|Stable release||2.4.9 / 10 January 2014|
|Preview release||2.6.0-rc2 / 21 March 2014|
|License||GNU AGPL v3.0 (drivers: Apache license)|
MongoDB (from "humongous") is a cross-platform document-oriented database system. Classified as a NoSQL database, MongoDB eschews the traditional table-based relational database structure in favor of JSON-like documents with dynamic schemas (MongoDB calls the format BSON), making the integration of data in certain types of applications easier and faster. Released under a combination of the GNU Affero General Public License and the Apache License, MongoDB is free and open-source software.
First developed by the software company 10gen (now MongoDB Inc.) in October 2007 as a component of a planned platform as a service product, the company shifted to an open source development model in 2009, with 10gen offering commercial support and other services. Since then, MongoDB has been adopted as backend software by a number of major websites and services, including Craigslist, eBay, Foursquare, SourceForge, and the New York Times, among others. MongoDB is the most popular NoSQL database system.
Development of MongoDB began in 2007, when the company (then named 10gen) was building a platform as a service similar to Windows Azure or Google App Engine. In 2009, MongoDB was open sourced as a stand-alone product with an AGPL license.
From version 1.4 (March 2010), MongoDB has been considered production ready.
The latest stable version, 2.6, was released on April 8, 2014.
Licensing and support
MongoDB is available for free under the GNU Affero General Public License. The language drivers are available under an Apache License. In addition, MongoDB Inc. offers commercial licenses for MongoDB.
Some of the main features include:
- Ad hoc queries
- Any field in a MongoDB document can be indexed (indices in MongoDB are conceptually similar to those in RDBMSes). Secondary indices are also available.
- MongoDB provides high availability and increased throughput with replica sets. A replica set consists of two or more copies of the data. Each replica may act in the role of primary or secondary replica at any time. The primary replica performs all writes and reads by default. Secondary replicas maintain a copy of the data on the primary using built-in replication. When a primary replica fails, the replica set automatically conducts an election process to determine which secondary should become the primary. Secondaries can also perform read operations, but the data is eventually consistent by default.
- Load balancing
- MongoDB scales horizontally using sharding. The user chooses a shard key, which determines how the data in a collection will be distributed. The data is split into ranges (based on the shard key) and distributed across multiple shards. (A shard is a master with one or more slaves.)
- MongoDB can run over multiple servers, balancing the load and/or duplicating data to keep the system up and running in case of hardware failure. Automatic configuration is easy to deploy, and new machines can be added to a running database.
- File storage
- MongoDB can be used as a file system, taking advantage of load balancing and data replication features over multiple machines for storing files.
- This function, called GridFS, is included with MongoDB drivers and available with no difficulty for development languages (see "Language Support" for a list of supported languages). MongoDB exposes functions for file manipulation and content to developers. GridFS is used, for example, in plugins for NGINX and lighttpd. Instead of storing a file in a single document, GridFS divides a file into parts, or chunks, and stores each of those chunks as a separate document.
- In a multi-machine MongoDB system, files can be distributed and copied multiple times between machines transparently, thus effectively creating a load-balanced and fault-tolerant system.
- MapReduce can be used for batch processing of data and aggregation operations. The aggregation framework enables users to obtain the kind of results for which the SQL GROUP BY clause is used.
- Capped collections
- MongoDB supports fixed-size collections called capped collections. This type of collection maintains insertion order and, once the specified size has been reached, behaves like a circular queue.
Prior to November 2012, MongoDB's default consistency model ("write concern") returned that data had been written when it had only entered the client's outgoing queue, meaning that the default setup was brittle against client crashes. Changing the default to a safer model caused severe performance regressions, while concerns still remain that the safer models still leave data vulnerable in case of a single-machine failure.
