This sample shows how to send and receive messages using Google Cloud Pub/Sub on Google App Engine standard environment and flexible environment.

Before you can run or deploy the sample, you will need to do the following:

1. Enable the Cloud Pub/Sub API in the Google Developers Console.

2. Create a topic and subscription.

    gcloud pubsub topics create <your-topic-name>
    gcloud pubsub subscriptions create <your-subscription-name> \
      --topic <your-topic-name> \
      --push-endpoint \
        https://<your-project-id>.appspot.com/pubsub/push?token=<your-verification-token> \
      --ack-deadline 30
   

3. Create a subscription for authenticated pushes. The push auth service account must have Service Account Token Creator Role assigned, which can be done in the Cloud Console IAM & admin UI. --push-auth-token-audience is optional. If set, remember to modify the audience field check in app.js (line 112).

    gcloud beta pubsub subscriptions create <your-subscription-name> \
      --topic <your-topic-name> \
      --push-endpoint \
        https://<your-project-id>.appspot.com/pubsub/authenticated-push?token=<your-verification-token> \
      --ack-deadline 30 \
      --push-auth-service-account=[your-service-account-email] \
      --push-auth-token-audience=example.com
   

4. Update the environment variables in app.standard.yaml or app.flexible.yaml (depending on your App Engine environment).

Refer to the appengine/README.md file for instructions on running and deploying.

When running locally, you can use the Google Cloud SDK to provide authentication to use Google Cloud APIs:

gcloud init

Then set environment variables before starting your application:

export PUBSUB_VERIFICATION_TOKEN=<your-verification-token>
export PUBSUB_TOPIC=<your-topic-name>
npm start

The application can send messages locally, but it is not able to receive push messages locally. You can, however, simulate a push message by making an HTTP request to the local push notification endpoint. There is an included sample_message.json. You can use curl or httpie to POST this:

curl -H "Content-Type: application/json" -i --data @sample_message.json ":8080/pubsub/push?token=<your-verification-token>"

Or

http POST ":8080/pubsub/push?token=<your-verification-token>" < sample_message.json

Response:

HTTP/1.1 200 OK
Connection: keep-alive
Date: Mon, 31 Aug 2015 22:19:50 GMT
Transfer-Encoding: chunked
X-Powered-By: Express

After the request completes, you can refresh localhost:8080 and see the message in the list of received messages.

Simulating authenticated push requests will fail because requests need to contain a Cloud Pub/Sub-generated JWT in the "Authorization" header.

http POST ":8080/pubsub/authenticated-push?token=<your-verification-token>" < sample_message.json

Response:

HTTP/1.1 400 Bad Request
Connection: keep-alive
Date: Thu, 25 Apr 2019 17:47:36 GMT
Transfer-Encoding: chunked
X-Powered-By: Express

Invalid token

Note: Not all the files in the current directory are needed to run your code on App Engine. Specifically, the test directory, which is for testing purposes only. It SHOULD NOT be included in when deploying your app. When your app is up and running, Cloud Pub/Sub creates tokens using a private key, then the Google Auth Node.js library takes care of verifying and decoding the token using Google's public certs, to confirm that the push requests indeed come from Cloud Pub/Sub.

In the current directory, deploy using gcloud:

    gcloud app deploy app.standard.yaml

To deploy to App Engine Node.js Flexible Environment for Node.js 16 and earlier, run:

    gcloud app deploy app.flexible.yaml

For App Engine Flexible deployments for 18 and later, deploy via:

    gcloud app deploy app.flexible_os.yaml

You can now access the application at https://[your-app-id].appspot.com. You can use the form to submit messages, but it's non-deterministic which instance of your application will receive the notification. You can send multiple messages and refresh the page to see the received message.