Python for Google App Engine

Table of Contents

Python for Google App Engine

Credits

About the Author

About the Reviewers

www.PacktPub.com

Support files, eBooks, discount offers, and more

Why subscribe?

Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Downloading the color images of this book

Errata

Piracy

Questions

1. Getting Started

The cloud computing stack – SaaS, PaaS, and IaaS

Google Cloud Platform

Hosting + Compute

Storage

BigQuery

Services

What Google App Engine does

The runtime environment

The services

Making our first Python application

Download and installation

Installing on Windows

Installing on Mac OS X

Installing on Linux

App Engine Launcher

Creating the application

The app.yaml configuration file

The main.py application script

Running the development server

Uploading the application to App Engine

Google Developer Console

Development Console

Summary

2. A More Complex Application

Experimenting on the Notes application

Authenticating users

HTML templates with Jinja2

Handling forms

Persisting data in Datastore

Defining the models

Basic querying

Transactions

Using static files

Summary

3. Storing and Processing Users' Data

Uploading files to Google Cloud Storage

Installing Cloud Storage Client Library

Adding a form to upload images

Serving files from Cloud Storage

Serving files through Google's Content Delivery Network

Serving images

Serving other types of files

Transforming images with the Images service

Processing long jobs with the task queue

Scheduling tasks with Cron

Sending notification e-mails

Receiving users' data as e-mail messages

Summary

4. Improving Application Performance

Advanced use of Datastore

More on properties – arrange composite data with StructuredProperty

More on queries – save space with projections and optimize iterations with mapping

Projection queries

Mapping

NDB asynchronous operations

Caching

Backup and restore functionalities

Indexing

Using Memcache

Breaking our application into modules

Summary

5. Storing Data in Google Cloud SQL

Creating a Cloud SQL instance

Configuring access

Setting the root password

Connecting to the instance with the MySQL console

Creating the notes database

Creating a dedicated user

Creating tables

Connecting to the instance from our application

Loading and saving data

Using the local MySQL installation for development

Summary

6. Using Channels to Implement a Real-time Application

Understanding how the Channel API works

Making our application real time

Implementing the server

The JavaScript code for clients

Tracking connections and disconnections

Summary

7. Building an Application with Django

Setting up the local environment

Configuring a virtual environment

Installing dependencies

Rewriting our application using Django 1.7

Using Google Cloud SQL as a database backend

Creating a reusable application in Django

Views and templates

Authenticating users with Django

Using the ORM and migrations system

Processing forms with the Forms API

Uploading files to Google Cloud Storage

Summary

8. Exposing a REST API with Google Cloud Endpoints

Reasons to use a REST API

Designing and building the API

Resources, URLs, HTTP verbs, and response code

Defining resource representations

Implementing API endpoints

Testing the API with API Explorer

Protecting an endpoint with OAuth2

Summary

Index

Python for Google App Engine

Python for Google App Engine

Copyright © 2015 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: January 2015

Production reference: 1210115

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham B3 2PB, UK.

ISBN 978-1-78439-819-4

www.packtpub.com

Credits

Author

Massimiliano Pippi

Reviewers

Dom Derrien

Samuel Goebert

Marcos Placona

Commissioning Editor

Taron Pereira

Acquisition Editor

Richard Brookes-Bland

Content Development Editor

Vaibhav Pawar

Technical Editor

Tanmayee Patil

Copy Editors

Deepa Nambiar

Vikrant Phadke

Stuti Srivastava

Project Coordinator

Kranti Berde

Proofreaders

Simran Bhogal

Maria Gould

Ameesha Green

Paul Hindle

Indexer

Priya Sane

Production Coordinator

Nitesh Thakur

Cover Work

Nitesh Thakur

About the Author

Massimiliano Pippi has been a software developer for over 10 years, more than half of which he spent working with scientific visualization and backend software for a private company, using C++ and Qt technologies. He started using Python in 2008 and currently works at Evonove, a small company where he has been leading a number of Python software projects, most of which are based on the Django web framework. He is also an open source advocate and active contributor, documentation fanatic, and speaker at conferences. He writes about Python and other development-related topics at http://dev.pippi.im.

