Remote procedure call

In distributed computing a remote procedure call (RPC) is when a computer program causes a procedure (subroutine) to execute in another address space (commonly on another computer on a shared network), which is coded as if it were a normal (local) procedure call, without the programmer explicitly coding the details for the remote interaction. That is, the programmer writes essentially the same code whether the subroutine is local to the executing program, or remote. This is a form of client–server interaction (caller is client, executer is server), typically implemented via a request–response message-passing system. The object-oriented programming analog is remote method invocation (RMI). The RPC model implies a level of location transparency, namely that calling procedures is largely the same whether it is local or remote, but usually they are not identical, so local calls can be distinguished from remote calls. Remote calls are usually orders of magnitude slower and less reliable than local calls, so distinguishing them is important.

RPCs are a form of inter-process communication (IPC), in that different processes have different address spaces: if on the same host machine, they have distinct virtual address spaces, even though the physical address space is the same; while if they are on different hosts, the physical address space is different. Many different (often incompatible) technologies have been used to implement the concept.

Response–request protocols date to early distributed computing in the late 1960s, theoretical proposals of remote procedure calls as the model of network operations date to the 1970s, and practical implementations date to the early 1980s. In the 1990s, with the popularity of object-oriented programming, the alternative model of remote method invocation (RMI) was widely implemented, such as in Common Object Request Broker Architecture (CORBA, 1991) and Java remote method invocation. RMIs in turn fell in popularity with the rise of the internet, particularly in the 2000s.

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