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Apache Cassandra is a free and open-source database management system designed to handle large volumes of data across multiple commodity servers. Cassandra supports computer clusters and spanning of multiple data centers,[2] 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.[3]
 | |
| Original author(s) | Avinash Lakshman, Prashant Malik / Facebook |
|---|---|
| Developer(s) | Apache Software Foundation |
| Initial release | July 2008 |
| Stable release | 5.0.2[1] 
/ October 19, 2024 |
| Repository | |
| Written in | Java |
| Operating system | Cross-platform |
| Available in | English |
| Type | NoSQL Database, data store |
| License | Apache License 2.0 |
| Website | cassandra |
History
editAvinash Lakshman, a co-author of Amazon's Dynamo, and Prashant Malik, developed Cassandra on Facebook to support the inbox search functionality. Facebook open-sourced - Cassandra on Google Code in July 2008.[4] It became an Apache Incubator project[5] in March 2009, and in February 17, 2010, it graduated to a top-level project.[6]
The developers at Facebook named their database after Cassandra, the Trojan prophetess from mythology, alluding to the classical curse placed on an oracle.[7]
Features
editApache Cassandra is designed to provide high availability and fault tolerance by enabling every node to perform the same functions, which helps eliminate single points of failure.
Data is distributed throughout the cluster using configurable replication strategies that can be implemented across multiple data centers, thereby enhancing redundancy and supporting disaster recovery.
The system is capable of linear scaling, which increases read and write throughput with the addition of new nodes, 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 integrates with Hadoop, supporting MapReduce, Apache Pig, and Apache Hive, and features the Cassandra Query Language (CQL) for simplified data access. Eventual consistency is managed through tombstones for reads, upserts, and deletes.
Cassandra Query Language
editCassandra utilizes the Cassandra Query Language (CQL), which is an 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++. [8]
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: [9]
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)
Known issues
editUp to Cassandra 1.0, Cassandra was not row-level consistent, meaning that inserts and updates into the table that affect the same row, and that are processed at approximately the same time, may affect the non-key columns in inconsistent ways.[10] 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.[11]
Cassandra is not supported on Windows as of version 4, see issue CASSANDRA-16171.[12]
Tombstones
editDeletion markers called "tombstones" are known to cause performance degradation in delete-heavy workloads.[13] Tombstones are common in many databases, and this problem is not unique to Cassandra.
Data model
editCassandra is wide-column store, and, as such, it is essentially a hybrid between a key-value and a tabular database management system. Its data model is a partitioned row store with tunable consistency.[14] 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.[15] Other columns may be indexed separately from the primary key.[16]
Tables may be created, dropped, or altered at run-time without blocking updates and queries.[17]
Cassandra cannot execute joins or subqueries. Rather, Cassandra emphasizes denormalization through features such as collections.[18]
A column family (called "table" since CQL 3) resembles a table in an RDBMS (Relational Database Management System). 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.[19]
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
editCassandra 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.[20] Nodetool also offers a number of commands to return Cassandra metrics pertaining to disk usage, latency, compaction, garbage collection, and more.[21]
Since the release of Cassandra 2.0.2 in 2013, measures of several metrics are produced via the Dropwizard metrics framework,[22] and may be queried via JMX using tools such as JConsole or passed to external monitoring systems via Dropwizard-compatible reporter plugins.[23]
Releases
editReleases after graduation include:
| Version | Original release date | Latest version | Release date | Status[24] |
|---|---|---|---|---|
| 0.6 | 2010-04-12 | 0.6.13 | 2011-04-18 | No longer maintained |
| 0.7 | 2011-01-10 | 0.7.10 | 2011-10-31 | No longer maintained |
| 0.8 | 2011-06-03 | 0.8.10 | 2012-02-13 | No longer maintained |
| 1.0 | 2011-10-18 | 1.0.12 | 2012-10-04 | No longer maintained |
| 1.1 | 2012-04-24 | 1.1.12 | 2013-05-27 | No longer maintained |
| 1.2 | 2013-01-02 | 1.2.19 | 2014-09-18 | No longer maintained |
| 2.0 | 2013-09-03 | 2.0.17 | 2015-09-21 | No longer maintained |
| 2.1 | 2014-09-16 | 2.1.22 | 2020-08-31 | No longer maintained |
| 2.2 | 2015-07-20 | 2.2.19 | 2020-11-04 | No longer maintained |
| 3.0 | 2015-11-09 | 3.0.29 | 2023-05-15 | No longer maintained |
| 3.11 | 2017-06-23 | 3.11.15 | 2023-05-05 | No longer maintained |
| 4.0 | 2021-07-26 | 4.0.13 | 2023-05-20 | Maintained until 5.1.0 release |
| 4.1 | 2022-06-17 | 4.1.6 | 2024-08-19 | Maintained until 5.2.0 release |
| 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
edit
- Bigtable – Original distributed database by Google
- Distributed database
- Distributed hash table (DHT)
- Dynamo (storage system) – Cassandra borrows many elements from Dynamo
References
edit- ^ https://github.com/apache/cassandra/releases/tag/cassandra-5.0.2.
