Transcript Cloud Computing - School of Computer Science

Web Service Programming and
Cloud Computing
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Bigger view of programming
• What we learnt are mostly small, standalone programming
tasks
• In real world an application involves several tiers and languages
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RPC
Client/server architecture
Browser, http server
Browser, http server, DB
Browser, http server, application server, DB
……
• Languages involved
– Client side: Html, javascript, xml, css, xslt;
– Server side: php, java, python, map/reduce, J2EE, sql, …
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Web Service
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Service Oriented Architecture
Discovery
agency
publish
find
Requester
interact
Provider
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A concrete SOA
Registry
Finds
Service
WSDL
Describes
Service
Service
Consumer
SOAP
Web Service
Provider
Communicates with
XML Messages
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Web Service definition
• “encapsulated, loosely coupled, contracted software objects
offered via standard protocols” --ZapThink Research
– Encapsulated
– Web Service implementation is invisible to entities outside the service
– Exposes an interface but hides details
– Loosely Coupled
– Service and consumer software can be redesigned independently
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History of Interface Definition Languages (IDLs)
• IDL has a long history in distributed computing
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DCE (Distributed Computing Environment)
CORBA IDL, OMG (Object Management Group)
COM IDL, Microsoft
WSDL
• Traditional IDLs
– Specifying what to call: the operation names, their signatures,
exceptions. This is the job of IDL.
– Agreeing on how to make an invocation: the mechanism of naming,
activation, data encoding. This is what distributed standards such as
CORBA or COM do.
• WSDL needs to specify the both: the operation provided by the
service, and the mechanism to access the service.
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Web Service Description Language
• WSDL defines
– What the service is: the operations the service provides, including the
signature of the operation –- what
– Access specification: details of the data format and protocol necessary to
access the service’s operation–- how
– Location of the service: details of the network address, such as a URL –where
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Legend:
WSDL functionality view
–What
–how
–where
Interface
Port Type
Supports
Formats & Protocols
Binding
Operation
Input & Output
How to encode
Message
Implements
Port
Provides
Service
Endpoints
In WSDL 2.0, portType is changed to interface.
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WSDL document structure view
WSDL specification
abstract part
types
messages
operations
port types
concrete part
bindings
services and
ports
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<?xml version="1.0"?>
<definitions name="Procurement"
targetNamespace="http://example.com/procurement/definitions"
xmlns:tns="http://example.com/procurement/definitions"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns="http://schemas.xmlsoap.org/wsdl/" >
<message name="OrderMsg">
<part name="productName" type="xs:string"/>
<part name="quantity" type="xs:integer"/>
</message>
<portType name="procurementPortType">
<operation name="orderGoods">
<input message = "OrderMsg"/>
</operation>
</portType>
<binding name="ProcurementSoapBinding" type="tns:procurementPortType">
<soap:binding style="document"
transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="orderGoods">
<soap:operation soapAction="http://example.com/orderGoods"/>
<input>
<soap:body use="literal"/>
</input>
<output>
<soap:body use="literal"/>
</output>
</operation>
</binding>
<service name="ProcurementService">
<port name="ProcurementPort" binding="tns:ProcurementSoapBinding">
<soap:address location="http://example.com/procurement"/>
</port>
</service>
</definitions>
abstract
part
messages
operation and
port type
concrete
part
binding
port and
service
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<definitions … name="BNQuoteService">
<message name="getPriceRequest"> <part name="isbn" type="xsd:string"/> </message>
<message name="getPriceResponse"><part name="return" type="xsd:float"/>
</message>
<portType name="BNQuotePortType">
<operation name="getPrice">
<input name="getPrice" message="tns:getPriceRequest"/>
<output name="getPriceResponse" message="tns:getPriceResponse"/>
</operation>
</portType>
<binding name="BNQuoteBinding" type="tns:BNQuotePortType">
<soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="getPrice"><soap:operation/>
<input><soap:body use="encoded"
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
namespace="urn:xmethods-BNPriceCheck"/>
</input>
<output>
<soap:body use="encoded"
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
namespace="urn:xmethods-BNPriceCheck"/>
</output>
</operation>
</binding>
