Mongoose

@relaybus/mongodb uses MongoDB multi-document transactions, which need a replica set or a sharded cluster (a single-node replica set is enough for development). Mongoose exposes the same driver session.

pnpm add @relaybus/core @relaybus/mongodb mongodb

Wire the store

import mongoose from 'mongoose';
import { RelayBus } from '@relaybus/core';
import { MongoEventStore } from '@relaybus/mongodb';
import type { ClientSession } from 'mongodb';

const bus = new RelayBus<ClientSession>({
  store: new MongoEventStore({ client: mongoose.connection.getClient(), database: 'shop' }),
});

Publish in a Mongoose transaction

const session = await mongoose.startSession();
await session.withTransaction(async () => {
  await Order.create([{ total: 10 }], { session });
  await bus.publish(new OrderPlaced({ orderId: '1' }), { transaction: session });
});

Things to know

• A session without a started transaction is rejected with a ConfigurationError: MongoDB would commit each write immediately and silently break atomicity.
• session.withTransaction may run your callback again after a transient error, so keep the callback free of side effects other than database writes.
• A standalone mongod is rejected with a clear error.

See @relaybus/mongodb for options, indexes and retention.