Couchbase

Couchbase Server is an open-source, distributed NoSQL document-oriented database. It is desgined for interactive applications involving multiple users and concurrency operations. Couchbase server provides well-scaled key-value or JSON document access. It supports the Memcached client protocol and provides extra features like disk persistence, data replication, rebalancing and multi-tenancy with data partitioning, etc.

History

In 2010, the origination of Couchbase, Membase, was developed by a company called NorthScale which was founded by developers from Memcached project.

In February, 2011, the Membase project founders and Membase, Inc. merged with CouchOne(a company with many engineers behind CouchDB) as a new company called Couchbase, Inc.

In January 2012, Couchbase Server 1.8 was released and 1.8 was the first version after rename from Membase.

In December 2012, CouchBase Server 2.0 was released. New features like JSON new document store, indexing and querying, incremental MapReduce and replication across data centers are added.

Checkpoints

Consistent Blocking

The replicator of Couchbase Server will checkpoint the source sequenceID corresponding to the last change sent to the target with a conflict resolver.

Query Interface

Custom API

Couchbase Server presents a new language called N1QL which is a SQL extension for JSON as the query interface.

Joins

Nested Loop Join

Couchbase Server supports lookup join, index join and ANSI join in its N1QL language.

Storage Architecture

Disk-oriented

Couchbase Server maintains recent accessed data in the memory to achieve high performance and scalability. The data which is not recently used will be swapped on to disks.

Storage Organization

Sorted Files

Couchbase Server uses Couchstore to store core data operations. Each Bucket (the smallest unit of Couchbase's storage model) is stored as a separate Couchstore file in the file system. Couchstore uses a B+tree structure to quickly access items through their keys. Append-only write model is used for efficient and safe writes.

Isolation Levels

Read Committed Serializable

Couchbase Server provides read committed isolation by default at the single document level. However, by using the provided optimistic locking and pessimistic locking, user can obtain serialized isolation of an individual document.

Stored Procedures

Supported

A similar feature called "Prepared queries" is supported in Couchbase Server.

Indexes

B+Tree Skip List Hash Table Inverted Index (Full Text)

A few of indexes are available in Couchbase Server:

  • Primary Index is based on on the unique key of every item in a specified bucket which contains a full set of keys in a given key space.

  • Global Secondary Index (GSI) is the most frequently used index in Couchbase Server, for queries performed with the N1Ql query-language. The indexer for GSI creates a B+ tree for fast scans on the index key. Also, there is a Memory-Optimized GSI index which uses the skip-list structure as opposed to B-tree indexes.

  • Full Text is provided by the Search Service and it contains targets derived from the textual contents of documents within one or more specified buckets.

  • View: Supports Couchbase Views, with fields and information extracted from documents.

Storage Model

Custom

Couchbase Server stores items in the Buckets. There are two kinds of Buckets in the Couchbase. One is Couchbase Buckets which could reside both in memory and disks. Another is Ephemeral bucket which only stays in the memory.

Data Model

Document / XML

The documents stored in Couchbase Server are in JSON or binary format.

System Architecture

Shared-Nothing

Each machine running Couchbase server is a single node, and multiple nodes could join together as a cluster. Every node of the cluster has a Cluster Manager module for communication. The data inside the cluster is evenly distributed and replicated over the nodes.

Compression

Bit Packing / Mostly Encoding

Couchbase Server (Enterprise Edition) applies data compression to documents with a 3rd party open-source library Snappy. It provides three modes of compression.

  • Off. The Couchbase Server decompresses the document if it is compressed, and stores the uncompressed document in memory but recompresses it when storing on disk. Also, Couchbase server sends the document in uncompressed form.

  • Passive. When Couchbase Server receives the compressed document, it stores the compressed document in memory and disk. Also, the documents are sent in compressed form.

  • Active. Couchbase Server stores and sends compressed document even the document is uncompressed.

Concurrency Control

Optimistic Concurrency Control (OCC)

Couchbase Server offers both optimistic and pessimistic locking to guarantee concurrency.

Views

Materialized Views

Three views are supported by Couchbase Server: MapReduce views, Spatial views and Global Secondary Indexes (GSI) views.

  • MapReduce views can be accessed via the View API.

  • Spatial views can be accessed via the Spatial View API.

  • N1QL queries with Global Secondary Indexes (GSI) and MapReduce views.

Couchbase Logo
Website

http://www.couchbase.com/

Source Code

https://github.com/couchbase/manifest

Tech Docs

https://docs.couchbase.com/home/index.html

Developer

Couchbase, Inc.

Country of Origin

US

Start Year

2010

Former Name

Membase

Project Type

Commercial, Open Source

Written in

C, C++, Erlang, Go

Supported languages

C, C#, Go, Java, JavaScript, PHP, Python

Derived From

CouchDB

Compatible With

Memcached

Operating Systems

Linux, OS X, Windows

Licenses

Apache v2

Wikipedia

https://en.wikipedia.org/wiki/Couchbase_Server