Apache CouchDB is an
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized so ...
document-oriented NoSQL
A NoSQL (originally referring to "non- SQL" or "non-relational") database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases. Such databases have existed ...
database, implemented in
Erlang.
CouchDB uses multiple formats and protocols to store, transfer, and process its data. It uses
JSON
JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other se ...
to store data,
JavaScript
JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...
as its query language using
MapReduce, and
HTTP
The Hypertext Transfer Protocol (HTTP) 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 We ...
for an
API.
CouchDB was first released in 2005 and later became an
Apache Software Foundation
The Apache Software Foundation (ASF) is an American nonprofit corporation (classified as a 501(c)(3) organization in the United States) to support a number of open source software projects. The ASF was formed from a group of developers of the ...
project in 2008.
Unlike a
relational database
A relational database is a (most commonly digital) database based on the relational model of data, as proposed by E. F. Codd in 1970. A system used to maintain relational databases is a relational database management system (RDBMS). Many relati ...
, a CouchDB database does not store data and relationships in tables. Instead, each database is a collection of independent documents. Each document maintains its own data and self-contained schema. An application may access multiple databases, such as one stored on a user's mobile phone and another on a server. Document metadata contains revision information, making it possible to merge any differences that may have occurred while the databases were disconnected.
CouchDB implements a form of
multiversion concurrency control
Multiversion concurrency control (MCC or MVCC), is a concurrency control method commonly used by database management systems to provide concurrent access to the database and in programming languages to implement transactional memory.
Description
...
(MVCC) so it does not lock the database file during writes. Conflicts are left to the application to resolve. Resolving a conflict generally involves first merging data into one of the documents, then deleting the stale one.
Other features include document-level
ACID
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a se ...
semantics with
eventual consistency, (incremental) MapReduce, and (incremental) replication. One of CouchDB's distinguishing features is
multi-master replication, which allows it to scale across machines to build high-performance systems. A built-in Web application called Fauxton (formerly Futon) helps with administration.
History
''Couch'' is an acronym for ''cluster of unreliable commodity hardware''.
The CouchDB project was created in April 2005 by Damien Katz, a former
Lotus Notes developer at
IBM. He self-funded the project for almost two years and released it as an open-source project under the
GNU General Public License
The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general ...
.
In February 2008, it became an
Apache Incubator project and was offered under the
Apache License instead. A few months after, it graduated to a top-level project. This led to the first stable version being released in July 2010.
In early 2012, Katz left the project to focus on
Couchbase Server.
Since Katz's departure, the Apache CouchDB project has continued, releasing 1.2 in April 2012 and 1.3 in April 2013. In July 2013, the CouchDB community merged the codebase for
BigCouch
BigCouch is an open-source, highly available, fault-tolerant, clustered & API-compliant version of Apache CouchDB, which was maintained by Cloudant. On January 5, 2012, Cloudant announced they would contribute the BigCouch horizontal scaling fra ...
,
Cloudant
Cloudant is an IBM software product, which is primarily delivered as a cloud-based service. Cloudant is a non-relational, distributed database service of the same name. Cloudant is based on the Apache-backed CouchDB project and the open source B ...
's clustered version of CouchDB, into the Apache project. The BigCouch clustering framework is included in the current release of Apache CouchDB.
Native clustering is supported at version 2.0.0. And the new Mango Query Server provides a simple JSON-based way to perform CouchDB queries without JavaScript or MapReduce.
Main features
; ACID Semantics
: CouchDB provides
ACID
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a se ...
semantics.
[CouchDB, Technical Overview](_blank)
It does this by implementing a form of
Multi-Version Concurrency Control, meaning that CouchDB can handle a high volume of concurrent readers and writers without conflict.
; Built for Offline
: CouchDB can replicate to devices (like smartphones) that can go offline and handle data sync for you when the device is back online.
; Distributed Architecture with Replication
: CouchDB was designed with bi-directional replication (or synchronization) and off-line operation in mind. That means multiple replicas can have their own copies of the same data, modify it, and then sync those changes at a later time.
; Document Storage
: CouchDB stores data as "documents", as one or more field/value pairs expressed as
JSON
JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other se ...
. Field values can be simple things like strings, numbers, or dates; but
ordered lists and
associative arrays can also be used. Every document in a CouchDB database has a unique id and there is no required document schema.
; Eventual Consistency
: CouchDB guarantees
eventual consistency to be able to provide both availability and partition tolerance.
; Map/Reduce Views and Indexes
: The stored data is structured using views. In CouchDB, each view is constructed by a
JavaScript
JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...
function that acts as the Map half of a
map/reduce operation. The function takes a document and transforms it into a single value that it returns. CouchDB can index views and keep those indexes updated as documents are added, removed, or updated.
; HTTP API
: All items have a unique URI that gets exposed via HTTP. It uses the
HTTP methods POST, GET, PUT and DELETE for the four basic
CRUD (Create, Read, Update, Delete) operations on all resources.
