Download Comp 655 - Distributed system examples

COMP 655:
Distributed/Operating Systems
Summer 2011
Dr. Chunbo Chu
Week 11: System Examples
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Distributed system examples
• Commercial middleware
– J2EE Overview
– .NET Overview
• Web services: where middleware
systems meet
• Web service from Open Source
middleware
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Java EE Overview
• The problem Java EE attempts to solve:
maximize the use of Java technologies by
providing a suite of Java technology
specifications that is
–
–
–
–
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Integrated
Suitable for enterprise applications
Widely available
Includes all of the basic middleware
capabilities for building distributed systems
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Enterprise applications require
• High throughput
– Load balancing
– Efficient communications
•
•
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High availability
Highly reliable communications
Persistent, asynchronous communication option
Distributed transactions
High security
Ability to interoperate with whatever
Structured naming with de-centralized
administration
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The Java™ Platform
Java Technology
Enabled Devices
Java Technology
Enabled Desktop
Workgroup
Server
High-End
Server
The 3 Cs of Java EE
Components
Containers
Connectors
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J2EE Overview
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Key middleware services
• Communication: RMI-IIOP, JMS
• Naming: JNDI (part of Java SE)
• Persistence: JPA, JDBC, JDO
• Transactions: JTA, JTS
• Security: (next page)
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Java SE 6 Security Features
• JAAS – Java Authentication and
Authorization Service
• JCE – Java Cryptography Extension
• JSSE – Java Secure Socket Extension
• Java GSS-API – Kerberos V5 secure
communications
• JSSE - Java Secure Socket Extension
• More…
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Java EE for web services
•
•
•
•
•
•
•
•
Java Architecture for XML Binding (JAXB)
Java API for RESTful Services (JAX-RS)
Java API for XML-Based Web Services (JAX-WS)
SOAP with Attachments API for Java (SAAJ)
Java API for XML Messaging (JAXM)
Java API for XML Processing (JAXP)
Java API for XML Registries (JAXR)
Java API for XML-Based Remote Procedure Call
(JAX-RPC)
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Enterprise Java Beans
• A server-side component technology
• Easy development and deployment of
Java technology-based application that
are:
– Transactional, distributed, multi-tier,
portable, scalable, secure, …
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Enterprise Java Beans
• Session beans
– Represent business processes and data about an
interaction with a client
– Two types:
• Stateless
• Stateful
• Entity beans (FROZEN at EJB 2.5)
– Represent persistent data and data integrity rules
– Two types of persistence:
• Container-managed persistence
• Bean-managed persistence
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Invoking an EJB method
Home
Object
3
Client
1
2
5
4
6
EJB
Object
JNDI
NS, eg
LDAP
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EJB Container
1.
2.
3.
4.
5.
6.
7.
7
Enterprise
Bean(s)
Request home object
Return home object reference
Request new EJB object
Create EJB object
Return EJB object reference
Invoke method
Delegate request to enterprise bean(s)
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Message-driven beans
• MDB are stateless beans that
– Listen for and handle JMS messages
– Participate in transactions if necessary
• MDB have no
– Home interface
– Remote interface
– Interfaces directly callable by clients (clients just
send messages)
An MDB tutorial
An MDB article
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If you remember one thing
• Enterprise beans are
–
–
–
–
Single-threaded
Ignorant of security
Ignorant of transactions
Ignorant of networking
• The container handles all that
• Containers tend to be pricey
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Leading EJB containers
• Oracle/BEA Weblogic
• IBM Websphere
• JBoss (open source)
• GlassFish (open source)
• Geronimo (open source)
