mco

mco 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].

way mco?

• Elegant coding,No need for async await
• Simple concurrency(CSP model), learning Golang
• Default MAX 6MB Stack Size use Virtual Memory(Virtual memory is loaded on demand, with minimal actual usage)
• many std like API

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

mco crates

mco Powerful standard library

• mco/std/queue Basic queue data structures
• mco/std/sync Includes Mutex/RwLock/WaitGroup/Semphore/chan!()/chan!(1000)...and more..
• mco/std/defer Defers evaluation of a block of code until the end of the scope.
• mco/std/map Provides the same concurrency map as Golang, with SyncHashMap and SyncBtreeMap.It is suitable for concurrent environments with too many reads and too few writes
• mco/std/vec Provides the same concurrency vec
• mco/std/time Improve the implementation of a high performance time
• mco/std/lazy Thread/coroutine safe global variable,Lazy struct,OnceCell

Crates based on mco implementation

• mco-http High-performance coroutine HTTP server and client
• cdbc Database Drivers include mysql, Postgres, AND SQLite
• fast_log High-performance log impl
• mco-redis Redis client for mco
• mco-redis-rs fork from redis-rs Replace only TcpStream with MCO ::TcpStream
• mco-rpc rpc server/client. support bincode/json rpc

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 chan(like golang)

• Support WaitGroup Support(like golang)

• Support defer!() (like golang)

• Support Rustls

• Support Time (like golang)

• Support error/err!() (like golang)

• Support select match Ok(v)/Err(e) (like golang)

• Support Lazy/OnceCell

• Support SyncMap(like golang)

• Support Ticker(like golang)

Usage

mco = "0.1"

A naive echo server implemented with mco:

#[macro_use]
extern crate mco;

use mco::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 I/O heavy bound examples

• An echo server
• An echo client
• simple HTTP
• simple HTTPS
• tiny HTTP
• WebSockets

Caveat

There is a detailed [document][caveat] that describes mco'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:
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;
• In most modern operating systems, when starting a process, the standard Thread stack size is usually 8 MB, and mco provides a maximum stack space of 6MB. Typically, operating systems load memory pages on demand, such as starting about 1 million processes on my Mac/Unix system, which requires 46GB of memory space. This means that a protocol requires a minimum of 50KB of stack space to be consumed until a maximum of 6MB of stack space is reached
• 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

mco::config().set_stack_size(6*1024*1024);

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