<service name="BNQuoteService">
<documentation>Returns price of a book at BN.com given an ISBN number</documentation>
<port name="BNQuotePort" binding="tns:BNQuoteBinding">
<soap:address location="http://services.xmethods.net:80/soap/servlet/rpcrouter"/>
</port>
</service>
</definitions>
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Visual representation
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Types (type information for the document, e.g., XML Schema)
Message 1 Message 2 Message 3
Operation 1
Message 4
Operation 2
Message 5
Operation 3
Interface (abstract service)
binding 1
binding 2
binding 3
binding 4
endpoint 1
endpoint 2
endpoint 3
endpoint 4
Service (the interface in all
its available implementations)
By Gustavo Alonso and Cesare
Concrete description
of the service
WSDL document
Abstract description of the service
WSDL structure—interconnection view
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A WSDL example
<?xml version="1.0"?>
<definitions name="PriceCheck"
targetNamespace="http://www.skatestown.com/services/PriceCheck"
xmlns:pc="http://www.skatestown.com/services/PriceCheck"
xmlns:avail="http://www.skatestown.com/ns/availability"
xmlns:wsi="http://ws-i.org/schemas/conformanceClaim/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns="http://schemas.xmlsoap.org/wsdl/">
<types> …</types>
<message> …</message>
<message> … </message>
<portType> … </portType>
<binding> … </binding>
<service> … </service>
</definitions>
This example is from Steve Graham et al: Building Web
Services with Java
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PortType
<portType name="PriceCheckPortType">
<operation name="checkPrice">
<input message="pc:PriceCheckRequest"/>
<output message="pc:PriceCheckResponse"/>
</operation>
</portType>
• <portType> defines the interface of web service. Just as Java Interface declaration;
– Will change the name to <interface> in WSDL 2.0.
• It consists of a sequence of operation declarations.
• WSDL can have zero or more <portType>s. Typically just one.
• It has a name attribute, must be unique.
– The binding will refer the portType by its name
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Operation
• Operation defines a method signature;
– Name, input, output, and fault
• Input and output elements are associated with messages;
• Different combinations of input/output define different
operations types.
<operation name="checkPrice">
<input message="pc:PriceCheckRequest"/>
<output message="pc:PriceCheckResponse"/>
</operation>
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Operation Types
• The request-response type is the most common operation type, but WSDL
defines four types:
– Request-response: The operation can receive a request and will return a response
<operation name="checkPrice">
<input message="pc:PriceCheckRequest"/>
<output message="pc:PriceCheckResponse"/>
</operation>
– One-way: The operation can receive a message but will not return a response.
<operation name=“cancellation”>
<input message=“tns:orderCancellation”/>
</operation>
– Notification:The operation can send a message but will not wait for a response
<operation name=“notification”>
<output message=“tns:promotionNotification”/>
</operation>
– Solicit-response:The operation can send a request and will wait for a response
<operation name=“cancellation”>
<output message=“tns:pushThis”/>
<input message=“tns:reponseToPush”/>
</operation>
• Different types are decided by the order/occurrences of input and output.
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Messages
<message name="PriceCheckRequest">
<part name="sku" element="avail:sku"/>
</message>
<message name="PriceCheckResponse">
<part name="result" element="avail:StockAvailability"/>
</message>
• Describe the abstract form of input, output, or fault.
• A WSDL file can have zero or more messages.
• Each message has a name, which is unique within the document.
• Each message has a collection of <part> elements.
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Part
<part name="sku" element="avail:sku"/>
<part name="result" element="avail:StockAvailability"/>
• A <part> element can be compared to a parameter in a method.
• A part element has two properties: one is name, the other is its
kind.
• Kind can be a type or an element
– Element refers to an element defined in XML Schema
– Type refers to a simpleType or a complexType in XSD
• In corresponding sku definition is:
<xsd:element name="sku" type="xsd:string" />
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Types in WSDL
<types>
<xsd:schema
targetNamespace="http://www.skatestown.com/ns/availability" >
<xsd:element name="sku" type="xsd:string" />
<xsd:complexType name="availabilityType">
<xsd:sequence>
<xsd:element ref="avail:sku"/>
<xsd:element name="price" type="xsd:double"/>
<xsd:element name="quantityAvailable" type="xsd:integer"/>
</xsd:sequence>
</xsd:complexType>
<xsd:element name="StockAvailability"
type="avail:availabilityType" />
</xsd:schema>
</types>
• The default type system is XML Schema;
– Theoretically you can use any type system, such as Java types.