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Deployment descriptors
• Deferred binding for many of the things
the bean developer need not worry
about, including
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–
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Access control
Transaction requirements
Persistence parameters
Type of bean
Classes used for home and remote
interfaces
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Deployment descriptor example
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Enterprise
JavaBeans 2.0//EN" "http://java.sun.com/dtd/ejb-jar_2_0.dtd">
<ejb-jar>
<description>Deployment descriptor for the samplemdb JOnAS example</description>
<display-name>samplemdb example</display-name>
<enterprise-beans>
<message-driven>
<description>Describe here the message driven bean Mdb</description>
<display-name>Message Driven Bean Mdb</display-name>
<ejb-name>Mdb</ejb-name>
<ejb-class>samplemdb.MdbBean</ejb-class>
<transaction-type>Container</transaction-type>
<acknowledge-mode>Auto-acknowledge</acknowledge-mode>
<message-driven-destination>
<destination-type>javax.jms.Topic</destination-type>
<subscription-durability>NonDurable</subscription-durability>
</message-driven-destination>
</message-driven>
</enterprise-beans>
<assembly-descriptor>
<container-transaction>
<method>
<ejb-name>Mdb</ejb-name>
<method-name>*</method-name>
</method>
<trans-attribute>Required</trans-attribute>
</container-transaction>
</assembly-descriptor>
</ejb-jar>
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Java EE
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Java EE 6
• Defined by JSR 316
• Adds
– JAX-RS (JSR 311)
– Web Beans (JSR 299)
– Java Authentication SPI for containers (JSR 196)
• Removes
– EJB Container-managed persistence
– JAX-RPC
• And other changes
• Approved over a variety of concerns and
objections
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EJB 3
• Developer does not have to implement EJB
interfaces
• EJB interface implementations inferred from
annotations (for example @Stateless)
• In many cases, explicit deployment
descriptors are not needed
• In many cases, deployment information can
be inferred from annotations (for example
@Stateless)
• Enterprise beans frozen at version 2.5,
replaced by Java Persistence API (JPA), based
on Hibernate
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EJB 3, continued
• In many cases, explicit JNDI lookups
are not necessary
• In many cases, system can infer the
required lookup from annotations (for
example, @EJB)
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Web sites (3 of thousands)
Sun’s J2EE site:
http://java.sun.com/javaee/
Mastering EJB 3.0 (downloadable)
EJB design patterns (downloadable)
J2EE Architect’s Handbook (downloadable)
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Connector
• Defines standard API for integrating J2EE
technology with EIS systems
– CICS, SAP, PeopleSoft, etc.
• Before Connector architecture, each App server
has to provide an proprietary adaptor for each
EIS system
– m (# of App servers) x n (# of EIS's) Adaptors
• With Connector architecture, same adaptor
works with all J2EE compliant containers
– 1 (common to all App servers) x n (# of EIS's) Adaptors
.NET Overview
• The problem .NET tries to solve:
maximize the sale of server-side
licenses by providing a suite of
Windows technologies that is
– Integrated
– Suitable for enterprise applications
– Includes all of the basic capabilities for
building distributed systems
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.NET Framework
• Platform for running
.NET managed code in
a virtual machine
• Provides a very good
environment to develop
networked applications
and Web Services
• Provides programming
API and unified
language-independent
development
framework
.NET Application
.NET Framework
Operating System + Hardware
The Core of .NET Framework
• Common Language Runtime
– Garbage collection
– Language integration
– Multiple versioning support (no more
DLL hell!)
– Integrated security
• Framework Class Library
– Provides the core functionality:
ASP.NET, Web Services, ADO.NET,
Windows Forms, IO, XML, etc.
.NET Framework
Common Language Runtime
– CLR manages code execution at
runtime
– Memory management, thread
management, etc.
