@kernpunkt/saga

Overview

This package is a Typescript implementation of the Saga Pattern, specifically in the form of a Saga Orchestrator.

The orchestrator helps you implement loose coupling in your procceses, especially if those deal with multiple microservices. This is achieved by dividing logic into multiple steps (see below), each implementing an execute function (which will change something about the context and do something in the world) and a rollback function (which will serve to undo the change if an error occurs further down the chain).

Installation

To install the package, simply run:

npm install @kernpunkt/saga
yarn add @kernpunkt/saga

Usage

After installation, simply import the SagaOrchestrator like so:

import { SagaOrchestrator } from "@kernpunkt/saga";

Afterwards, you can start by defining a context applicable to your domain, and using it in a step:

import { TSagaContext, ISagaStep } from "@kernpunkt/saga";
type TVacationContext = TSagaContext & {
  flightNumber?: number;
};

class BookFlightStep implements ISagaStep<TVacationContext> {
  getKey(): string {
    return "book-flight";
  }

  async execute(context: TVacationContext): Promise<TVacationContext> {
    // booking logic
  }

  async rollback(context: TVacationContext): Promise<TVacationContext> {
    // rollback logic
  }
}

Then, you can start the saga!

import { SagaOrchestrator } from "@kernpunkt/saga";

const saga = new SagaOrchestrator().addStep(new BookFlightStep());

const context: TVacationContext = {
  log: { successes: [], errors: [] },
};

const result = await saga.orchestrate(context);

shouldRollbackSelf

Steps that implement the ISagaStep interface have the opportunity to provide a shouldRollbackSelf method. If this method exists (and returns true), a potential rollback will start with this current step. Otherwise, the current step will be ommitted.

Testing

To run tests, simply run:

npm run test
yarn test

Contact

	Jörn Meyer Team CodeJunkeys joern.meyer@kernpunkt.de