Apache Cassandra

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Apache Cassandra
Cassandra logo
Original author(s) Avinash Lakshman, Prashant Malik
Developer(s) Apache Software Foundation
Initial release 07/2008
Stable release
3.11.2 / February 19, 2018 (2018-02-19)
Repository Edit this at Wikidata
Written in Java
Operating system Cross-platform
Available in English
Type NoSQL Database, data store
License Apache License 2.0
Website cassandra.apache.org

Apache Cassandra is a free and open-source distributed wide column store NoSQL database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. Cassandra offers robust support for clusters spanning multiple datacenters,[1] with asynchronous masterless replication allowing low latency operations for all clients.

History[edit]

Avinash Lakshman, one of the authors of Amazon's Dynamo, and Prashant Malik initially developed Cassandra at Facebook to power the Facebook inbox search feature. Facebook released Cassandra as an open-source project on Google code in July 2008.[2] In March 2009 it became an Apache Incubator project.[3] On February 17, 2010 it graduated to a top-level project.[4]

Facebook developers named their database after the Trojan mythological prophet Cassandra - with classical allusions to a curse on an oracle.[5]

Releases[edit]

Releases after graduation include

  • 0.6, released Apr 12 2010, added support for integrated caching, and Apache Hadoop MapReduce[6]
  • 0.7, released Jan 08 2011, added secondary indexes and online schema changes[7]
  • 0.8, released Jun 2 2011, added the Cassandra Query Language (CQL), self-tuning memtables, and support for zero-downtime upgrades[8]
  • 1.0, released Oct 17 2011, added integrated compression, leveled compaction, and improved read-performance[9]
  • 1.1, released Apr 23 2012, added self-tuning caches, row-level isolation, and support for mixed ssd/spinning disk deployments[10]
  • 1.2, released Jan 2 2013, added clustering across virtual nodes, inter-node communication, atomic batches, and request tracing[11]
  • 2.0, released September 4, 2013; 4 years ago (2013-09-04), added lightweight transactions (based on the Paxos consensus protocol), triggers, improved compactions
  • 2.1 released Sep 10 2014 [12]
  • 2.2 released July 20, 2015
  • 3.0 released November 11, 2015
  • 3.1 through 3.10 releases were monthly releases using a tick-tock-like release model, with even-numbered releases providing both new features and bug fixes while odd-numbered releases will include bug fixes only.[13]
  • 3.11 released June 23, 2017 as a stable 3.11 release series and bug fix from the last tick-tock feature release.
Version Original release date Latest version Release date Status[14]
Old version, no longer supported: 0.6 2010-04-12 0.6.13 2011-04-18 No longer supported
Old version, no longer supported: 0.7 2011-01-10 0.7.10 2011-10-31 No longer supported
Old version, no longer supported: 0.8 2011-06-03 0.8.10 2012-02-13 No longer supported
Old version, no longer supported: 1.0 2011-10-18 1.0.12 2012-10-04 No longer supported
Old version, no longer supported: 1.1 2012-04-24 1.1.12 2013-05-27 No longer supported
Old version, no longer supported: 1.2 2013-01-02 1.2.19 2014-09-18 No longer supported
Old version, no longer supported: 2.0 September 3, 2013; 4 years ago (2013-09-03) 2.0.17 2015-09-21 No longer supported
Older version, yet still supported: 2.1 2014-09-16 2.1.20 2018-02-16 Still supported, critical fixes only
Older version, yet still supported: 2.2 2015-07-20 2.2.12 2018-02-16 Still supported
Older version, yet still supported: 3.0 2015-11-09 3.0.16 2018-02-19 Still supported
Current stable version: 3.11 2017-06-23 3.11.2 2018-02-10 Latest release
Legend:
Old version
Older version, still supported
Latest version
Latest preview version
Future release

Main features[edit]

