1 / 46

Distributed Computing Technologies – Selecting an Appropriate Approach

Distributed Computing Technologies – Selecting an Appropriate Approach . Philip Maechling Web Services Workshop UNAVCO/IRIS Joint Workshop 8 June 2005. Outline. Discuss different approaches to distributed computing with examples from real life.

guang
Download Presentation

Distributed Computing Technologies – Selecting an Appropriate Approach

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Distributed Computing Technologies – Selecting an Appropriate Approach Philip Maechling Web Services Workshop UNAVCO/IRIS Joint Workshop 8 June 2005

  2. Outline • Discuss different approaches to distributed computing with examples from real life. • Based largely on: Seismic Hazard Analysis Using Distributed Computing in the SCEC Community Modeling Environment : March/April 2005 Electronic Seismologist Column UNAVCO/IRIS Web Services Workshop

  3. A New Computing Model for Scientific Computing • Can we utilize a distributed, component-based computing model to do science? • What technologies are available? • What are the advantages/disadvantages for each? UNAVCO/IRIS Web Services Workshop

  4. A New Computing Model for Scientific Computing • Premise is that there is no “one-best” approach that fits all Projects or needs (unfortunately). • Encourage Discussion and groups experiences with these technologies UNAVCO/IRIS Web Services Workshop

  5. A New Computing Model for Scientific Computing Program 1 Program 2 Program 3 Program 4 Program 5 USC P1 P2 P3 P4 P5 IRIS SDSC SCEC JPL UNAVCO/IRIS Web Services Workshop

  6. A New Computing Model for Scientific Computing UNAVCO/IRIS Web Services Workshop

  7. Why is this a hard problem ? • Multiple programming languages • Multiple hardware platforms • Multiple operating systems • Multiple data types and data formats • Reliability/Stability of components • Discovering what is available • Communications bandwidth and reliability • Practical issues of support, development, tools, infrastructure, funding etc. UNAVCO/IRIS Web Services Workshop

  8. Characteristics of Technologies that impact selection • Where does program run (Client Side or Server Side) • Input and output and output data types • How a components is called (API) • Support for Objects • Statefulness of components • Blocking versus non-blocking calls • Communication Protocol • Speed • Robustness • Scalability Number of Clients by a Server • Server Security • Client and Server Program languages • Peer to Peer between computers or Client Server Model UNAVCO/IRIS Web Services Workshop

  9. Desirable Characteristics of a Solution • Distributed • Secure • Multi-organizational • Multi-language • Loose coupling • High cohesion • Minimal modifications to existing codes • Minimal costs • Minimal training time • Standards-based UNAVCO/IRIS Web Services Workshop

  10. Component Characteristic • Stateful • A stateful component maintains information about previous calls. • Object Oriented • An object oriented component allows you to create an stateful instance of the component. It provides user defined interfaces to the component. UNAVCO/IRIS Web Services Workshop

  11. Technologies Not Considered Existing Distributed Computing technologies not consider here due to limited inroads into geophysics community: • Remote Procedure Calls (RPC) • DCOM • Enterprise Java Beans • .Net • Common Component Architecture (CCA) UNAVCO/IRIS Web Services Workshop

  12. Client Side Techniques Example Client Side Technologies • Java Applets • JavaScript • Macromedia Flash • Active X UNAVCO/IRIS Web Services Workshop

  13. Client Side Techniques • Java Applet Advantages • Download the program into your browser • Program runs on your computer • Rich User Interfaces • Reasonably Secure UNAVCO/IRIS Web Services Workshop

  14. Client Side Techniques • Java Applet Disadvantages • Uses CPU on the client • Distribution of code only, not shared computing processing • Required JVM in browser on client • Security limitations on what applet can do (e.g. accessing files on local machine may be restricted) UNAVCO/IRIS Web Services Workshop

  15. Considering Using Java Applets When…. • Want rich interface including graphics • Want users to use their own computer • Want secure run-time on users platform • Want to distribute new versions of code • Want platform independence UNAVCO/IRIS Web Services Workshop

  16. Common Distributed Programs • Web Browsers • Variety of Client side and Server Side execution • Standards-based (W3C) • Great Interoperability for non-dynamic content • Interoperability issues typically on client side technologies (JavaScript, Flash etc) • Where’s the click stream UNAVCO/IRIS Web Services Workshop

  17. Common Gateway Interface (CGI Scripts) UNAVCO/IRIS Web Services Workshop

  18. HTTP based Program calls • Parameters are passed as parameter_name=parameter_value pair during invocation of cgi-bin or servlet Examples: • http://www.SOMEWHERE.org/cgi-bin/ice_cream.plx?flavor=mint • http://66.102.7.104/search?q=cache:AU7xpnWlL0wJ:pyre.third-bit.com/2004-fall/tomcat.ppt+History+of+Servlet+Containers&hl=en UNAVCO/IRIS Web Services Workshop

