Best practices for designing long-running background daemons in Rust?

Hi everyone,

I'm looking for some advice and best practices on how to properly design and structure a long-running background daemon thread (or task) in Rust.

Specifically, I want to make sure I'm handling the architecture elegantly, especially around graceful shutdowns and resource sharing. Here are a few specific points I'm wrestling with:

1. **Shutdown & Cancellation:** What is the idiomatic way to signal a background thread to stop? Should I rely on an `AtomicBool` flag, or use channels (`crossbeam` / `std::sync::mpsc`) to send a shutdown signal? If I'm using an async ecosystem like Tokio, is `tokio::select!` with a cancellation token the gold standard?

2. **State Management:** The daemon needs to share state with the main application thread. I'm currently leaning towards `Arc<Mutex<T>>` or `Arc<RwLock<T>>`, but I'm worried about lock contention if the daemon updates the state frequently. Are there better architectural patterns (like actor-like models via channels) to avoid heavy locking?

3. **Error Handling & Panics:** If the background daemon panics or encounters a fatal error, what's the best way to bubble that up to the main thread so the entire application can restart or log it properly?

I would love to hear how you guys usually structure this in production, or if there are any open-source crates/repositories that showcase excellent daemon design patterns in Rust.

Thanks in advance!