typescript-pubsub.md

PubSub Event Function in Typescript

This guide is an example of how to develop a function to receive PubSub messages in Typescript with the Functions Framework.

1. Use gts to configure Typescript.

   npx gts init

2. Install the required packages:

   npm install @google-cloud/functions-framework
   npm install @google-cloud/pubsub 
   npm install concurrently nodemon --save-dev

3. Replace the contents of src/index.ts with:

   import {Context, EventFunction} from "@google-cloud/functions-framework/build/src/functions";
   import {PubsubMessage} from "@google-cloud/pubsub/build/src/publisher";
   
   export const helloPubSub: EventFunction = (message: PubsubMessage, context: Context) => {
     const data = message.data ? Buffer.from(message.data as string, "base64").toString() : "No Message";
     console.log(data);
   };

4. Compile your Typescript code:

   npm run compile

   This should compile your index.ts to build/src/index.js.

Deploying with gcloud CLI

1. Adjust main field in package.json to point to the compiled javascript source.

     "main": "build/src/index.js",
     ...

2. Remove prepare script in package.json created by gts. This is because the prepare script requires typescript to be installed and will cause the function to fail to deploy if not removed.

3. Create a Pub/Sub topic, where COOL_TOPIC is the name of the new topic you are creating:

   gcloud pubsub topics create COOL_TOPIC

4. Deploy:

   gcloud functions deploy helloPubSub \
   --runtime nodejs16 \
   --trigger-topic COOL_TOPIC

5. Publish a message to the topic to test your function:

   gcloud pubsub topics publish COOL_TOPIC --message="hello"