Transcript Web Architecture - Carnegie Mellon University

eCommerce Technology
20-751
Lecture 4: Web Architecture
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Two-Tier Architecture
TIER 1:
CLIENT
TIER 2:
SERVER
Server performs
all processing
Web Server
Application Server
Database Server
This architecture is deprecated. Server does too much work.
SOURCE: FOURNIER
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Three-Tier Architecture
TIER 1:
CLIENT
TIER 2:
SERVER
TIER 3:
BACKEND
Application server
offloads processing
to tier 3
Web Server +
Application Server
Note: Using 2 computers instead of 1 can result in a huge increase in
simultaneous clients. Depends on % of CPU time spent on database access.
SOURCE: FOURNIER
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
N-Tier Architecture
Optimized for
web page
delivery
Coded for
specific
application
Managed and
tuned by DBA
Achieves full separation of function and administration
Huge number of simultaneous clients
SOURCE: FOURNIER
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
InterShop Architecture
SOURCE: INTERSHOP
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Connecting to Legacy Systems
by “Wrapping”
“WRAPPER”
Web Server
Web
App
20-751 ECOMMERCE TECHNOLOGY
MAINFRAME
Wrapper
Middleware
SUMMER 2002
Legacy
App
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Connecting to Legacy Systems
The “screen scraper”
HTML
data
HTML
data
Terminal
screen data
Screen
scraper
Client
Legacy system
(mainframe)
Existing
application
Legacy
database
Web server
SOURCE: WIM GEVERS
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Screen Scraping
• Some systems produce as their only output
commands to 80 x 24 display terminals
• Sequences of characters telling the terminal to move
its cursor and display data, e.g.
^M0238Jan. ^M024416, ^M02482000
displays “Jan. 16, 2000” in row 2, starting at col. 38
• Screen scraping involves virtual simulation of the
display terminal to retrieve the data
• Vendors
– Intelligent Environments
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Web Broker Architecture
TIER 1
FEATURES
• More distributed than
InterShop
• Broker acts as distribution
agent
TIER 2
TIER 3
TIER 4
SOURCE: INTERWORLD
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Server Accelerators (Surrogates)
Origin
Server
requests to
origin server
all content
requests for
the origin server
Client A
Server Accelerator (surrogate)
maintains cache of
frequently accessed
web pages
Client B
SOURCE: G. TOMLINSON
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Server Clusters (Farms)
EACH REQUEST SENT
TO A FREE SERVER
REPLICATED
CONTENT
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Server Clusters (Farms)
Origin
Server A
Origin
Server B
Origin
Server C
Origin
Server n
RequestSurrogate Surrogate Surrogate Router
2
3
1
Client
1. Client’s content request.
2.
Response indicates best
surrogate.
3.
Client connects to best
Surrogate for content.
SOURCE: G. TOMLINSON
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Server Clusters (using DNS)
MULTIPLE SURROGATES
Surrogate
SOURCE: NOVELL
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Today’s Storage Architecture
Servers
Clients
Storage
Channels
BACKUP
LAN
SOURCE: UNISYS
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Storage-Area Network (SAN) Solution
Servers
Clients
Storage
SAN
BACKUP OR
REPLICATION
LAN
SOURCE: UNISYS
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
SAN Definition
• Multiple paths to each resource
• Any-to-any connections
• Global Address view
• Open structure using industry standard protocol
• No node dependencies, (can function even if one or more
nodes are inoperative)
• Optimized for large block transfers
• High bandwidth and high availability
• Scales up with no performance loss
SOURCE: UNISYS
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Applets: Mobile Internet Code
HTML:
<applet>
code=clock.class
codebase=“http://www.sun.com/classes”
</applet>
SOURCE: FOURNIER
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
What Applets Can’t Do
•
•
•
•
•
•
•
Reference specified area of memory
Access local file system
Execute other programs
Load local libraries
Create or manage threads in others
Connect to other hosts except originator
Open windows
• Applets identify themselves through code signing
(digital signature)
SOURCE: POSTECH
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Java 2 Security Model
Applications are
identified by
digital signatures
Every application
is subject to a
security policy
Domain = Set of
classes given the
same permissions
Range of
security policies
Trusted native
applications
run here
Untrusted foreign
applets run here
Security manager
controls access to
system resources
SOURCE: SUN MICROSYSTEMS
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Java Beans
• Java Beans: reusable software components containing business
logic for manipulation in a visual builder tool (e.g. Borland
JBuilder, IBM Visual Age for Java)
• Write once, run anywhere (WORA)
• Properties of Beans:
– Introspection: builder tool can analyze how a Bean works.
getBeanInfo(BeanClass)
– Customization: developer can use an app builder tool to customize
the appearance and behavior of a Bean
– Events: enables Beans to communicate and connect together
– Properties: property editors to customize Beans
– Persistence: developers can customize Beans, store and retrieve
them, with customized features intact, for future use
• Can buy and sell Beans. Visit Sun.
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Enterprise Java Beans (EJB)
• An interface specification for building scalable,
distributed, component-based, multi-tier enterprisewide applications
• Java Beans for server-side business applications
• Platform and vendor-neutral
• Java Beans extended with
– transaction processing
– state management
– services not offered by the Java Virtual Machine
• Idea: incorporate data and business logic into objects
in one place in the enterprise
• Employ reusable components
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Enterprise Java Beans
SERVER MANAGES
EJB CONTAINERS
CONTAINER HANDLES:
• TRANSACTION MGMT
• SECURITY
• CLIENT CONNECTIVITY
• LIFE CYCLE MGMT
ENTERPRISE BEANS
HANDLE BUSINESS LOGIC
SOURCE: SUN MICROSYSTEMS
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Enterprise Java Beans
DATABASE STORES
ENTITY BEAN STATES
ENTITY BEAN
• REPRESENTS BUSINESS
ENTITY OBJECT
• SHARED BY MANY CLIENTS
• IS PERSISTENT
SESSION BEAN
• PERFORMS TASK FOR
1 CLIENT
• IS NOT PERSISTENT
CUSTOMER
ON WEB
SERVLET RESPONDS
TO CART APPLET
SESSION BEAN
CLIENT
SOURCE: SUN MICROSYSTEMS
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Java Server Pages (JSP)
Delivering customized content
SOURCE: SUN
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Looks like an
HTML page
JSP Page Example
Page invokes a Java
bean from a servlet
(Similar to an applet)
<html>
<jsp:useBean
id=“clock” class=“calendar.JspCalendar”/>
<ul>
<li>Day of Month: is <%=clock.getDayOfMonth)_%>
<li>Year: is <%=clock.getYear()%>
</ul>
Page invokes methods on
</html>
the servlet to generate
dynamic content
SOURCE: SUN
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Major Ideas
•
•
•
•
Three-tiered (n-tiered) architecture
Web development tools
Storage Area Networks
Enterprise Java Beans
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS
Q&A
20-751 ECOMMERCE TECHNOLOGY
SUMMER 2002
COPYRIGHT © 2002 MICHAEL I. SHAMOS