Common Language Runtime
Operating System
.NET Framework
Base Class Library
– Object-oriented collection of reusable
types
– Collections, I/O, Strings, …
.NET Framework (Base Class Library)
Common Language Runtime
Operating System
.NET Framework
Data Access Layer
– Access relational databases
– Disconnected data model
– Work with XML
ADO .NET and XML
.NET Framework (Base Class Library)
Common Language Runtime
Operating System
.NET Framework
ASP.NET & Windows Forms
– Create application’s front-end –
Web-based user interface,
Windows GUI, Web services, …
ASP .NET
Web Forms Web Services
Mobile Internet Toolkit
Windows
Forms
ADO .NET and XML
.NET Framework (Base Class Library)
Common Language Runtime
Operating System
.NET Framework
Programming Languages
– Use your favorite language
C++
C#
VB.NET Perl
…
J#
ASP .NET
Web Forms Web Services
Mobile Internet Toolkit
Windows
Forms
ADO .NET and XML
.NET Framework (Base Class Library)
Common Language Runtime
Operating System
.NET Framework
Common Language Specification
C++
VB
Common
Language
C#
Perl Specification
J#
…
ASP .NET
Web Forms Web Services
Mobile Internet Toolkit
Windows
Forms
ADO .NET and XML
.NET Framework (Base Class Library)
Common Language Runtime
Operating System
.NET Framework
Visual Studio .NET
C++
C#
VB
Perl
…
J#
Common Language Specification
Web Forms Web Services
Mobile Internet Toolkit
Windows
Forms
ADO .NET and XML
.NET Framework (Base Class Library)
Common Language Runtime
Operating System
Visual Studio .NET
ASP .NET
.NET Framework
Standards Compliance
C++
C#
VB
Perl
C# Language –
Submitted to ECMA
…
J#
Common Language Specification
Web Services Web Forms
Mobile Internet Toolkit
Windows Web services –
Forms XML, SOAP-based
ADO .NET and XML
.NET Framework (Base Class Library)
Common Language Runtime
Operating System
Visual Studio .NET
ASP .NET
Open Language
Specification
XML-based
data access
.NET programming languages
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Key middleware services (.NET)
• Communication: SOAP, http, ORPC
• Naming: URI, DNS, COM+ Catalog,
Windows Registry
• Persistence: ADO, OLE-DB
• Transactions: MTS
• Security: SSL, Kerberos, NTLM
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J2EE vs .NET
• Microsoft says:
– .NET is faster
– You write less code and easier code with
.NET
– www.gotdotnet.com/team/compare/default.aspx
• Sun says:
– .NET is a closed system
– .NET is immature
– .NET lacks community
– java.sun.com/features/2002/07/rimapatel.html
(NOTE: this is getting old) (Java in grade school?)
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J2EE vs .Net continued
• IBM says
– Only 26% of mid-market companies have
Windows only
– .Net locks you into Windows
– Microsoft competes with its partners
– Our WebSphere-based J2EE platform is
cheaper than a comparable server-side .Net
platform
– Read all about it
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Web Services
• Where middleware systems meet
• The idea: allow clients to find and
interact with services over the web
without regard to how the clients or
services are built
• How do you do that? With standards …
• This is a MAJOR industry bandwagon,
as you probably know
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SOAP overview
Protocols
include
HTTP,
SMTP, TCP,
MSMQ, …
What’s the
difference
between
RPC and
request/
response?
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SOAP intermediaries
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SOAP is (v1.2)
SOAP is a lightweight protocol intended for exchanging
structured information in a decentralized, distributed
environment. SOAP uses XML technologies to define an
extensible messaging framework, which provides a
message construct that can be exchanged over a variety
of underlying protocols. The framework has been
designed to be independent of any particular
programming model and other implementation specific
semantics.
msdn.microsoft.com/library/default.asp?
url=/library/en-us/dnsoap/html/understandsoap.asp
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SOAP message structure
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Header> <!-- optional -->
<!-- header blocks go here... -->
</soap:Header>
<soap:Body>
<!-- payload or Fault element goes here... -->
</soap:Body>
</soap:Envelope>
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SOAP message example
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<x:TransferFunds xmlns:x="urn:examples-org:banking">
<from>22-342439</from>
<to>98-283843</to>
<amount>100.00</amount>
</x:TransferFunds>
</soap:Body>
</soap:Envelope>
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SOAP response message example
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<x:TransferFundsResponse
xmlns:x="urn:examples-org:banking">
<balances>
<account>
<id>22-342439</id>
<balance>33.45</balance>
</account>
<account>
<id>98-283843</id>
<balance>932.73</balance>
</account>
</balances>
</x:TransferFundsResponse>
</soap:Body>
</soap:Envelope>
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SOAP error message example
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<soap:Fault>
<faultcode>soap:Server</faultcode>
<faultstring>Insufficient funds</faultstring>
<detail>
<x:TransferError xmlns:x="urn:examples-org:banking">
<sourceAccount>22-342439</sourceAccount>
<transferAmount>100.00</transferAmount>
<currentBalance>89.23</currentBalance>
</x:TransferError>
</detail>
</x:TransferFunds>
</soap:Body>
</soap:Envelope>
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SOAP extensibility example
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Header>
<!-- security credentials -->
<s:credentials xmlns:s="urn:examples-org:security">
<username>dave</username>
<password>evad</password>
</s:credentials>
</soap:Header>
<soap:Body>
<x:TransferFunds xmlns:x="urn:examples-org:banking">
<from>22-342439</from>
<to>98-283843</to>
<amount>100.00</amount>
</x:TransferFunds>
</soap:Body>
</soap:Envelope>
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Must-understand
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Header>
<!-- security credentials -->
<s:credentials xmlns:s="urn:examples-org:security"
soap:mustUnderstand="1"
>
<username>dave</username>
<password>evad</password>
</s:credentials>
</soap:Header>
...
