribing 10000 listeners took 178ms
(DefaultDispatcher-worker-1 @coroutine#3) Subscribing 10000 listeners took 178ms
(DefaultDispatcher-worker-3 @coroutine#2) Subscribing 10000 listeners took 178ms
(DefaultDispatcher-worker-6 @coroutine#6) Subscribing 10000 listeners took 178ms
(main @coroutine#1) Unsubscribing all 49962 listeners took 0ms

[uli]

Could it be due to extension functions being used on MutableMap/Collection instead of some concurrent implementations?

[uli]

Check! contains is a kotlin extension on maps which inlines to containsKey

[uli]

And it is also a member on ConcurrentHashMap which calls …. contanisValue

[uli]

So your ConcurrentHashMap version is simply wrong 😉

[uli]

could you check timing on both versions with containsKey instead of contains

[uli]

As a side note, this code races between multiple threads and is not protected by the guarantees of `ConcurrentHashMap`:

while(observers.contains(uuid)) {
            Thread.sleep(1)
            uuid = UUID.randomUUID()
        }

[uli]

You should probably use putIfAbsent

[uli]

Untested example:

fun addListener(observer: Observer<T>): Subscription<T> {
        var uuid = UUID.randomUUID()
        while (observers.putIfAbsent(uuid, observer) != null) {
            Thread.sleep(1)
            uuid = UUID.randomUUID()
        }
        val subscription = Subscription(uuid, this)
        return subscription
    }

[SecretX]

When I changed the contain to containKey, both MutableMap and ConcurrentHashMap performed the same, thank you. Also, your untested example worked just fine, I'm going with it, thank you! @uli

[uli]

Do you still need the Thread.sleep(1)? Or was that to avoid races?