Xgrid is a proprietary

grid computing Grid computing is the use of widely distributed computer resources to reach a common goal. A computing grid can be thought of as a distributed system with non-interactive workloads that involve many files. Grid computing is distinguished fro ...

program and protocol developed by the Advanced Computation Group subdivision of

Apple Inc Apple Inc. is an American multinational corporation and technology company headquartered in Cupertino, California, in Silicon Valley. It is best known for its consumer electronics, software, and services. Founded in 1976 as Apple Computer ...

. It provides network administrators a method of creating a

computing cluster A computer cluster is a set of computers that work together so that they can be viewed as a single system. Unlike grid computers, computer clusters have each node set to perform the same task, controlled and scheduled by software. The newes ...

, which allows them to exploit previously unused computational power for calculations that can be divided easily into smaller operations, such as Mandelbrot maps. The setup of an Xgrid cluster can be achieved at next to no cost, as Xgrid client is pre-installed on all computers running

Mac OS X 10.4 Mac OS X Tiger (version 10.4) is the 5th major release of macOS, Apple's desktop and server operating system for Mac computers. Tiger was released to the public on April 29, 2005, for US$129.95 as the successor to Mac OS X 10.3 Panther. Incl ...

to Mac OS X 10.7. The Xgrid client was not included in Mac OS X 10.8. The Xgrid controller, the

job scheduler A job scheduler is a computer application for controlling unattended background program execution of jobs. This is commonly called batch scheduling, as execution of non-interactive jobs is often called batch processing, though traditional ''job ...

of the Xgrid operation, is also included within

Mac OS X Server Mac OS X Server is a series of Discontinued software, discontinued Unix-like server operating systems developed by Apple Inc., based on macOS. It provided server functionality and system administration tools, and tools to manage both macOS ...

and as a free download from Apple. Apple has kept the command-line job control mechanism minimalist while providing an API to develop more sophisticated tools built around it. The program employs its own communication protocol layered on top of a schema to communicate to other nodes. This communication protocol interfaces with the BEEP infrastructure, a network application protocol framework. Computers discovered by the Xgrid system, that is computers with Mac OS X's Xgrid service enabled, are automatically added to the list of available computers to use for processing tasks. When the initiating computer sends the complete instructions, or

job Work, labor (labour in Commonwealth English), occupation or job is the intentional activity people perform to support the needs and desires of themselves, other people, or organizations. In the context of economics, work can be seen as the huma ...

, for processing to the controller, the controller splits the task up into these small instruction packets, known as tasks. The design of the Xgrid system consists of these small packets being transferred to all the Xgrid-enabled computers on the network. These computers, or

node In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex). Node may refer to: In mathematics * Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two or more curves, lines ...

execute Execution, in capital punishment Capital punishment, also known as the death penalty and formerly called judicial homicide, is the state-sanctioned killing of a person as punishment for actual or supposed misconduct. The sentence (law), s ...

the instructions provided by the controller and then return the results. The controller assembles the individual task results into the whole job results and returns them to the initiating computer. Apple modeled the design of Xgrid on the Zilla program, distributed with

NeXT NeXT, Inc. (later NeXT Computer, Inc. and NeXT Software, Inc.) was an American technology company headquartered in Redwood City, California that specialized in computer workstations for higher education and business markets, and later develope ...

OpenStep OpenStep is an object-oriented application programming interface (API) specification developed by NeXT. It provides a framework for building graphical user interfaces (GUIs) and developing software applications. OpenStep was designed to be plat ...

operating system application programming interface (

API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...

), which Apple owned the rights to. The company also opted to provide the client version of Mac OS X with only command-line functions and little flexibility, while giving the

version of Xgrid a GUI control panel and a full set of features.

History

Xgrid's origins can be traced back to

's Zilla application created by scientist Richard Crandall in the late 1980s. Zilla was the first distributed computing program released on an

end-user In product development, an end user (sometimes end-user) is a person who ultimately uses or is intended to ultimately use a product. The end user stands in contrast to users who support or maintain the product, such as sysops, system administrato ...

operating system and which used the idle screen-saver motif, a design feature since found in widely used projects such as

Seti@Home SETI@home ("SETI at home") is a project of the Berkeley SETI Research Center to analyze radio signals with the aim of Search for extraterrestrial intelligence, searching for signs of extraterrestrial intelligence. Until March 2020, it was run ...