• To be used in<part> element;
• We can also import XML Schemas
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SOAP request message
<soapenv:Envelope
xmlns:soapenv=“http://schema.xmlsoap.org/soap/evelope/”
xmlns:xsd=“http://www.w3.org/2001/XMLSchema”
xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance”>
<soapenv:Body>
<sku xmlns=“http://www.skatestown.com/ns/availability”>123</sku>
</soapenv:Body>
</soapenv:Envelope>
• Relevant part of the WSDL file:
<xsd:element name="sku" type="xsd:string" />
Envelope
Header #0
Header #1
<message name="PriceCheckRequest">
<part name="sku" element="avail:sku"/>
</message>
<operation name="checkPrice">
<input message="pc:PriceCheckRequest"/>
Body
Message
Payload
<output message="pc:PriceCheckResponse"/>
</operation>
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SOAP response message
<soapenv:Envelope
xmlns:soapenv= …
xmlns:xsd=…
xmlns:xsi=… >
<soapenv:Body>
<StockAvailability xmlns= … >
<sku> 123 </sku>
<price xmlns=“”>100.00</price>
<quantityAvailable xmlns=“”>
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</quantityAvailable>
</StockAvailability>
</soapenv:Body>
</soapenv:Envelope>
• Relevant part of the WSDL file:
<xsd:complexType
name="availabilityType">
<xsd:sequence>
<xsd:element ref="avail:sku"/>
<xsd:element name="price" type="xsd:double"/>
<xsd:element name="quantityAvailable"
type="xsd:integer"/>
</xsd:sequence>
</xsd:complexType>
<message name="PriceCheckResponse">
<part name="result"
element="avail:StockAvailability"/>
</message>
<operation name="checkPrice">
<input message="pc:PriceCheckRequest"/>
<output message="pc:PriceCheckResponse"/>
</operation>
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Binding
<binding name="PriceCheckSOAPBinding" type="pc:PriceCheckPortType">
<soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" />
<operation name="checkPrice">
<soap:operation soapAction = "http://www.skatestown.com/services/PriceCheck/checkPrice"
/>
<input>
<soap:body use="literal" />
</input>
<output>
<soap:body use="literal" /
</output>
</operation>
</binding>
• Name of the binding should be unique;
• Link to the portType is achieved by the portType name
– This explains why portType name should be unique.
• Typically, there is only one <binding> element;
• Defines:
–
–
–
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Invocation style: rpc vs. document
SOAPAction
Input message appearance: literal or encoded
Output message appearance
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Service
<service name="PriceCheck">
<port name="Pricecheck" binding="pc:PriceCheckSOAPBinding">
<documentation>
<wsi:Claim conformsTo="http://ws-i.org/profiles/basic/1.0" />
</documentation>
<soap:address location ="http://www.skatestown.com/services/PriceCheck"/>
</port>
</service>
• Contains a set of <port> elements;
• <port> combines the interface binding with a network address specified by a
URI;
• A web service can be available in different web addresses;
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Tools
• WSDL parser: WSDL4J
• Apache Axis
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Invoking SOAP web service;
Translate WSDL to Java, and vice versa;
Mapping Java into XML Schema, and vice versa;
Host web service;
API for manipulating SOAP;
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Mapping between Java and WSDL in JAX-RPC
•
A simple example
<message name="fooRequest">
<part name="para1" type="xs:string"/>
</message>
<message name="fooResponse">
<part name="para2" type="xs:float"/>
</message>
<portType name="FooBar">
<operation name="foo">
<input message="y:fooRequest"/>
<output message="y:fooResponse"/>
</operation>
</portType>
public interface FooBar extends java.rmi.Remote{
public float foo(java.lang.String para1)
throws java.rmi.RemoteException;
}
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• Multiple input parameters
<message name="fooRequest">
<part name="param1" type="xs:string"/>
<part name="param2" type="xs:int"/>
<part name="param3" type="xs:boolean"/>
</message>
<message name="fooResponse">
<part name="para2" type="xs:float"/>
</message>
<portType name="FooBar">
<operation name="foo">
<input message="y:fooRequest"/>
<output message="y:fooResponse"/>
</operation>
</portType>
public interface FooBar extends java.rmi.Remote{
public float foo(String param1, int param2, boolean param3)
throws java.rmi.RemoteException;
}
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• Multiple output parameters
<message name="fooRequest">
<part name="param1" type="xs:string"/>
</message>
<message name="fooResponse">
<part name="param2" type="xs:int"/>
<part name="param3" type="xs:boolean"/>
<part name="param4" type="xs:float"/>
</message>
<portType name="FooBar">
<operation name="foo">
<input message="y:fooRequest"/>
