Remote procedure call

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Remote procedure call (RPC) is an Inter-process communication technology that allows a computer program to cause a subroutine or procedure to execute in another address space (commonly on another computer on a shared network) without the programmer explicitly coding the details for this remote interaction. That is, the programmer would write essentially the same code whether the subroutine is local to the executing program, or remote. When the software in question is written using object-oriented principles, RPC may be referred to as remote invocation or remote method invocation.

Note that there are many different technologies commonly used to accomplish this which are often incompatible, such as ONC RPC and DCE/RPC.

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[edit] History and origins

The idea of RPC goes back at least as far as 1976, when it was described in RFC 707. One of the first business uses of RPC was by Xerox under the name "Courier" in 1981. The first popular implementation of RPC on Unix was Sun's RPC (now called ONC RPC), used as the basis for Sun's NFS. ONC RPC is still widely used today on several platforms.

Another early Unix implementation was Apollo Computer's Network Computing System (NCS). NCS later was used as the foundation of DCE/RPC in the OSF's Distributed Computing Environment (DCE). A decade later Microsoft adopted DCE/RPC as the basis of their Microsoft RPC (MSRPC) mechanism, and implemented DCOM atop it. Around the same time (mid-90's), Xerox PARC's ILU, and the Object Management Group's CORBA, offered another RPC paradigm based on distributed objects with an inheritance mechanism.

[edit] Message passing

RPC is an obvious and popular paradigm for implementing the client-server model of distributed computing. An RPC is initiated by the client sending a request message to a known remote server in order to execute a specified procedure using supplied parameters. A response is returned to the client where the application continues along with its process. There are many variations and subtleties in various implementation, resulting in a variety of different (incompatible) RPC protocols. While the server is processing the call, the client is blocked.

An important difference between remote procedure calls and local calls is that remote calls can fail because of unpredictable network problems. Also, callers generally must deal with such failures without knowing whether the remote procedure was actually invoked. Idempotent procedures (those which have no additional effects if called more than once) are easily handled, but enough difficulties remain that code which calls remote procedures is often confined to carefully written low-level subsystem.

[edit] Standard contact mechanisms

In order to allow servers to be accessed by differing clients, a number of standardized RPC systems have been created. Most of these use an interface description language (IDL) to allow various platforms to call the RPC.

The IDL files can then be used to generate code to interface between the client and server. The most common tool used for this is RPCGEN.

[edit] Other RPC analogues

RPC analogues found elsewhere:

[edit] Web services RPC

Further information: Web service#Styles_of_use

[edit] References

[edit] See also

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.