Google App Engine is a platform as a service that allows developers to build and host web applications on Google's infrastructure. It provides automatic scaling, load balancing, malfunction detection, and data storage. Developers can use Google App Engine to develop applications using Java or Python. While it provides common web development technologies, there are also restrictions on application behavior and library usage due to its sandbox environment.

1. Google App Engine
N. Koprowski, W. Sanchez, K. Thissen, M. Tryniecki,
A. Klos
The slides are licensed under a
1 Web Technologies – Prof. Dr. Ulrik Schroeder – WS 2010/11 Creative Commons Attribution 3.0 License

2. Cloud Computing
 Resources and software on demand
 Providers offer APIs
 Platform as a service
 Software as a Service
 Infrastructure as a service
2 Web Technologies

3. Google App Engine – Idea/Concept
 Developing & hosting web applications
 Run web applications on Google's Cloud infrastructure
 Free up to a certain quota of used resources
 Metered bandwidth/CPU time/storage use
3 Web Technologies

4. General Features
 Automatic scaling and load balancing
 Malfunction detection & Backup
 Managing of cache and databases
 SDK for local development and testing
 Persistent data storage
4 Web Technologies

5. Programming Features
 Supports Java and Python
 APIs for additional features
 Sandbox environment
 Each environment provides standard protocols and common
technologies, but there are restrictions
5 Web Technologies

6. General Restrictions
 Datastore: Limitation of inequality filters
 Answer a request in 30 seconds
 No saving of environment between requests
 Filesystem: read-only access
 Code execution only via HTTP request
 SSL/HTTPS: only via *.appspot.com domains
6 Web Technologies

7. Programming Restrictions
 Typical restrictions of a sandbox
 Java: only subset of classes from standard JRE
 Java applications cannot create new threads
 Python modules: only pure Python
(no C)
7 Web Technologies

8. Java/Python differences in GAE
 Java:
 Big set of advanced libraries available
 Datastore: Standard method is to use JDO or JPA
 Flexibility: The possibility of running JVM bytecode made by
different languages
 Python:
 Lacks third-party libraries
 Specific API for Google Datastore
 More support and extensive knowledge base available
8 Web Technologies

9. Google Datastore
 Distributed data storage service
 SQL-like syntax (no JOINS)
 Communication over a provided API
 No traditional relational database
 Datastore entities are schemaless
9 Web Technologies

10. IDEs - Eclipse
 Plugin available for Eclipse:
 Create empty app engine projects
 Test applications with local sandbox
 Deployment
 Compatible with Google Web Toolkit
 As-you-type validation
 Ant is not needed
10 Web Technologies

11. Programming Example
 Creating a new Google Project
 Testing the Project
 Test run on local server
 Modifying the Project
 Working with the Datastore
 Deploying the Project
 Creating the Application ID
 Deploying on Appengine
11 Web Technologies

12. Comparison – Amazon Web Services
Google: Amazon:
• Platform as a Service • Infrastructure as a Service
• Only supports a limited • Wide support for languages
range of languages, APIs, and databases
frameworks
• Simple deployment • Deployment is more akin to
using single servers
12 Web Technologies

13. Comparison – Amazon Web Services
Google: Amazon:
• No relational database • Supports relational
databases
• Lower hosting costs and a
free quota • Higher hosting costs
• Easier to write scalable
applications
-> Low costs and easy to use, -> Flexible, but higher costs
but limited
13 Web Technologies

14. Literature
 http://code.google.com/appengine/ is the Google App Engine
official website
 Google provides extensive articles, tutorials, videos and
documentation both for Python and Java with and without the use
of the Eclipse IDE which can be found on
 http://code.google.com/appengine/articles/
 http://code.google.com/appengine/docs/
 http://code.google.com/appengine/community.html
 http://www.youtube.com/user/GoogleDevelopers
14 Web Technologies