Distributed
Every node in the cluster has the same role. There is no single point of failure. Data is distributed across the cluster (so each node contains different data), but there is no master as every node can service any request.
Supports replication and multi data center replication
Replication strategies are configurable.[15] Cassandra is designed as a distributed system, for deployment of large numbers of nodes across multiple data centers. Key features of Cassandra’s distributed architecture are specifically tailored for multiple-data center deployment, for redundancy, for failover and disaster recovery.
Scalability
Designed to have read and write throughput both increase linearly as new machines are added, with the aim of no downtime or interruption to applications.
Fault-tolerant
Data is automatically replicated to multiple nodes for fault-tolerance. Replication across multiple data centers is supported. Failed nodes can be replaced with no downtime.
Tunable consistency
Cassandra is typically classified as an AP system, meaning that availability and partition tolerance are generally considered to be more important than consistency in Cassandra[16], Writes and reads offer a tunable level of consistency, all the way from "writes never fail" to "block for all replicas to be readable", with the quorum level in the middle.[17]
MapReduce support
Cassandra has Hadoop integration, with MapReduce support. There is support also for Apache Pig and Apache Hive.[18]
Query language
Cassandra introduced the Cassandra Query Language (CQL). CQL is a simple interface for accessing Cassandra, as an alternative to the traditional Structured Query Language (SQL).

Cassandra Query Language[edit]

Cassandra introduced the Cassandra Query Language (CQL). CQL is a simple interface for accessing Cassandra, as an alternative to the traditional Structured Query Language (SQL). CQL adds an abstraction layer that hides implementation details of this structure and provides native syntaxes for collections and other common encodings. Language drivers are available for Java (JDBC), Python (DBAPI2), Node.JS (Helenus), Go (gocql) and C++.[19]

Below an example of keyspace creation, including a column family in CQL 3.0:[20]

CREATE KEYSPACE MyKeySpace
  WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 3 };

USE MyKeySpace;

CREATE COLUMNFAMILY MyColumns (id text, Last text, First text, PRIMARY KEY(id));

INSERT INTO MyColumns (id, Last, First) VALUES ('1', 'Doe', 'John');

SELECT * FROM MyColumns;

Which gives:

 id | first | last
----+-------+------
  1 |  John |  Doe

(1 rows)

Known issues[edit]

Up to Cassandra 1.0, Cassandra was not row level consistent,[21] meaning that inserts and updates into the table that affect the same row that are processed at approximately the same time may affect the non-key columns in inconsistent ways. One update may affect one column while another affects the other, resulting in sets of values within the row that were never specified or intended. Cassandra 1.1 solved this issue by introducing row-level isolation.[22]

Data model[edit]

Cassandra is wide column store, and, as such, essentially a hybrid between a key-value and a tabular database management system. Its data model is a partitioned row store with tunable consistency.[17] Rows are organized into tables; the first component of a table's primary key is the partition key; within a partition, rows are clustered by the remaining columns of the key.[23] Other columns may be indexed separately from the primary key.[24]

Tables may be created, dropped, and altered at run-time without blocking updates and queries.[25]

Cassandra cannot do joins or subqueries. Rather, Cassandra emphasizes denormalization through features like collections.[26]

A column family (called "table" since CQL 3) resembles a table in an RDBMS. Column families contain rows and columns. Each row is uniquely identified by a row key. Each row has multiple columns, each of which has a name, value, and a timestamp. Unlike a table in an RDBMS, different rows in the same column family do not have to share the same set of columns, and a column may be added to one or multiple rows at any time.[27]

Each key in Cassandra corresponds to a value which is an object. Each key has values as columns, and columns are grouped together into sets called column families. Thus, each key identifies a row of a variable number of elements. These column families could be considered then as tables. A table in Cassandra is a distributed multi dimensional map indexed by a key. Furthermore, applications can specify the sort order of columns within a Super Column or Simple Column family.

