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SWIM Protocol
The Scalable Weakly Consistent Infection-style Process Group Membership (SWIM) Protocol is a group membership protocol based on "outsourced heartbeats" used in distributed systems, first introduced by Indranil Gupta in 2001. It is a hybrid algorithm which combines failure detection with group membership dissemination. Protocol The protocol has two components, the ''Failure Detector Component'' and the ''Dissemination Component''. The ''Failure Detector Component'' functions as follows: # Every ''T time units, each node (N_1) sends a ping to random other node (N_2) in its membership list. # If N_1 receives a response from N_2, N_2 is decided to be healthy and N1 updates its "last heard from" timestamp for N_2 to be the current time. # If N_1 does not receive a response, N_1 contacts ''k'' other nodes on its list (\), and requests that they ping N_2. # If after ''T units of time: if no successful response is received, N_1 marks N_2 as failed. The ''Dissemination Component'' fu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heartbeat (computing)
In computer science, a heartbeat is a periodic signal generated by hardware or software to indicate normal operation or to synchronize other parts of a computer system. Heartbeat mechanism is one of the common techniques in mission critical systems for providing high availability and fault tolerance of network services by detecting the network or systems failures of nodes or daemons which belongs to a network cluster—administered by a master server—for the purpose of automatic adaptation and rebalancing of the system by using the remaining redundant nodes on the cluster to take over the load of failed nodes for providing constant services. Usually a heartbeat is sent between machines at a regular interval in the order of seconds; a heartbeat message. If the endpoint does not receive a heartbeat for a time—usually a few heartbeat intervals—the machine that should have sent the heartbeat is assumed to have failed. Heartbeat messages are typically sent non-stop on a perio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
O'Reilly Media
O'Reilly Media (formerly O'Reilly & Associates) is an American learning company established by Tim O'Reilly that publishes books, produces tech conferences, and provides an online learning platform. Its distinctive brand features a woodcut of an animal on many of its book covers. Company Early days The company began in 1978 as a private consulting firm doing technical writing, based in the Cambridge, Massachusetts area. In 1984, it began to retain publishing rights on manuals created for Unix vendors. A few 70-page "Nutshell Handbooks" were well-received, but the focus remained on the consulting business until 1988. After a conference displaying O'Reilly's preliminary Xlib manuals attracted significant attention, the company began increasing production of manuals and books. The original cover art consisted of animal designs developed by Edie Freedman because she thought that Unix program names sounded like "weird animals". Global Network Navigator In 1993 O'Reilly Media creat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Systems
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 science that studies distributed systems. The components of a distributed system interact with one another in order to achieve a common goal. Three significant challenges of distributed systems are: maintaining concurrency of components, overcoming the lack of a global clock, and managing the independent failure of components. When a component of one system fails, the entire system does not fail. Examples of distributed systems vary from SOA-based systems to massively multiplayer online games to peer-to-peer applications. A computer program that runs within a distributed system is called a distributed program, and ''distributed programming'' is the process of writing such programs. There are many different types of implementations for t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Failure Detector
In a distributed computing system, a failure detector is a computer application or a subsystem that is responsible for the detection of node failures or crashes. Failure detectors were first introduced in 1996 by Chandra and Toueg in their book ''Unreliable Failure Detectors for Reliable Distributed Systems''. The book depicts the failure detector as a tool to improve consensus (the achievement of reliability) and atomic broadcast (the same sequence of messages) in the distributed system. In other word, failure detectors seek for errors in the process, and the system will maintain a level of reliability. In practice, after failure detectors spot crashes, the system will ban the processes that are making mistakes to prevent any further serious crashes or errors. In the 21st century, failure detectors are widely used in distributed computing systems to detect application errors, such as a software application stops functioning properly. As the distributed computing projects (see L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multicast
In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused with physical layer point-to-multipoint communication. Group communication may either be application layer multicast or network-assisted multicast, where the latter makes it possible for the source to efficiently send to the group in a single transmission. Copies are automatically created in other network elements, such as routers, switches and cellular network base stations, but only to network segments that currently contain members of the group. Network assisted multicast may be implemented at the data link layer using one-to-many addressing and switching such as Ethernet multicast addressing, Asynchronous Transfer Mode (ATM), point-to-multipoint virtual circuits (P2MP) or InfiniBand multicast. Network-assisted multicast may also be impl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piggybacking (data Transmission)