MongoDB uses a readers-writer lock that allows concurrent read access to a database but exclusive write access to a single write operation. Before version 2.2, this lock was implemented on a per-mongod basis. Since version 2.2, the lock has been implemented at the database level. One approach to increase concurrency is to use sharding. In some situations, reads and writes will yield their locks. If MongoDB predicts a page is unlikely to be in memory, operations will yield their lock while the pages load. The use of lock yielding expanded greatly in 2.2.
Another criticism related to the limitations of MongoDB when used on 32-bit systems. In some cases, this was due to inherent memory limitations. MongoDB recommends 64-bit systems and that users provide sufficient RAM for their working set. Some users encounter issues when their working set exceeds available RAM and the system encounters page faults. MongoHQ, a provider of managed MongoDB infrastructure, recommends a scaling checklist for large systems.
Additionally, MongoDB provides very limited support for sorting on utf-8 encoded string data, which poses a substantial problem when storing non-English text. Specifically, MongoDB currently uses the memcmp function when sorting strings, which doesn't correctly handle utf-8 data under different locales.
MongoDB has official drivers for a variety of popular programming languages and development environments. Web programming language Opa also has built-in support for MongoDB, which is tightly integrated in the language and offers a type-safety layer on top of MongoDB. There are also a large number of unofficial or community-supported drivers for other programming languages and frameworks.
Management and graphical front-ends
In a MongoDB installation the following commands are available:
- Administrative information can also be accessed through a web interface, a simple webpage that serves information about the current server status. By default, this interface is 1000 ports above the database port (28017).
- mongostat is a command-line tool that displays a summary list of status statistics for a currently running MongoDB instance: how many inserts, updates, removes, queries, and commands were performed, as well as what percentage of the time the database was locked and how much memory it is using. This tool is similar to the UNIX/Linux vmstat utility.
- mongotop is a command-line tool providing a method to track the amount of time a MongoDB instance spends reading and writing data. mongotop provides statistics on the per-collection level. By default, mongotop returns values every second. This tool is similar to the UNIX/Linux top utility.
- mongosniff is a command-line tool providing a low-level tracing/sniffing view into database activity by monitoring (or "sniffing") network traffic going to and from MongoDB. mongosniff requires the Libpcap network library and is only available for Unix-like systems. A cross-platform alternative is the open source Wireshark packet analyzer which has full support for the MongoDB wire protocol.
- mongoimport, mongoexport
- mongoimport is a command-line utility to import content from a JSON, CSV, or TSV export created by mongoexport or potentially other third-party data exports.
- mongodump, mongorestore
- mongodump is a command-line utility for creating a binary export of the contents of a Mongo database; mongorestore can be used to reload a database dump.
According db-engines.com in March 2014, MongoDB is in the 5th place of the most popular all types databases management systems, and first place for NoSQL databases management systems.
Some of the prominent users of MongoDB include:
- MetLife uses MongoDB for “The Wall", a customer service application providing a "360-degree view" of MetLife customers.
- Craigslist stores over 2 billion records in MongoDB.
- SAP uses MongoDB in the SAP PaaS.
- Forbes stores articles and companies data in MongoDB.
- The New York Times uses MongoDB in its form-building application for photo submissions.
- Sourceforge uses MongoDB for its back-end storage pages.
- Codecademy uses MongoDB as the datastore for its online learning system.
- Shutterfly uses MongoDB for its photo platform. As of 2013, the photo platform stores 18 billion photos uploaded by Shutterfly's 7 million users.
- The Guardian uses MongoDB for its identity system.
- CERN uses MongoDB as the primary back-end for the Data Aggregation System for the Large Hadron Collider.
- Foursquare deploys MongoDB on Amazon AWS to store venues and user check-ins into venues.
- eBay uses MongoDB in the search suggestion and the internal Cloud Manager State Hub.
