6 releases
0.2.16 | Jan 30, 2020 |
---|---|
0.2.15 | Jan 23, 2020 |
#1327 in Asynchronous
1.5MB
23K
SLoC
Don't use
lib.rs
:
A runtime for writing reliable, asynchronous, and slim applications.
Tokio is an event-driven, non-blocking I/O platform for writing asynchronous applications with the Rust programming language. At a high level, it provides a few major components:
- Tools for working with asynchronous tasks, including synchronization primitives and channels and timeouts, delays, and intervals.
- APIs for performing asynchronous I/O, including TCP and UDP sockets, filesystem operations, and process and signal management.
- A runtime for executing asynchronous code, including a task scheduler, an I/O driver backed by the operating system's event queue (epoll, kqueue, IOCP, etc...), and a high performance timer.
Guide level documentation is found on the website.
A Tour of Tokio
Tokio consists of a number of modules that provide a range of functionality essential for implementing asynchronous applications in Rust. In this section, we will take a brief tour of Tokio, summarizing the major APIs and their uses.
The easiest way to get started is to enable all features. Do this by
enabling the full
feature flag:
tokio = { version = "0.2", features = ["full"] }
Feature flags
Tokio uses a set of feature flags to reduce the amount of compiled code. It
is possible to just enable certain features over others. By default, Tokio
does not enable any features but allows one to enable a subset for their use
case. Below is a list of the available feature flags. You may also notice
above each function, struct and trait there is a set of feature flags
that are required for that item to be enabled. If you are new to Tokio it is
recommended that you use the full
feature flag which will enable everything.
Beware though that this will pull in many extra dependencies that you may not
need.
full
: Enables all Tokio features and every API will be available.rt-core
: Enablestokio::spawn
and the basic (single-threaded) scheduler.rt-threaded
: Enables the heavier, multi-threaded, work-stealing scheduler.rt-util
: Enables non-scheduler utilities.io-driver
: Enables themio
based IO driver.io-util
: Enables the IO basedExt
traits.io-std
: EnableStdout
,Stdin
andStderr
types.net
: Enablestokio::net
types such asTcpStream
,UnixStream
andUdpSocket
.tcp
: Enables alltokio::net::tcp
types.udp
: Enables alltokio::net::udp
types.uds
: Enables alltokio::net::unix
types.time
: Enablestokio::time
types and allows the schedulers to enable the built in timer.process
: Enablestokio::process
types.macros
: Enables#[tokio::main]
and#[tokio::test]
macros.sync
: Enables alltokio::sync
types.stream
: Enables optionalStream
implementations for types within Tokio.signal
: Enables alltokio::signal
types.fs
: Enablestokio::fs
types.dns
: Enables asynctokio::net::ToSocketAddrs
.test-util
: Enables testing based infrastructure for the Tokio runtime.blocking
: Enablesblock_in_place
andspawn_blocking
.
Note: AsyncRead
and AsyncWrite
do not require any features and are
enabled by default.
Authoring applications
Tokio is great for writing applications and most users in this case shouldn't
worry to much about what features they should pick. If you're unsure, we suggest
going with full
to ensure that you don't run into any road blocks while you're
building your application.
Example
This example shows the quickest way to get started with Tokio.
tokio = { version = "0.2", features = ["full"] }
Authoring libraries
As a library author your goal should be to provide the lighest weight crate that is based on Tokio. To achieve this you should ensure that you only enable the features you need. This allows users to pick up your crate without having to enable unnecessary features.
Example
This example shows how you may want to import features for a library that just
needs to tokio::spawn
and use a TcpStream
.
tokio = { version = "0.2", features = ["rt-core", "tcp"] }
Working With Tasks
Asynchronous programs in Rust are based around lightweight, non-blocking
units of execution called tasks. The tokio::task
module provides
important tools for working with tasks:
- The
spawn
function andJoinHandle
type, for scheduling a new task on the Tokio runtime and awaiting the output of a spawned task, respectively, - Functions for running blocking operations in an asynchronous task context.
The tokio::task
module is present only when the "rt-core" feature flag
is enabled.
The tokio::sync
module contains synchronization primitives to use when
needing to communicate or share data. These include:
- channels (
oneshot
,mpsc
, andwatch
), for sending values between tasks, - a non-blocking
Mutex
, for controlling access to a shared, mutable value, - an asynchronous
Barrier
type, for multiple tasks to synchronize before beginning a computation.
The tokio::sync
module is present only when the "sync" feature flag is
enabled.
The tokio::time
module provides utilities for tracking time and
scheduling work. This includes functions for setting timeouts for
tasks, delaying work to run in the future, or repeating an operation at an
interval.
In order to use tokio::time
, the "time" feature flag must be enabled.
Finally, Tokio provides a runtime for executing asynchronous tasks. Most
applications can use the #[tokio::main]
macro to run their code on the
Tokio runtime. In use-cases where manual control over the runtime is
required, the tokio::runtime
module provides APIs for configuring and
managing runtimes.
Using the runtime requires the "rt-core" or "rt-threaded" feature flags, to
enable the basic single-threaded scheduler and the thread-pool
scheduler, respectively. See the runtime
module
documentation for details. In addition, the "macros" feature
flag enables the #[tokio::main]
and #[tokio::test]
attributes.
Asynchronous IO
As well as scheduling and running tasks, Tokio provides everything you need to perform input and output asynchronously.
The tokio::io
module provides Tokio's asynchronous core I/O primitives,
the AsyncRead
, AsyncWrite
, and AsyncBufRead
traits. In addition,
when the "io-util" feature flag is enabled, it also provides combinators and
functions for working with these traits, forming as an asynchronous
counterpart to std::io
. When the "io-driver" feature flag is enabled, it
also provides utilities for library authors implementing I/O resources.
Tokio also includes APIs for performing various kinds of I/O and interacting with the operating system asynchronously. These include:
tokio::net
, which contains non-blocking versions of TCP, UDP, and Unix Domain Sockets (enabled by the "net" feature flag),tokio::fs
, similar tostd::fs
but for performing filesystem I/O asynchronously (enabled by the "fs" feature flag),tokio::signal
, for asynchronously handling Unix and Windows OS signals (enabled by the "signal" feature flag),tokio::process
, for spawning and managing child processes (enabled by the "process" feature flag).
Examples
A simple TCP echo server:
use tokio::net::TcpListener;
use tokio::prelude::*;
#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
let mut listener = TcpListener::bind("127.0.0.1:8080").await?;
loop {
let (mut socket, _) = listener.accept().await?;
tokio::spawn(async move {
let mut buf = [0; 1024];
// In a loop, read data from the socket and write the data back.
loop {
let n = match socket.read(&mut buf).await {
// socket closed
Ok(n) if n == 0 => return,
Ok(n) => n,
Err(e) => {
eprintln!("failed to read from socket; err = {:?}", e);
return;
}
};
// Write the data back
if let Err(e) = socket.write_all(&buf[0..n]).await {
eprintln!("failed to write to socket; err = {:?}", e);
return;
}
}
});
}
}
Dependencies
~0.3–1MB
~16K SLoC