public actual object Dispatchers {
/**
* The default [CoroutineDispatcher] that is used by all standard builders like
* [launch][CoroutineScope.launch], [async][CoroutineScope.async], etc
* if no dispatcher nor any other [ContinuationInterceptor] is specified in their context.
*
* It is backed by a shared pool of threads on JVM. By default, the maximal level of parallelism used
* by this dispatcher is equal to the number of CPU cores, but is at least two.
* Level of parallelism X guarantees that no more than X tasks can be executed in this dispatcher in parallel.
*/
@JvmStatic
public actual val Default: CoroutineDispatcher = createDefaultDispatcher()internal fun createDefaultDispatcher(): CoroutineDispatcher =
if (useCoroutinesScheduler) DefaultScheduler else CommonPoolinternal val useCoroutinesScheduler = systemProp(COROUTINES_SCHEDULER_PROPERTY_NAME).let { value ->
when (value) {
null, "", "on" -> true
"off" -> false
else -> error("System property '$COROUTINES_SCHEDULER_PROPERTY_NAME' has unrecognized value '$value'")
}
}internal object DefaultScheduler : ExperimentalCoroutineDispatcher()@InternalCoroutinesApi
public open class ExperimentalCoroutineDispatcher(
private val corePoolSize: Int,
private val maxPoolSize: Int,
private val idleWorkerKeepAliveNs: Long,
private val schedulerName: String = "CoroutineScheduler"
) : ExecutorCoroutineDispatcher() {
public constructor(
corePoolSize: Int = CORE_POOL_SIZE,
maxPoolSize: Int = MAX_POOL_SIZE,
schedulerName: String = DEFAULT_SCHEDULER_NAME
) : this(corePoolSize, maxPoolSize, IDLE_WORKER_KEEP_ALIVE_NS, schedulerName)
@Deprecated(message = "Binary compatibility for Ktor 1.0-beta", level = DeprecationLevel.HIDDEN)
public constructor(
corePoolSize: Int = CORE_POOL_SIZE,
maxPoolSize: Int = MAX_POOL_SIZE
) : this(corePoolSize, maxPoolSize, IDLE_WORKER_KEEP_ALIVE_NS)
override val executor: Executor
get() = coroutineScheduler
// This is variable for test purposes, so that we can reinitialize from clean state
private var coroutineScheduler = createScheduler()
override fun dispatch(context: CoroutineContext, block: Runnable): Unit =
try {
coroutineScheduler.dispatch(block)
} catch (e: RejectedExecutionException) {
// CoroutineScheduler only rejects execution when it is being closed and this behavior is reserved
// for testing purposes, so we don't have to worry about cancelling the affected Job here.
DefaultExecutor.dispatch(context, block)
}
override fun dispatchYield(context: CoroutineContext, block: Runnable): Unit =
try {
coroutineScheduler.dispatch(block, tailDispatch = true)
} catch (e: RejectedExecutionException) {
// CoroutineScheduler only rejects execution when it is being closed and this behavior is reserved
// for testing purposes, so we don't have to worry about cancelling the affected Job here.
DefaultExecutor.dispatchYield(context, block)
}
override fun close(): Unit = coroutineScheduler.close()
override fun toString(): String {
return "${super.toString()}[scheduler = $coroutineScheduler]"
}/**
* Underlying executor of current [CoroutineDispatcher].
*/
public abstract val executor: Executorprivate var coroutineScheduler = createScheduler()private fun createScheduler() = CoroutineScheduler(corePoolSize, maxPoolSize, idleWorkerKeepAliveNs, schedulerName)nternal class CoroutineScheduler(
@JvmField val corePoolSize: Int,
@JvmField val maxPoolSize: Int,
@JvmField val idleWorkerKeepAliveNs: Long = IDLE_WORKER_KEEP_ALIVE_NS,
@JvmField val schedulerName: String = DEFAULT_SCHEDULER_NAME
) : Executor, Closeable {/**
* State of worker threads.
* [workers] is array of lazily created workers up to [maxPoolSize] workers.
* [createdWorkers] is count of already created workers (worker with index lesser than [createdWorkers] exists).
* [blockingTasks] is count of pending (either in the queue or being executed) tasks
*
* **NOTE**: `workers[0]` is always `null` (never used, works as sentinel value), so
* workers are 1-indexed, code path in [Worker.trySteal] is a bit faster and index swap during termination
* works properly
*/
@JvmField
val workers = AtomicReferenceArray<Worker?>(maxPoolSize + 1)internal inner class Worker private constructor() : Thread() {