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Fallacies Of Distributed Computing
The fallacies of distributed computing are a set of assertions made by L Peter Deutsch and others at Sun Microsystems describing false assumptions that programmers new to distributed applications invariably make. The fallacies The fallacies are # The network is reliable; # Latency is zero; # Bandwidth is infinite; # The network is secure; # Topology doesn't change; # There is one administrator; # Transport cost is zero; # The network is homogeneous. The effects of the fallacies # Software applications are written with little error-handling on networking errors. During a network outage, such applications may stall or infinitely wait for an answer packet, permanently consuming memory or other resources. When the failed network becomes available, those applications may also fail to retry any stalled operations or require a (manual) restart. # Ignorance of network latency, and of the packet loss it can cause, induces application- and transport-layer developers to allow unbounded t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
L Peter Deutsch
L Peter Deutsch (born Laurence Peter Deutsch on August 7, 1946, in Boston, Massachusetts) is the founder of Aladdin Enterprises and creator of Ghostscript, a free software PostScript and Portable Document Format, PDF interpreter. Deutsch's other work includes the Smalltalk implementation that inspired Java (software platform), Java just-in-time compilation technology about 15 years later. Some stories about him are included in the Hackers: Heroes of the Computer Revolution book. Contributions to computer science Deutsch wrote the PDP-1 Lisp (programming language), Lisp 1.5 implementation and first REPL, Basic PDP-1 LISP, "while still in short pants" and finished it in 1963, when he was 17 years old. He collaborated with Calvin Mooers on the TRAC (programming language), TRAC programming language and wrote its first implementation, on the PDP-1, in 1964.full text From 1964 to 1967, during his study at the University of California, Berkeley, he worked with Butler Lampson and Char ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet Loss
Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is either caused by errors in data transmission, typically across wireless networks, or network congestion.Kurose, J.F. & Ross, K.W. (2010). ''Computer Networking: A Top-Down Approach''. New York: Addison-Wesley. Packet loss is measured as a percentage of packets lost with respect to packets sent. The Transmission Control Protocol (TCP) detects packet loss and performs retransmissions to ensure reliable messaging. Packet loss in a TCP connection is also used to avoid congestion and thus produces an intentionally reduced throughput for the connection. In real-time applications like streaming media or online games, packet loss can affect a user's quality of experience (QoE). Causes The Internet Protocol (IP) is designed according to the end-to-end principle as a best-effort delivery service, with the intention of keeping the logic routers mus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microservices
A microservice architecture – a variant of the service-oriented architecture structural style – is an architectural pattern that arranges an application as a collection of loosely-coupled, fine-grained services, communicating through lightweight protocols. One of its goals is that teams can develop and deploy their services independently of others. This is achieved by the reduction of several dependencies in the code base, allowing for developers to evolve their services with limited restrictions from users, and for additional complexity to be hidden from users. As a consequence, organizations are able to develop software with fast growth and size, as well as use off-the-shelf services more easily. Communication requirements are reduced. These benefits come at a cost to maintaining the decoupling. Interfaces need to be designed carefully and treated as a public API. One technique that is used is having multiple interfaces on the same service, or multiple versions of the sam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PACELC Theorem
In theoretical computer science, the PACELC theorem is an extension to the CAP theorem. It states that in case of network partitioning (P) in a distributed computer system, one has to choose between availability (A) and consistency (C) (as per the CAP theorem), but else (E), even when the system is running normally in the absence of partitions, one has to choose between latency (L) and consistency (C). Overview PACELC builds on the CAP theorem. Both theorems describe how distributed databases have limitations and tradeoffs regarding consistency, availability, and partition tolerance. PACELC however goes further and states that an additional trade-off exists: between latency and consistency, even in absence of partitions, thus providing a more complete portrayal of the potential consistency trade-offs for distributed systems. A high availability requirement implies that the system must replicate data. As soon as a distributed system replicates data, a trade-off between consisten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CAP Theorem
In theoretical computer science, the CAP theorem, also named Brewer's theorem after computer scientist Eric Brewer, states that any distributed data store can provide only two of the following three guarantees:Seth Gilbert and Nancy Lynch"Brewer's conjecture and the feasibility of consistent, available, partition-tolerant web services" ''ACM SIGACT News'', Volume 33 Issue 2 (2002), pg. 51–59. . ; Consistency: Every read receives the most recent write or an error. ; Availability: Every request receives a (non-error) response, without the guarantee that it contains the most recent write. ; Partition tolerance: The system continues to operate despite an arbitrary number of messages being dropped (or delayed) by the network between nodes. When a network partition failure happens, it must be decided whether to do one of the following: * cancel the operation and thus decrease the availability but ensure consistency * proceed with the operation and thus provide availability but risk i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Java (programming Language)
Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. It is a general-purpose programming language intended to let programmers ''write once, run anywhere'' ( WORA), meaning that compiled Java code can run on all platforms that support Java without the need to recompile. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of the underlying computer architecture. The syntax of Java is similar to C and C++, but has fewer low-level facilities than either of them. The Java runtime provides dynamic capabilities (such as reflection and runtime code modification) that are typically not available in traditional compiled languages. , Java was one of the most popular programming languages in use according to GitHub, particularly for client–server web applications, with a reported 9 million developers. Java was originally developed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Gosling
James Gosling (born May 19, 1955) is a Canadian computer scientist, best known as the founder and lead designer behind the Java programming language. Gosling was elected a member of the National Academy of Engineering in 2004 for the conception and development of the architecture for the Java programming language and for contributions to window systems. Early life Gosling attended William Aberhart High School in Calgary, Alberta. While in high school, he wrote some of the software to analyze data from the ISIS 2 satellite, working for the University of Calgary physics department. He received a Bachelor of Science from the University of Calgary and his M.A. and Ph.D. from Carnegie Mellon University, all in computer science. He wrote a version of Emacs called Gosling Emacs (Gosmacs) while working toward his doctorate. He built a multi-processor version of Unix for a 16-way computer system while at Carnegie Mellon University, before joining Sun Microsystems. He also develop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bill Joy
William Nelson Joy (born November 8, 1954) is an American computer engineer and venture capitalist. He co-founded Sun Microsystems in 1982 along with Scott McNealy, Vinod Khosla, and Andy Bechtolsheim, and served as Chief Scientist and CTO at the company until 2003. He played an integral role in the early development of BSD UNIX while being a graduate student at Berkeley, and he is the original author of the vi text editor. He also wrote the 2000 essay " Why The Future Doesn't Need Us", in which he expressed deep concerns over the development of modern technologies. Joy was elected a member of the National Academy of Engineering (1999) for contributions to operating systems and networking software. Early career Joy was born in the Detroit suburb of Farmington Hills, Michigan, to William Joy, a school vice-principal and counselor, and Ruth Joy. He earned a Bachelor of Science in electrical engineering from the University of Michigan and a Master of Science in electrical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fellow
A fellow is a concept whose exact meaning depends on context. In learned or professional societies, it refers to a privileged member who is specially elected in recognition of their work and achievements. Within the context of higher educational institutions, a fellow can be a member of a highly ranked group of teachers at a particular college or university or a member of the governing body in some universities (such as the Fellows of Harvard College); it can also be a specially selected postgraduate student who has been appointed to a post (called a fellowship) granting a stipend, research facilities and other privileges for a fixed period (usually one year or more) in order to undertake some advanced study or research, often in return for teaching services. In the context of research and development-intensive large companies or corporations, the title "fellow" is sometimes given to a small number of senior scientists and engineers. In the context of medical education in No ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subnetwork
A subnetwork or subnet is a logical subdivision of an IP network. Updated by RFC 6918. The practice of dividing a network into two or more networks is called subnetting. Computers that belong to the same subnet are addressed with an identical most-significant bit-group in their IP addresses. This results in the logical division of an IP address into two fields: the ''network number'' or ''routing prefix'' and the ''rest field'' or ''host identifier''. The ''rest field'' is an identifier for a specific host or network interface. The ''routing prefix'' may be expressed in Classless Inter-Domain Routing (CIDR) notation written as the first address of a network, followed by a slash character (''/''), and ending with the bit-length of the prefix. For example, is the prefix of the Internet Protocol version 4 network starting at the given address, having 24 bits allocated for the network prefix, and the remaining 8 bits reserved for host addressing. Addresses in the range to belon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Topology
Network topology is the arrangement of the elements ( links, nodes, etc.) of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks. Network topology is the topological structure of a network and may be depicted physically or logically. It is an application of graph theory wherein communicating devices are modeled as nodes and the connections between the devices are modeled as links or lines between the nodes. Physical topology is the placement of the various components of a network (e.g., device location and cable installation), while logical topology illustrates how data flows within a network. Distances between nodes, physical interconnections, transmission rates, or signal types may differ between two different networks, yet their logical topologies may be identical. A network’s physical topology is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Administrator
A network administrator is a person designated in an organization whose responsibility includes maintaining computer infrastructures with emphasis on local area networks (LANs) up to wide area networks (WANs). Responsibilities may vary between organizations, but installing new Computer hardware, hardware, on-site servers, enforcing licensing agreements, software-network interactions as well as network integrity and resilience are some of the key areas of focus. Duties The role of the network administrator can vary significantly depending on an organization's size, location, and socioeconomic considerations. Some organizations work on a user-to-technical support ratio, Network administrators are often involved in proactive work. This type of work will often include: * network monitoring. * penetration test, testing the network for weakness. * keeping an eye out for needed updates. * installing and implementing security programs. * in many cases, E-mail and Internet filters. * eva ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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