Google App Engine is a platform for hosting web applications in Google's data centers. It allows developers to build applications on scalable infrastructure without having to manage servers. Key features include automatic scaling, high availability, easy deployment, and built-in services like Datastore, Memcache and Task Queue. The development process involves using the App Engine SDK, which includes a local development server that emulates the live environment. Applications are deployed to App Engine by uploading the compiled code.

1. Google App Engine
Assoc.Prof. Dr.Thanachart Numnonda
Asst.Prof. Thanisa Kruawaisayawan
www.imcinstitute.com
July 2012

2. Agenda
What is Cloud Computing?
What is Google App Engine?
Google App Engine for Java
Google App Engine Development cycle

3. What is Cloud Computing?

4. Cloud computing : Definition (Wikipedia)
Cloud Computing is Internet-based computing,
whereby shared resources, software, and information
are provided to computers and other devices on
demand, like the electricity grid.

5. Cloud computing characteristics
Massive, abstracted infrastructure
Dynamic allocation, scaling, movement of applications
Pay per use
No long-term commitments
OS, application architecture independent
No hardware or software to install

6. Grid to Cloud Evolution

7. Web 2.0 & Cloud Computing
Web 2,0 concentrate on the private user and clouds
are decscendents of data centers which services the
enterprise
Web 2.0 promote SaaS
Web 2.0 needs massive scaling technologies
User centric Web 2.0 companies (Twitter, Slideshare)
are relying on Cloud Services

8. ISP to Cloud Evolution

9. Software as a Service (SaaS)
SaaS is at the highest layer and features a complete
application offered as a service, on-demand,
via multitenancy — meaning a single instance of the
software runs on the provider’s infrastructure and
serves multiple client organizations.

10. Platform as a Service (PaaS)
The middle layer, or PaaS, is the encapsulation of a
development environment abstraction and the
packaging of a payload of services
PaaS offerings can provide for every phase of software
development and testing, or they can be specialized
around a particular area, such as content management

11. Infrastructure as a Service (IaaS)
IaaS is at the lowest layer and is a means of delivering basic
storage and compute capabilities as standardized services
over the network.
Servers, storage systems, switches,routers, and other
systems are pooled (through virtualization technology, for
example) to handle specific types of workloads — from batch
processing to server/storage augmentation during peak loads.

13. Deployment Model
Public Cloud: provider refers to the cloud platform that
targets any types of customers.
Private Cloud: infrastructure that’s hosted internally, targeting
specific customers or sometimes exclusively within an
organization.
Hybrid Cloud: the combination of public and private clouds,
or sometimes on-premise services.

14. IaaS & PaaS: Developer's Perspectives
IaaS normally provides up to O/S level as your choice; for
example Amazon Web Services (AWS) offers several types of
Operating Systems such as Windows Server, Linux SUSE, and
Linux Red Hat. Developer need to install own middleware,
database, etc.
PaaS, given that the database server, VM, and web server VM
are readily provisioned,

15. Setting Up App in IaaS
Source:http://acloudyplace.com/2012/01/comparing-iaas-and-paas-a-developers-perspective/

16. Setting Up App in PaaS
Source:http://acloudyplace.com/2012/01/comparing-iaas-and-paas-a-developers-perspective/

17. PaaS for Java
Amazon Elastic Beanstalk
CloudBees
Cloud Foundry
Google App Engine
Heroku for Java
Red Hat OpenShift

18. PaaS for Java: Comparison

19. PaaS for Java: Comparison
Source: http://www.infoq.com/articles/paas_comparison

20. What is Google App Engine?

21. Google App Engine : Definition (Wikipedia)
It is a platform for hosting web applications in Google-
managed data centers. It is cloud computing
technology which virtualizes applications across
multiple servers and data centers.

