Jump to content

Apache Cassandra

From Wikipedia, the free encyclopedia
This is an old revision of this page, as edited by Cononsense (talk | contribs) at 15:01, 9 December 2024 (add defining characteristic to lede, and add ref to Cassandra: The Definitive Guide). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Apache Cassandra
Original author(s)Avinash Lakshman, Prashant Malik / Facebook
Developer(s)Apache Software Foundation
Initial releaseJuly 2008; 16 years ago (2008-07)
Stable release
5.0.2[1] Edit this on Wikidata / October 19, 2024; 7 months ago (October 19, 2024)
Repository
Written inJava
Operating systemCross-platform
Available inEnglish
TypeNoSQL Database, data store
LicenseApache License 2.0
Websitecassandra.apache.org Edit this on Wikidata

Apache Cassandra is a free and open-source database management system designed to handle large volumes of data across multiple commodity servers. The system prioritizes availability and scalability over consistency, making it particularly suited for systems with high write throughput requirements due to its LSM tree indexing storage layer.[2] Cassandra supports computer clusters which may span multiple data centers,[3] featuring asynchronous and masterless replication. It enables low-latency operations for all clients and incorporates Amazon's Dynamo distributed storage and replication techniques, combined with Google's Bigtable data storage engine model.[4]

History

Avinash Lakshman, a co-author of Amazon's Dynamo, and Prashant Malik developed Cassandra at Facebook to support the inbox search functionality. Facebook released Cassandra as open-source software on Google Code in July 2008.[5] In March 2009, it became an Apache Incubator project[6] and on February 17, 2010, it graduated to a top-level project.[7]

The developers at Facebook named their database after Cassandra, the mythological Trojan prophetess, referencing her curse of making prophecies that were never believed.[8]

Features

Cassandra uses a distributed architecture where all nodes perform identical functions, eliminating single points of failure. The system employs configurable replication strategies to distribute data across clusters, providing redundancy and disaster recovery capabilities. It achieves linear scaling by increasing read and write throughput with each additional node while maintaining continuous service.

Cassandra is categorized as an AP (Availability and Partition Tolerance) system, emphasizing availability and partition tolerance over consistency. It also offers tunable consistency levels for both read and write operations. Additionally, Cassandra's compatibility with Hadoop and related tools allows for integration with existing big data processing workflows. Eventual consistency is maintained using tombstones to manage reads, upserts, and deletes.

Cassandra Query Language

Cassandra Query Language (CQL) is the 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 (DataStax), Go (gocql), and C++. [9]

The key space in Cassandra is a namespace that defines data replication across nodes. Therefore, replication is defined at the key space level. Below is an example of key space creation, including a column family in CQL 3.0: [10]

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

USE MyKeySpace;

CREATE COLUMNFAMILY MyColumns (id text, lastName text, firstName text, PRIMARY KEY(id));

INSERT INTO MyColumns (id, lastName, firstName) VALUES ('1', 'Doe', 'John');

SELECT * FROM MyColumns;

Which gives: 

 id | lastName | firstName
----+----------+----------
  1 | Doe      | John

(1 rows)

Tombstones

Deletion markers called "tombstones" are known to cause performance degradation in delete-heavy workloads.[11] Tombstones are common in many databases, and this problem is not unique to Cassandra.

Data model

As a wide-column store, Cassandra combines features of both key-value and tabular database systems. It implements a partitioned row store model with adjustable consistency levels.[12] 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.[13] Other columns may be indexed separately from the primary key.[14]

Tables may be created, dropped, or altered at run-time without blocking updates and queries.[15]

Cassandra cannot execute joins or subqueries. Rather, Cassandra emphasizes denormalization through features such as collections.[16]

A column family (called "table" since CQL 3) resembles a table in a relational database management system (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 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.[17]

Each key in Cassandra corresponds to a value which is an object. Each key has values as columns, and these 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 multidimensional 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

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.[18] Nodetool also offers a number of commands to return Cassandra metrics pertaining to disk usage, latency, compaction, garbage collection, and more.[19]

Since the release of Cassandra 2.0.2 in 2013, measures of several metrics are produced via the Dropwizard metrics framework,[20] and may be queried via JMX using tools such as JConsole or passed to external monitoring systems via Dropwizard-compatible reporter plugins.[21]

Releases

Releases after graduation include:

