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Events

This guide shows you how to use the Functions Framework for local testing with:

  • CloudEvents
  • The Pub/Sub Emulator

Local Testing of CloudEvents

In your package.json, specify --signature-type=event" for the functions-framework:

{
  "scripts": {
    "start": "functions-framework --target=helloPubSub --signature-type=event"
  }
}

Create an index.js file:

exports.helloPubSub = (data, context) => {
  console.log(data);
}

Start the Functions Framework:

npm start

Your function will be serving at http://localhost:8080/, however, it is no longer accessible via HTTP GET requests from the browser.

Instead, send a POST request where the request body conforms to the API defined by push subscriptions.

Send POST Request to Simulate Pub/Sub messages

Create a new file mockPubsub.json with the following contents:

{
  "message": {
    "attributes": {
      "key": "value"
    },
    "data": "SGVsbG8gQ2xvdWQgUHViL1N1YiEgSGVyZSBpcyBteSBtZXNzYWdlIQ==",
    "messageId": "136969346945"
  },
  "subscription": "projects/myproject/subscriptions/mysubscription"
}

In the same directory as mockPubsub.json, use curl to invoke the Functions Framework including the Pub/Sub JSON in the POST data:

curl -d "@mockPubsub.json" \
  -X POST \
  -H "Ce-Type: true" \
  -H "Ce-Specversion: true" \
  -H "Ce-Source: true" \
  -H "Ce-Id: true" \
  -H "Content-Type: application/json" \
  http://localhost:8080

In the shell that is running the Functions Framework, you'll see the message logged:

{
  message: {
    attributes: { key: 'value' },
    data: 'SGVsbG8gQ2xvdWQgUHViL1N1YiEgSGVyZSBpcyBteSBtZXNzYWdlIQ==',
    messageId: '136969346945'
  },
  subscription: 'projects/myproject/subscriptions/mysubscription'
}

Using the Pub/Sub emulator

Another way to test your cloud function Pub/Sub endpoint is to use the Pub/Sub Emulator. This allows you to use the Pub/Sub notification from another service to trigger your cloud function.

The high level approach is to:

  1. Start the Pub/Sub Emulator
  2. Use the Pub/Sub client library to create a subscription and set the pushEndpoint to http://localhost:8080/[TOPIC NAME].

After setup, all notifications to the subscription topic will be pushed to your cloud function.

Here is a sample script for creating subscription with a pushEndpoint:

const { PubSub } = require('@google-cloud/pubsub');

async function main() {
 const apiEndpoint = 'localhost:8085';
 console.log(`Listening to the Pub/Sub emulator event at: ${apiEndpoint}`);
 const pubsub = new PubSub({
   apiEndpoint, // Pub/Sub emulator endpoint
   projectId: 'myproject',
 });
 const topic = await pubsub.topic('my-topic');
 const [topicExists] = await topic.exists();
 if (!topicExists) {
   await topic.create();
 }
 const createSubscriptionResponse = await topic.createSubscription('my_subscription', {
   pushEndpoint: 'http://localhost:8080/projects/myproject/topics/my-topic',
 });
}

main();