In
distributed computing
A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another from any system. Distributed computing is a field of computer sci ...
, a remote procedure call (RPC) is when a computer program causes a procedure (
subroutine
In computer programming, a function or subroutine is a sequence of program instructions that performs a specific task, packaged as a unit. This unit can then be used in programs wherever that particular task should be performed.
Functions ma ...
) to execute in a different
address space
In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity.
For software programs to save and retrieve ...
(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, executor is server), typically implemented via a request–response message-passing system. In the object-oriented programming paradigm, RPCs are represented by remote method invocation (RMI). The RPC model implies a level of location transparency, namely that calling procedures are largely the same whether they are 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.
History and origins
Request–response 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.
Bruce Jay Nelson
Bruce Jay Nelson (January 19, 1952 – September 19, 1999) was an American computer scientist best known as the inventor of the remote procedure call concept for computer network communications.
Bruce Nelson graduated from Harvey Mudd College in ...
is generally credited with coining the term "remote procedure call" in 1981.
Remote procedure calls used in modern operating systems trace their roots back to the
RC 4000 multiprogramming system, which used a request-response communication protocol for process synchronization. The idea of treating network operations as remote procedure calls goes back at least to the 1970s in early
ARPANET
The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical foun ...
documents. In 1978,
Per Brinch Hansen proposed Distributed Processes, a language for distributed computing based on "external requests" consisting of procedure calls between processes.
One of the earliest practical implementations was in 1982 by
Brian Randell
Brian Randell (born 1936) is a British computer scientist, and Emeritus Professor at the School of Computing, Newcastle University, United Kingdom. He specialises in research into software fault tolerance and dependability, and is a noted aut ...
and colleagues for their
Newcastle Connection
The Newcastle Connection (or UNIX United) was a software subsystem from the early 1980s that could be added to each of a set of interconnected UNIX-like systems to build a distributed system. The latter would be functionally indistinguishable, a ...
between UNIX machines.
This was soon followed by "Lupine" by Andrew Birrell and Bruce Nelson in the
Cedar environment at
Xerox PARC
PARC (Palo Alto Research Center; formerly Xerox PARC) is a research and development company in Palo Alto, California. Founded in 1969 by Jacob E. "Jack" Goldman, chief scientist of Xerox Corporation, the company was originally a division of Xer ...
.
Lupine automatically generated stubs, providing type-safe bindings, and used an efficient protocol for communication.
[ One of the first business uses of RPC was by ]Xerox
Xerox Holdings Corporation (; also known simply as Xerox) is an American corporation that sells print and digital document products and services in more than 160 countries. Xerox is headquartered in Norwalk, Connecticut (having moved from St ...
under the name "Courier" in 1981. The first popular implementation of RPC on Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
was Sun's RPC (now called ONC RPC), used as the basis for Network File System (NFS).
In the 1990s, with the popularity of object-oriented programming
Object-oriented programming (OOP) is a programming paradigm based on the concept of " objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of ...
, an 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.
Message passing
RPC is a request–response protocol. An RPC is initiated by the ''client'', which sends a request message to a known remote ''server'' to execute a specified procedure with supplied parameters. The remote server sends a response to the client, and the application continues its process. While the server is processing the call, the client is blocked (it waits until the server has finished processing before resuming execution), unless the client sends an asynchronous request to the server, such as an XMLHttpRequest. There are many variations and subtleties in various implementations, resulting in a variety of different (incompatible) RPC protocols.
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
Idempotence (, ) is the property of certain operations in mathematics and computer science whereby they can be applied multiple times without changing the result beyond the initial application. The concept of idempotence arises in a number of pl ...
procedures (those that have no additional effects if called more than once) are easily handled, but enough difficulties remain that code to call remote procedures is often confined to carefully written low-level subsystems.
Sequence of events
# The client calls the client stub. The call is a local procedure call, with parameters pushed on to the stack in the normal way.
