Google App Engine

Google App Engine
Assoc.Prof. Dr.Thanachart Numnonda
Asst.Prof. Thanisa Kruawaisayawan

Mini Master of Java Technology
KMITL
July 2012

Agenda
What is Cloud Computing?

What is Google App Engine?

Google App Engine for Java

Google App Engine Development cycle

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.

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

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

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.

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

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.

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.

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,

Setting Up App in IaaS

Source:http://acloudyplace.com/2012/01/comparing-iaas-and-paas-a-developers-perspective/

Setting Up App in PaaS

Source:http://acloudyplace.com/2012/01/comparing-iaas-and-paas-a-developers-perspective/

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

PaaS for Java: Comparison

Source: http://www.infoq.com/articles/paas_comparison

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.

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

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

Google Datacenters at Dallas, Oregon

GAE Physical Deployment Diagram

Architecture : Application Server

Distributed web hosting platform

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

App Engine for Java : One Year

Source: What’s Hot in Java for App Engine Google Con 2010

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

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

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)

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

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

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 == "Welcome! <a href="" ++ userService.createLoginURL("/")
navBar "Welcome! <a href="" userService.createLoginURL("/")
+"">Sign in or register</a> to customize.";
+"">Sign in or register</a> to customize.";
}} else {{
else
navBar == "Welcome, "" ++ user.getEmail() ++ "! You can <a href=""
navBar "Welcome, user.getEmail() "! You can <a href=""
+userService.createLogoutURL("/") +"">sign out</a>.";
+userService.createLogoutURL("/") +"">sign out</a>.";
}}

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();

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);

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

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);

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);

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>

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

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.

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.

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

Development Server
http://localhost:8888

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

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

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

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

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

Thank you

thananum@gmail.com
twitter.com/thanachart
www.facebook.com/thanachart

Google App Engine

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