. Zilla won the national Computerworld Smithsonian Award (Science Category) in 1991 for ease of use and good design. Apple acquired Zilla along with the rest of NeXT in 1997, and used Zilla as inspiration for Xgrid. Xgrid Technology Preview 1 was released in January 2004, followed by Technology Preview 2 in November 2004. Xgrid 1.0 was released as part of Mac OS X 10.4 Tiger in April 2005. Several organizations have adopted Xgrid in large international computing networks. One example of an Xgrid cluster is MacResearch's OpenMacGrid, where scientists can request access to large amounts of processing power to run tasks related to their research. Another was the now defunct Xgrid@Stanford project, which used a range of computers on the

Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...

campus and around the world to perform biochemical research. In a report covering the announcement, ''

Macworld ''Macworld'' is a digital magazine and website dedicated to products and software of Apple Inc., published by Foundry, a subsidiary of IDG. History ''Macworld'' was founded by David Bunnell and Cheryl Woodard (publishers) and Andrew Fl ...

'' cited Xgrid among the

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user 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 ...

features in "10 Things to Know about Tiger", calling it "handy if you work with huge amounts of experimental data or render complex animations". After Xgrid's introduction in 2004, ''

InfoWorld ''InfoWorld'' (''IW'') is an American information technology media business. Founded in 1978, it began as a monthly magazine. In 2007, it transitioned to a Web-only publication. Its parent company is International Data Group, and its sister pu ...

'' noted that it was a "'preview' grade technology" which would directly benefit from the Xserve G5's launch later that year. ''InfoWorld'' commentator Ephraim Schwartz also predicted that Xgrid was an opening move in Apple's entry into the enterprise computing market. Apple discontinued Xgrid with OS X 10.8 Mountain Lion, along with dependent services such as Podcast Producer.

Protocol

The Xgrid protocol uses the BEEP network framework to communicate with nodes on the network. The system's infrastructure includes three types of computers which communicate over the protocol: * The client, which submits

calculation A calculation is a deliberate mathematical process that transforms a plurality of inputs into a singular or plurality of outputs, known also as a result or results. The term is used in a variety of senses, from the very definite arithmetical ...

jobs to the controller * The controller, which segregates the jobs into tasks, and assigns these tasks to agents * The agents, which process their own allocated part of the calculation and return results to the controller, which returns them to the client. A computer can act as one or all three of these components at the same time. The Xgrid protocol provides the basic infrastructure for computers to

communicate Communication is commonly defined as the transmission of information. Its precise definition is disputed and there are disagreements about whether unintentional or failed transmissions are included and whether communication not only transmit ...

, but is not involved in the processing of the specified calculation. Xgrid is targeted towards time-consuming computations that can be easily segregated into smaller tasks, sometimes called ''embarrassingly parallel'' tasks. This includes Monte Carlo calculations,

3D rendering 3D rendering is the 3D computer graphics process of converting 3D models into 2D images on a computer. 3D renders may include photorealistic effects or non-photorealistic styles. Rendering methods Rendering is the final process of creati ...

and Mandelbrot maps. Within the Xgrid protocol, three types of messages can be passed to other computers on the same

cluster may refer to: Science and technology Astronomy * Cluster (spacecraft), constellation of four European Space Agency spacecraft * Cluster II (spacecraft), a European Space Agency mission to study the magnetosphere * Asteroid cluster, a small ...

: requests,

notifications Notification may refer to: *Notification (Holy See), an announcement by a department of the Roman Curia *Casualty notification, the process of notifying relatives of people who have been killed or seriously injured *Death notification, the proces ...

and replies. Requests must be responded to by the recipient with a reply, notifications do not require a reply, and replies are responses to sent messages. They are identified by their

name A name is a term used for identification by an external observer. They can identify a class or category of things, or a single thing, either uniquely, or within a given context. The entity identified by a name is called its referent. A person ...

