Apache Cassandra

Apache Cassandra
Original author(s) Avinash Lakshman, Prashant Malik
Developer(s) Apache Software Foundation
Initial release 2008
Stable release
3.9 / September 29, 2016 (2016-09-29)
Development status Active
Written in Java
Operating system Cross-platform
Available in English
Type Database
License Apache License 2.0
Website cassandra.apache.org
Helenos is a graphical user interface for Cassandra

Apache Cassandra is a free and open-source distributed 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.

Cassandra also places a high value on performance. In 2012, University of Toronto researchers studying NoSQL systems concluded that "In terms of scalability, there is a clear winner throughout our experiments. Cassandra achieves the highest throughput for the maximum number of nodes in all experiments" although "this comes at the price of high write and read latencies."[2]

History

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.[3] In March 2009 it became an Apache Incubator project.[4] On February 17, 2010 it graduated to a top-level project.[5]

Facebook developers named their database after the Trojan mythological prophet Cassandra - with classical allusions to a curse on an oracle.[6]

Releases after graduation include

Version Original release date Latest version Release date Status[16]
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 2013-09-03 2.0.17 2015-09-21 No longer supported
Older version, yet still supported: 2.1 2014-09-16 2.1.16 2016-10-10 Still supported
Current stable version: 2.2 2015-07-20 2.2.8 2016-09-28 Most stable release
Latest preview version of a future release: 3.0 2015-11-09 3.0.10 2016-11-16 Stable release
Latest preview version of a future release: 3.9 2015-12-08 3.9 2016-09-29 Latest release
Legend:
Old version
Older version, still supported
Latest version
Latest preview version
Future release

Main features

Decentralized
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.[17] 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
Read and write throughput both increase linearly as new machines are added, with 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
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.[18]
MapReduce support
Cassandra has Hadoop integration, with MapReduce support. There is support also for Apache Pig and Apache Hive.[19]
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). CQL adds an abstraction layer that hides implementation details of this structure and provides native syntaxes for collections and other common encodings.[20] Language drivers are available for Java (JDBC), Python (DBAPI2), Node.JS (Helenus), Go (gocql) and C++.[21]

Below an example of keyspace creation, including a column family in CQL 3.0:[22]

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

Cassandra is not row level consistent.[23]

Data model

Cassandra is essentially a hybrid between a key-value and a column-oriented (or tabular) database management system. Its data model is a partitioned row store with tunable consistency.[18] 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.[24] Other columns may be indexed separately from the primary key.[25]

Tables may be created, dropped, and altered at run-time without blocking updates and queries.[26]

Cassandra cannot do joins or subqueries. Rather, Cassandra emphasizes denormalization through features like collections.[27]

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.[28]

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.

Clustering

When the cluster for Apache Cassandra is designed, an important point is to select the right partitioner. Two partitioners exist:[29]

  1. OrderPreservingPartitioner (OPP): This partitioner distributes the key-value pairs in a natural way so that similar keys are not far away. The advantage is that fewer nodes have to be accessed. The drawback is the uneven distribution of the key-value pairs.
  2. RandomPartitioner (RP): This partitioner randomly distributes the key-value pairs over the network, resulting in a good load balancing. Compared to OPP, more nodes have to be accessed to get a number of keys.

Management and monitoring

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).[30] Nodetool also offers a number of commands to return Cassandra metrics pertaining to disk usage, latency, compaction, garbage collection, and more.[31] Additional metrics are available via JMX tools such as JConsole and via pluggable metrics reporters for external monitoring tools, which became available with Cassandra version 2.0.2.[32]

Prominent users

Cassandra is the most popular wide column store,[33] and in September 2014 surpassed Sybase to become the 9th most popular database, close behind Microsoft Access and SQLite.[34]