22. Google App Engine
Running your web application in Google infrastructure
Support different runtime environments
Java (JRE 6 with limitation, Servlet 2.5, JDO, JPA)
Python (2.5.2)
Apps run in sandbox.
Automatic scaling and load balancing
No server restart, no network issues

23. Hosting Java web apps traditionally
Not so popular except enterprise
High rates as compared to PHP hosting
Shared Tomcat instance among users
Restrictions on any time deployments due to shared
server
Dedicated hosts works fine but they are costly

24. You end up with all this

26. Google Datacenters at Dallas, Oregon

27. GAE Architecture

28. GAE Physical Deployment Diagram

29. Architecture : Application Server

30. Distributed web hosting platform

31. Distributed Datastore

32. Distributed memcache

33. Specialized services

34. Google Apps + your apps

35. Google App Engine for Java

36. GAE/J
Was released on April 08 with Python support. Java
included on August 09

37. App Engine for Java : One Year
Source: What’s Hot in Java for App Engine Google Con 2010

38. GAE Java Runtime Environment
Java 6 VM
Servlet 2.5 Container
HTTP Session support (need to enable explicitly)
JDO/JPA for Datastore API
JSR 107 for Memcache API
javax.mail for Mail API
javax.net.URLConnection for URLFetch API

39. Java Standards on GAE

40. Services by App Engine
Memcache API – high performance in-memory key-value cache
Datastore – database storage and operations
URLFetch – invoking external URLs
Mail – sending mail from your application
Task Queues – for invoking background processes
Images – for image manipulation
Cron Jobs – scheduled tasks on defined time
User Accounts – using Google accounts for authentication

41. Limitations
Programming Model : Application runs in sandbox and
can not
Write to file system
Make arbitrary network connections
Use multiple threads/processes
Perform long-lasting processing
Permissions
Know about other instances/applications
Quotas (Requests, In/Out bandwidth, CPU time, API
calls)

42. GAE Datastore

43. GAE Datastore
Storing data and manipulation
Based on Bigtable
Bigtable is proprietary and hidden from the app developers
Not a relational database (No SQL)
GQL (Google Query Language) to query
Stores data as entities
Distribution, replication, load balancing behind the scene
Need to use JDO/JPA

44. User Service : Google Accounts
Google Accounts are encouraged as the preferred
authentication mechanism for App Engine
– It assumes that all users have a Google Account
– Google authentication for private domains isn’t available yet
Access to Google account data -> email, id
The Development Server simulates Google Accounts
Access constraints based on roles

45. User API : Example
import com.google.appengine.api.users.*;
import com.google.appengine.api.users.*;
UserService userService == UserServiceFactory.getUserService();
UserService userService UserServiceFactory.getUserService();
User user == userService.getCurrentUser();
User user userService.getCurrentUser();
String navBar;
String navBar;
if (user == null) {{
if (user == null)
navBar == "<p>Welcome! <a href="" ++ userService.createLoginURL("/")
navBar "<p>Welcome! <a href="" userService.createLoginURL("/")
+"">Sign in or register</a> to customize.</p>";
+"">Sign in or register</a> to customize.</p>";
}} else {{
else
navBar == "<p>Welcome, "" ++ user.getEmail() ++ "! You can <a href=""
navBar "<p>Welcome, user.getEmail() "! You can <a href=""
+userService.createLogoutURL("/") +"">sign out</a>.</p>";
+userService.createLogoutURL("/") +"">sign out</a>.</p>";
}}

46. URLFetch API
Invoking external URLs from your application over HTTP and
HTTPs
import java.net.*;
import java.net.*;
import java.io.*;
import java.io.*;
URL url == new URL("htp://...");
URL url new URL("htp://...");
InputStream inp == new InputStreamReader(url.openStream());
InputStream inp new InputStreamReader(url.openStream());
BufferedReader reader == new BufferedReader(inp);
BufferedReader reader new BufferedReader(inp);
String line;
String line;
while ((line == reader.readLine()) != null) {{
while ((line reader.readLine()) != null)
//do something
//do something
}}
reader.close();
reader.close();

47. Mail API
Send emails on the behalf of app administrator to the Google
account use.
You can not receive emails
import javax.mail.*;
import javax.mail.*;
Session session == Session.getDefaultInstance(new Properties(), null);
Session session Session.getDefaultInstance(new Properties(), null);
InternetAddress admins == new InternetAddress("admins");
InternetAddress admins new InternetAddress("admins");
Message msg == new MimeMessage(session);
Message msg new MimeMessage(session);
msg.setFrom(admins);
msg.setFrom(admins);
msg.addRecipient(Message.RecipientType.TO, admins);
msg.addRecipient(Message.RecipientType.TO, admins);
msg.setSubject("subject");
msg.setSubject("subject");
msg.setText("text");
msg.setText("text");
Transport.send(msg);
Transport.send(msg);