In two-way communication, whenever a frame is received, the receiver waits and does not send the control frame (acknowledgment or ACK) back to the sender immediately. The receiver waits until its network layer passes in the next data packet. The delayed acknowledgment is then attached to this outgoing data frame. This technique of temporarily delaying the acknowledgment so that it can be hooked with next outgoing data frame is known as piggybacking. Working principle Piggybacking data is a bit different from sliding window protocols used in the OSI model. In the data frame itself, we incorporate one additional field for acknowledgment (i.e., ACK). Whenever party A wants to send data to party B, it will carry additional ACK information in the PUSH as well. For example, if A has received 5 bytes from B, with a sequence number starting from 12340 (through 12344), A will place "ACK 12345" as well in the current PUSH packet to inform B it has received the bytes up to sequence number ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gossip Protocol
A gossip protocol or epidemic protocol is a procedure or process of computer peer-to-peer communication that is based on the way epidemics spread. Some distributed systems use peer-to-peer gossip to ensure that data is disseminated to all members of a group. Some ad-hoc networks have no central registry and the only way to spread common data is to rely on each member to pass it along to their neighbors. Communication The concept of ''gossip communication'' can be illustrated by the analogy of office workers spreading rumors. Let's say each hour the office workers congregate around the water cooler. Each employee pairs off with another, chosen at random, and shares the latest gossip. At the start of the day, Dave starts a new rumor: he comments to Bob that he believes that Charlie dyes his mustache. At the next meeting, Bob tells Alice, while Dave repeats the idea to Eve. After each water cooler rendezvous, the number of individuals who have heard the rumor roughly doubles (thoug ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Round-robin Scheduling
Round-robin (RR) is one of the algorithms employed by process and network schedulers in computing.Guowang Miao, Jens Zander, Ki Won Sung, and Ben Slimane, Fundamentals of Mobile Data Networks, Cambridge University Press, , 2016. As the term is generally used, time slices (also known as time quanta) are assigned to each process in equal portions and in circular order, handling all processes without priority (also known as cyclic executive). Round-robin scheduling is simple, easy to implement, and starvation-free. Round-robin scheduling can be applied to other scheduling problems, such as data packet scheduling in computer networks. It is an operating system concept. The name of the algorithm comes from the round-robin principle known from other fields, where each person takes an equal share of something in turn. Process scheduling To schedule processes fairly, a round-robin scheduler generally employs time-sharing, giving each job a time slot or ''quantum'' (its allowance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crash (computing)
In computing, a crash, or system crash, occurs when a computer program such as a software application or an operating system stops functioning properly and exits. On some operating systems or individual applications, a crash reporting service will report the crash and any details relating to it (or give the user the option to do so), usually to the developer(s) of the application. If the program is a critical part of the operating system, the entire system may crash or hang, often resulting in a kernel panic or fatal system error. Most crashes are the result of a software bug. Typical causes include accessing invalid memory addresses, incorrect address values in the program counter, buffer overflow, overwriting a portion of the affected program code due to an earlier bug, executing invalid machine instructions (an illegal opcode), or triggering an unhandled exception. The original software bug that started this chain of events is typically considered to be the cause of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault-tolerant Computer Systems
Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the severity of the failure, as compared to a naively designed system, in which even a small failure can cause total breakdown. Fault tolerance is particularly sought after in high-availability, mission-critical, or even life-critical systems. The ability of maintaining functionality when portions of a system break down is referred to as graceful degradation. A fault-tolerant design enables a system to continue its intended operation, possibly at a reduced level, rather than failing completely, when some part of the system fails. The term is most commonly used to describe computer systems designed to continue more or less fully operational with, perhaps, a reduction in throughput or an increase in response time in the event of some partial f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Algorithms
A distributed algorithm is an algorithm designed to run on computer hardware constructed from interconnected processors. Distributed algorithms are used in different application areas of distributed computing, such as telecommunications, scientific computing, distributed information processing, and real-time process control. Standard problems solved by distributed algorithms include leader election, consensus, distributed search, spanning tree generation, mutual exclusion, and resource allocation. Distributed algorithms are a sub-type of parallel algorithm, typically executed concurrently, with separate parts of the algorithm being run simultaneously on independent processors, and having limited information about what the other parts of the algorithm are doing. One of the major challenges in developing and implementing distributed algorithms is successfully coordinating the behavior of the independent parts of the algorithm in the face of processor failures and unreliable communica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
