| /* |
| * Copyright 2016-2023 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license. |
| */ |
| |
| package kotlinx.coroutines |
| |
| import kotlinx.coroutines.internal.* |
| import kotlinx.coroutines.scheduling.* |
| import kotlin.coroutines.* |
| |
| /** |
| * Name of the property that defines the maximal number of threads that are used by [Dispatchers.IO] coroutines dispatcher. |
| */ |
| public const val IO_PARALLELISM_PROPERTY_NAME: String = "kotlinx.coroutines.io.parallelism" |
| |
| /** |
| * Groups various implementations of [CoroutineDispatcher]. |
| */ |
| public actual object Dispatchers { |
| @JvmStatic |
| public actual val Default: CoroutineDispatcher = DefaultScheduler |
| |
| @JvmStatic |
| public actual val Main: MainCoroutineDispatcher get() = MainDispatcherLoader.dispatcher |
| |
| @JvmStatic |
| public actual val Unconfined: CoroutineDispatcher = kotlinx.coroutines.Unconfined |
| |
| /** |
| * The [CoroutineDispatcher] that is designed for offloading blocking IO tasks to a shared pool of threads. |
| * |
| * Additional threads in this pool are created and are shutdown on demand. |
| * The number of threads used by tasks in this dispatcher is limited by the value of |
| * "`kotlinx.coroutines.io.parallelism`" ([IO_PARALLELISM_PROPERTY_NAME]) system property. |
| * It defaults to the limit of 64 threads or the number of cores (whichever is larger). |
| * |
| * ### Elasticity for limited parallelism |
| * |
| * `Dispatchers.IO` has a unique property of elasticity: its views |
| * obtained with [CoroutineDispatcher.limitedParallelism] are |
| * not restricted by the `Dispatchers.IO` parallelism. Conceptually, there is |
| * a dispatcher backed by an unlimited pool of threads, and both `Dispatchers.IO` |
| * and views of `Dispatchers.IO` are actually views of that dispatcher. In practice |
| * this means that, despite not abiding by `Dispatchers.IO`'s parallelism |
| * restrictions, its views share threads and resources with it. |
| * |
| * In the following example |
| * ``` |
| * // 100 threads for MySQL connection |
| * val myMysqlDbDispatcher = Dispatchers.IO.limitedParallelism(100) |
| * // 60 threads for MongoDB connection |
| * val myMongoDbDispatcher = Dispatchers.IO.limitedParallelism(60) |
| * ``` |
| * the system may have up to `64 + 100 + 60` threads dedicated to blocking tasks during peak loads, |
| * but during its steady state there is only a small number of threads shared |
| * among `Dispatchers.IO`, `myMysqlDbDispatcher` and `myMongoDbDispatcher`. |
| * |
| * ### Implementation note |
| * |
| * This dispatcher and its views share threads with the [Default][Dispatchers.Default] dispatcher, so using |
| * `withContext(Dispatchers.IO) { ... }` when already running on the [Default][Dispatchers.Default] |
| * dispatcher typically does not lead to an actual switching to another thread. In such scenarios, |
| * the underlying implementation attempts to keep the execution on the same thread on a best-effort basis. |
| * |
| * As a result of thread sharing, more than 64 (default parallelism) threads can be created (but not used) |
| * during operations over IO dispatcher. |
| */ |
| @JvmStatic |
| public val IO: CoroutineDispatcher = DefaultIoScheduler |
| |
| /** |
| * Shuts down built-in dispatchers, such as [Default] and [IO], |
| * stopping all the threads associated with them and making them reject all new tasks. |
| * Dispatcher used as a fallback for time-related operations (`delay`, `withTimeout`) |
| * and to handle rejected tasks from other dispatchers is also shut down. |
| * |
| * This is a **delicate** API. It is not supposed to be called from a general |
| * application-level code and its invocation is irreversible. |
| * The invocation of shutdown affects most of the coroutines machinery and |
| * leaves the coroutines framework in an inoperable state. |
| * The shutdown method should only be invoked when there are no pending tasks or active coroutines. |
| * Otherwise, the behavior is unspecified: the call to `shutdown` may throw an exception without completing |
| * the shutdown, or it may finish successfully, but the remaining jobs will be in a permanent dormant state, |
| * never completing nor executing. |
| * |
| * The main goal of the shutdown is to stop all background threads associated with the coroutines |
| * framework in order to make kotlinx.coroutines classes unloadable by Java Virtual Machine. |
| * It is only recommended to be used in containerized environments (OSGi, Gradle plugins system, |
| * IDEA plugins) at the end of the container lifecycle. |
| */ |
| @DelicateCoroutinesApi |
| public fun shutdown() { |
| DefaultExecutor.shutdown() |
| // Also shuts down Dispatchers.IO |
| DefaultScheduler.shutdown() |
| } |
| } |
| |
| /** |
| * `actual` counterpart of the corresponding `expect` declaration. |
| * Should never be used directly from JVM sources, all accesses |
| * to `Dispatchers.IO` should be resolved to the corresponding member of [Dispatchers] object. |
| * @suppress |
| */ |
| @Suppress("EXTENSION_SHADOWED_BY_MEMBER") |
| @Deprecated(message = "Should not be used directly", level = DeprecationLevel.HIDDEN) |
| public actual val Dispatchers.IO: CoroutineDispatcher get() = Dispatchers.IO |