@Synchronized is not working as expected in KMM

Question

I have a Ktor class where I need to do action on unauthorized exception(when token is expired), for this action I need to have synchronized action, otherwise it is not working correctly, the problem is that @Synchronized is not synchronize the action and is not waiting for action to finish for next one.

       fun ktorFunction(){

        HttpResponseValidator {
        handleResponseException { exception ->
            kermit.e { "In ${exception.message}" }

            val clientException =
                exception as? ClientRequestException ?: return@handleResponseException
            val exceptionResponse = clientException.response

            when (exceptionResponse.status) {
                HttpStatusCode.Unauthorized -> {
                    test(){
                        kermit.v { "Error message" }
                    }
            }
         }
      }
   }




@Synchronized
fun test(messageTest: () -> Unit) {
CoroutineScope(Dispatchers.Default).launch {
    delay(3000)
    messageTest()

    }
}

The idea is I want test function to not be called from other thread until it is finished, whatever the action is in it.

Answer 1

launch is a function that starts a coroutine asynchronously and immediately returns, so this is behaving as it should. If you want to synchronize coroutines, you should use Mutex .

I'll leave it alone in the example before, but IMO, it's a code smell to create a CoroutineScope if you're not going to manage its lifecycle.

private val testMutex = Mutex()

fun test(messageTest: () -> Unit) {
    CoroutineScope(Dispatchers.Default).launch {
        testMutex.withLock {
            delay(3000)
            messageTest()
        }
    }
}