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 alpha pubsub topics create [your-topic-name]
    $ gcloud alpha pubsub subscriptions create [your-subscription-name] \
        --topic [your-topic-name] \
        --push-endpoint \
            https://[your-app-id].appspot.com/pubsub/push?token=[your-token] \
        --ack-deadline 30
   

3. Update the environment variables in app.yaml.

Deploy using gcloud:

gcloud app deploy app.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.