48. Memcache Service
Distributed in memory cache, better than DataStore
Key-value pair mapping
Configurable expiration time but
Unreliable might be vanished at any time
Supported Interfaces :
– JACHE (JSR 107: JCACHE – Java Temporary Caching API)
– The Low-Level Memcache API

49. Memcache API : Example
import static java.util.Collections.emptyMap;
import static java.util.Collections.emptyMap;
import javax.cache.*;
import javax.cache.*;
CacheFactory cacheFactory == CacheManager.getInstance().getCacheFactory();
CacheFactory cacheFactory CacheManager.getInstance().getCacheFactory();
Cache cache == cacheFactory.createCache(emptyMap());
Cache cache cacheFactory.createCache(emptyMap());
cache.put(key, value);
cache.put(key, value);
cache.get(key);
cache.get(key);

50. Task Queues API
Perform background processes by inserting tasks into queues.
Instructions need to be mention in file queue.xml, in the WEB-INF/ dir
import com.google.appengine.api.labs.taskqueue.Queue;
import com.google.appengine.api.labs.taskqueue.Queue;
import com.google.appengine.api.labs.taskqueue.QueueFactory;
import com.google.appengine.api.labs.taskqueue.QueueFactory;
import com.google.appengine.api.labs.taskqueue.TaskOptions;
import com.google.appengine.api.labs.taskqueue.TaskOptions;
// ...
// ...
TaskOptions taskOptions ==
TaskOptions taskOptions
TaskOptions.Builder.url("/send_invitation_task")
TaskOptions.Builder.url("/send_invitation_task")
.param("address", "juliet@example.com")
.param("address", "juliet@example.com")
.param("firstname", "Juliet");
.param("firstname", "Juliet");
Queue queue == QueueFactory.getDefaultQueue();
Queue queue QueueFactory.getDefaultQueue();
queue.add(taskOptions);
queue.add(taskOptions);

51. Cron Jobs
Up to 20 scheduled tasks per app
Cron jobs (scheduled tasks) supported in cron.xml in WEB-INF dir
Schedule instructions contain Englis-like format
<?xml version="1.0" encoding="UTF-8"?>
<?xml version="1.0" encoding="UTF-8"?>
<cronentries>
<cronentries>
<cron>
<cron>
<url>/listbooks</url>
<url>/listbooks</url>
<description>Repopulate the cache every day at
<description>Repopulate the cache every day at
5am</description>
5am</description>
<schedule>every day 05:00</schedule>
<schedule>every day 05:00</schedule>
</cron>
</cron>
</cronentries>
</cronentries>

52. Images API
Manipulation of images
Transformation of images
Changing image formats

53. GAE Development Cycle

54. GAE Development Cycle

55. Getting Started
The application owner must have a Google Account to
get the tools regardless of language.
Use Java 6 for development.
Eclipse and Netbeans have official plugins.
Both SDKs ship with a Development Web Server that
runs locally and provides a sandbox almost identical to
the real run-time.

56. Software Development Kit
App Engine SDK
– Includes web server (Jetty)
– Emulates all the GAE services
SDK includes an upload tool to deploy app to GAE
Command line tools included.

57. Google Plugin for Eclipse

58. Development Environment
Development Server
Application lifecycle
management
Eclipse/NetBeans plugins /
Firefox plugin (GWT).

59. Google Plugin for Eclipse

60. Development Server
http://localhost:8888

61. Development Server Admin Console
http://localhost:8888/_ah/admin

62. Deployment Environment
Application is deployed as .war which contains.
Deployment is integrated in IDE
Deploy multiple version of the application at the same
time
Your app lives at
– <app_id>.appspot.com or
– Custom domain with Google Apps

63. Running your app on Google
http://<version>.<appid>.appspot.com/some/path

64. Managing Applications
Administration Console
http://appengine.google.com/a/yourdomain.com
Application Dashboard
Multiple application versions
Analyzing log files (including admin)
Analyzing resource usag

65. GAE Dashboard

66. Resources
Google App Engine at a glance, Stefan Christoph
Developing Java Based Web Applications in
Google App Engine, Tahir Akram, Dec. 2009
Google App Engine, Patrick Chanezon, Mar 2010

67. Thank you
thananum@gmail.com
www.facebook.com/imcinstitute
www.imcinstitute.com