<output message="y:fooResponse"/>
</operation>
</portType>
public interface FooBar extends java.rmi.Remote{
public void foo(String param1,
javax.xml.rpc.holders.IntHolder param2,
javax.xml.rpc.holders.BooleanHolder param3,
javax.xml.rpc.holders.FloatHolder param4,
) throws java.rmi.RemoteException;
}
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Mapping XML Schema to Java
public class Address {
private String street;
private String city;
public String getCity(){return city; }
public void setCity(String c){city=c; }
……
}
<complexType name="Address">
<sequence>
<element name="city" nillable="true" type="xsd:string"/>
<element name="street" nillable="true" type="xsd:string"/>
</sequence>
</complexType>
• Class has to have correct getters and setters;
• In axis, you can use WSDL2Java and Java2WSDL to do the mapping.
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03-60-440 Mashups
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03-60-440 Mashups
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Mashups
• From Wikipedia
Mashup
– Mashup (music), a musical genre of songs that consist entirely of parts of
other songs
– Mashup (video), a video that is edited from more than one source to
appear as one
– Mashup (web application hybrid), a web application that combines data
and/or functionality from more than one source
• Combine data from multiple sources.
– Mostly the data sources lay outside of the organizational boundaries
• Create a new and distinct web service that was not originally
provided by either source.
• Content is typically sourced via a web API or a RSS Feed
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Mashup example
• The ChicagoCrime.org Web site
Mashup
– A mapping mashup
– One of the first popular mashups
– Mashes crime data from the Chicago Police Department’s online database with
cartography from Google Maps
– The concept and the presentation are simple and the composition of crime and
map data is visually powerful
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The following slides are borrowed from Umut Orhan
Why mashup
• Everybody needs customized applications, tailored to his/her
own requirements, taste, style.
• DIY in software/web application construction
– There are many building blocks (web APIs, web services)
– there are also some tools to assemble the building blocks
• It is like end-user programming
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Mashup flavours
•
Presentation mashups: e.g. Google Maps apps, with emphasis
on presentation
Mashup
• This is the shallowest form of mashup in the sense that underlying
data and functionality don’t meet. Information and layout is retrieved
and either remix or just placed next to each other. Many of the Ajax
desktops today fall into this category and so do portals and other
presentation mashup techniques.
•
Data mashups: merging data from different sources
•
Business mashup: combination of above. combines data
integration, presentation plus addition functionality, such as
collaboration features
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Map mashups
• Locational information presented graphically using maps in a
specified context
Mashup Genres
• Google Maps API opened the floodgates
– mash all sort of data from nuclear disasters to Boston’s CowParade cows
onto maps
• Other APIs
– Microsoft (Virtual Earth)
– Yahoo (Yahoo Maps)
– AOL (MapQuest)
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Photo and Video
• Photo/video hosting and social networking sites resulted
interesting mashups.
Mashup Genres
– Flickr
– YouTube
– Facebook
• Metadata associated with the hosted images and videos
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–
–
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Who took the picture
What it is a picture of
Where and when it was taken
So on…
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Search and shopping
• Exist long before the term Mashup was coined
Mashup Genres
– Combinations of B2B technologies or screen-scraping to aggregate
comparative price data
– eBay
– Amazon
– …
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News
• News sources such as BBC and Reuters have used syndication
technologies like RSS and Atom since 2002.
Mashup Genres
• Personalized newspaper by Syndication feed mashups
• Doggdot.us, combines feeds from the techie-oriented news
sources Digg.com, Slashdot.org and Del.icio.us
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Content provider
• Web Protocols
– REST Services
– SOAP Web Services
– RSS/Atom
• Screen Scraping
– Scraping is the process of using software tools to parse and analyze
content that was originally written for human consumption in order to
extract semantic data structures representative of that information that
can be used and manipulated programmatically.
