Kevin Leimkuhler
a819584849
Broadcast uses a ring buffer to store values sent to the channel. In order to deal with slow receivers, the oldest values are overwritten with new values once the buffer wraps. A receiver should be able to calculate how many values it has missed. Additionally, when the broadcast closes, a final value of `None` is sent to the channel. If the buffer has wrapped, this value overwrites the oldest value. This is an issue mainly in a single capacity broadcast when a value is sent and then the sender is dropped. The original value is immediately overwritten with `None` meaning that receivers assume they have lagged behind. **Solution** A value of `None` is no longer sent to the channel when the final sender has been dropped. This solves the single capacity broadcast case by completely removing the behavior of overwriting values when the channel is closed. Now, when the final sender is dropped a closed bit is set on the next slot that the channel is supposed to send to. In the case of a fast receiver, if it finds a slot where the closed bit is set, it knows the channel is closed without locking the tail. In the case of a slow receiver, it must first find out if it has missed any values. This is similar to before, but must be able to account for channel closure. If the channel is not closed, the oldest value may be located at index `n`. If the channel is closed, the oldest value is located at index `n - 1`. Knowing the index where the oldest value is located, a receiver can calculate how many values it may have missed and starts to catch up. Closes #2425
Tokio
A runtime for writing reliable, asynchronous, and slim applications with the Rust programming language. It is:
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Fast: Tokio's zero-cost abstractions give you bare-metal performance.
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Reliable: Tokio leverages Rust's ownership, type system, and concurrency model to reduce bugs and ensure thread safety.
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Scalable: Tokio has a minimal footprint, and handles backpressure and cancellation naturally.
Website | Guides | API Docs | Roadmap | Chat
Overview
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:
- A multithreaded, work-stealing based task scheduler.
- A reactor backed by the operating system's event queue (epoll, kqueue, IOCP, etc...).
- Asynchronous TCP and UDP sockets.
These components provide the runtime components necessary for building an asynchronous application.
Example
A basic TCP echo server with Tokio:
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;
}
}
});
}
}
More examples can be found here.
Getting Help
First, see if the answer to your question can be found in the Guides or the API documentation. If the answer is not there, there is an active community in the Tokio Discord server. We would be happy to try to answer your question. Last, if that doesn't work, try opening an issue with the question.
Contributing
🎈 Thanks for your help improving the project! We are so happy to have you! We have a contributing guide to help you get involved in the Tokio project.
Related Projects
In addition to the crates in this repository, the Tokio project also maintains several other libraries, including:
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hyper: A fast and correct HTTP/1.1 and HTTP/2 implementation for Rust. -
tonic: A gRPC over HTTP/2 implementation focused on high performance, interoperability, and flexibility. -
warp: A super-easy, composable, web server framework for warp speeds. -
tower: A library of modular and reusable components for building robust networking clients and servers. -
tracing(formerlytokio-trace): A framework for application-level tracing and async-aware diagnostics. -
rdbc: A Rust database connectivity library for MySQL, Postgres and SQLite. -
mio: A low-level, cross-platform abstraction over OS I/O APIs that powerstokio. -
bytes: Utilities for working with bytes, including efficient byte buffers. -
loom: A testing tool for concurrent Rust code
Supported Rust Versions
Tokio is built against the latest stable, nightly, and beta Rust releases. The minimum version supported is the stable release from three months before the current stable release version. For example, if the latest stable Rust is 1.29, the minimum version supported is 1.26. The current Tokio version is not guaranteed to build on Rust versions earlier than the minimum supported version.
License
This project is licensed under the MIT license.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Tokio by you, shall be licensed as MIT, without any additional terms or conditions.