COMP 655: Distributed/Operating Systems Summer 2011 Dr. Chunbo Chu Week 11: System Examples 9/4/20151Distributed Systems - COMP 655

COMP 655:Distributed/Operating

SystemsSummer 2011

Dr. Chunbo ChuWeek 11: System Examples

04/21/23 1Distributed Systems - COMP 655

04/21/23 Distributed Systems - Comp 655 2

Distributed system examples

• Commercial middleware– J2EE Overview– .NET Overview

• Web services: where middleware systems meet

• Web service from Open Source middleware


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– Integrated– Suitable for enterprise applications– Widely available– Includes all of the basic middleware

capabilities for building distributed systems


Enterprise applications require• High throughput

– Load balancing– Efficient communications

• High availability• Highly reliable communications• Persistent, asynchronous communication

option• Distributed transactions• High security• Ability to interoperate with whatever• Structured naming with de-centralized

administration

The Java™ Platform

High-EndServer

Java Technology Enabled Desktop

WorkgroupServer

Java Technology Enabled Devices


The 3 Cs of Java EE

Components

Containers

Connectors


J2EE Overview


Key middleware services• Communication: RMI-IIOP, JMS• Naming: JNDI (part of Java SE)• Persistence: JPA, JDBC, JDO• Transactions: JTA, JTS• Security: (next page)


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…


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)


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, …

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



Invoking an EJB method

Client

HomeObject

EnterpriseBean(s)

EJB Container

JNDI

NS, egLDAP

1. Request home object

1 2

2. Return home object reference

3

3. Request new EJB object

EJBObject

4

4. Create EJB object

5

5. Return EJB object reference

6

6. Invoke method

7

7. Delegate request to enterprise bean(s)


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 tutorialAn MDB article

http://www.theserverside.com/articles/article.tss?l=Pramati-MDB

http://www.onjava.com/lpt/a/851


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


Leading EJB containers• Oracle/BEA Weblogic• IBM Websphere• JBoss (open source)• GlassFish (open source)• Geronimo (open source)


Deployment descriptors• Deferred binding for many of the

things the bean developer need not worry about, including– Access control– Transaction requirements– Persistence parameters– Type of bean– Classes used for home and remote

interfaces


Deployment descriptor example

<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD EnterpriseJavaBeans 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>

Java EE



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

http://jcp.org/en/jsr/detail?id=316

http://www.h-online.com/open/Apache-votes-no-on-Java-EE-6--/news/112776


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


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)


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)

http://www.theserverside.com/tt/books/wiley/masteringEJB3/index.tss

http://www.theserverside.com/books/wiley/EJBDesignPatterns/index.tss

http://www.theserverside.com/books/DVTPress/J2EEArchitectsHandbook/index.tss

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

Operating System + Hardware

.NET Framework

.NET Application

• 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 Framework

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

Operating SystemOperating System

Common Language RuntimeCommon Language Runtime

– CLR manages code execution at runtime

– Memory management, thread management, etc.

.NET Framework Base Class Library



.NET Framework (Base Class Library).NET Framework (Base Class Library)

– Object-oriented collection of reusable types

– Collections, I/O, Strings, …

.NET Framework Data Access Layer




ADO .NET and XMLADO .NET and XML

– Access relational databases– Disconnected data model– Work with XML

.NET Framework ASP.NET & Windows Forms





ASP .NETASP .NETWeb Forms Web ServicesWeb Forms Web Services

Mobile Internet ToolkitMobile Internet Toolkit

WindowsWindowsFormsForms

– Create application’s front-end – Web-based user interface, Windows GUI, Web services, …

.NET Framework Programming Languages








C++C++ C#C# VB.NETVB.NET PerlPerl J#J# ……

– Use your favorite language

.NET Framework Common Language Specification








Common Language SpecificationCommon Language SpecificationC++C++ C#C# VBVB PerlPerl J#J# ……

.NET Framework Visual Studio .NET








Common Language SpecificationCommon Language Specification

C++C++ C#C# VBVB PerlPerl J#J# ……

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ASP .NETASP .NETWeb Services Web FormsWeb Services Web Forms



Common Language SpecificationCommon Language Specification

C++C++ C#C# VBVB PerlPerl J#J# ……

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Open LanguageSpecification

C# Language – Submitted to ECMA

XML-baseddata access

Web services –XML, SOAP-based

.NET Framework Standards Compliance


.NET programming languages


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


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?)


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


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


SOAP overview

What’s the difference between RPC and request/response?

Protocols include HTTP, SMTP, TCP, MSMQ, …


SOAP intermediaries


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


SOAP message structure<soap:Envelope

xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">

<soap:Header> 



</soap:Header>

<soap:Body>



</soap:Body>

</soap:Envelope>


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>


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>


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>


SOAP extensibility example<soap:Envelope

xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Header>  <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>


Must-understand<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Header>  <s:credentials xmlns:s="urn:examples-org:security" soap:mustUnderstand="1" > <username>dave</username> <password>evad</password> </s:credentials> </soap:Header> ...


SOAP in HTTP


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


WSDL• WSDL is an XML format for

describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information.

• http://www.w3.org/TR/wsdl

• Protocol bindings described: SOAP 1.1, HTTP GET/POST, MIME


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/


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

code-on-demand • A protocol that is:

– Client/Server – Stateless – Cacheable – Layered


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


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://sys-con.com/webservices/article.cfm?id=728


Decisions, decisions …• Linux distribution• DBMS• Programming language• Java runtime• Java IDE• Web container• Web service container• Build environment• Testing


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


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.


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


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_results.asp


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-insHP is developing several plug-ins


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


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.


More on Apache AxisSome 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.


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

Documents

COMP 655: Distributed/Operating Systems Summer 2011 Dr. Chunbo Chu Week 11: System Examples 9/4/20151Distributed Systems - COMP 655