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SOAP in HTTP
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SOAP in context
• SOAP is an extensible way to encode
requests and responses in XML
• WSDL (Web Services Description
Language) is a way to describe the
requests and responses a web service uses
• UDDI (Universal Description, Discovery
and Integration) is a way of locating web
services
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WSDL
• WSDL is an XML format for describing
network services as a set of endpoints
operating on messages containing
either document-oriented or procedureoriented information.
• http://www.w3.org/TR/wsdl
• Protocol bindings described: SOAP 1.1,
HTTP GET/POST, MIME
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UDDI
• UDDI enables a business to
– describe its business and its services
– discover other businesses that offer desired
services
– integrate with these other businesses.
• http://www.uddi.org/
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Dissent: REST
• REST's proponents: the Web’s scalability and growth
result directly from a few key design principles:
– Application state and functionality are divided into
resources
– Every resource is uniquely addressable using a universal
syntax for use in hypermedia links
– All resources share a uniform interface for the transfer of
state between client and resource:
• Constrained set of well-defined operations
• Constrained set of content types, optionally supporting codeon-demand
• A protocol that is:
–
–
–
–
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Client/Server
Stateless
Cacheable
Layered
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REST resources
• The previous slide came from
Wikipedia’s article
• JAX-RS
• Roy Fielding’s dissertation started the
“movement”
• Del.icio.us is a well-known (almost)
example
• Joe Gregorio on REST and WS-*
• RESTful Web Services book
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Web service from open source
• Two authors from HP
– Chris Peltz
– Claire Rogers
• Goal: set up a weather-forecast web
service on a laptop, using all Open
Source infrastructure
• http://syscon.com/webservices/article.cfm?id=728
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Decisions, decisions …
• Linux distribution
• DBMS
• Programming language
• Java runtime
• Java IDE
• Web container
• Web service container
• Build environment
• Testing
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Linux distribution
• RedHat – closes the gap between Windows
and Unix, good for Linux novices
• SuSE – good for existing Windows users
• Debian – used by well-seasoned Linux
developers [selected]
They also liked GNOME
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Open source database
• PostgreSQL – robust, full-featured
• MySQL – maximize Web application
performance, but no stored procedures
or triggers [selected]
It took several tries to get MySQL
installed, but it worked well once it was
set up.
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Java SDK
• J2SE SDK from Sun
• Blackdown JDK
• BEA’s JRockit [selected, primarily for
performance reasons]
• http://www.spec.org/
• http://www.theserverside.com/ecperf/
• They liked the “M x N” threading model
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Another industry benchmark
• www.tpc.org
• TPC is best known for TPC-C, which
pioneered the $/tpmC approach
• www.tpc.org/tpcc/results/tpcc_perf_re
sults.asp
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Java IDE
• vi or emacs
• NetBeans (based on Swing, considered
more platform-independent)
• Eclipse (based on SWT, considered
faster and more attractive on-screen)
[selected]
They liked Eclipse’s plug-ins
HP is developing several plug-ins
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Web container
• Resin
• Jboss
• Jetty
• Tomcat [selected, for performance,
stability, and because it’s the default
web container for Apache Axis]
They were able to start and stop Tomcat
from Eclipse, with the help of a plug-in
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Web services container
• They concluded that Apache Axis is
currently the only “robust” open source
web services platform.
They recommend writing your own
WSDL for complex services, but for
simple ones, Axis’ Java2WSDL is OK.
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More on Apache Axis
Some manual coding was needed to
adapt their server-side code to the web
service environment (example: had to
make the Forecast class a Bean so it
could be serialized)
The hardest part was figuring out what
had to change.
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Build and test
• Ant for building.
• WSDL2Java from Axis generates a client proxy
class from the WSDL. Handy for testing.
• Axis tcpmon for monitoring SOAP traffic.
• Web service testing tools
–
–
–
–
JUnit
Grinder
Anteater
PushToTest TestMaker [selected]
• TestMaker scripts are written in Jython
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