Pub/Sub Sample for App Engine Standard (#1606)

* Example of Pub/Sub API Client Lib in GAE Standard

* Added Pub/Sub in AppEngine Standard

Author: anguillanneuf

appengine/standard/pubsub/README.md

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+# Python Google Cloud Pub/Sub sample for Google App Engine Standard Environment
+
+[![Open in Cloud Shell][shell_img]][shell_link]
+
+[shell_img]: http://gstatic.com/cloudssh/images/open-btn.png
+[shell_link]: https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/GoogleCloudPlatform/python-docs-samples&page=editor&open_in_editor=appengine/standard/pubsub/README.md
+
+This demonstrates how to send and receive messages using [Google Cloud Pub/Sub](https://cloud.google.com/pubsub) on [Google App Engine Standard Environment](https://cloud.google.com/appengine/docs/standard/).
+
+## Setup
+
+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](https://console.developers.google.com/project/_/apiui/apiview/pubsub/overview).
+
+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-app-id].appspot.com/_ah/push-handlers/receive_messages/token=[your-token] \
+            --ack-deadline 30
+
+3. Update the environment variables in ``app.yaml``.
+
+## Running locally
+
+Refer to the [top-level README](../README.md) for instructions on running and deploying.
+
+When running locally, you can use the [Google Cloud SDK](https://cloud.google.com/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 GOOGLE_CLOUD_PROJECT=[your-project-name]
+    $ export PUBSUB_VERIFICATION_TOKEN=[your-verification-token]
+    $ export PUBSUB_TOPIC=[your-topic]
+    $ python main.py
+
+### Simulating push notifications
+
+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](https://github.com/jkbrzt/httpie) to POST this:
+
+    $ curl -i --data @sample_message.json ":8080/_ah/push-handlers/receive_messages?token=[your-token]"
+
+Or
+
+    $ http POST ":8080/_ah/push-handlers/receive_messages?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.
+
+## Running on App Engine
+
+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.

appengine/standard/pubsub/app.yaml

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+runtime: python27
+api_version: 1
+threadsafe: yes
+
+handlers:
+- url: /
+  script: main.app
+
+- url: /_ah/push-handlers/.*
+  script: main.app
+  login: admin
+
+#[START env]
+env_variables:
+    PUBSUB_TOPIC: your-topic
+    # This token is used to verify that requests originate from your
+    # application. It can be any sufficiently random string.
+    PUBSUB_VERIFICATION_TOKEN: 1234abc
+#[END env]

appengine/standard/pubsub/main.py

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+# Copyright 2018 Google, LLC.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# [START app]
+import base64
+import json
+import logging
+import os
+
+from flask import current_app, Flask, render_template, request
+from googleapiclient.discovery import build
+
+
+app = Flask(__name__)
+
+# Configure the following environment variables via app.yaml
+# This is used in the push request handler to veirfy that the request came from
+# pubsub and originated from a trusted source.
+app.config['PUBSUB_VERIFICATION_TOKEN'] = \
+    os.environ['PUBSUB_VERIFICATION_TOKEN']
+app.config['PUBSUB_TOPIC'] = os.environ['PUBSUB_TOPIC']
+app.config['GCLOUD_PROJECT'] = os.environ['GOOGLE_CLOUD_PROJECT']
+
+
+# Global list to storage messages received by this instance.
+MESSAGES = []
+
+
+# [START index]
+@app.route('/', methods=['GET', 'POST'])
+def index():
+    if request.method == 'GET':
+        return render_template('index.html', messages=MESSAGES)
+
+    data = request.form.get('payload', 'Example payload').encode('utf-8')
+
+    service = build('pubsub', 'v1')
+    topic_path = 'projects/{project_id}/topics/{topic}'.format(
+        project_id=app.config['GCLOUD_PROJECT'],
+        topic=app.config['PUBSUB_TOPIC']
+    )
+    service.projects().topics().publish(
+        topic=topic_path, body={
+          "messages": [{
+              "data": base64.b64encode(data)
+          }]
+        }).execute()
+
+    return 'OK', 200
+# [END index]
+
+
+# [START push]
+@app.route('/_ah/push-handlers/receive_messages', methods=['POST'])
+def receive_messages_handler():
+    if (request.args.get('token', '') !=
+            current_app.config['PUBSUB_VERIFICATION_TOKEN']):
+        return 'Invalid request', 400
+
+    envelope = json.loads(request.data.decode('utf-8'))
+    payload = base64.b64decode(envelope['message']['data'])
+
+    MESSAGES.append(payload)
+
+    # Returning any 2xx status indicates successful receipt of the message.
+    return 'OK', 200
+# [END push]
+
+
+@app.errorhandler(500)
+def server_error(e):
+    logging.exception('An error occurred during a request.')
+    return """
+    An internal error occurred: <pre>{}</pre>
+    See logs for full stacktrace.
+    """.format(e), 500
+
+
+if __name__ == '__main__':
+    # This is used when running locally. Gunicorn is used to run the
+    # application on Google App Engine. See entrypoint in app.yaml.
+    app.run(host='127.0.0.1', port=8080, debug=True)
+# [END app]

appengine/standard/pubsub/main_test.py

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+# Copyright 2018 Google, LLC.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import base64
+import json
+import os
+
+import pytest
+
+import main
+
+
+@pytest.fixture
+def client():
+    main.app.testing = True
+    return main.app.test_client()
+
+
+def test_index(client):
+    r = client.get('/')
+    assert r.status_code == 200
+
+
+def test_post_index(client):
+    r = client.post('/', data={'payload': 'Test payload'})
+    assert r.status_code == 200
+
+
+def test_push_endpoint(client):
+    url = '/_ah/push-handlers/receive_messages?token=' + \
+        os.environ['PUBSUB_VERIFICATION_TOKEN']
+
+    r = client.post(
+        url,
+        data=json.dumps({
+            "message": {
+                "data": base64.b64encode(
+                    u'Test message'.encode('utf-8')
+                ).decode('utf-8')
+            }
+        })
+    )
+
+    assert r.status_code == 200
+
+    # Make sure the message is visible on the home page.
+    r = client.get('/')
+    assert r.status_code == 200
+    assert 'Test message' in r.data.decode('utf-8')
+
+
+def test_push_endpoint_errors(client):
+    # no token
+    r = client.post('/_ah/push-handlers/receive_messages')
+    assert r.status_code == 400
+
+    # invalid token
+    r = client.post('/_ah/push-handlers/receive_messages?token=bad')
+    assert r.status_code == 400

appengine/standard/pubsub/requirements.txt

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+Flask==0.12.2
+google-api-python-client==1.7.3

appengine/standard/pubsub/sample_message.json

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+{
+    "message": {
+        "data": "SGVsbG8sIFdvcmxkIQ=="
+    }
+}

appengine/standard/pubsub/templates/index.html

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+{#
+# Copyright 2015 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#}
+<!doctype html>
+<html>
+<head>
+  <title>Pub/Sub Python on Google App Engine Flexible Environment</title>
+</head>
+<body>
+<div>
+  <p>Messages received by this instance:</p>
+  <ul>
+    {% for message in messages: %}
+      <li>{{message}}</li>
+    {% endfor %}
+  </ul>
+  <p><small>Note: because your application is likely running multiple instances, each instance will have a different list of messages.</small></p>
+</div>
+<!-- [START form] -->
+<form method="post">
+  <textarea name="payload" placeholder="Enter message here"></textarea>
+  <input type="submit">
+</form>
+<!-- [END form] -->
+</body>
+</html>