Editing Pipeline (software) (section)

{{Short description|Chain of software processing elements}}
{{About|software pipelines in general|the original implementation for shells|Pipeline (Unix)}}
{{For-text|the broader concept of pipelines as they occur in computing|[[Pipeline (computing)]]}}

In [[software engineering]], a '''pipeline''' consists of a chain of processing elements ([[Process (computing)|processes]], [[Thread (computer science)|threads]], [[coroutine]]s, [[Subroutine|functions]], ''etc.''), arranged so that the output of each element is the input of the next. The concept is analogous to a physical [[Pipeline transport|pipeline]]. Usually some amount of [[Buffer (computer science)|buffering]] is provided between consecutive elements. The information that flows in these pipelines is often a [[Stream (computing)|stream]] of [[Record (computer science)|records]], [[Byte stream|bytes]], or [[Bitstream|bits]], and the elements of a pipeline may be called [[Filter (software)|filters]]. This is also called the '''pipe(s) and filters''' [[software design pattern|design pattern]] which is [[Monolithic application|monolithic]]. Its advantages are simplicity and low cost while its disadvantages are lack of [[Elasticity (system resource)|elasticity]], [[Software fault tolerance|fault tolerance]] and [[scalability]].<ref>{{Cite book |title=Fundamentals of Software Architecture: An Engineering Approach |publisher=O'Reilly Media |year=2020 |isbn=978-1492043454}}</ref> Connecting elements into a pipeline is analogous to [[function composition (computer science)|function composition]].

Narrowly speaking, a pipeline is linear and one-directional, though sometimes the term is applied to more general flows. For example, a primarily one-directional pipeline may have some communication in the other direction, known as a ''[[return channel]]'' or ''backchannel,'' as in [[the lexer hack]], or a pipeline may be fully bi-directional. Flows with one-directional trees and [[directed acyclic graph]] topologies behave similarly to linear pipelines. The lack of cycles in such flows makes them simple, and thus they may be loosely referred to as "pipelines".