@saga-bus/store-mongo

MongoDB saga store for saga-bus.

Installation

pnpm add @saga-bus/store-mongo mongodb

Usage

import { MongoClient } from "mongodb";
import { MongoSagaStore } from "@saga-bus/store-mongo";
import { createBus } from "@saga-bus/core";

const client = new MongoClient("mongodb://localhost:27017");
await client.connect();

const store = new MongoSagaStore({
  db: client.db("myapp"),
  collectionName: "saga_instances",
});

const bus = createBus({
  sagas: [{ definition: mySaga, store }],
  transport,
});

Document Schema

Documents are stored with this structure:

{
  _id: "OrderSaga:saga-123",      // Composite key
  sagaName: "OrderSaga",
  sagaId: "saga-123",
  correlationId: "order-456",
  version: 1,
  isCompleted: false,
  state: { /* saga state */ },
  createdAt: ISODate("..."),
  updatedAt: ISODate("...")
}

Indexes

The store automatically creates indexes on:

• _id (primary key)
• sagaName + correlationId (for correlation lookups)
• isCompleted + updatedAt (for cleanup queries)

Features

• Optimistic concurrency via version field
• Atomic updates with findOneAndUpdate
• Efficient correlation ID lookups
• TTL-based cleanup support

Configuration

| Option | Type | Default | Description | |--------|------|---------|-------------| | db | Db | required | MongoDB database instance | | collectionName | string | "saga_instances" | Collection name |

Sharing Across Sagas

A single store instance can be shared across multiple sagas:

const store = new MongoSagaStore({ db });

const bus = createBus({
  transport,
  store, // shared by all sagas
  sagas: [
    { definition: orderSaga },
    { definition: paymentSaga },
  ],
});

Data is isolated by sagaName in the collection, so different saga types won't conflict.

Cleanup

Query completed sagas for cleanup:

const completedSagas = await db
  .collection("saga_instances")
  .find({
    isCompleted: true,
    updatedAt: { $lt: thirtyDaysAgo },
  })
  .toArray();

License

MIT