, type (request/notification/reply) and contents. Each message is encapsulated in a BEEP message (BEEP MSG) and is acknowledged on receipt by an empty reply (RPY). Xgrid does not leverage BEEPs message/reply infrastructure. Any received message which requires a response merely generates an independent BEEP message containing the reply. The Xgrid messages are encoded as dictionaries of key/value pairs which are converted to XML before being sent across the BEEP network.

Architecture

The architecture of the Xgrid system is designed around a job based system; the controller sends agents jobs, and the agents return the responses. The actual computation that the controller executes in an Xgrid system is known as a job. The job contains all the files required to complete the task successfully, such as the input

parameter A parameter (), generally, is any characteristic that can help in defining or classifying a particular system (meaning an event, project, object, situation, etc.). That is, a parameter is an element of a system that is useful, or critical, when ...

data file A data file is a computer file which stores data to be used by a computer application or system, including input and output data. A data file usually does not contain instructions or code to be executed (that is, a computer program). Most of th ...

s, directories,

executable In computer science, executable code, an executable file, or an executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instruction (computer science), in ...

s and/or

shell script A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be command languages. Typical operations performed by shell scripts include file manipu ...

s, the files included in an Xgrid job must be able to be executed either simultaneously or asynchronously, or any benefits of running such a job on an Xgrid is lost. Once the job completes, the controller can be set to notify the client of the task's completion or failure, for example by

email Electronic mail (usually shortened to email; alternatively hyphenated e-mail) is a method of transmitting and receiving Digital media, digital messages using electronics, electronic devices over a computer network. It was conceived in the ...

. The client can leave the network while the tasks are running. It can also monitor the job status on demand by querying the controller, although it cannot track the ongoing progress of individual tasks. The controller is central to the correct function of an Xgrid, as this node is responsible for the distribution, supervision and coordination of tasks on agents. The program running on the controller can assign and reassign tasks to handle individual agent failures on demand. The number of tasks assigned to an agent depend on two factors: the number of agents on an Xgrid and the number of processors in each node. The number of agents on an Xgrid determines how the controller will assign tasks. The tasks may be assigned simultaneously for a large number of agents, or queued for a small number of agents. When a node with more than one processor is detected on an Xgrid, the controller may assign one task per processor; this only occurs if the number of agents on the network is lower than the number of tasks the controller has to complete. Xgrid is layered upon the Blocks Extensible Exchange Protocol (BEEP), an

IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet standard, Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster ...

standard comparable to

HTTP HTTP (Hypertext Transfer Protocol) 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, wher ...

, but with a focus on two-way multiplexed communication, such as that found in

peer-to-peer network Peer-to-peer (P2P) computing or networking is a distributed application Distributed computing is a field of computer science that studies distributed systems, defined as computer systems whose inter-communicating components are located on d ...

s. BEEP, in turn, uses

XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing data. It defines a set of rules for encoding electronic document, documents in a format that is both human-readable and Machine-r ...

to define profiles for communicating between multiple agents over a single network or internet connection. Xgrid agent software was available for

and

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

systems.

Interface

While it is possible to access Xgrid from the command line, the Xgrid graphical user interface, a program bundled with

and, as of March 2009, available online, is a much more efficient way of administering an Xgrid system. Originally, the Xgrid agent was included in all Mac OS X 10.4 Tiger installations but the GUI was reserved for users of

. This decision limited the efforts of the computer community to embrace the platform. Eventually, Apple released the Mac OS X Server Administration Tools to the public, which included the Xgrid administration application bundled with Mac OS X Server. Despite the lack of a graphical controller interface in the standard (non-server)

Mac OS X macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

distribution, it is possible to set up an Xgrid controller via the

command line A command-line interface (CLI) is a means of interacting with software via command (computing), commands each formatted as a line of text. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user ...

tools xgridctl and xgrid. Once the Xgrid controller

daemon A demon is a malevolent supernatural being, evil spirit or fiend in religion, occultism, literature, fiction, mythology and folklore. Demon, daemon or dæmon may also refer to: Entertainment Fictional entities * Daemon (G.I. Joe), a character ...

is running, administration of the grid with Apple's Xgrid Admin tool is possible. Some applications, such as VisualHub, provided Xgrid controller capability through their user interfaces.

History

Protocol

Architecture

Interface

See also

Notes

Further reading