Google App Engine Overview - BarCamp Phnom Penh 2011

Guy Flysher

Google App Engine

(Google App Engine Overview)

Barcamp Phnom Penh 2011

Phnom Penh, Cambodia

About me

● Developer in the Emerging markets team.

● Joined Google in 2007.

● Previously worked on Social graphs,
Gmail and Google Accounts.

● Currently work on SMS products (Chat SMS, G+ SMS and
more to come...)

● G+ profile: http://gplus.name/GuyFlysher

Agenda

● Part I: What is App Engine?

● Part II: App Engine Product Usage

● Part III: How to use App Engine
○ Hello world example
○ App Engine Services
○ Code examples
○ Demos of non web uses

App Engine is a full development platform

App Engine provides great
Hosting tools, APIs & hosting

Easy to build

APIs Easy to manage

Easy to scale

Tools

Language Runtime Options

GO
Experimental Java

App Engine APIs/Services

Memcache Datastore URL Fetch

Mail XMPP Task Queue

Images Blobstore User Service

App Engine - A Larger Number

1,500,000,000+
Page views per
day

Royal Wedding - Scalability Success

Official blog & live stream apps
hosted on App Engine

On Wedding day...
Blog app served:
● Up to 2k requests per second
● 15 million pageviews
● 5.6 million visitors
Live stream app served:
● Up to 32k requests per second
● 37.7 million pageviews
● 13.7 million visitors

http://goo.gl/F1SGc

Not all apps user-facing or web-based!

● Need backend server processing? Want to build your own?
● Go cloud with App Engine!
● No UI needed for app to talk to App Engine, just need HTTP or XMPP
● Great place for user info e.g., high scores, contacts, levels/badges, etc.
● Better UI: move user data off phone & make universally available

Agenda

● Part I: What is App Engine?

● Part II: App Engine Product Usage

● Part III: How to use App Engine
○ Servlets and JSP files
○ Hello world example
○ App Engine Services and code examples
○ Demos of non web uses

Java HttpServlet

● Abstract class for processing HTTP requests.

● Override its methods for processing various HTTP requests,
e.g:
○ doGet
○ doPost
○ doHead
○ etc

● Part of Java (not App Engine specific)

HttpServlet example

public class Hello_worldServlet extends HttpServlet {

public void doGet(HttpServletRequest req,
HttpServletResponse resp) throws IOException {

String userIp = req.getRemoteAddr();
resp.setContentType("text/plain");
resp.getWriter().println("Hello, " + userIp);
}
}

JSP - JavaServer Pages

● Used to create dynamically generated web pages based on
HTML.

● A mix of Java and HTML.

● Can be though of as the Java equivalent of PHP.

JSP example

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html><head> <title> Welcome!</title></head><body>

<%
if (request.getParameter("name") != null) {
%>
Hello, <%= request.getParameter("name") %> 
<%
} else {
%>
Hello, stranger. 
<%
}
%>

Hello World Demo

Deploy from scratch
(In under 3 minutes)

App Engine setup

Servlets and other Java
code

JSP, html and other static
files

App Engine setup

Configuration files

web.xml

Used to map URLs to the servlets that will handle them:

App Engine Services

The User Service

The user system

Building your own user system is a lot of work

● Needs to be very secure - destructive result if broken into.

● Needs to be very reliable - if it is down your app can't be
used.

● Lots of other services you need to build - a recovery
mechanism etc.

The Google user system

App Engine User Service lets you use Google's user
system for your app.
Benefits:

● Users don't need to create a new account to use your app,
they can use their Google account

● Very secure, highly reliable.

● Already has recovery mechanisms etc.

● Very easy to use!

The User Service

Checking if a user is logged in:
<%
UserService userService = UserServiceFactory.getUserService();
User user = userService.getCurrentUser();
if (user != null) {
%>

Hello, <%= user.getNickname() %> !
Our records show your email as: <%= user.getEmail() %> 

<%
} else {
%>

Hello! Please log in. 

<%
}
%>

The User Service
Creating a sign in/out links
<%
UserService userService = UserServiceFactory.getUserService();
User user = userService.getCurrentUser();
if (user != null) {
%>

Hello, <%= user.getNickname() %>!
 <a href="<%= userService.createLogoutURL(request.getRequestURI()) %>">Sign out </a>

<%
} else {
%>
<a href="<%= userService.createLoginURL(request.getRequestURI()) %>">Sign in</a
...

App Engine Services

The XMPP (chat) Service

Sending a chat message
...

JID fromJid = new JID("gday-chat@appspot.com");
JID toJid = new JID("chatty.cathy@gmail.com");
Message msg = new MessageBuilder()
.withRecipientJids(toJid)
.withFromJid(fromJid)
.withBody("Hi there. Is this easy or what?")
.build();
XMPPService xmpp = XMPPServiceFactory.getXMPPService();
SendResponse status = xmpp.sendMessage(msg);
boolean messageSent =
(status.getStatusMap().get(toJid) ==
SendResponse.Status.SUCCESS);

...

App Engine Services

The Mail Service

Sending an email message
...

Properties props = new Properties();
Session session = Session.getDefaultInstance(props, null);

try {
Message msg = new MimeMessage(session);
msg.setFrom(new InternetAddress(
"anything@my-app-name.appspotmail.com",
"Guy's App Engine App"));
msg.addRecipient(Message.RecipientType.TO,
new InternetAddress("my.client@gmail.com"));
msg.setSubject("You confirmation email");
msg.setText("...");
Transport.send(msg);

} catch (AddressException e) { ... }
catch (MessagingException e) { ... }
catch (UnsupportedEncodingException e) { ... }

...

!
Q&A
More documentation and information:
http://code.google.com/appengine

Receiving a chat message
Signup your app to receive chat messages
appengine-web.xml
<inbound-services>
<service>xmpp_message</service>
</inbound-services>

web.xml

<servlet>
<servlet-name>xmppreceiver</servlet-name>
<servlet-class>gday.ReceiveChatMessageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>xmppreceiver</servlet-name>
<url-pattern>/_ah/xmpp/message/chat/</url-pattern>
</servlet-mapping>

Receiving a chat message

protected void doPost(HttpServletRequest req,
HttpServletResponse resp)
throws ServletException, IOException {

XMPPService xmpp = XMPPServiceFactory.getXMPPService();
Message message = xmpp.parseMessage(req);

JID fromJid = message.getFromJid();
String body = message.getBody();
String emailAddress = fromJid.getId().split("/")[0];
if (body.equalsIgnoreCase("hello")) {
...
return;
}

...

Google App Engine Overview - BarCamp Phnom Penh 2011

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