Rust Basics - Concurrency

Rust Basics - Concurrency

Rust makes concurrent programming safe and fearless. The ownership and type systems prevent data races at compile time.

Threads

Creating threads with std::thread:

use std::thread;
use std::time::Duration;
fn main() {
    let handle = thread::spawn(|| {
        for i in 1..10 {
            println!("Hi from spawned thread {}", i);
            thread::sleep(Duration::from_millis(1));
        }
    });
    for i in 1..5 {
        println!("Hi from main thread {}", i);
        thread::sleep(Duration::from_millis(1));
    }
    handle.join().unwrap();
}

Moving Data to Threads

use std::thread;
fn main() {
    let v = vec![1, 2, 3];
    let handle = thread::spawn(move || {
        println!("Here's a vector: {:?}", v);
    });
    handle.join().unwrap();
}

Message Passing with Channels

use std::sync::mpsc;
use std::thread;
fn main() {
    let (tx, rx) = mpsc::channel();
    thread::spawn(move || {
        let val = String::from("hi");
        tx.send(val).unwrap();
    });
    let received = rx.recv().unwrap();
    println!("Got: {}", received);
}

Multiple Producers

let (tx, rx) = mpsc::channel();
let tx1 = tx.clone();
thread::spawn(move || {
    tx1.send("from thread 1").unwrap();
});
thread::spawn(move || {
    tx.send("from thread 2").unwrap();
});
for received in rx {
    println!("Got: {}", received);
}

Shared State with Mutex

use std::sync::{Arc, Mutex};
use std::thread;
fn main() {
    let counter = Arc::new(Mutex::new(0));
    let mut handles = vec![];
    for _ in 0..10 {
        let counter = Arc::clone(&counter);
        let handle = thread::spawn(move || {
            let mut num = counter.lock().unwrap();
            *num += 1;
        });
        handles.push(handle);
    }
    for handle in handles {
        handle.join().unwrap();
    }
    println!("Result: {}", *counter.lock().unwrap());
}

Send and Sync Traits

• Send: Type can be transferred between threads
• Sync: Type can be shared between threads (&T is Send)

Async/Await

use std::future::Future;
async fn do_something() {
    println!("doing something");
}
async fn async_main() {
    let future = do_something();
    future.await;
}
fn main() {
    // Using tokio runtime
    // tokio::runtime::Runtime::new().unwrap().block_on(async_main());
}

Concurrent Async

use tokio::time::{sleep, Duration};
async fn task1() {
    sleep(Duration::from_secs(1)).await;
    println!("Task 1 done");
}
async fn task2() {
    sleep(Duration::from_secs(1)).await;
    println!("Task 2 done");
}
async fn main_async() {
    // Run concurrently
    tokio::join!(task1(), task2());
}

Choosing Your Approach

| Use Case | Recommendation | |----------|---------------| | CPU-bound work | thread::spawn | | I/O-bound work | async/await with tokio | | Message passing | mpsc::channel | | Shared mutable state | Arc> | | Read-heavy shared data | Arc> |

Rust's type system ensures thread safety without runtime overhead!