See also

Academic background

Commercial companies

Alternatives

References

  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. Rabl, Tilmann; Sadoghi, Mohammad; Jacobsen, Hans-Arno; Villamor, Sergio Gomez-; Mulero -, Victor Muntes; Mankovskii, Serge (2012-08-27). "Solving Big Data Challenges for Enterprise Application Performance Management" (PDF). VLDB. Retrieved 2013-07-25. In terms of scalability, there is a clear winner throughout our experiments. Cassandra achieves the highest throughput for the maximum number of nodes in all experiments... this comes at the price of high write and read latencies
  3. Hamilton, James (July 12, 2008). "Facebook Releases Cassandra as Open Source". Retrieved 2009-06-04.
  4. "Is this the new hotness now?". Mail-archive.com. 2009-03-02. Archived from the original on 25 April 2010. Retrieved 2010-03-29.
  5. "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.
  6. "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[.]
  7. "The Apache Software Foundation Announces Apache Cassandra Release 0.6  : The Apache Software Foundation Blog". Retrieved 5 January 2016.
  8. "The Apache Software Foundation Announces Apache Cassandra 0.7 : The Apache Software Foundation Blog". Retrieved 5 January 2016.
  9. Eric Evans. "[Cassandra-user] [RELEASE] 0.8.0". Retrieved 5 January 2016.
  10. "Cassandra 1.0.0. Is Ready for the Enterprise". InfoQ. Retrieved 5 January 2016.
  11. "The Apache Software Foundation Announces Apache Cassandra™ v1.1 : The Apache Software Foundation Blog". Retrieved 5 January 2016.
  12. "The Apache Software Foundation Announces Apache Cassandra™ v1.2 : The Apache Software Foundation Blog". apache.org. Retrieved 11 December 2014.
  13. Eric Evans. "[Cassandra-User] [RELEASE] Apache Cassandra 2.0.4". qnalist.com. Retrieved 11 December 2014.
  14. Sylvain Lebresne (10 September 2014). "[VOTE SUCCESS] Release Apache Cassandra 2.1.0". mail-archive.com. Retrieved 11 December 2014.
  15. "Cassandra 2.2, 3.0, and beyond". 16 June 2015. Retrieved 22 April 2016.
  16. "Cassandra Server Releases". cassandra.apache.org. Retrieved 15 December 2015.
  17. "Deploying Cassandra across Multiple Data Centers". DataStax. Retrieved 11 December 2014.
  18. 1 2 DataStax (2013-01-15). "About data consistency". Retrieved 2013-07-25.
  19. "Hadoop Support" article on Cassandra's wiki
  20. Intellipaat. "Cassandra Tutorial". Intellipaat. Retrieved 5 January 2016.
  21. "DataStax C/C++ Driver for Apache Cassandra". DataStax. Retrieved 15 December 2014.
  22. "CQL". Retrieved 5 January 2016.
  23. "WAT - Cassandra: Row level consistency #$@&%*! - datanerds.io". datanerds.io. Retrieved 28 November 2016.
  24. Ellis, Jonathan (2012-02-15). "Schema in Cassandra 1.1". DataStax. Retrieved 2013-07-25.
  25. Ellis, Jonathan (2010-12-03). "What's new in Cassandra 0.7: Secondary indexes". DataStax. Retrieved 2013-07-25.
  26. Ellis, Jonathan (2012-03-02). "The Schema Management Renaissance in Cassandra 1.1". DataStax. Retrieved 2013-07-25.
  27. Lebresne, Sylvain (2012-08-05). "Coming in 1.2: Collections support in CQL3". DataStax. Retrieved 2013-07-25.
  28. DataStax. "Apache Cassandra 0.7 Documentation - Column Families". Apache Cassandra 0.7 Documentation. Retrieved 29 October 2012.
  29. Williams, Dominic. "Cassandra: RandomPartitioner vs OrderPreservingPartitioner". http://wordpress.com/: WordPress.com. Retrieved 2011-03-23. When building a Cassandra cluster, the “key” question (sorry, that’s weak) is whether to use the RandomPartitioner (RP), or the OrdengPartitioner (OPP). These control how your data is distributed over your nodes. Once you have chosen your partitioner, you cannot change without wiping your data, so think carefully! The problem with OPP: If the distribution of keys used by individual column families is different, their sets of keys will not fall evenly across the ranges assigned to nodes. Thus nodes will end up storing preponderances of keys (and the associated data) corresponding to one column family or another. If as is likely column families store differing quantities of data with their keys, or store data accessed according to differing usage patterns, then some nodes will end up with disproportionately more data than others, or serving more “hot” data than others.
