How to Handle Backpressure in Async Rust

Handle backpressure in async Rust by using bounded channels to limit the number of in-flight tasks and prevent memory exhaustion. When the channel is full, the sender blocks until a receiver consumes an item, naturally throttling the producer.

use tokio::sync::mpsc;

#[tokio::main]
async fn main() {
    let (tx, mut rx) = mpsc::channel::<String>(10);

    // Sender blocks if channel is full (backpressure)
    for i in 0..100 {
        tx.send(format!("msg-{i}")).await.unwrap();
    }

    while let Some(msg) = rx.recv().await {
        println!("Received: {msg}");
    }
}

Backpressure is a mechanism that slows down a fast producer when a slow consumer cannot keep up, preventing your application from running out of memory. It works like a water valve that automatically closes when the bucket below is full, ensuring you don't overflow. You use this pattern whenever you are processing streams of data where the input speed might exceed your processing capacity.