1. What is MPSC?
MPSC stands for Multiple-Producer, Single Consumer. It allows:
- many tasks to send messages
- one task to receive them
- without locks
- without shared mutable state
2. Implementation
let (reload_tx, mut reload_rx) = mpsc::unbounded_channel();
This gives us:
- reload_tx — a clonable sender
- reload_rx — a receiver
Then we pass the sender to some background task or subsystem:
manager.watch_file(path.clone(), reload_tx);
Whenever the watcher detects a file change, it sends an event:
let _ = reload_tx.send(());
Meanwhile, your test (or runtime code) awaits the event:
reload_rx.recv().await;
3. Benefits
Using mpsc channels lets us:
- avoid locks
- avoid shared mutable state
- allow multiple watchers to notify one receiver
- send events across threads
- avoid polling or busy-waiting
4. Usecases
This pattern is very common in:
- hot-reload systems
- background worker notifications
- graceful shutdown signals
- task coordination
- file watchers
- timers
- cancellation systems