MongoDB

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MongoDB
MongoDB Logo.png
Developer(s) MongoDB Inc.
Initial release 2009 (2009)
Stable release 2.4.9 / 10 January 2014 (2014-01-10)
Preview release 2.6.0-rc2 / 21 March 2014 (2014-03-21)
Development status Active
Written in C++
Operating system Cross-platform
Available in English
Type Document-oriented database
License GNU AGPL v3.0 (drivers: Apache license)
Website www.mongodb.org

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.[1] 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.[2]

History[edit]

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.[3] In 2009, MongoDB was open sourced as a stand-alone product[4] with an AGPL license.

From version 1.4 (March 2010), MongoDB has been considered production ready.[5]

The latest stable version, 2.6, was released on April 8, 2014.

Licensing and support[edit]

MongoDB is available for free under the GNU Affero General Public License.[4] The language drivers are available under an Apache License. In addition, MongoDB Inc. offers commercial licenses for MongoDB.[6]

Main features[edit]

Some of the main features include:[7]

Ad hoc queries
MongoDB supports search by field, range queries, regular expression searches. Queries can return specific fields of documents and also include user-defined JavaScript functions.
Indexing
Any field in a MongoDB document can be indexed (indices in MongoDB are conceptually similar to those in RDBMSes). Secondary indices are also available.
Replication
MongoDB provides high availability and increased throughput with replica sets.[8] 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.[9] 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,[10] 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[11] and lighttpd.[12] 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.[13]
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.
Aggregation
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.
Server-side JavaScript execution
JavaScript can be used in queries, aggregation functions (such as MapReduce), and sent directly to the database to be executed.
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.

Criticisms[edit]

Prior to November 2012,[14] 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[15], while concerns still remain that the safer models still leave data vulnerable in case of a single-machine failure.[16]

MongoDB uses a readers-writer lock that allows concurrent read access to a database but exclusive write access to a single write operation.[17] 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.[18] One approach to increase concurrency is to use sharding.[19] 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.[20]

Another criticism related to the limitations of MongoDB when used on 32-bit systems.[21] In some cases, this was due to inherent memory limitations.[22] MongoDB recommends 64-bit systems and that users provide sufficient RAM for their working set.[23] 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.[24]

Additionally, MongoDB provides very limited support for sorting on utf-8 encoded string data,[25] 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.

Language support[edit]

MongoDB has official drivers for a variety of popular programming languages and development environments.[26] 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.[27] There are also a large number of unofficial or community-supported drivers for other programming languages and frameworks.[26]

Management and graphical front-ends[edit]

MongoDB tools[edit]

In a MongoDB installation the following commands are available:

mongo
MongoDB offers an interactive shell called mongo,[28] which lets developers view, insert, remove, and update data in their databases, as well as get replication information, set up sharding, shut down servers, execute JavaScript, and more.
Administrative information can also be accessed through a web interface,[29] a simple webpage that serves information about the current server status. By default, this interface is 1000 ports above the database port (28017).
mongostat
mongostat[30] 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
mongotop[31] 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
mongosniff[32] 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[33] is a command-line utility to import content from a JSON, CSV, or TSV export created by mongoexport[34] or potentially other third-party data exports.
mongodump, mongorestore
mongodump[35] is a command-line utility for creating a binary export of the contents of a Mongo database; mongorestore[36] can be used to reload a database dump.

Popularity[edit]

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.

