Guides concurrency and async decisions in Rust. Use when encountering Send/Sync errors (E0277), choosing between threads vs async, designing shared state, or debugging deadlocks.
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Layer 1: Language Mechanics
Is this CPU-bound or I/O-bound, and what's the sharing model?
Before choosing concurrency primitives:
Before adding concurrency:
What's the workload?
std::thread, rayon)What's the sharing model?
Arc<T>Arc<Mutex<T>> or Arc<RwLock<T>>What are the Send/Sync requirements?
SendSyncspawn_localWhat type of work?
├─ CPU-bound → std::thread or rayon
├─ I/O-bound → async/await
└─ Mixed → hybrid (spawn_blocking)
Need to share data?
├─ No → message passing (channels)
├─ Immutable → Arc<T>
└─ Mutable →
├─ Read-heavy → Arc<RwLock<T>>
└─ Write-heavy → Arc<Mutex<T>>
└─ Simple counter → AtomicUsize
Async context?
├─ Type is Send → tokio::spawn
├─ Type is !Send → spawn_local
└─ Blocking code → spawn_blocking
| Marker | Meaning | Example |
|---|---|---|
Send | Can transfer ownership between threads | Most types |
Sync | Can share references between threads | Arc<T> |
!Send | Must stay on one thread | Rc<T> |
!Sync | No shared refs across threads | RefCell<T> |
| Pattern | Thread-Safe | Blocking | Use When |
|---|---|---|---|
std::thread | Yes | Yes | CPU-bound parallelism |
async/await | Yes | No | I/O-bound concurrency |
Mutex<T> | Yes | Yes | Shared mutable state |
RwLock<T> | Yes | Yes | Read-heavy shared state |
mpsc::channel | Yes | Optional | Message passing |
Arc<Mutex<T>> | Yes | Yes | Shared mutable across threads |
// Bad: guard held across await
let guard = mutex.lock().await;
do_async().await; // guard still held!
// Good: scope the lock
{
let guard = mutex.lock().await;
// use guard
} // guard dropped
do_async().await;
// Rc is !Send, can't cross await in spawned task
// Option 1: use Arc instead
// Option 2: use spawn_local (single-thread runtime)
// Option 3: ensure Rc is dropped before .await
| Error | Don't Just Say | Ask Instead |
|---|---|---|
| E0277 Send | "Add Send bound" | Should this type cross threads? |
| E0277 Sync | "Wrap in Mutex" | Is shared access really needed? |
| Future not Send | "Use spawn_local" | Is async the right choice? |
| Deadlock | "Reorder locks" | Is the locking design correct? |
| Anti-Pattern | Why Bad | Better |
|---|---|---|
Arc<Mutex<T>> everywhere | Contention, complexity | Message passing |
thread::sleep in async | Blocks executor | tokio::time::sleep |
| Holding locks across await | Blocks other tasks | Scope locks tightly |
| Ignoring deadlock risk | Hard to debug | Lock ordering, try_lock |
ownership — data ownership and borrowingperformance — choosing between rayon, threads, and async for throughputanti-patterns — common concurrency mistakes还没有评价。欢迎分享你的使用感受。
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Automates browser interactions for web testing, form filling, screenshots, and data extraction. Use when the user needs to navigate websites, interact with web pages, fill forms, take screenshots, test web applications, or extract information from web pages.
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Add Agentation visual feedback toolbar to a Next.js project
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