@algoan/pubsub
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6.2.0 • Public • Published

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

Usage

Google Cloud PubSub

Run tests

To run tests or to try the PubSubFactory class, you need to have a google account and have installed gcloud sdk.

Then, to install the Google PubSub simulator, run:

gcloud components install pubsub-emulator
gcloud components install beta
gcloud components update

Start tests running:

npm test

It will launch a Google PubSub emulator thanks to the google-pubsub-emulator library.

Example

To create a PubSub instance using Google Cloud:

import { EmittedMessage, GCPubSub, PubSubFactory, Transport } from '@algoan/pubsub'

const pubsub: GCPubSub = 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: EmittedMessage<{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

Thank you for your future contribution 😁 Please follow these instructions before opening a pull request!

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.
    • pinoOptions: If debug is set to true, set the pino logger options. Default to level: debug and prettyPrint: true 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}.
    • topicsSeparator: Customize separator between topicsPrefix and topic name. Example: topicsSeparator: '-', all topics will be {topic prefix}-{your topic name} (default to '+').
    • subscriptionsPrefix: Add a prefix to all created subscriptions. Example: subscriptionsPrefix: 'my-sub', all subscriptions will begin with my-sub%{your topic name}.
    • subscriptionsSeparator: Customize separator between subscriptionsPrefix and topic name. Example: subscriptionsSeparator: '-', all subscriptions will be {subscription prefix}-{your topic name} (default to '%').
    • 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, opts)

Listen to a specific event.

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

  • event: Name of the event.
  • opts: Options related to the Listener method
    • onMessage: Method called when receiving a message
    • onError: Method called when an error occurs
    • options: Option related to the chosen transport

If the chosen transport is Google Cloud PubSub, then options would be:

  • autoAck: Automatically ACK an event as soon as it is received (default to true)
  • subscriptionOptions: Options related to the created Subscription:
    • name: Custom name for the subscription. Default: event (also equal to the topic name)
    • get: Options applied to the getSubscription method (have a look at Subscription options)
    • sub: Options applied to the subscription instance (see also setOptions method)
    • create: Options applied to the createSubscription method (have a look at Create Subscription options)
  • topicOptions: Options applied to the created topic (have a look at Topic options)
  • topicName: Set the topic name. By default, it uses the default name with a prefix.

pubsub.emit(event, payload, opts)

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.
  • opts: Options related to the Emit method
    • metadata: Custom metadata added to the message
    • options: Option related to the chosen transport

If the chosen transport is Google Cloud PubSub, then options would be:

  • topicOptions: Options applied to the created topic (have a look at Topic options)
  • publishOptions: Publish options set to the topic after its creation. Refer to Publish Options
  • messageOptions: Additional message options added to the message. Refer to Message Options

pubsub.unsubscribe(event)

Stop the server connection for a given subscription.

  • event: Name of of the event to stop listening for.

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npm i @algoan/pubsub

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