/rust-async-patterns

name: rust-async-patterns
description: Master Rust async programming with Tokio, async traits, error handling, and concurrent patterns. Use when building async Rust applications, implementing concurrent systems, or debugging async code.

Rust Async Patterns

Production patterns for async Rust programming with Tokio runtime, including tasks, channels, streams, and error handling.

When to Use This Skill

• Building async Rust applications
• Implementing concurrent network services
• Using Tokio for async I/O
• Handling async errors properly
• Debugging async code issues
• Optimizing async performance

Core Concepts

1. Async Execution Model

Future (lazy) → poll() → Ready(value) | Pending
                ↑           ↓
              Waker ← Runtime schedules

2. Key Abstractions

| Concept | Purpose | | ---------- | ---------------------------------------- | | `Future` | Lazy computation that may complete later | | `async fn` | Function returning impl Future | | `await` | Suspend until future completes | | `Task` | Spawned future running concurrently | | `Runtime` | Executor that polls futures |

Quick Start

# Cargo.toml
[dependencies]
tokio = { version = "1", features = ["full"] }
futures = "0.3"
async-trait = "0.1"
anyhow = "1.0"
tracing = "0.1"
tracing-subscriber = "0.3"

use tokio::time::{sleep, Duration};
use anyhow::Result;

#[tokio::main]
async fn main() -> Result<()> {
    // Initialize tracing
    tracing_subscriber::fmt::init();

    // Async operations
    let result = fetch_data("https://api.example.com").await?;
    println!("Got: {}", result);

    Ok(())
}

async fn fetch_data(url: &str) -> Result<String> {
    // Simulated async operation
    sleep(Duration::from_millis(100)).await;
    Ok(format!("Data from {}", url))
}

Detailed patterns and worked examples

Detailed pattern documentation lives in `references/details.md`. Read that file when the navigation tier above is insufficient.

Best Practices

Do's

• **Use `tokio::select!`** - For racing futures
• **Prefer channels** - Over shared state when possible
• **Use `JoinSet`** - For managing multiple tasks
• **Instrument with tracing** - For debugging async code
• **Handle cancellation** - Check `CancellationToken`

Don'ts

• **Don't block** - Never use `std::thread::sleep` in async
• **Don't hold locks across awaits** - Causes deadlocks
• **Don't spawn unboundedly** - Use semaphores for limits
• **Don't ignore errors** - Propagate with `?` or log
• **Don't forget Send bounds** - For spawned futures