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Mashup platforms
Mashup platforms
• IGoogle
• Yahoo Pipes
• Openkapow
• IBM QedWiki
• Microsoft popfly
• Google Mashup Editor (migrated to Google App
Engine)
• ……
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Yahoo! pipes
Mashup platforms
• Visual development
environment for generating
data-oriented mashups
• Development is based on:
– Dragging gadgets (pipes) from a
toolbox and dropping them in
work zone
– Specifying data input
– Interconnecting gadgets
through pipes
– Specifying data output format
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Ajax
• AJAX (Asynchronous JavaScript and XML)
• Ajax and AJAX
Web 2.0
• Characteristic: increased responsiveness and interactiveness of
web pages
– exchanging small amounts of data with the server
– entire web page does not have to be reloaded each time the user
performs an action.
• Not a technology itself, but a term refer to the use of a group of
technologies
• The "core" and defining element of Ajax is the XMLHttpRequest
object, which gives browsers the ability to make dynamic and
asynchronous data requests without having to reload a page,
eliminating the need for page refreshes.
The following slides are from Jimmy Lin
The iSchool
University of Maryland
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60-440
“Old-School” Web Applications
server generates
Web page as a
response to the
request
browser sends
request to server
user does something
1
3
browser
server-side systems
Interface
2 HTTP request
5
HTTP response
Web
server
backend
database
4
browser replaces view
with data sent from server
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data is returned
in response to
the request
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Characteristics
• User-driven: Things only happen when the user does something
(e.g., clicks on a link or button)
• Views defined by URLs: You can bookmark something and
come back to it; use the forward/backward button
• Simple user interaction model: Not that many things you can
do in browser
• Synchronous Interaction: System responses are synchronized
with user-driven events
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Synchronous Interactions
browser
user activity
user activity
1
user activity
5
2
Time
4
server-side
3
server processing
1
HTTP request
browser
5
4
HTTP response
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server processing
2
server-side systems
3
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So what do you run on the server side?
L
A
M
P
Linux
Apache
MySQL
PHP/Python/Perl
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From “Old-School” to Ajax
Ajax intermediates between the interface and the server.
browser
server-side systems
Interface
request
Ajax
“engine”
interaction management
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response
Web
server
backend
database
data
management
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Inside the Browser
browser
Rendering Engine
Interface
HTTP request
HTML / CSS
data
other data
(e.g. images)
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HTTP response
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Enter JavaScript
Rendering Engine
Interface
browser
HTTP request
JavaScript Engine
HTML / CSS
data
other data
(e.g. images)
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JavaScript
code
HTTP response
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Enter Ajax
HTTP request
Rendering Engine
Interface
browser
XMLHttpRequest
HTTP request
JavaScript Engine
HTML / CSS
data
other data
(e.g. images)
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XML
data
JavaScript
code
HTTP response
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From Synchronous Interactions…
browser
user activity
user activity
user activity
Time
server-side
server processing
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server processing
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To asynchronous Interactions
browser
user activity
client-side processing
Time
server-side
server processing
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server processing
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Components of an Ajax Interaction
1. A client event occurs (captured by JavaScript event handlers)
2. An XMLHttpRequest object is created and configured
3. An asynchronous request is made to the server via the
XMLHttpRequest object
4. Server processes request and returns data, executing a
callback in the XMLHttpRequest object
5. The HTML DOM is updated based on response data
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DOM
• Document Object Model: platform- and language-independent
way to represent XML
– Adopts a tree-based representation
– W3C standard, supported by modern browsers
• JavaScript uses DOM to manipulate content
– To process user events
– To process server responses (via XMLHttpRequest)
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Ajax: Things to watch out for!
• Hype
• Application development/maintenance cost
– Brower incompatibilities
– Many different approaches and tools
– For many things, lack of agreed-on best practices
• Behavior is not ‘Web-like’
– Standard things often don’t work correctly (e.g., browser ‘back’ button,
bookmarks)
– Usability issues for users with disabilities
• Security issues
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Cloud computing
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What is cloud computing
• Cloud
– Datacenter hardware and software that the
vendors use to offer the computing resources and
services
• Cloud computing
– Refer to both the cloud and the services provided
• Why called cloud computing
– the computing happens out there "in the clouds”
– wikipedia: "the term derives from the fact that
most technology diagrams depict the Internet or
IP availability by using a drawing of a cloud."