CouchDB also offers a built-in administration interface accessible via Web called Futon.
Use cases and production deployments
Replication and synchronization capabilities of CouchDB make it ideal for using it in mobile devices, where network connection is not guaranteed, and the application must keep on working offline.
CouchDB is well suited for applications with accumulating, occasionally changing data, on which pre-defined queries are to be run and where versioning is important (CRM, CMS systems, by example). Master-master replication is an especially interesting feature, allowing easy multi-site deployments.
[Cassandra vs MongoDB vs CouchDB vs Redis vs Riak vs HBase comparison](_blank)
from Kristóf Kovács
Users
Users of CouchDB include:
*
CERN
The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gen ...
uses CouchDB as database for the Data Management System at the
Large Hadron Collider
The Large Hadron Collider (LHC) is the world's largest and highest-energy particle collider. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundr ...
.
*
Red Cross
The International Red Cross and Red Crescent Movement is a Humanitarianism, humanitarian movement with approximately 97 million Volunteering, volunteers, members and staff worldwide. It was founded to protect human life and health, to ensure re ...
use the application iDAT for completing casework electronically in disaster areas. Here CouchDB is used as multi-node peer-to-peer offline-first database.
*
IBM Cloud services are based at a fundamental level on CouchDB.
*
United Airlines
United Airlines, Inc. (commonly referred to as United), is a major American airline headquartered at the Willis Tower in Chicago, Illinois. uses CouchDB for the in-flight entertainment systems in over 3,000 planes.
*
Amadeus IT Group, for some of their back-end systems.
*
Credit Suisse
Credit Suisse Group AG is a global investment bank and financial services firm founded and based in Switzerland. Headquartered in Zürich, it maintains offices in all major financial centers around the world and is one of the nine global " ...
, for internal use at commodities department for their marketplace framework.
["CouchDB in the wild"](_blank)
article of the product's Web, a list of software projects and websites using CouchDB
*
Meebo
Meebo (often stylized as meebo) was an instant messaging and social networking service provider. It was founded in September 2005 by Sandy Jen, Seth Sternberg, and Elaine Wherry, and was based in Mountain View, California. Initially the company ...
, for their social platform (Web and applications). Meebo was acquired by Google and most products were shut down on July 12, 2012.
*
npm uses CouchDB as replicating database for their package registry.
*
Sophos
Sophos Group plc is a British based security software and hardware company. Sophos develops products for communication endpoint, encryption, network security, email security, mobile security and unified threat management. Sophos is primarily ...
, for some of their back-end systems.
*
BBC, for a dynamic CMS-Platform.
*
Canonical began using it in 2009 for its synchronization service "Ubuntu One", but stopped using it in November 2011.
*
CANAL+ for international on-demand platform at CANAL+ Overseas.
*
Protogrid, as storage back-end for their rapid application development framework
Data manipulation: documents and views
CouchDB manages a collection of
JSON
JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other se ...
documents. The documents are organised via views. Views are defined with
aggregate functions and filters are computed in parallel, much like
MapReduce.
Views are generally stored in the database and their indexes are updated continuously. CouchDB supports a view system using external socket servers and a JSON-based protocol.
[View Server Documentation]
on wiki.apache.org As a consequence, view servers have been developed in a variety of languages (JavaScript is the default, but there are also PHP, Ruby, Python and Erlang).
Accessing data via HTTP
Applications interact with CouchDB via HTTP. The following demonstrates a few examples using
cURL
cURL (pronounced like "curl", UK: , US: ) is a computer software project providing a library (libcurl) and command-line tool (curl) for transferring data using various network protocols. The name stands for "Client URL".
History
cURL was ...
, a command-line utility. These examples assume that CouchDB is running on
localhost
In computer networking, localhost is a hostname that refers to the current device used to access it. It is used to access the network services that are running on the host via the loopback network interface. Using the loopback interface bypasses ...
(127.0.0.1) on port 5984.
Open source components
CouchDB includes a number of other open source projects as part of its default package.
See also
*
Document-oriented database
*
XML database
An XML database is a data persistence software system that allows data to be specified, and sometimes stored, in XML format. This data can be queried, transformed, exported and returned to a calling system. XML databases are a flavor of document ...
References
Bibliography
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External links
*
CouchDB: The Definitive GuideComplete HTTP API ReferenceSimple PHP5 library to communicate with CouchDBAsynchronous CouchDB client for JavaAsynchronous CouchDB client for Scala*
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{{DEFAULTSORT:CouchDB
CouchDB
Client-server database management systems
Cross-platform software
Database-related software for Linux
Distributed computing architecture
Document-oriented databases
Erlang (programming language)
Free database management systems
NoSQL
Structured storage
Unix network-related software
Free software programmed in Erlang
2005 software