# The client stub packs the parameters into a message and makes a system call to send the message. Packing the parameters is called marshalling.
# The client's local operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
sends the message from the client machine to the server machine.
# The local operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
on the server machine passes the incoming packets to the server stub.
# The server stub unpacks the parameters from the message. Unpacking the parameters is called unmarshalling.
# Finally, the server stub calls the server procedure. The reply traces the same steps in the reverse direction.
Standard contact mechanisms
To let different clients access servers, a number of standardized RPC systems have been created. Most of these use an interface description language
interface description language or interface definition language (IDL), is a generic term for a language that lets a program or object written in one language communicate with another program written in an unknown language. IDLs describe an inter ...
(IDL) to let various platforms call the RPC. The IDL files can then be used to generate code to interface between the client and servers.
Analogues
Notable RPC implementations and analogues include:
Language-specific
* Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
's Java Remote Method Invocation (Java RMI) API provides similar functionality to standard Unix RPC methods.
Go
provide
package rpc
for implementing RPC, with support for asynchronous calls.
* Modula-3's network objects, which were the basis for Java's RMI
* RPyC
RPyC (pronounced ''are-pie-see''), or Remote Python Call, is a Python library for remote procedure calls (RPC), as well as distributed computing. Unlike regular RPC mechanisms, such as ONC RPC, CORBA or Java RMI, RPyC is transparent, symmetri ...
implements RPC mechanisms in Python, with support for asynchronous calls.
* Distributed Ruby (DRb) allows Ruby programs to communicate with each other on the same machine or over a network. DRb uses remote method invocation (RMI) to pass commands and data between processes.
* Erlang is process oriented and natively supports distribution and RPCs via message passing between nodes and local processes alike.
* Elixir
ELIXIR (the European life-sciences Infrastructure for biological Information) is an initiative that will allow life science laboratories across Europe to share and store their research data as part of an organised network. Its goal is to bring t ...
builds on top of the Erlang VM and allows process communication (Elixir/Erlang processes, not OS processes) of the same network out-of-the-box via Agents and message passing.
Application-specific
* Action Message Format (AMF) allows Adobe Flex applications to communicate with back-ends or other applications that support AMF.
* Remote Function Call is the standard SAP interface for communication between SAP systems. RFC calls a function to be executed in a remote system.
General
* NFS (Network File System
Network File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems (Sun) in 1984, allowing a user on a client computer to access files over a computer network much like local storage is accessed. NFS, li ...
) is one of the most prominent users of RPC
* Open Network Computing Remote Procedure Call, by Sun Microsystems
Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, ...
* D-Bus
In computing, D-Bus (short for "Desktop Bus")
is a message-oriented middleware mechanism that allows communication between multiple processes running concurrently on the same machine. D-Bus was developed as part of the freedesktop.org project, ...
open source IPC
IPC may refer to:
Computing
* Infrastructure protection centre or information security operations center
* Instructions per cycle or instructions per clock, an aspect of central-processing performance
* Inter-process communication, the sharin ...
program provides similar function to CORBA.
* SORCER provides the API and ;exertion-oriented language (EOL) for a federated method invocation
* XML-RPC
XML-RPC is a remote procedure call (RPC) protocol which uses XML to encode its calls and HTTP as a transport mechanism.Simon St. Laurent, Joe Johnston, Edd Dumbill. (June 2001) ''Programming Web Services with XML-RPC.'' O'Reilly. First Editi ...
is an RPC protocol that uses XML
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. ...
to encode its calls and HTTP
The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...
as a transport mechanism.
* JSON-RPC is an RPC protocol that uses JSON
JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other s ...
-encoded messages
* JSON-WSP is an RPC protocol that uses JSON
JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other s ...
-encoded messages
* SOAP
Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are used ...
is a successor of XML-RPC and also uses XML to encode its HTTP-based calls.
