Remote Procedure Call 程过程调用.pptVIP

CS-502 Fall 2007 Remote Procedure Call Remote Procedure Call(continued) CS-502, Operating SystemsFall 2007 (Slides include materials from Operating System Concepts, 7th ed., by Silbershatz, Galvin, Gagne, Modern Operating Systems, 2nd ed., by Tanenbaum, and Distributed Systems: Principles Paradigms, 2nd ed. By Tanenbaum and Van Steen) Remote Procedure Call (RPC) The most common framework for newer protocols and for middleware Used both by operating systems and by applications NFS is implemented as a set of RPCs DCOM, CORBA, Java RMI, etc., are just RPC systems Reference Birrell, Andrew D., and Nelson, Bruce, “Implementing Remote Procedure Calls,” ACM Transactions on Computer Systems, vol. 2, #1, February 1984, pp 39-59. (.pdf) Remote Procedure Call (RPC) Fundamental idea: – Server process exports an interface of procedures or functions that can be called by client programs similar to library API, class definitions, etc. Clients make local procedure/function calls As if directly linked with the server process Under the covers, call is converted into a message exchange with remote server process All messaging details handled automatically by stub compiler RPC Stubs – Summary Client-side stub Looks like local server function Same interface as local function Bundles arguments into a message, sends to server-side stub Waits for reply, un-bundles results returns Server-side stub Looks like local client function to server Listens on a socket for message from client stub Un-bundles arguments to local variables Makes a local function call to server Bundles result into reply message to client stub Result – a very useful Abstraction The hard work of building messages, formatting, uniform representation, etc., is buried in the stubs Where it can be automated! Designers of client and server can concentrate on semantics of application Programs behave in familiar way RPC Model A server defines the service interface using an interface definition language (IDL) the IDL spec