Management and monitoring[edit]

Cassandra is a Java-based system that can be managed and monitored via Java Management Extensions (JMX). The JMX-compliant nodetool utility, for instance, can be used to manage a Cassandra cluster (adding nodes to a ring, draining nodes, decommissioning nodes, and so on).[28] Nodetool also offers a number of commands to return Cassandra metrics pertaining to disk usage, latency, compaction, garbage collection, and more.[29]

Since Cassandra 2.0.2 in 2013, measures of several metrics are produced via the Dropwizard metrics framework[30], and may be queried via JMX using tools such as JConsole or passed to external monitoring systems via Dropwizard-compatible reporter plugins[31].

Notable applications[edit]

According to DB-Engines ranking, Cassandra is the most popular wide column store,[32] and in September 2014 become the 9th most popular database.[33]

  • Apple uses 100,000 Cassandra nodes, as revealed at Cassandra Summit San Francisco 2015,[34] although it has not elaborated for which products, services or features.
  • AppScale uses Cassandra as a back-end for Google App Engine applications[35]
  • BlackRock uses Cassandra in their Aladdin investment management platform[36][37]
  • CERN used Cassandra-based prototype for its ATLAS experiment to archive the online DAQ system's monitoring information[38]
  • Cisco's WebEx uses Cassandra to store user feed and activity in near real time.[39]
  • Constant Contact uses Cassandra in their email and social media marketing applications.[40] Over 200 nodes are deployed.
  • Digg, a social news website, announced on Sep 9th, 2009 that it is rolling out its use of Cassandra[41] and confirmed this on March 8, 2010.[42] TechCrunch has since linked Cassandra to Digg v4 reliability criticisms and recent company struggles.[43] Lead engineers at Digg later rebuked these criticisms as red herring and blamed a lack of load testing.[44]
  • Formspring uses Cassandra to count responses, as well as store Social Graph data (followers, following, blockers, blocking) for 26 Million accounts with 10 million responses a day[45]
  • Globo.com uses Cassandra as a back-end database for their streaming services[46]
  • Mahalo.com uses Cassandra to record user activity logs and topics for their Q&A website[47][48]
  • Netflix uses Cassandra as their back-end database for their streaming services[49][50]
  • Nutanix appliances use Cassandra to store metadata and stats.[51]
  • Ooyala built a scalable, flexible, real-time analytics engine using Cassandra[52]
  • Openwave uses Cassandra as a distributed database and as a distributed storage mechanism for their next generation messaging platform[53]
  • OpenX is running over 130 nodes on Cassandra for their OpenX Enterprise product to store and replicate advertisements and targeting data for ad delivery[54]
  • Rackspace uses Cassandra internally.[55]
  • Reddit switched to Cassandra from memcacheDB on March 12, 2010[56] and experienced some problems in May of that year due to insufficient nodes in their cluster.[57]
  • RockYou uses Cassandra to record every single click for 50 million Monthly Active Users in real-time for their online games[58]
  • SoundCloud uses Cassandra to store the dashboard of their users[59]
  • Uber uses Cassandra to store around 10,000 features in their daily updated company-wide Feature Store for low-latency access during live model predictions[60]
  • Urban Airship uses Cassandra with the mobile service hosting for over 160 million application installs across 80 million unique devices[61]

See also[edit]

References[edit]