About the Reviewers

Dom Derrien is a full-stack web developer who has been defining application environments with a focus on high availability and scalability. He's been in the development field for more than 15 years and has worked for big and small companies and also as an entrepreneur.

He's currently working for the game company Ubisoft Inc., where he defines the next generation services platform for its successful AAA games. To extend the gamer experience on the Web and on mobiles, he provides technical means that are transparent, efficient, and highly flexible.

On receiving the invitation to review this book, after a comparable work for the books Google App Engine Java and GWT Application Development, Packt Publishing, he was pleased to share his knowledge about Google App Engine again.

I want to thank my wife, Sophie, and our sons, Erwan and Goulven, with whom I enjoy a peaceful life in Montréal, Québec, Canada.

Samuel Goebert is a computer science PhD student at Plymouth University, UK. Samuel has over 12 years of experience in software development and associated technologies. For further details about him, check out his LinkedIn profile at www.linkedin.com/in/samuelgoebert.

Marcos Placona grew up in Sao Paulo, Brazil, and started tinkering with web development when 14.400 kbs modems were the coolest thing.

He then eagerly pursued a computer science degree and soon after an opportunity arose on the other side of the Atlantic. In his 20s, he decided to move to England where he worked as a software engineer at a software house. He also started blogging on www.placona.co.uk.

Marcos has published and printed articles in several web portals, magazines, and books.

He is currently working as a developer evangelist at Twilio; he actively works with developers and communities to equip and inspire them while making their applications better.

www.PacktPub.com

Support files, eBooks, discount offers, and more

For support files and downloads related to your book, please visit www.PacktPub.com.

Did you know that Packt offers eBook versions of every book published, with PDF and ePub files available? You can upgrade to the eBook version at www.PacktPub.com and as a print book customer, you are entitled to a discount on the eBook copy. Get in touch with us at for more details.

At www.PacktPub.com, you can also read a collection of free technical articles, sign up for a range of free newsletters and receive exclusive discounts and offers on Packt books and eBooks.

https://www2.packtpub.com/books/subscription/packtlib

Do you need instant solutions to your IT questions? PacktLib is Packt's online digital book library. Here, you can search, access, and read Packt's entire library of books.

Why subscribe?

Fully searchable across every book published by Packt

Copy and paste, print, and bookmark content

On demand and accessible via a web browser

Free access for Packt account holders

If you have an account with Packt at www.PacktPub.com, you can use this to access PacktLib today and view 9 entirely free books. Simply use your login credentials for immediate access.

To Azzurra and Valerio, thanks for being patient with me. But I also have been patient with you, so I think we're even.

Preface

In April 2008, 10,000 developers from all around the world were lucky enough to get an account to access the preview release of Google App Engine, which is a tool designed to let users run their web applications on the same infrastructure Google uses for its own services. Announced during Google's Campfire One event, App Engine was described as something easy to use, easy to scale and free to get started; three design goals that perfectly matched the requirements of a typical tech start-up trying to reduce the time to market.

While other big companies at that time were already offering to lease part of their own infrastructure, selling reliability and scalability in an affordable, pay-per-use fashion, Google set App Engine one step ahead by providing developers with application-building blocks instead of simple access to hardware; it is a hosting model followed by many others later on. The goal of this model is to let developers focus on the code and forget about failing machines, network issues, scalability problems, and performance tuning; the choice of Python as the first programming language supported by App Engine was a natural choice for a tool whose aim is to make writing and running web applications easier.

During the Google I/O event in 2012, Google announced that several other building blocks from its own infrastructure would be made available under the name of Google Cloud Platform, first as a partner program and then as a general availability product. Currently, App Engine is not only a notable member of the Cloud Platform family but also a mature and well-maintained platform, widely adopted and with a huge list of customers' success stories.