  30. "NodeTool". Cassandra Wiki. Retrieved 5 January 2016.
  31. "How to monitor Cassandra performance metrics". Datadog. Retrieved 5 January 2016.
  32. "Metrics". Cassandra Wiki. Retrieved 5 January 2016.
  33. DB-Engines. "DB-Engines Ranking of Wide Column Stores".
  34. DB-Engines. "DB-Engines Ranking".
  35. "@WalmartLabs". walmartlabs.com. Retrieved 11 December 2014.
  36. Luca Martinetti: Apple runs more than 100k [production] Cassandra nodes. on Twitter
  37. "Datastores on Appscale".
  38. "Top Cassandra Summit Sessions For Advanced Cassandra Users".
  39. "Multi-Tenancy in Cassandra at BlackRock".
  40. "A Persistent Back-End for the ATLAS Online Information Service (P-BEAST)".
  41. "Re: Cassandra users survey". Mail-archive.com. 2009-11-21. Archived from the original on 17 April 2010. Retrieved 2010-03-29.
  42. 4 Months with Cassandra, a love story |Cloudkick, manage servers better
  43. Finley, Klint (2011-02-18). "This Week in Consolidation: HP Buys Vertica, Constant Contact Buys Bantam Live and More". Read Write Enterprise.
  44. Eure, Ian. "Looking to the future with Cassandra".
  45. Quinn, John. "Saying Yes to NoSQL; Going Steady with Cassandra". Archived from the original on 2012-03-07.
  46. Schonfeld, Erick. "As Digg Struggles, VP Of Engineering Is Shown The Door".
  47. "Is Cassandra to Blame for Digg v4's Failures?".
  48. "Niet compatibele browser". Facebook. Retrieved 2010-03-29.
  49. 1 2 Muthukkaruppan, Kannan. "The Underlying Technology of Messages".
  50. Rick Branson (2013-06-26). "Cassandra at Instagram". DataStax. Retrieved 2013-07-25.
  51. Cozzi, Martin (2011-08-31). "Cassandra at Formspring".
  52. "BlueRunner: Building an Email Service in the Cloud" (PDF). ieee.org. 2009-07-20. Retrieved 2010-03-29.
  53. "Mahalo.com powered by Apache Cassandra™" (PDF). DataStax.com. Santa Clara, CA, USA: DataStax. 2012-04-10. Retrieved 2014-06-13.
  54. Watch Cassandra at Mahalo.com |DataStax Episodes |Blip
  55. Cockcroft, Adrian (2011-07-11). "Migrating Netflix from Datacenter Oracle to Global Cassandra". slideshare.net. Retrieved 2014-06-13.
  56. Izrailevsky, Yury (2011-01-28). "NoSQL at Netflix".
  57. "Nutanix Bible".
  58. Ooyala (2010-05-18). "Designing a Scalable Database for Online Video Analytics" (PDF). DataStax.com. Mountain View CA, USA. Retrieved 2014-06-14.
  59. Mainstay LLC (2013-11-11). "DataStax Case Study of Openwave Messaging" (PDF). DataStax.com. Santa Clara, CA, USA: DataStax. Retrieved 2014-06-15.
  60. Ad Serving Technology - Advanced Optimization, Forecasting, & Targeting |OpenX
  61. Smalley, Preston (2011-03-20). "An important milestone - and it's only the beginning!".
  62. "Plexistor for Apache Cassandra".
  63. Grigorik, Ilya (2011-03-29). "Webpulp TV: Scaling PostRank with Ilya Grigorik".
  64. "Hadoop and Cassandra (at Rackspace)". Stu Hood. 2010-04-23. Retrieved 2011-09-01.
  65. 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.
  66. 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.
  67. Pattishall, Dathan Vance (2011-03-23). "Cassandra is my NoSQL Solution but".
  68. "Cassandra at SoundCloud".
  69. http://www.talentica.com. Missing or empty |title= (help)
  70. Popescu, Alex. "Cassandra @ Twitter: An Interview with Ryan King". myNoSQL. Archived from the original on 1 March 2010. Retrieved 2010-03-29.
  71. Babcock, Charles. "Twitter Drops MySQL For Cassandra - Cloud databases". InformationWeek. Archived from the original on 2 April 2010. Retrieved 2010-03-29.
  72. King, Ryan (2010-07-10). "Cassandra at Twitter Today". blog.twitter.com. San Francisco, CA, USA: Twitter. Retrieved 2014-06-20.
  73. Onnen, Erik. "From 100s to 100s of Millions".
  74. Wicke, Gabriel. "Wikimedia REST content API is now available in beta".

Bibliography

External links

Wikimedia Commons has media related to Apache Cassandra.
Wikiversity has learning materials about Big Data/Cassandra
This article is issued from Wikipedia - version of the 12/3/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.