Lec08 - Last Class: RPCs RPCs make distributed computations...

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Computer Science Lecture 8, page CS677: Distributed OS Last Class: RPCs RPCs make distributed computations look like local computations Issues: Parameter passing Binding Failure handling 1 Computer Science Lecture 8, page CS677: Distributed OS Today: Lightweight RPCs Remote Method Invocation (RMI) Design issues 2
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Computer Science Lecture 8, page CS677: Distributed OS Lightweight RPCs Many RPCs occur between client and server on same machine Need to optimize RPCs for this special case => use a lightweight RPC mechanism (LRPC) Server S exports interface to remote procedures Client C on same machine imports interface OS kernel creates data structures including an argument stack shared between S and C 3 Computer Science Lecture 8, page CS677: Distributed OS Lightweight RPCs RPC execution Push arguments onto stack Trap to kernel Kernel changes mem map of client to server address space Client thread executes procedure (OS upcall) Thread traps to kernel upon completion Kernel changes the address space back and returns control to client Called “doors” in Solaris 4
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Lecture 8, page CS677: Distributed OS Doors Which RPC to use? - run-time bit allows stub to choose between LRPC and RPC 5 Computer Science Lecture 8, page CS677: Distributed OS Other RPC Models Asynchronous RPC Request-reply behavior often not needed Server can reply as soon as request is received and execute procedure later Deferred-synchronous RPC Use two asynchronous RPCs Client needs a reply but can’t wait for it; server sends reply via another asynchronous RPC One-way RPC Client does not even wait for an ACK from the server Limitation: reliability not guaranteed (Client does not know if procedure was executed by the server). 6
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Lec08 - Last Class: RPCs RPCs make distributed computations...

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