This book will teach you how to write and run web applications in Python with App Engine, getting the most out of Google Cloud Platform. Starting with a simple application, you will add more and more features to it, each time with the help of the components and services provided by Google's infrastructure.

What this book covers

Chapter 1, Getting Started, will help you get your hands dirty with a very simple functional Python application running on a production server. The chapter begins with making a survey of Google's cloud infrastructure, showing where App Engine is placed and how it compares to other well-known cloud services. It then walks readers through downloading and installing the runtime for Linux, Windows, and OS X, coding a Hello, World! application and deploying it on App Engine. The last part introduces administration consoles both for the development and production servers.

Chapter 2, A More Complex Application, teaches you how to implement a complex web application running on App Engine. It begins with an introduction to the bundled webapp2 framework and possible alternatives; then, you will get in touch with user authentication and form handling and then an introduction to Google's Datastore nonrelational database. The last part shows you how to make HTML pages through templates rendering and how to serve all the static files needed to style the page.

Chapter 3, Storing and Processing Users' Data, will show you how to add more functionalities to the app from the previous chapter. The chapter begins by showing you how to let users upload files using Google Cloud Storage and how to manipulate such files when they contain image data with the Image API. It then introduces you to the task queues used to execute long jobs (such as image manipulation) outside the request process and how to schedule batches of such jobs. The last part shows you how to send and receive e-mails through the Mail API.

Chapter 4, Improving Application Performance, begins by showing how to improve application performance using advanced features of Datastore. It then shows you how to use the cache provided by App Engine and how to break the application into smaller services using Modules.

Chapter 5, Storing Data in Google Cloud SQL, is dedicated to the Google Cloud SQL service. It shows you how to create and manage a database instance and how to connect and perform queries. It then demonstrates how an App Engine application can save and retrieve data and how to use a local MySQL installation during development.

Chapter 6, Using Channels to Implement a Real-time Application, shows you how to make our application real time, in other words, how to update what clients see without reloading the page in the browser. The first part shows how the Channel API works, what happens when a client connects, and what roundtrip of a message is from the server to the client. Then, it shows you how to add a real-time feature to our application from previous chapters.

Chapter 7, Building an Application with Django, teaches you how to build an App Engine application using the Django web framework instead of webapp2. The first part shows you how to configure the local environment for development, and then the application from previous chapters is rewritten using some of the features provided by Django. The last part shows you how to deploy the application on a production server.

Chapter 8, Exposing a REST API with Google Cloud Endpoints, shows you how to rewrite part of our application to expose data through a REST API. The first part explores all the operations needed to set up and configure a project and how to implement a couple of endpoints for our API. The last part shows explores how to add OAuth protection to the API endpoints.

What you need for this book

In order to run the code demonstrated in this book, you need a Python interpreter for version 2.7.x and the App Engine Python SDK as described in the Download and installation section from Chapter 1, Getting Started.

Additionally, to access the example application once it runs on App Engine, you need a recent version of a web browser such as Google Chrome, Mozilla Firefox, Apple Safari, or Microsoft Internet Explorer.

Who this book is for

If you are a Python programmer who wants to apply your skills to write web applications using Google App Engine and Google Cloud Platform tools and services, this is the book for you. Solid Python programming knowledge is required as well as a basic understanding of the anatomy of a web application. Prior knowledge of Google App Engine is not assumed, nor is any experience with a similar tool required.

By reading this book, you will become familiar with the functionalities provided by Google Cloud Platform with particular reference to Google App Engine, Google Cloud Storage, Google Cloud SQL, and Google Cloud Endpoints at the latest versions available at the time of writing this book.

Conventions

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text are shown as follows: If a user is already logged in, the get_current_user() method returns a User object, otherwise it returns None parameter.

A block of code is set as follows:

import webapp2

class HomePage(webapp2.RequestHandler):

    def get(self):

        self.response.headers['Content-Type'] = 'text/plain'

        self.response.out.write('Hello, World!')

app = webapp2.WSGIApplication([('/', HomePage)], debug=True)

New terms and important words are shown in bold. Words that you see on the screen,