cogo

cogo coroutine for rust

Cogo is a high-performance library for programming stackful coroutines with which you can easily develop and maintain massive concurrent programs. It can be thought as the Rust version of the popular [Goroutine][go].

Initial code frok from May and we add Many code improvements(Inspired by Golang and crossbeam)

cogo-std libraray

• cogo/std/channel An MPMC queues, which support buffering, are also implementations of channel
• cogo/std/http An HTTP server is available，An HTTP Client(TODO)
• cogo/std/queue
• cogo/std/sync Includes basic mutex, WaitGroup, and other common synchronization constructs

Crates based on cogo implementation

• cdbc High-performance database drivers include mysql, Postgres, AND SQLite
• fast_log an fast log impl

Table of contents

• Features
• Usage
• More examples
  • The CPU heavy load examples
  • The I/O heavy bound examples
• Performance
• Caveat
• How to tune a stack size
• License

Features

• The stackful coroutine implementation is based on [generator][generator];

• Support schedule on a configurable number of threads for multi-core systems;

• Support coroutine version of a local storage ([CLS][cls]);

• Support efficient asynchronous network I/O;

• Support efficient timer management;

• Support standard synchronization primitives, a semaphore, an MPMC channel, etc;

• Support cancellation of coroutines;

• Support graceful panic handling that will not affect other coroutines;

• Support scoped coroutine creation;

• Support general selection for all the coroutine API;

• All the coroutine API are compatible with the standard library semantics;

• All the coroutine API can be safely called in multi-threaded context;

• Both stable, beta, and nightly channels are supported;

• x86_64 GNU/Linux, x86_64 Windows, x86_64 Mac, aarch64 Linux OS are supported.

• Support High performance channel(3 times better performance, Support the buffer), adapted from CrossBeam's channel(from crossbeam);

• Support WaitGroup(like golang)

• Support Disable stealing and commit directly to the local queue(3 times better go!()/spawn() performance)

Usage

A naive echo server implemented with Cogo:

#[macro_use]
extern crate cogo;

use cogo::net::TcpListener;
use std::io::{Read, Write};

fn main() {
    let listener = TcpListener::bind("127.0.0.1:8000").unwrap();
    while let Ok((mut stream, _)) = listener.accept() {
        go!(move || {
            let mut buf = vec![0; 1024 * 16]; // alloc in heap!
            while let Ok(n) = stream.read(&mut buf) {
                if n == 0 {
                    break;
                }
                stream.write_all(&buf[0..n]).unwrap();
            }
        });
    }
}

More examples

The CPU heavy load examples

• [The "Quick Sort" algorithm][sort]
• [A prime number generator][prime]

The I/O heavy bound examples

• [An echo server][echo_server]
• [An echo client][echo_client]
• [A simple HTTP][http_sever]
• [A simple HTTPS][https_sever]
• [WebSockets][websocket]

Performance

You can refer to https://tfb-status.techempower.com/ to get the latest [may_minihttp][may_minihttp] comparisons with other most popular frameworks.

Caveat

There is a detailed [document][caveat] that describes Cogo's main restrictions. In general, there are four things you should follow when writing programs that use coroutines:

• Don't call thread-blocking API (It will hurt the performance);
• Carefully use Thread Local Storage (access TLS in coroutine might trigger undefined behavior).

It's considered unsafe with the following pattern:

set_tls();
// Or another coroutine API that would cause scheduling:
coroutine::yield_now(); 
use_tls();

but it's safe if your code is not sensitive about the previous state of TLS. Or there is no coroutines scheduling between set TLS and use TLS.

• Don't run CPU bound tasks for long time, but it's ok if you don't care about fairness;
• Don't exceed the coroutine stack. There is a guard page for each coroutine stack. When stack overflow occurs, it will trigger segment fault error.

Note:

The first three rules are common when using cooperative asynchronous libraries in Rust. Even using a futures-based system also have these limitations. So what you should really focus on is a coroutine stack size, make sure it's big enough for your applications.

How to tune a stack size

If you want to tune your coroutine stack size, please check out [this document][stack].