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Definition of cloud computing
• A large-scale distributed computing paradigm
• Driven by economies of scale
• Provider has a pool of abstracted, virtualized, dynamicallyscalable resources
– Computing power, storage, platforms, and services
• Delivered to customers on demand
• 5 Characteristics (NIST 2009)
–
–
–
–
–
On demand self-service
Broad network access
Resource pooling
Rapid elasticity
Measured service
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Timeline of cloud computing
From Dr. Javier Soriano
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Evolution of cloud computing
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Economic reason for cloud computing
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Challenge of cloud computing: Elasticity
• Animoto.com:
– Started with 50 servers on Amazon EC2
– Growth of 25,000 users/hour
– Needed to scale to 3,500 servers in 2 days (RightScale@SantaBarbara)
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RPC
• In the early 1980’s, software was not yet “distributed”, only “copied around”
• Programmers wanted to install software once on a server, and then call it
remotely over a network from many clients
• “Remote Procedure Call” (RPC)
• Several major efforts were made to do RPC over the next 25 years
• All suffered from at least one of the common “fallacies of distributed
computing”:
– The network is secure
– The network is homogeneous
– The network is fast enough
• HTTP partially fulfilled the need in the early 1990’s
– Programmers could make HTTP GET requests in those days, but the language
support for it was not great until recent years
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Early days of distributed computing
• 1980’s:
– RPC using C/C++
– EDI (Electronic Data Interchange)
– Microsoft DCOM
• 1990’s:
– CORBA (for Unix/Linux only)
– HTTP (so-called REST web services)
• Still no way to distribute an application across multiple
computers that was:
– standards-based
– platform-independent
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SOA (Service Oriented Architecture)
• They would be standards-based, platform-independent, and
immune to firewalls
– some kind of XML would be the wire format
• Each service’s contract would be expressed in a formal manner
and registered in a catalog
– programming languages could “parse” this contract and utilize it at runtime, like
an interface in Java
– there would be a “factory” call that returned a reference to the currently
preferred implementation of a given service contract
– software architects would “compose” designs by shopping among available
services
• Network and machine speed and capacity would increase to
make the overhead of XML tolerable
– massive software reuse would be achieved
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Another form of out sourcing
• Differences
– Scalability
– ‘pay per use’, flexible arrangement
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Three basic service models
• Users: use software on thin
clients.
– Do not need to download and
install the software
– E.g. google doc, online tax
• Developers: use some
languages, APIs, servers to
develop and deploy an
application
– Do not need a server to host
the application
• Network architect
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Basic service models
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Service Model Architectures
Cloud Infrastructure
Cloud Infrastructure
Cloud Infrastructure
IaaS
PaaS
PaaS
SaaS
SaaS
SaaS
Cloud Infrastructure
Cloud Infrastructure
IaaS
PaaS
Cloud Infrastructure
IaaS
PaaS
Software as a Service
(SaaS)
Architectures
Platform as a Service (PaaS)
Architectures
Infrastructure as a Service (IaaS)
Architectures
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Cloud Infrastructure as a Service (IaaS)
• Also known as Hardware as a Service (HaaS).
• Service provider owns the equipment; responsible for housing, running and
maintaining it.
• Client typically pays on a per-use basis, creates virtual machines (VMs) on
demand
– They have full access to these VMs
• Strengths:
– Can control and configure environment
– Familiar technologies
– Limited code lock-in
• Weaknesses:
– Must control and configure environment
– Requires administrative skills to use
• e.g. Amazon Web Service, Rackspace, GoGrid
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PaaS
• Platform provides hardware architecture and software
framework (including application frameworks)
• Developers provide an application, which the platform runs
– They don’t work directly with VMs
• Strengths:
– Provides higher-level services than IaaS
– Requires essentially no administrative skills
• Weaknesses:
– Allows less control of the environment
– Can be harder to move existing software
• e.g. Google App Engine, which supports Java and Python, and
Engine Yard, which supports Ruby on Rails.
