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Varnish (software)
Varnish is an HTTP accelerator designed for content-heavy dynamic web sites as well as APIs. In contrast to other web accelerators, such as Squid (software), Squid, which began life as a client-side cache, or Apache HTTP server, Apache and nginx, which are primarily Upstream server, origin servers, Varnish was designed as an HTTP accelerator. Varnish is focused exclusively on HTTP, unlike other proxy servers that often support FTP, SMTP and other network protocols. History The project was initiated by the online branch of the Norwegian tabloid newspaper ''Verdens Gang''. The architect and lead developer is Danish independent consultant Poul-Henning Kamp (a well-known FreeBSD developer), with management, infrastructure and additional development originally provided by the Norwegian Linux consulting company Linpro. The support, management and development of Varnish was later spun off into a separate company, Varnish Software. Varnish is free and open source software, available und ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poul-Henning Kamp
Poul-Henning Kamp (; born 1966) is a Danish computer software developer known for work on various projects including FreeBSD and Varnish. He currently resides in Slagelse, Denmark. Involvement in the FreeBSD project Poul-Henning Kamp has been committing to the FreeBSD project for most of its duration. He is responsible for the widely used MD5crypt implementation of the MD5 password hash algorithm, a vast quantity of systems code including the FreeBSD GEOM storage layer, GBDE cryptographic storage transform, part of the UFS2 file system implementation, FreeBSD Jails, malloc library, and the FreeBSD and NTP timecounters code. Varnish cache He is the lead architect and developer for the open source Varnish cache project, an HTTP accelerator. Dispute with D-Link In 2006, Kamp had a dispute with electronics manufacturer D-Link in which he claimed they were committing NTP vandalism by embedding the IP address of his NTP servers in their routers. The dispute was resolved in Apr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Verdens Gang
''Verdens Gang'' ("The course of the world"), generally known under the abbreviation ''VG'', is a Norwegian tabloid newspaper. In 2016, circulation numbers stood at 93,883, having declined from a peak circulation of 390,510 in 2002. ''VG'' is nevertheless the most read online newspaper in Norway, with about 2 million daily readers. Verdens Gang AS is a private company wholly owned by the public company Schibsted. History and profile ''VG'' was established by members of the Norwegian resistance movement shortly after the country was liberated from German occupation in 1945. The first issue of the paper was published on 23 June 1945. Christian A. R. Christensen was the first editor-in-chief of ''VG'' from its start in 1945 to 1967 when he died. ''VG'' is based in Oslo. The paper is published in tabloid format. The owner is the media conglomerate Schibsted, which also owns Norway's largest newspaper, ''Aftenposten'', as well as newspapers in Sweden and Estonia and shares in some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Load Balancing (computing)
In computing, load balancing is the process of distributing a set of tasks over a set of resources (computing units), with the aim of making their overall processing more efficient. Load balancing can optimize the response time and avoid unevenly overloading some compute nodes while other compute nodes are left idle. Load balancing is the subject of research in the field of parallel computers. Two main approaches exist: static algorithms, which do not take into account the state of the different machines, and dynamic algorithms, which are usually more general and more efficient but require exchanges of information between the different computing units, at the risk of a loss of efficiency. Problem overview A load-balancing algorithm always tries to answer a specific problem. Among other things, the nature of the tasks, the algorithmic complexity, the hardware architecture on which the algorithms will run as well as required error tolerance, must be taken into account. Therefore c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Front And Back Ends
In software engineering, the terms frontend and backend (or sometimes referred to as back end or back-end) refer to the separation of concerns between the presentation layer (''frontend''), and the data access layer (''backend'') of a piece of software, or the physical infrastructure or hardware. In the client–server model, the client is usually considered the frontend and the server is usually considered the backend, even when some presentation work is actually done on the server itself. Introduction In software architecture, there may be many layers between the hardware and end user. The ''front'' is an abstraction, simplifying the underlying component by providing a user-friendly interface, while the ''back'' usually handles data storage and business logic. In telecommunication, the ''front'' can be considered a device or service, while the ''back'' is the infrastructure that supports provision of service. A rule of thumb is that the client-side (or "frontend") is any comp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cache (computing)
