cloudevents-router-gcp v2.1.0

GCP CloudEvents mapping

This library is designed to work with cloudevents-router package.

We generate a mapping for all Google CloudEvents based on JSON Schema catalog published at googleapis/google-cloudevents

Install

npm install cloudevents-router-gcp

Use just types

import type { GoogleEvents } from "cloudevents-router-gcp";

/*
Will be equal to the following code snippet:

import { LogEntryData } from '@google/events/cloud/audit/v1/LogEntryData'
import { MessagePublishedData } from '@google/events/cloud/pubsub/v1/MessagePublishedData'
...

export type GoogleEvents = {
  'google.cloud.audit.log.v1.written': LogEntryData
  'google.cloud.pubsub.topic.v1.messagePublished': MessagePublishedData
  ...
}
*/

Use with cloudevents-router

import type { GoogleEvents } from "cloudevents-router-gcp";
import { CloudEventsRouter, getMiddleware } from "cloudevents-router";
import http from "http";

const router = new CloudEventsRouter<GoogleEvents>();

router.on("google.cloud.pubsub.topic.v1.messagePublished", async (event) => {
  console.log("PubSub ordering key", event.data.message?.orderingKey);
});

// See cloudevents-router documentation for more integration examples
const middleware = getMiddleware(router, { path: "/" });
const server = http.createServer(middleware);

server.listen(5000);

PubSub instructions

While consuming PubSub events with cloudevents is simple the type definition for PubSub is not very useful.

Payload is passed as string or undefined, and all topics end up in the same handler (as message type is always google.cloud.pubsub.topic.v1.messagePublished).

interface MessagePublishedData {
  subscription?: string;
  message?: {
    attributes?: { [key: string]: string };
    data?: string;
    messageId?: string;
    orderingKey?: string;
    publishTime?: Date | string;
  };
}

To make it a bit less painful we ship a PubSubParsedMessage<T> generic type and some helper functions to parse and re-route the PubSub messages.

1. Define your JSON message types

import type { GoogleEvents, PubSubParsedMessage } from "cloudevents-router-gcp";

// Define message payload type
type EventMap = GoogleEvents & {
  "pubsub.userAdded": PubSubParsedMessage<{
    username: string;
    password: string;
    age?: number;
  }>;
  "pubsub.profileChanged": PubSubParsedMessage<{
    username: string;
    profilePicture: string;
  }>;
};

This will replace data attribute (data?: string) in the original MessagePublishedData type with a more useful extracted type definition.

2. Write handlers for your messages

import { CloudEventsRouter } from "cloudevents-router";

const router = new CloudEventsRouter<EventMap>();

router.on("pubsub.profileChanged", async (event) => {
  console.log("Profile picture added", event.data.message?.data.profilePicture);
});

3. Parse and consume PubSub messages

To use the above handler we need to parse and republish PubSub messages

import { republishPubSubByTopic } from "cloudevents-router-gcp";

// use the router from above
// const router = ...

republishPubSubByTopic(router, {
  topics: {
    "user-added-topic": "pubsub.userAdded",
    "profile-changed-topic": "pubsub.profileChanged",
  },
});

// setup server as above
// const server = ...
server.listen(5000);

GCP PubSub payloads

GCP is publishing data in some known but not too well documented formats.

There are many more, if you are using one of them and its not implemented, please feel free to create a pull request so others can also benefit.

usage is the same as for manually typed messages.

import { messages } from "cloudevents-router-gcp";

const EventMap = {
  "artifact.published": messages.ArtifactMessage,
};

// ...

Thats it ...

... happy coding :)