  19. CGI Disadvantages • May overwhelm server • Security issues • Not stateful • Practical issue relating to web server technologies such as web server capacities and communications timeouts. UNAVCO/IRIS Web Services Workshop

  20. Considering Using CGI When…. • Want minimal installation and operation • Small number of users • Want to use common programming/scripting languages (perl, php) • Dynamic web pages • Display data from database UNAVCO/IRIS Web Services Workshop

  21. Java Servlets • Java-based server side technology • Adds memory and process management (improves scalability) through the user of a “servlet engine” or “servlet container” • Security and performance improvements UNAVCO/IRIS Web Services Workshop

  22. Java Servlet Interface UNAVCO/IRIS Web Services Workshop

  23. Servlet Advantages • Executable stays in memory once it is called • Container provides memory and process management • Added safety and security • Easy to add statefulness • Server side code is Java, so it’s platform independent. UNAVCO/IRIS Web Services Workshop

  24. Servlet Advantages • Executable stays in memory once it is called • Container provides memory and process management • Added safety and security • Easy to add statefulness UNAVCO/IRIS Web Services Workshop

  25. Servlet Disadvantages • Not Object Oriented Interface • Not inherently Stateful • Limitations on input and output types • Practical issues with size of data in and out (e.g. web server time-outs) UNAVCO/IRIS Web Services Workshop

  26. Considering Using Servlets When…. • Want higher performance from server • Want to protect server from being overwhelmed by calls • Want to build Dynamic web pages • Display data from database • Want platform independence on server side code • Want to work in Java including access to all the Java Libraries UNAVCO/IRIS Web Services Workshop

  27. Web Services • Standards-based approach to distributed computing. • Follows Model of Web Browser/Web Server Technology • Establishes Exchange Format (XML), Communication Protocol (SOAP), and Interface Definition (WSDL) UNAVCO/IRIS Web Services Workshop

  28. Web Services Interface UNAVCO/IRIS Web Services Workshop

  29. Web Services XML Request/Response UNAVCO/IRIS Web Services Workshop

  30. Web Services Advantages • Could transform distributed computing like WWW has transformed information sharing • Standards-based • Uses standard ports • Interoperability between languages • Hardware independent UNAVCO/IRIS Web Services Workshop

  31. Web Services Disadvantages • Not Object Oriented Interface • Not Stateful • Limitations on input and output types • Trades performance for interoperability • Many standards • Large data transfers typically done out of band losing interoperability advantages UNAVCO/IRIS Web Services Workshop

  32. Considering Using Web Services When…. • Interoperability is more important performance • Want to interoperate between languages • Want standards based system • Want access to commercial tools and techniques UNAVCO/IRIS Web Services Workshop

  33. Common Object Request Broker Architecture (CORBA) • CORBA is a specification for distributed object technology • Language independent (Supports C, C++, Fortran, Java, others) • Full Object Support • Robust communication Protocol • Stable, mature CORBA implementations are available including open source and real-time versions. UNAVCO/IRIS Web Services Workshop

  34. CORBA Operation UNAVCO/IRIS Web Services Workshop

  35. CORBA Operation UNAVCO/IRIS Web Services Workshop

  36. CORBA Advantages • Object oriented, robust, well supported • Many features such as object discovery UNAVCO/IRIS Web Services Workshop

  37. CORBA Disadvantages • Fairly complex • May have more features than you need UNAVCO/IRIS Web Services Workshop

  38. CORBA Pro/Cons UNAVCO/IRIS Web Services Workshop

  39. Considering Using CORBA When…. • Multi-language support • Very high reliability • Object oriented systems • Dynamic discovery of object and services UNAVCO/IRIS Web Services Workshop

  40. Java Remote Method Invocation (Java RMI) • Java RMI is distributed object technology developed to work with the Java Language • Comprehensive, Object-oriented, platform independent, robust, mature • Distributed without cost by Sun UNAVCO/IRIS Web Services Workshop

  41. Java RMI Architecture UNAVCO/IRIS Web Services Workshop

  42. Java Remote Method Invocation (RMI Interface) import java.rmi.Remote; import java.rmi.RemoteException; public interface EUStats extends Remote { String getMainLanguages(String CountryName) throws RemoteException; int getPopulation(String CountryName) throws RemoteException; String getCapitalName(String CountryName) throws RemoteException; } UNAVCO/IRIS Web Services Workshop

  43. Java RMI Disadvantages • Java RMI only supports Java • Proprietary protocol by single vendor • Requires RMI-lookup • Requires non-standard port UNAVCO/IRIS Web Services Workshop

  44. Java RMI Advantages • Full object support • Cross platform capabilities • Robust communications • Large objects • Security for client and servers • Distribution/updates of codes UNAVCO/IRIS Web Services Workshop

  45. RMI Pros/Cons UNAVCO/IRIS Web Services Workshop

  46. Conclusions • Distributed computing allows sharing and re-use • Introduces uncertainties • Explore existing solutions before inventing your own. UNAVCO/IRIS Web Services Workshop

More Related