Production deployments[edit]

Some of the prominent users of MongoDB include:[37]

  • MetLife uses MongoDB for “The Wall", a customer service application providing a "360-degree view" of MetLife customers.[38]
  • Craigslist stores over 2 billion records in MongoDB.[39]
  • SAP uses MongoDB in the SAP PaaS.[40]
  • Forbes stores articles and companies data in MongoDB.[41]
  • The New York Times uses MongoDB in its form-building application for photo submissions.[42]
  • Sourceforge uses MongoDB for its back-end storage pages.[43]
  • Codecademy uses MongoDB as the datastore for its online learning system.[44]
  • Shutterfly uses MongoDB for its photo platform. As of 2013, the photo platform stores 18 billion photos uploaded by Shutterfly's 7 million users.[45][46]
  • The Guardian uses MongoDB for its identity system.[47]
  • CERN uses MongoDB as the primary back-end for the Data Aggregation System for the Large Hadron Collider.[48]
  • Foursquare deploys MongoDB on Amazon AWS to store venues and user check-ins into venues.[49]
  • eBay uses MongoDB in the search suggestion and the internal Cloud Manager State Hub.[50]

See also[edit]

References[edit]

  1. ^ "10gen embraces what it created, becomes MongoDB Inc.". Gigaom. Retrieved 27 August 2013. 
  2. ^ "DB-Engines Ranking". Retrieved 8 September 2013. 
  3. ^ MongoDB daddy: My baby beats Google BigTable
  4. ^ a b The MongoDB NoSQL Database Blog, The AGPL
  5. ^ The MongoDB NoSQL Database Blog, MongoDB 1.4 Ready for Production
  6. ^ MongoDB Support by 10gen
  7. ^ MongoDB Developer Manual
  8. ^ [1]
  9. ^ [2]
  10. ^ GridFS article on MongoDB Developer's Manual
  11. ^ NGINX plugin for MongoDB source code
  12. ^ lighttpd plugin for MongoDB source code
  13. ^ Expertstown - MongoDB overview
  14. ^ "Default Write Concern Change". MongoDB Release Notes. Retrieved April 17, 2014. 
  15. ^ Shekhar Gulati (December 8, 2011). "How MongoDB Different Write Concern Values Affect Performance On A Single Node?". Retrieved April 17, 2014. 
  16. ^ Emin Gün Sirer (January 29, 2013). "Broken by Design: MongoDB Fault Tolerance". Hacking, Distributed. Retrieved April 17, 2014. 
  17. ^ FAQ: Concurrency
  18. ^ FAQ Concurrency - How Granular Are Locks
  19. ^ FAQ Concurrency - How Does Sharding Affect Concurrency
  20. ^ FAQ Concurrency - Do Operations Ever Yield the Lock
  21. ^ 32-bit Limitations
  22. ^ Does Everybody Hate MongoDB
  23. ^ What is the Working Set
  24. ^ Optimizing Your MongoDB Dataset
  25. ^ MongoDB Jira ticket 1920
  26. ^ a b "MongoDB Drivers and Client Libraries — MongoDB Ecosystem 2.2.2". Mongodb.org. Retrieved 2013-07-08. 
  27. ^ / (2012-11-27). "The database · MLstate/opalang Wiki · GitHub". Github.com. Retrieved 2013-07-08. 
  28. ^ mongo - The Interactive Shell
  29. ^ HTTP Console
  30. ^ mongostat Manual
  31. ^ mongotop Manual
  32. ^ mongosniff Manual
  33. ^ mongoimport Manual
  34. ^ mongoexport Manual
  35. ^ mongodump Manual
  36. ^ mongorestore Manual
  37. ^ Production Deployments
  38. ^ MetLife Uses NoSQL For Customer Service Breakthrough
  39. ^ Lessons Learned from Migrating 2+ Billion Documents at Craigslist
  40. ^ The Quest to Understand the Use of MongoDB in the SAP PaaS
  41. ^ Supporting Distributed Global Workforce of Contributors with MongoDB
  42. ^ NYT + MongoDB in Production
  43. ^ Scaling SourceForge with MongoDB
  44. ^ How Codecademy is Using MongoDB
  45. ^ Real World NoSQL: MongoDB at Shutterfly
  46. ^ Here's How We Think Of Shutterfly's Stock Value
  47. ^ MongoDB at The Guardian
  48. ^ Holy Large Hadron Collider, Batman!
  49. ^ Experiences Deploying MongoDB on AWS
  50. ^ MongoDB at eBay

Bibliography[edit]

External links[edit]