[][src]Module futures::executor

Task execution.

All asynchronous computation occurs within an executor, which is capable of spawning futures as tasks. This module provides several built-in executors, as well as tools for building your own.

This module is only available when the std feature of this library is activated, and it is activated by default.

Using a thread pool (M:N task scheduling)

Most of the time tasks should be executed on a thread pool. A small set of worker threads can handle a very large set of spawned tasks (which are much lighter weight than threads).

The simplest way to use a thread pool is to run an initial task on it, which can then spawn further tasks back onto the pool to complete its work:

use futures::executor::ThreadPool;

// assuming `my_app: Future`
ThreadPool::new().expect("Failed to create threadpool").run(my_app);

The call to run will block the current thread until the future defined by my_app completes, and will return the result of that future.

Spawning additional tasks

Tasks can be spawned onto a spawner by calling its spawn_obj method directly. In the case of !Send futures, spawn_local_obj can be used instead.

Single-threaded execution

In addition to thread pools, it's possible to run a task (and the tasks it spawns) entirely within a single thread via the LocalPool executor. Aside from cutting down on synchronization costs, this executor also makes it possible to spawn non-Send tasks, via spawn_local_obj. The LocalPool is best suited for running I/O-bound tasks that do relatively little work between I/O operations.

There is also a convenience function, block_on, for simply running a future to completion on the current thread, while routing any spawned tasks to a global thread pool.



An iterator which blocks on values from a stream until they become available.


Represents an executor context.


An error returned by enter if an execution scope has already been entered.


A single-threaded task pool for polling futures to completion.


A handle to a LocalPool that implements Spawn.


A general-purpose thread pool for scheduling tasks that poll futures to completion.


Thread pool configuration object.



Run a future to completion on the current thread.


Turn a stream into a blocking iterator.


Marks the current thread as being within the dynamic extent of an executor.