In computing, a cache ( ) is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere. A ''cache hit'' occurs when the requested data can be found in a cache, while a ''cache miss'' occurs when it cannot. Cache hits are served by reading data from the cache, which is faster than recomputing a result or reading from a slower data store; thus, the more requests that can be served from the cache, the faster the system performs. To be cost-effective and to enable efficient use of data, caches must be relatively small. Nevertheless, caches have proven themselves in many areas of computing, because typical computer applications access data with a high degree of locality of reference. Such access patterns exhibit temporal locality, where data is requested that has been recently requested already, and spatial locality, where d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shared Memory (interprocess Communication)
In computer science, shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies. Shared memory is an efficient means of passing data between programs. Depending on context, programs may run on a single processor or on multiple separate processors. Using memory for communication inside a single program, e.g. among its multiple threads, is also referred to as shared memory. In hardware In computer hardware, ''shared memory'' refers to a (typically large) block of random access memory (RAM) that can be accessed by several different central processing units (CPUs) in a multiprocessor computer system. Shared memory systems may use: * uniform memory access (UMA): all the processors share the physical memory uniformly; * non-uniform memory access (NUMA): memory access time depends on the memory location relative to a processor; * cache-only memory architecture (COMA): the local memor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Domain-specific Language
A domain-specific language (DSL) is a computer language specialized to a particular application domain. This is in contrast to a general-purpose language (GPL), which is broadly applicable across domains. There are a wide variety of DSLs, ranging from widely used languages for common domains, such as HTML for web pages, down to languages used by only one or a few pieces of software, such as MUSH soft code. DSLs can be further subdivided by the kind of language, and include domain-specific ''markup'' languages, domain-specific ''modeling'' languages (more generally, specification languages), and domain-specific ''programming'' languages. Special-purpose computer languages have always existed in the computer age, but the term "domain-specific language" has become more popular due to the rise of domain-specific modeling. Simpler DSLs, particularly ones used by a single application, are sometimes informally called mini-languages. The line between general-purpose languages and domain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thread (computer Science)
In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating system. The implementation of threads and processes differs between operating systems. In Modern Operating Systems, Tanenbaum shows that many distinct models of process organization are possible.TANENBAUM, Andrew S. Modern Operating Systems. 1992. Prentice-Hall International Editions, ISBN 0-13-595752-4. In many cases, a thread is a component of a process. The multiple threads of a given process may be executed concurrently (via multithreading capabilities), sharing resources such as memory, while different processes do not share these resources. In particular, the threads of a process share its executable code and the values of its dynamically allocated variables and non- thread-local global variables at any given time. History Threads made an early appearance under the name of "tasks ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer from cellular phones and video game consoles to web servers and supercomputers. The dominant general-purpose personal computer operating system is Microsoft Windows with a market share of around 74.99%. macOS by Apple Inc. is in second place (14.84%), and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Memory
In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very large (main) memory". The computer's operating system, using a combination of hardware and software, maps memory addresses used by a program, called '' virtual addresses'', into ''physical addresses'' in computer memory. Main storage, as seen by a process or task, appears as a contiguous address space or collection of contiguous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit (MMU), automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities, utilizing, e.g., disk storage, to provide a virtual address space that ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BSD License
BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD license was used for its namesake, the Berkeley Software Distribution (BSD), a Unix-like operating system. The original version has since been revised, and its descendants are referred to as modified BSD licenses. BSD is both a license and a class of license (generally referred to as BSD-like). The modified BSD license (in wide use today) is very similar to the license originally used for the BSD version of Unix. The BSD license is a simple license that merely requires that all code retain the BSD license notice if redistributed in source code format, or reproduce the notice if redistributed in binary format. The BSD license (unlike some other licenses e.g. GPL) does not require that source code be distributed at all. Terms In addition t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
