PubSub

This is a generic PubSub Factory exposing a listen and a emit method.

NOTE: Today, only Google Cloud PubSub has been added.

Installation

npm install --save @algoan/pubsub

Setup for simulator

You need to have a google account and have installed gcloud sdk.

Then, you need to install the simulator with:

gcloud components install pubsub-emulator
gcloud components update

Launch the tests

Start the tests in another terminal with:

npm test

It will launch a Google PubSub emulator

Usage

To create a PubSub instance using Google Cloud:

import { ExtendedMessage, PubSub, PubSubFactory, Transport } from '@algoan/pubsub'

const pubSub: PubSub = PubSubFactory.create({
  transport: Transport.GOOGLE_PUBSUB,
  options: {
    projectId: 'test',
    // And all other Google PubSub properties
  }
});
const topicName: string = 'some_topic';

await pubsub.listen(topicName, {
  autoAck: true,
  onMessage: (data: ExtendedMessage<{foo: string}>) => {
    console.log(data.parsedData); // { foo: 'bar', time: {Date.now}, _eventName: 'some_topic' }
    // do whatever you want. The message has already been acknowledged
  },
  onError: (error: Error) => {
    // Handle error as you wish
  }
});

await pubsub.emit(topicName, { foo: 'bar' });

Contribution

This module uses semantic-release, please follow these instructions to contribute to the project or use npm run commit.

API

`PubSubFactory.create({ transport, options })`

The only static method from the PubSubFactory class. It initiates a new PubSub instance depending on the transport. By default, it connects to Google Cloud PubSub.

transport: PubSub technology to use. Only GOOGLE_PUBSUB is available for now.
options: Options related to the transport.
- If transport === Transport.GOOGLE_PUBSUB, then have a look at the Google Cloud PubSub config client.
- debug: Display logs if it is set to true. It uses a pino logger and pino-pretty if NODE_ENV is not equal to production.
- topicsPrefix: Add a prefix to all created topics. Example: topicsPrefix: 'my-topic', all topics will begin with my-topic+{your topic name}.
- subscriptionsPrefix: Add a prefix to all created subscriptions. Example: subscriptionsPrefix: 'my-sub', all topics will begin with my-sub%{your topic name}.
- namespace: Add a namespace property to Message attributes when publishing on a topic.
- environment: Add a environment property to Message attributes when publishing on a topic.

`pubsub.listen(event, options)`

Listen to a specific event.

NOTE: It only uses the Google Cloud subscription pull delivery for now.

event: Name of the event.
options: Options related to the Listener method
- onMessage: Method called when receiving a message
- onError: Method called when an error occurs
- autoAck: Automatically ACK an event as soon as it is received (default to true)
- subscriptionOptions: Options applied to the subscription (have a look at Subscription options)
- topicOptions: Options applied to the created topic (have a look at Topic options)

`pubsub.emit(event, payload, options)`

Emit a specific event with a payload. It added attributes in the message if you have added a namespace or an environment when setting the PubSubFactory class. It also adds an _eventName and a time property in the emitted payload.

event: Name of the event to emit.
payload: Payload to send. It will be buffered by Google, and then parsed by the listen method.
options: Options related to the Emit method
- customAttributes: Add custom attributes which will be stored in the message.attributes property.
- subscriptionOptions: Options applied to the subscription (have a look at Subscription options)
- topicOptions: Options applied to the created topic (have a look at Topic options)

diephil / pubsub