- MEAN, a solutions stack using MongoDB as the database
- Apache's Erlang-based CouchDB (open source)
- Couchbase (open source)
- Apache's Cassandra (open source)
- Apache's Java-based HBase and Accumulo (open source)
- Basho Riak (open source, Apache License 2.0)
- TokuMX high-performance distribution of MongoDB (open source)
- Apache's Java-based ElasticSearch (open source)
- ArangoDB (open source, Apache License 2.0)
- "10gen embraces what it created, becomes MongoDB Inc.". Gigaom. Retrieved 27 August 2013.
- "DB-Engines Ranking". Retrieved 8 September 2013.
- MongoDB daddy: My baby beats Google BigTable
- The MongoDB NoSQL Database Blog, The AGPL
- The MongoDB NoSQL Database Blog, MongoDB 1.4 Ready for Production
- MongoDB Support by 10gen
- MongoDB Developer Manual
- GridFS article on MongoDB Developer's Manual
- NGINX plugin for MongoDB source code
- lighttpd plugin for MongoDB source code
- Expertstown - MongoDB overview
- "Default Write Concern Change". MongoDB Release Notes. Retrieved April 17, 2014.
- Shekhar Gulati (December 8, 2011). "How MongoDB Different Write Concern Values Affect Performance On A Single Node?". Retrieved April 17, 2014.
- Emin Gün Sirer (January 29, 2013). "Broken by Design: MongoDB Fault Tolerance". Hacking, Distributed. Retrieved April 17, 2014.
- FAQ: Concurrency
- FAQ Concurrency - How Granular Are Locks
- FAQ Concurrency - How Does Sharding Affect Concurrency
- FAQ Concurrency - Do Operations Ever Yield the Lock
- 32-bit Limitations
- Does Everybody Hate MongoDB
- What is the Working Set
- Optimizing Your MongoDB Dataset
- MongoDB Jira ticket 1920
- "MongoDB Drivers and Client Libraries — MongoDB Ecosystem 2.2.2". Mongodb.org. Retrieved 2013-07-08.
- / (2012-11-27). "The database · MLstate/opalang Wiki · GitHub". Github.com. Retrieved 2013-07-08.
- mongo - The Interactive Shell
- HTTP Console
- mongostat Manual
- mongotop Manual
- mongosniff Manual
- mongoimport Manual
- mongoexport Manual
- mongodump Manual
- mongorestore Manual
- Production Deployments
- MetLife Uses NoSQL For Customer Service Breakthrough
- Lessons Learned from Migrating 2+ Billion Documents at Craigslist
- The Quest to Understand the Use of MongoDB in the SAP PaaS
- Supporting Distributed Global Workforce of Contributors with MongoDB
- NYT + MongoDB in Production
- Scaling SourceForge with MongoDB
- How Codecademy is Using MongoDB
- Real World NoSQL: MongoDB at Shutterfly
- Here's How We Think Of Shutterfly's Stock Value
- MongoDB at The Guardian
- Holy Large Hadron Collider, Batman!
- Experiences Deploying MongoDB on AWS
- MongoDB at eBay
- Banker, Kyle (March 28, 2011), MongoDB in Action (1st ed.), Manning, p. 375, ISBN 978-1-935182-87-0
- Chodorow, Kristina; Dirolf, Michael (September 23, 2010), MongoDB: The Definitive Guide (1st ed.), O'Reilly Media, p. 216, ISBN 978-1-4493-8156-1
- Pirtle, Mitch (March 3, 2011), MongoDB for Web Development (1st ed.), Addison-Wesley Professional, p. 360, ISBN 978-0-321-70533-4
- Hawkins, Tim; Plugge, Eelco; Membrey, Peter (September 26, 2010), The Definitive Guide to MongoDB: The NoSQL Database for Cloud and Desktop Computing (1st ed.), Apress, p. 350, ISBN 978-1-4302-3051-9
- Official website
- MongoDB Manual
- Designing for the Cloud at MIT Technology Review
- A vendor-independent comparison of NoSQL databases: Cassandra, HBase, MongoDB, Riak (NetworkWorld)
- MongoDB Cheat Sheet for Quick Reference