  1. ^ Casares, Joaquin (2012-11-05). "Multi-datacenter Replication in Cassandra". DataStax. Retrieved 2013-07-25. Cassandra’s innate datacenter concepts are important as they allow multiple workloads to be run across multiple datacenters… 
  2. ^ Hamilton, James (July 12, 2008). "Facebook Releases Cassandra as Open Source". Retrieved 2009-06-04. 
  3. ^ "Is this the new hotness now?". Mail-archive.com. 2009-03-02. Archived from the original on 25 April 2010. Retrieved 2010-03-29. 
  4. ^ "Cassandra is an Apache top level project". Mail-archive.com. 2010-02-18. Archived from the original on 28 March 2010. Retrieved 2010-03-29. 
  5. ^ "The meaning behind the name of Apache Cassandra". Retrieved 2016-07-19. Apache Cassandra is named after the Greek mythological prophet Cassandra. [...] Because of her beauty Apollo granted her the ability of prophecy. [...] When Cassandra of Troy refused Apollo, he put a curse on her so that all of her and her descendants' predictions would not be believed. [...] Cassandra is the cursed Oracle[.] 
  6. ^ "The Apache Software Foundation Announces Apache Cassandra Release 0.6 : The Apache Software Foundation Blog". Retrieved 5 January 2016. 
  7. ^ "The Apache Software Foundation Announces Apache Cassandra 0.7 : The Apache Software Foundation Blog". Retrieved 5 January 2016. 
  8. ^ Eric Evans. "[Cassandra-user] [RELEASE] 0.8.0". Retrieved 5 January 2016. 
  9. ^ "Cassandra 1.0.0. Is Ready for the Enterprise". InfoQ. Retrieved 5 January 2016. 
  10. ^ "The Apache Software Foundation Announces Apache Cassandra™ v1.1 : The Apache Software Foundation Blog". Retrieved 5 January 2016. 
  11. ^ "The Apache Software Foundation Announces Apache Cassandra™ v1.2 : The Apache Software Foundation Blog". apache.org. Retrieved 11 December 2014. 
  12. ^ Sylvain Lebresne (10 September 2014). "[VOTE SUCCESS] Release Apache Cassandra 2.1.0". mail-archive.com. Retrieved 11 December 2014. 
  13. ^ "Cassandra 2.2, 3.0, and beyond". 16 June 2015. Retrieved 22 April 2016. 
  14. ^ "Cassandra Server Releases". cassandra.apache.org. Retrieved 15 December 2015. 
  15. ^ "Deploying Cassandra across Multiple Data Centers". DataStax. Retrieved 11 December 2014. 
  16. ^ "The CAP Theorem - Learn Cassandra". teddyma.gitbooks.io. 
  17. ^ a b DataStax (2013-01-15). "About data consistency". Retrieved 2013-07-25. 
  18. ^ "Hadoop Support" article on Cassandra's wiki
  19. ^ "DataStax C/C++ Driver for Apache Cassandra". DataStax. Retrieved 15 December 2014. 
  20. ^ "CQL". Retrieved 5 January 2016. 
  21. ^ "WAT - Cassandra: Row level consistency #$@&%*! - datanerds.io". datanerds.io. Retrieved 28 November 2016. 
  22. ^ Lebresne, Sylvain (2012-02-21). "Coming up in Cassandra 1.1: Row Level Isolation". DataStax: always-on data platform | NoSQL | Apache Cassandra. Retrieved 2018-07-18. 
  23. ^ Ellis, Jonathan (2012-02-15). "Schema in Cassandra 1.1". DataStax. Retrieved 2013-07-25. 
  24. ^ Ellis, Jonathan (2010-12-03). "What's new in Cassandra 0.7: Secondary indexes". DataStax. Retrieved 2013-07-25. 
  25. ^ Ellis, Jonathan (2012-03-02). "The Schema Management Renaissance in Cassandra 1.1". DataStax. Retrieved 2013-07-25. 
  26. ^ Lebresne, Sylvain (2012-08-05). "Coming in 1.2: Collections support in CQL3". DataStax. Retrieved 2013-07-25. 
