@meridianjs/event-bus-local

In-process event bus for MeridianJS, backed by Node.js EventEmitter. Designed for local development and single-process deployments.

For production multi-process deployments, use @meridianjs/event-bus-redis instead.

Installation

npm install @meridianjs/event-bus-local

Configuration

Register in meridian.config.ts:

export default defineConfig({
  modules: [
    { resolve: "@meridianjs/event-bus-local" },
  ],
})

No options required. The event bus is registered under the eventBus token and used automatically by all domain modules.

Behaviour

• Events are dispatched via setImmediate, making emission non-blocking for the caller while preserving per-event ordering.
• Up to 500 listeners per event name (configurable internally).
• Errors thrown inside a subscriber are caught and logged — they do not crash the process or affect other subscribers.
• unsubscribe() removes all listeners for the event name (a limitation of anonymous wrapper functions). Use @meridianjs/event-bus-redis if you need fine-grained handler removal.

Switching to Redis in Production

The event bus interface (IEventBus) is identical between the two implementations. Switching is a single line change:

// development
{ resolve: "@meridianjs/event-bus-local" }

// production
{ resolve: "@meridianjs/event-bus-redis", options: { url: process.env.REDIS_URL } }

Direct Usage

If you need to emit or subscribe programmatically:

import type { IEventBus } from "@meridianjs/types"

const eventBus = container.resolve("eventBus") as IEventBus

// Emit
await eventBus.emit({ name: "issue.created", data: { issueId: "..." } })

// Subscribe
eventBus.subscribe("issue.created", async ({ event, container }) => {
  console.log("Issue created:", event.data)
})

License

MIT