Managing Complexity: Middleware Explained By Andrew Campbell, Geoff Coulson, Michael Kounavis

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Managing Complexity Middleware
ExplainedByAndrew Campbell, Geoff Coulson,
Michael Kounavis

• Presented
• By
• Manav Purohit
• Nick Morgowicz

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Distributed Computing

• Computing is said to be Distributed when the
  programs and data that computers work on are
  spread over more than one computers in a network.

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Features of Distributed Computing Platform

• Addressing
• In order for components of a distributed system
  to find each other, each must have an address.
  Servers must be able to publish their address,
  and clients must be able to acquire a server's
  address, either by administrative intervention or
  looking it up in a naming service.
• Synchronization
• All participating parties must agree on a
  certain protocol when data may be sent or
  received.
• Encoding
• Defines the format used for transferring data.
• Interoperability
• The distributed platform should not be limited
  to a certain hardware, operating system or
  programming language.

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Middleware

• Middleware is a general term for any programming
  that serves to "glue together" or mediate between
  two separate and often already existing programs.

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Benefits of using middleware

• Simplifies the task of sharing data between
  applications and provide a common interface to
  different applications
• Provides persistence
• Provide general purpose services which aid
  application development and deployment.

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Types of Middleware
Technology Metaphor Example What it does
ORB Translator CORBA, EJB Allows components written in different languages to transparently inter-operate across a network
TP Monitors Illusionist CICS - IBM Using sophisticated resource management techniques hundreds of clients appear to have 1-1 connections with data server and offers scalability and reliability
Database Access Gateway JDBC Facilitates access to databases
Messaging Postal Services MQSeries IBM Relays data from one application to another in message format
Security and Directory Card Key Reader LDAP Intercedes between incoming requests and requested resources to enforce access policies
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Remote Procedure Call (RPC)

• Remote Procedure Call (RPC) is a protocol that
  one program can use to request a service from a
  program located in another computer in a network
  without having to understand network details.

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Remote Procedure Call (RPC)
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Common Object Request Broker Architecture

• The basic idea of CORBA is much the same as it is
  for RPC. However, whereas RPC is based on a
  procedural language and allows remote procedure
  calls, CORBA is based on object-oriented
  programming and allows remote method invocations
  on objects.
• Interface Definition
• Interface Definition Language (IDL) is used to
  describe object interfaces.
• Interface declarations are independent of the
  programming language.
• Addressing
• Interoperable Object References (IOR) are used as
  addresses of remote objects.
• IORs are strings stored in files which can be
  converted to an object references by ORB.

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Common Object Request Broker Architecture

• Invocation
• Using the interface and the address, methods can
  be invoked and executed remotely
• Interoperability
• General Inter-ORB Protocol (GIOP) to describe the
  format for requests and replies when transported
  from one ORB to another as part of a method
  invocation.

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Remote Method Invocation

• RMI allows programmers to develop distributed
  Java programs with the same syntax and semantics
  used for non-distributed systems.
• RMI supports two classes that implement the same
  interface. The first class is the implementation
  of the behavior, and it runs on the server. The
  second class acts as a proxy for the remote
  service and it runs on the client.

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Remote Method Invocation

• Stubs and Skeletons are proxies which know how to
  forward method calls between participating
  objects
• Remote reference layer defines and supports
  invocation
• The transport layer makes connection between JVMs

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Microsofts DCOM Technology

• History
• Based on Microsofts COM (Component Object Model)
  technology which provides a framework for
  application interoperation within Windows.
• Operation
• Similar to CORBA since operating system calls are
  intercepted, processed, and redirected.
• Provides persistence, security, and transactions.
• Specifications
• Closed technology owned and developed soley by
  Microsoft.
• Quick evolution due to no external politics.
• Experience?
• How does DCOM actually fit within Windows and
  developing?

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Microsofts DCOM Technology

• Operation
• DCOM intercepts Client calls to deliver to the
  end component

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Open Implementations

• Popularity of Middleware causes technology to
  spread
• Multimedia, real-time and embedded systems,
  handheld devices, and mobile networking
• Active projects?
• Intellisync (Palm/CE to Groupware)

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Network Programming

• Networking technology and connectivity is
  standard and is governed by RFCs and whitepapers
• Programming routers, switches, DSUs, etc, are
  manufacture specific
• Would this be in essence a glorified SNMP?

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Middleware Glossary

• Common Object Request Broker Architecture
  (CORBA)
• Specification from the Object Management Group
  that describes how object-oriented networked
  applications communicate with one another.
• Distributed Component Object Model (DCOM)
• Microsofts specification/model that allows
  developers to create objects and have other
  programs and objects operate on them in a
  distributed environment.

• Message-oriented middleware (MOM)
• Comprised of message-passing and message-queuing
  middleware in which information is passed in the
  form of a message from one program to one or more
  other programs.
• Stub
• A client-side proxy for the remote object that
  implements all the interfaces supported by the
  remote object.

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Current Middleware Developments

• Components
• Piece applications together with multiple
  components.
• Popular in MS DCOM and Suns JavaBeans.
• CORBA cannot support until upcoming version 3.0.
• Plans
• Improve reliability, availability, and
  scalability to support millions of objects that
  must adhere to strict performance requirements.

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Problems with Middleware

• Speed and Performance
• Current products have a reputation of being slow.
• Development is going into understanding why.
• Quality of Service
• Lack of interfaces for QoS specification and
  enforcement

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Questions/Discussion ?

• Personal experience
• Web based middleware and development
• Automation