  27. ^ DataStax. "Apache Cassandra 0.7 Documentation - Column Families". Apache Cassandra 0.7 Documentation. Retrieved 29 October 2012. 
  28. ^ "NodeTool". Cassandra Wiki. Retrieved 5 January 2016. 
  29. ^ "How to monitor Cassandra performance metrics". Datadog. Retrieved 5 January 2016. 
  30. ^ "Metrics". Cassandra Wiki. Retrieved 5 January 2016. 
  31. ^ "Monitoring". Cassandra Documentation. Retrieved 1 February 2018. 
  32. ^ DB-Engines. "DB-Engines Ranking of Wide Column Stores". 
  33. ^ DB-Engines. "DB-Engines Ranking". 
  34. ^ Luca Martinetti: Apple runs more than 100k [production] Cassandra nodes. on Twitter
  35. ^ "Datastores on Appscale". 
  36. ^ "Top Cassandra Summit Sessions For Advanced Cassandra Users". 
  37. ^ "Multi-Tenancy in Cassandra at BlackRock". 
  38. ^ "A Persistent Back-End for the ATLAS Online Information Service (P-BEAST)". 
  39. ^ "Re: Cassandra users survey". Mail-archive.com. 2009-11-21. Archived from the original on 17 April 2010. Retrieved 2010-03-29. 
  40. ^ Finley, Klint (2011-02-18). "This Week in Consolidation: HP Buys Vertica, Constant Contact Buys Bantam Live and More". Read Write Enterprise. 
  41. ^ Eure, Ian. "Looking to the future with Cassandra". 
  42. ^ Quinn, John. "Saying Yes to NoSQL; Going Steady with Cassandra". Archived from the original on 2012-03-07. 
  43. ^ Schonfeld, Erick. "As Digg Struggles, VP Of Engineering Is Shown The Door". 
  44. ^ "Is Cassandra to Blame for Digg v4's Failures?". 
  45. ^ Cozzi, Martin (2011-08-31). "Cassandra at Formspring". 
  46. ^ Nunes, Alexandre (2016-06-22). "Cassandra At The Heart Of Globo's Live Streaming Platform". 
  47. ^ "Mahalo.com powered by Apache Cassandra™" (PDF). DataStax.com. Santa Clara, CA, USA: DataStax. 2012-04-10. Retrieved 2014-06-13. 
  48. ^ Watch Cassandra at Mahalo.com |DataStax Episodes |Blip Archived 2011-12-10 at the Wayback Machine.
  49. ^ Cockcroft, Adrian (2011-07-11). "Migrating Netflix from Datacenter Oracle to Global Cassandra". slideshare.net. Retrieved 2014-06-13. 
  50. ^ Izrailevsky, Yury (2011-01-28). "NoSQL at Netflix". 
  51. ^ "Nutanix Bible". 
  52. ^ Ooyala (2010-05-18). "Designing a Scalable Database for Online Video Analytics" (PDF). DataStax.com. Mountain View CA, USA. Retrieved 2014-06-14. 
  53. ^ Mainstay LLC (2013-11-11). "DataStax Case Study of Openwave Messaging" (PDF). DataStax.com. Santa Clara, CA, USA: DataStax. Retrieved 2014-06-15. 
  54. ^ Ad Serving Technology - Advanced Optimization, Forecasting, & Targeting |OpenX Archived 2011-10-07 at the Wayback Machine.
  55. ^ "Hadoop and Cassandra (at Rackspace)". Stu Hood. 2010-04-23. Retrieved 2011-09-01. 
  56. ^ david [ketralnis] (2010-03-12). "what's new on reddit: She who entangles men". blog.reddit. Archived from the original on 25 March 2010. Retrieved 2010-03-29. 
  57. ^ Posted by the reddit admins at (2010-05-11). "blog.reddit -- what's new on reddit: reddit's May 2010 "State of the Servers" report". blog.reddit. Archived from the original on 14 May 2010. Retrieved 2010-05-16. 
  58. ^ Pattishall, Dathan Vance (2011-03-23). "Cassandra is my NoSQL Solution but". 
  59. ^ "Cassandra at SoundCloud". 
  60. ^ Hermann, Jeremy. "Meet Michelangelo: Uber's Machine Learning Platform". 
  61. ^ Onnen, Erik. "From 100s to 100s of Millions". 

Bibliography[edit]

External links[edit]