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SaaS
• Very common in the IT community
• Software companies host their software themselves and then
upgrade to maintain users
• e.g. Salesforce.com –online CRM, Live.com, Zoho, Google Docs,
Microsoft Web Apps 2010
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Three Features of Mature SaaS Applications
• Scalable
– Handle growing amounts of work in a graceful manner
• Multi-tenancy
– One application instance may be serving hundreds of companies
– Opposite of multi-instance where each customer is provisioned
their own server running one instance
• Metadata driven configurability
– Instead of customizing the application for a customer (requiring
code changes), one allows the user to configure the application
through metadata
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SaaS Maturity Levels
• Level 1: Ad-Hoc/Custom
• Level 2: Configurable
• Level 3: Configurable, MultiTenant-Efficient
• Level 4: Scalable,
Configurable, Multi-TenantEfficient
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Source: Microsoft MSDN Architecture Center77
Service Delivery Model Examples
Amazon
Google
Microsoft
Salesforce
SaaS
PaaS
IaaS
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Cloud Deployment Models
• Private cloud
– enterprise owned or leased
• Community cloud
– shared infrastructure for specific community
• Public cloud
– Sold to the public, mega-scale infrastructure
• Hybrid cloud
– composition of two or more clouds
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Case studies
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Google Cloud
• Started with Google Apps
• Platform as Service later on
• Replace office software
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Gmail
Google Docs (word processing and spreadsheets)
Google video for business
Google sites (intranet sites and wikis)
• Google Cloud Connect
• 500,000+ organizations use Google Apps
• GE moved 400,000 desktops from Microsoft Office to Google Apps
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Google App Engine
• Exposes the Google Infrastructure to the outside world
– BigTable
– Python Language runtime
– Access to some google api’s (authentication , image, manipulation)
• APIs
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Python Runtime, The Python environment in which your app runs; CGI,
sandbox features, application caching, logging
Datastore API, BigTable – Google’s Database
Images API, the image data manipulation service
Mail API, sending email from your app
Memcache API, the distributed memory cache
URL Fetch API, accessing other Internet hosts from your app
Users API, integrating your app with Google Accounts
You should expect to see more API’s exposed. More specifically the
Google API’s for Docs , GWT , etc
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Amazon Cloud
• Amazon cloud components
– Elastic Compute Cloud (EC2)
– Simple Storage Service (S3)
– SimpleDB
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Amazon Cloud Users: New York Times and Nasdaq
• Both companies used Amazon’s cloud offering
• New York Times
– Used EC2 and S3 to convert 15 million scanned news articles to PDF (4TB
data)
– Took 100 Linux computers 24 hours (would have taken months on NYT
computers
– “It was cheap experimentation, and the learning curve isn't steep.” –
Derrick Gottfrid, Nasdaq
• Nasdaq
– Uses S3 to deliver historic stock and fund information
– Millions of files showing price changes of entities over 10 minute
segments
– “The expenses of keeping all that data online [in Nasdaq servers] was too
high.” – Claude Courbois, Nasdaq VP
– Created lightweight Adobe AIR application to let users view data
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Salesforce Cloud
• Started with information management service that could
replace traditional business software technology
• Pioneered software-as-a-service market (esp. CRM tools)
• 5,000+ Public Sector and Nonprofit Customers use
Salesforce Cloud Computing Solutions
• Moving beyond SaaS into the platform-as-a-service
market
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Salesforce.com in Government
• President Obama’s Citizen’s Briefing Book
– 134,077 Registered Users
– 1.4 M Votes
– 52,015 Ideas
– Peak traffic of 149 hits per second
• US Census Bureau Uses Salesforce.com Cloud Application
– Project implemented in under 12 weeks
– 2,500+ partnership agents use Salesforce.com for 2010
decennial census
– Allows projects to scale from 200 to 2,000 users overnight to
meet peak periods with no capital expenditure
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Facebook’s Use of Open Source and Commodity
Hardware
• 400 million users + 250,000 new users per day
• 100,000 transactions per second, 10,000+ servers
• Built on open source software
– Web and App tier: Apache, PHP, AJAX
– Middleware tier: Memcached (Open source caching)
– Data tier:
MySQL (Open source DB)
• Thousands of DB instances store data in distributed
fashion (avoids collisions of many users accessing the
same DB)
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Drawbacks
• Excessive dependence on the Internet
• Subject to ISP and Cloud Service Providers’ disclosure policy
• Inappropriate for sensitive, classified data
• Data replication, coherency, integrity loss
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