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Distributed Computing Systems

Distributed Computing Systems. 電機三 B90901047 陳家宏. Outlines. Introduction to Distributed System Middleware layers Application -- Web Services OS support. Distributed Systems :Why?. Parallel applications -scalability Resource sharing -disks, CPU, memory

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Distributed Computing Systems

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  1. Distributed Computing Systems 電機三 B90901047 陳家宏

  2. Outlines • Introduction to Distributed System • Middleware layers • Application -- Web Services • OS support

  3. Distributed Systems :Why? • Parallel applications -scalability • Resource sharing -disks, CPU, memory -services ( e.g., name servers, games, etc.) -data (e.g., file systems, databases, etc.)

  4. Challenges • Heterogeneity • Networks, OS, hardware, language • Openness • Documents and specifications • Security • Encryption, DOS( denial of service ) • Scalability • Data should be structured hierarchically

  5. Challenges (con ‘t) • Failure handling • Any process, computer fails indep • Concurrency • Concurrent requests to resources • Transparency • the system is perceived as a whole

  6. Architectural model Applications, services Middleware Operating System Computer and network hardware

  7. Middleware layers RMI and RPC Request-reply protocol marshalling and external data representation

  8. Middleware layers (con’ t) • Communicate using OS calls -using send() and receive • Communicate using procedure -RPC : remote procedure calls system translates RPC to send/receive • Communicate using object -RMI : remote method invocations Naming of remote data

  9. Distributed object Model C A E B F D

  10. Middleware layers (con’ t) • Traditional distributed systems • CORBA –common object request broker architecture - cross language • Java RMI - limits to java

  11. Applications • Create a web service by yourself!

  12. A Web Service Listener (web server) Client Web Service SOAP Object Object

  13. Web Services • New generation distributed systems • Built on open technologies and protocols • Scalable, can build systems incrementally • Less complicated and easier to program • Future – Web services are becoming fundamental building blocks in the move to distributed computing

  14. Web Services (con’ t) • UDDI • Discovery mechanism • WSDL • Description language -> defines the web service interface • SOAP • Communication protocols • XML & HTTP • data representation format

  15. SOAP = 肥皂？

  16. OS support • Alternative server threading architecture • Microkernels & monolithic kernels

  17. Thread concept Activation Stack Process Text ( program code) Heap System-provided resources ( socket , files)

  18. Alternative server threading architecture Worker thread I/O thread Remote object Thread per connection Thread per object

  19. Monolithic kernel S4 Server program S1 S2 S3 Kernel can contain some server processes that execute within its address space, including file servers and some networking

  20. Microkernel Dynamic loaded server program S3 S1 S2 Kernel

  21. Middleware OS emulation subsystem Language support subsystem … Microkernel Hardware

  22. References • Distributed systems concepts and design • George Coulouris, Jean Dollimore, Tim Kindberg

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