TypeBridge

Typescript toolbox for AWS EventBridge

Advantages

• Programmatical definition of your application events
• Typed publish and consume APIs
• Automatically batches putEvents call when publishing more than 10 events at a time
• Check for event payload size before publishing

Quick install

Add typebridge dependency

npm i typebridge --save

Define your bus and events

import { EventBridge } from 'aws-sdk';
import { Bus, Event } from 'typebridge';

export const MyBus = new Bus({
  name: 'applicationBus',
  EventBridge: new EventBridge(),
});

export const MyEventPayloadSchema = {
  type: 'object',
  properties: {
    stringAttribute: { type: 'string' },
    numberAttribute: { type: 'integer' },
  },
  required: ['stringAttribute'],
  additionalProperties: false
} as const;

export const MyEvent = new Event({
  name: 'MyEvent',
  bus: MyBus,
  schema: MyEventPayloadSchema,
  source: 'mySource'
});

Use the Event class to publish

import { MyEvent } from './events.ts';

export const handler = async (event) => {
  await MyEvent.publish({
    stringAttribute: 'string',
    numberAttribute: 12,
  })

  return 'Event published !'
};

Typechecking is automatically enabled:

  await MyEvent.publish({
    stringAttribute: 'string',
    numberAttribute: 12,
    // the following line will trigger a Typescript error
    anotherAttribute: 'wrong'
  })

Use the Event class to create an event

import { MyBus, MyEvent } from './events.ts';

export const handler = async (event) => {
  const events = event.details.map(detail => MyEvent.create({
    stringAttribute: detail.stringAttribute,
    numberAttribute: detail.numberAttribute,
  })
  await MyBus.put(events);

  return 'Event published !'
};

Use the Event class to generate trigger rules

Using the serverless framework with serverless.ts service file:

import type { Serverless } from 'serverless/aws';

const serverlessConfiguration: Serverless = {
  service: 'typebridge-test',
  provider: {
    name: 'aws',
    runtime: 'nodejs12.x',
  },
  functions: {
    hello: {
      handler: 'MyEventHandler.handler',
      events: [
        {
          eventBridge: {
            eventBus: 'applicationBus',
            pattern: NewUserConnectedEvent.pattern,
          },
        },
      ],
    }
  }
}

module.exports = serverlessConfiguration;

Use the Event class to type input event

import { PublishedEvent } from 'typebridge';
import { MyEvent } from './events.ts';

export const handler = (event: PublishedEvent<typeof MyEvent>) => {
  // Typed as string
  return event.detail.stringAttribute;
}

Use the Event class to validate the input event

Using middy middleware stack in your lambda's handler, you can throw an error before your handler's code being executed if the input event source or detail-type were not expected, or if the detail property does not satisfy the JSON-schema used in MyEvent constructor.

import middy from '@middy/core';
import jsonValidator from '@middy/validator';
import { MyEvent } from './events.ts';

const handler = (event) => {
  return 'Validation succeeded';
};

// If event.detail does not match the JSON-schema supplied to MyEvent constructor, the middleware will throw an error
export const main = middy(handler).use(
  jsonValidator({ inputSchema: MyEvent.publishedEventSchema }),
);