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Code Migration

Russell T. Potee, III. Code Migration. Overview. Why Code Migration? Code Migration Models Migration and Handling Resources Heterogeneous Systems Migration Security. Why Code Migration?. Process Migration - definition Transfer an entire running process from one machine to another

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Code Migration

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  1. Russell T. Potee, III Code Migration

  2. Overview • Why Code Migration? • Code Migration Models • Migration and Handling Resources • Heterogeneous Systems • Migration Security

  3. Why Code Migration? • Process Migration - definition • Transfer an entire running process from one machine to another • Load distribution • Measured by CPU queue length or utilization • Good for computational systems • Reduce Network Bandwidth • Migrate part of client application to server • Migrate part of client application to database server to perform many database operations • Send only result across network

  4. Why Code Migration? • Reduce Network Bandwidth • Migrate part of server application to client • Migrate part of database server to client to process forms on client side • Reduces database operations over the network • XSS - Javascript • Parallelism • Mobile Agent • Dynamic Configuration of Distributed Systems • Download and Initialize Code

  5. Code Migration Models • Code Migration Framework • Code Segment • Set of instructions being executed • Resource Segment • References to external resources • Files, printers, devices, et cetera • Execution Segment • Process state • Private data • Stack • Instruction pointer

  6. Code Migration Models • Weak Mobility • Transfer code segment and initialized data • Portable code • Predefined starting positions • Java Applets • Strong Mobility • Transfer includes execution segment • Process can be stopped, moved to another machine, and resumed

  7. Code Migration Models • Sender-initiated • Code transfer is initiated by machine currently executing the code • Example • Uploading programs to a computational server • Receiver-initiated • Transfer is initiated by machine that will execute code • Example • Java applets

  8. Handling Resources • Process-to-resource binding • Binding by identifier (strong)‏ • Process refers to resources by their identifiers • Example • URL • Binding by value (weaker)‏ • Process refers to another resource with the same value • Binding by type (weakest)‏ • Process refers to local devices

  9. Handling Resources • Resource-to-machine binding • Unattached resources • Can be moved easily • Data Files • Fastened resources • Can be moved at high cost • Database • Fixed resources • Cannot be moved • Local devices

  10. Heterogeneous Systems • Heterogeneous systems are platforms with different operating systems and/or different machine architectures • Problems with heterogeneous systems is similar to those of portability • Solutions • Highly portable languages • Scripting languages, interpreted languages (Java)‏ • Migrating computing environments • Migrating virtual machines

  11. Migration Security • Protecting mobile agents • need to protect sensitive data • Three mechanisms for securing mobile agents • Read-only state • Data items are signed by agent's owner • Append-only state • Data can only be appended to logs • Selective reading • Each data entry can only be updated by selected servers

  12. Migration Security • Protecting hosts against malicious mobile code • Sandbox • Monitor specific instructions, registers, memory regions • Easier to do with interpreted languages • Java sandbox • Playground • Separate machines exist to execute mobile code • Code-signing • Stack introspection • Name space management

  13. Sources • Tanenbaum, A., Van Steen, M.: Distributed Systems: Principles and Paradigms, Upper Saddle River, NJ: Prentice Hall, 2007 • Fuggetta, A., Picco, G.P., and Vigna, G: “Understanding Code Mobility.” IEEE Trans. Soft. Eng., May 1998. • Milojicic, D., Douglis, F., Paindeveine, Y., Wheeler, R., Zhou, S.: “Process Migration.” ACM Computing Surv., Sept 2000.

  14. Sources • Clark, C., Fraser K., Hand, S., Hansen, J.G., Jul, E., Limpoch, C., Pratt, I., Warfield, A.: “Live Migration of Virtual Machines.” Proc. Second Symp. Network Systems and Design Impl., (Boston, MA). Berkley, CA: USENIX, 2005.

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