Event Bus

The EventBus is the central nervous system of Mercury. It is a thin wrapper around a crossbeam bounded channel.

Design

• Capacity: 100,000 events (configurable at construction).
• Back-pressure: producers block when the channel is full, providing natural flow control.
• Lock-free: no mutex on the hot path — crossbeam’s channel uses atomic operations internally.
• Single channel: all event types share one channel. Components filter by EventPayload variant.

Event types (EventPayload)

Arc wrapping

BookUpdate is wrapped in Arc before publishing so that multiple subscribers can hold a reference to the same allocation without copying the order-book snapshot.

Usage

#![allow(unused)]
fn main() {
// Publish
bus.publish(EventPayload::Signal(signal));

// Subscribe (returns a Receiver)
let rx = bus.subscribe();
while let Ok(event) = rx.recv() {
    match event.payload {
        EventPayload::Fill(fill) => { /* handle */ }
        _ => {}
    }
}
}