This demonstrates how to send and receive messages using Google Cloud Pub/Sub on Google App Engine 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 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.

Refer to the top-level README 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

Install dependencies, preferably with a virtualenv:

$ virtualenv env
$ source env/bin/activate
$ pip install -r requirements.txt

Then set environment variables before starting your application:

$ export PUBSUB_VERIFICATION_TOKEN=[your-verification-token]
$ export PUBSUB_TOPIC=[your-topic]
$ python main.py

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 -i --data @sample_message.json ":8080/pubsub/push?token=[your-token]"

Or

$ http POST ":8080/pubsub/push?token=[your-token]" < sample_message.json

Response:

HTTP/1.0 200 OK
Content-Length: 2
Content-Type: text/html; charset=utf-8
Date: Mon, 10 Aug 2015 17:52:03 GMT
Server: Werkzeug/0.10.4 Python/2.7.10

OK

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

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.