rust-async-patterns

# 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 ```toml # 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" ``` ```rust 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