Version Original release date Latest version Release date Status[22]
Old version, not maintained: 0.6 2010-04-12 0.6.13 2011-04-18 No longer maintained
Old version, not maintained: 0.7 2011-01-10 0.7.10 2011-10-31 No longer maintained
Old version, not maintained: 0.8 2011-06-03 0.8.10 2012-02-13 No longer maintained
Old version, not maintained: 1.0 2011-10-18 1.0.12 2012-10-04 No longer maintained
Old version, not maintained: 1.1 2012-04-24 1.1.12 2013-05-27 No longer maintained
Old version, not maintained: 1.2 2013-01-02 1.2.19 2014-09-18 No longer maintained
Old version, not maintained: 2.0 2013-09-03 2.0.17 2015-09-21 No longer maintained
Old version, not maintained: 2.1 2014-09-16 2.1.22 2020-08-31 No longer maintained
Old version, not maintained: 2.2 2015-07-20 2.2.19 2020-11-04 No longer maintained
Old version, not maintained: 3.0 2015-11-09 3.0.29 2023-05-15 No longer maintained
Old version, not maintained: 3.11 2017-06-23 3.11.15 2023-05-05 No longer maintained
Old version, still maintained: 4.0 2021-07-26 4.0.13 2023-05-20 Maintained until 5.1.0 release
Old version, still maintained: 4.1 2022-06-17 4.1.6 2024-08-19 Maintained until 5.2.0 release
Latest version: 5.0 2024-09-05 5.0.2 2024-10-19 Latest release. Maintained until 5.3.0 release
Legend:
Old version, not maintained
Old version, still maintained
Latest version
Latest preview version

See also

References

  1. ^ "Release cassandra-5.0.2".
  2. ^ Carpenter, Jeff; Hewitt, Eben (2022). Cassandra: The Definitive Guide (3rd ed.). O'Reilly Media. ISBN 978-1-4920-9710-5.
  3. ^ Casares, Joaquin (November 5, 2012). "Multi-datacenter Replication in Cassandra". DataStax. Retrieved July 25, 2013. Cassandra's innate datacenter concepts are important as they allow multiple workloads to be run across multiple datacenters...
  4. ^ "Apache Cassandra Documentation Overview". Retrieved January 21, 2021.
  5. ^ Hamilton, James (July 12, 2008). "Facebook Releases Cassandra as Open Source". Retrieved June 4, 2009.
  6. ^ "Is this the new hotness now?". Mail-archive.com. March 2, 2009. Archived from the original on April 25, 2010. Retrieved March 29, 2010.
  7. ^ "Cassandra is an Apache top level project". Mail-archive.com. February 18, 2010. Archived from the original on March 28, 2010. Retrieved March 29, 2010.
  8. ^ "The meaning behind the name of Apache Cassandra". Archived from the original on November 1, 2016. Retrieved July 19, 2016. 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[.]
  9. ^ "DataStax C/C++ Driver for Apache Cassandra". DataStax. Retrieved December 15, 2014.
  10. ^ "CQL". Archived from the original on January 13, 2016. Retrieved January 5, 2016.
  11. ^ Rodriguez, Alain (July 27, 2016). "About Deletes and Tombstones in Cassandra".
  12. ^ DataStax (January 15, 2013). "About data consistency". Archived from the original on July 26, 2013. Retrieved July 25, 2013.
  13. ^ Ellis, Jonathan (February 15, 2012). "Schema in Cassandra 1.1". DataStax. Retrieved July 25, 2013.
  14. ^ Ellis, Jonathan (December 3, 2010). "What's new in Cassandra 0.7: Secondary indexes". DataStax. Retrieved July 25, 2013.
  15. ^ Ellis, Jonathan (March 2, 2012). "The Schema Management Renaissance in Cassandra 1.1". DataStax. Retrieved July 25, 2013.
  16. ^ Lebresne, Sylvain (August 5, 2012). "Coming in 1.2: Collections support in CQL3". DataStax. Retrieved July 25, 2013.
  17. ^ DataStax. "Apache Cassandra 0.7 Documentation - Column Families". Apache Cassandra 0.7 Documentation. Retrieved October 29, 2012.
  18. ^ "NodeTool". Cassandra Wiki. Archived from the original on January 13, 2016. Retrieved January 5, 2016.
  19. ^ "How to monitor Cassandra performance metrics". Datadog. December 3, 2015. Retrieved January 5, 2016.
  20. ^ "Metrics". Cassandra Wiki. Archived from the original on November 12, 2015. Retrieved January 5, 2016.
  21. ^ "Monitoring". Cassandra Documentation. Retrieved February 1, 2018.
  22. ^ "Cassandra Server Releases". cassandra.apache.org. Retrieved December 15, 2015.

Bibliography

Wikimedia Commons has media related to Apache Cassandra.
Wikiversity has learning resources about Big Data/Cassandra
Retrieved from "https://en.wikipedia.org/w/index.php?title=Apache_Cassandra&oldid=1262087417"