Welcome to Saga Bus

Saga Bus is a MassTransit-style saga orchestration library for TypeScript and Node.js. Build resilient, distributed workflows with ease.

Why Saga Bus?

Modern applications often need to coordinate complex, multi-step processes across multiple services. Saga Bus provides:

• Type-Safe DSL - Fluent builder API with full TypeScript inference
• Multiple Transports - RabbitMQ, Kafka, SQS, Azure Service Bus, GCP Pub/Sub, Redis, NATS
• Multiple Stores - PostgreSQL, MySQL, SQL Server, MongoDB, DynamoDB, Redis, SQLite, Prisma
• Production-Ready Middleware - Logging, tracing, metrics, validation, idempotency, multi-tenancy
• Framework Integrations - NestJS, Next.js, Express, Fastify, Hono

Quick Example

import { createSagaMachine, createBus } from '@saga-bus/core';
import { RabbitMqTransport } from '@saga-bus/transport-rabbitmq';
import { PostgresSagaStore } from '@saga-bus/store-postgres';

// Define your saga with a fluent DSL
const orderSaga = createSagaMachine<OrderState, OrderMessages>()
  .name('OrderSaga')
  .correlate('OrderSubmitted', msg => msg.orderId, { canStart: true })
  .correlate('*', msg => msg.orderId)
  .initial<OrderSubmitted>(msg => ({
    orderId: msg.orderId,
    status: 'pending',
    items: msg.items,
  }))
  .on('PaymentCaptured')
    .handle(async (msg, state, ctx) => {
      await ctx.publish({ type: 'ReserveInventory', orderId: state.orderId });
      return { ...state, status: 'payment_captured' };
    })
  .on('InventoryReserved')
    .handle(async (msg, state, ctx) => {
      await ctx.publish({ type: 'CreateShipment', orderId: state.orderId });
      return { ...state, status: 'inventory_reserved' };
    })
  .on('ShipmentCreated')
    .handle(async (msg, state, ctx) => {
      ctx.complete();
      return { ...state, status: 'shipped' };
    })
  .build();

// Create and start the bus
const bus = createBus({
  transport: new RabbitMqTransport({ url: 'amqp://localhost' }),
  store: new PostgresSagaStore({ connectionString: process.env.DATABASE_URL }),
  sagas: [{ definition: orderSaga }],
});

await bus.start();

Features at a Glance

Feature	Description
Correlation	Link messages to saga instances via correlation IDs
State Guards	Conditional message handling with .when()
Timeouts	Built-in timeout tracking with automatic expiry messages
Optimistic Concurrency	Version-based conflict detection prevents lost updates
Distributed Tracing	W3C trace context propagation out of the box
Compensation	Handle failures gracefully with compensating actions

Getting Started

Ready to build your first saga? Follow our step-by-step guide:

1. Installation - Add Saga Bus to your project
2. Quick Start - Get running in 5 minutes
3. Your First Saga - Build a complete workflow

Packages

Saga Bus is organized as a monorepo with focused packages:

Core

• @saga-bus/core - Core types, DSL, and bus runtime

Transports

Choose the message broker that fits your infrastructure:

Package	Broker
@saga-bus/transport-rabbitmq	RabbitMQ
@saga-bus/transport-kafka	Apache Kafka
@saga-bus/transport-sqs	AWS SQS
@saga-bus/transport-azure-servicebus	Azure Service Bus
@saga-bus/transport-gcp-pubsub	Google Cloud Pub/Sub
@saga-bus/transport-redis	Redis Streams
@saga-bus/transport-nats	NATS JetStream
@saga-bus/transport-inmemory	In-Memory (testing)

Stores

Persist saga state in your preferred database:

Package	Database
@saga-bus/store-postgres	PostgreSQL
@saga-bus/store-mysql	MySQL / MariaDB
@saga-bus/store-sqlserver	SQL Server
@saga-bus/store-mongodb	MongoDB
@saga-bus/store-dynamodb	AWS DynamoDB
@saga-bus/store-redis	Redis
@saga-bus/store-sqlite	SQLite
@saga-bus/store-prisma	Prisma ORM
@saga-bus/store-inmemory	In-Memory (testing)

Middleware

Add cross-cutting concerns:

Package	Purpose
@saga-bus/middleware-logging	Structured logging
@saga-bus/middleware-tracing	OpenTelemetry tracing
@saga-bus/middleware-metrics	Prometheus metrics
@saga-bus/middleware-validation	Zod schema validation
@saga-bus/middleware-idempotency	Message deduplication
@saga-bus/middleware-tenant	Multi-tenant isolation

Framework Integrations

First-class support for popular frameworks:

Package	Framework
@saga-bus/nestjs	NestJS
@saga-bus/nextjs	Next.js
@saga-bus/express	Express
@saga-bus/fastify	Fastify
@saga-bus/hono	Hono

Need Help?

• GitHub Issues - Report bugs or request features
• Examples - Working example applications