* ZeroC
ZeroC is a software company based in Jupiter, Florida, United States.
The company develops and publishes tools for software developers. Its main product is Ice, an open-source RPC framework that helps software developers build distributed appli ...
's Internet Communications Engine
The Internet Communications Engine, or Ice, is an open-source RPC framework developed by ZeroC. It provides SDKs for C++, C#, Java, JavaScript, MATLAB, Objective-C, PHP, Python, Ruby and Swift, and can run on various operating systems, incl ...
(Ice) distributed computing platform.
* Etch framework for building network services.
* Apache Thrift protocol and framework.
* CORBA provides remote procedure invocation through an intermediate layer called the ''object request broker''.
* Libevent provides a framework for creating RPC servers and clients.
* Windows Communication Foundation is an application programming interface in the .NET framework for building connected, service-oriented applications.
* Microsoft .NET Remoting
In distributed computing, a remote procedure call (RPC) is when a computer program causes a procedure (subroutine) to execute in a different address space (commonly on another computer on a shared network), which is coded as if it were a normal (l ...
offers RPC facilities for distributed systems implemented on the Windows platform. It has been superseded by WCF.
* The Microsoft DCOM uses MSRPC which is based on DCE/RPC DCE/RPC, short for "Distributed Computing Environment / Remote Procedure Calls", is the remote procedure call system developed for the Distributed Computing Environment (DCE). This system allows programmers to write distributed software as if it ...
* The Open Software Foundation DCE/RPC DCE/RPC, short for "Distributed Computing Environment / Remote Procedure Calls", is the remote procedure call system developed for the Distributed Computing Environment (DCE). This system allows programmers to write distributed software as if it ...
Distributed Computing Environment (also implemented by Microsoft).
* Google Protocol Buffers (protobufs) package includes an interface definition language used for its RPC protocols open sourced in 2015 as gRPC.
* WAMP combines RPC and Publish-Subscribe into a single, transport-agnostic protocol.
* Google Web Toolkit uses an asynchronous RPC to communicate to the server service.
* Apache Avro
Avro is a row-oriented remote procedure call and data serialization framework developed within Apache's Hadoop project. It uses JSON for defining data types and protocols, and serializes data in a compact binary format. Its primary use is in ...
provides RPC where client and server exchange schemas in the connection handshake and code generation is not required.
See also
* 9P
* Microsoft RPC
* Local Procedure Call The Local Inter-Process Communication (LPC, often also referred to as Local Procedure Call or Lightweight Procedure Call) is an internal, undocumented inter-process communication facility provided by the Microsoft Windows NT kernel for lightweight ...
* HTTP
The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...
* ODBC
In computing, Open Database Connectivity (ODBC) is a standard application programming interface (API) for accessing database management systems (DBMS). The designers of ODBC aimed to make it independent of database systems and operating systems. A ...
* Remote evaluation
* External Data Representation
External Data Representation (XDR) is a standard data serialization format, for uses such as computer network protocols. It allows data to be transferred between different kinds of computer systems. Converting from the local representation to ...
(serialization format used by e.g. NFS)
* Network Data Representation Network Data Representation (NDR) is an implementation of the presentation layer in the OSI model. It is used for DCE/RPC and Microsoft RPC (MSRPC).
See also
* DCE/RPC
* Microsoft RPC
Microsoft RPC (Microsoft Remote Procedure Call) is a modified v ...
(serialization format used by e.g. Microsoft RPC)
* Resource-oriented architecture
* Distributed object middleware
* Fragmented object
* gRPC
References
External links
* - Specifies version 1 of ONC RPC
*{{IETF RFC, 5531, link=no - Specifies version 2 of ONC RPC
Remote Procedure Calls (RPC)
— A tutorial on ONC RPC by Dr Dave Marshall of Cardiff University
— A developer's introduction to RPC and XDR, from SGI IRIX documentation.
Inter-process communication
Middleware
Distributed computing