RPC, RMI and CORBA
RPC, RMI and CORBA RPC, RMI and CORBA
Duplicate Requests• Since client may retransmit requests, server mayreceive duplicates• e.g., server may be slow processing a request, exceedsclient timeout, client retries• with requestIds globally unique, can discard duplicates
Lost Replies• If a server has already sent a reply when it receivesa duplicate, it may need to resend• cause may be lost reply message• resending may require recomputing original request• if operation is x=7 this poses no problem• if operation is x+=1 recomputing the request will lead toincorrect values of x• recomputation is only allowable when the operationsare idempotent• an idempotent operation is one that can be performed repeatedlywith the same effect as if it had been performed exactly once• Servers with only idempotent operations canrecompute duplicates
- Page 1: Object-based DistributedSystemsEEE4
- Page 4 and 5: Design Exercise - a remote procedur
- Page 6: Programming Model• integrated int
- Page 10 and 11: Define a Remote Interface• the in
- Page 12 and 13: Make Available to Users• “boots
- Page 14 and 15: Client Side: Obtain a Remote Refere
- Page 16 and 17: Java RMI Development ProcessDevelop
- Page 18 and 19: Structure of an RMI Application•
- Page 20 and 21: Remote Object Implementation
- Page 22 and 23: RMI Mechanism• Work through colla
- Page 24 and 25: package server;import java.rmi.regi
- Page 26 and 27: This file was generated by the RMI
- Page 28 and 29: Review• RMI Semantics
- Page 30 and 31: Specification of the OperationsIn p
- Page 32 and 33: Possible Exchange Protocols• Look
- Page 36 and 37: History• When a server cannot saf
- Page 38: Examples:• Specify:• the semant
Lost Replies• If a server has already sent a reply when it receivesa duplicate, it may need to resend• cause may be lost reply message• resending may require recomputing original request• if operation is x=7 this poses no problem• if operation is x+=1 recomputing the request will lead toincorrect values of x• recomputation is only allowable when the operationsare idempotent• an idempotent operation is one that can be performed repeatedlywith the same effect as if it had been performed exactly once• Servers with only idempotent operations canrecompute duplicates
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