{{cite web}}: Missing or empty|title=(help) - ^ 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...
- ^ "Apache Cassandra Documentation Overview". Retrieved January 21, 2021.
- ^ Hamilton, James (July 12, 2008). "Facebook Releases Cassandra as Open Source". Retrieved June 4, 2009.
- ^ "Is this the new hotness now?". Mail-archive.com. March 2, 2009. Archived from the original on April 25, 2010. Retrieved March 29, 2010.
- ^ "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.
- ^ "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[.]
- ^ "DataStax C/C++ Driver for Apache Cassandra". DataStax. Retrieved December 15, 2014.
- ^ "CQL". Archived from the original on January 13, 2016. Retrieved January 5, 2016.
- ^ "WAT - Cassandra: Row level consistency #$@&%*! - datanerds.io". datanerds.io. Archived from the original on November 26, 2016. Retrieved November 28, 2016.
- ^ Lebresne, Sylvain (February 21, 2012). "Coming up in Cassandra 1.1: Row Level Isolation". DataStax: always-on data platform | NoSQL | Apache Cassandra. Retrieved July 18, 2018.
- ^ "Remove Windows scripts". Cassandra issue tracker. April 4, 2023. Retrieved April 4, 2023.
- ^ Rodriguez, Alain (July 27, 2016). "About Deletes and Tombstones in Cassandra".
- ^ DataStax (January 15, 2013). "About data consistency". Archived from the original on July 26, 2013. Retrieved July 25, 2013.
- ^ Ellis, Jonathan (February 15, 2012). "Schema in Cassandra 1.1". DataStax. Retrieved July 25, 2013.
- ^ Ellis, Jonathan (December 3, 2010). "What's new in Cassandra 0.7: Secondary indexes". DataStax. Retrieved July 25, 2013.
- ^ Ellis, Jonathan (March 2, 2012). "The Schema Management Renaissance in Cassandra 1.1". DataStax. Retrieved July 25, 2013.
- ^ Lebresne, Sylvain (August 5, 2012). "Coming in 1.2: Collections support in CQL3". DataStax. Retrieved July 25, 2013.
- ^ DataStax. "Apache Cassandra 0.7 Documentation - Column Families". Apache Cassandra 0.7 Documentation. Retrieved October 29, 2012.
- ^ "NodeTool". Cassandra Wiki. Archived from the original on January 13, 2016. Retrieved January 5, 2016.
- ^ "How to monitor Cassandra performance metrics". Datadog. December 3, 2015. Retrieved January 5, 2016.
- ^ "Metrics". Cassandra Wiki. Archived from the original on November 12, 2015. Retrieved January 5, 2016.
- ^ "Monitoring". Cassandra Documentation. Retrieved February 1, 2018.
- ^ "Cassandra Server Releases". cassandra.apache.org. Retrieved December 15, 2015.
Bibliography
edit- Carpenter, Jeff; Hewitt, Eben (July 24, 2016). Cassandra: The Definitive Guide (2nd ed.). O'Reilly Media. p. 370. ISBN 978-1-4919-3366-4.
- Capriolo, Edward (July 15, 2011). Cassandra High Performance Cookbook (1st ed.). Packt Publishing. p. 324. ISBN 978-1-84951-512-2.
- Hewitt, Eben (December 15, 2010). Cassandra: The Definitive Guide (1st ed.). O'Reilly Media. p. 300. ISBN 978-1-4493-9041-9.
External links
edit
- Lakshman, Avinash (August 25, 2008). "Cassandra - A structured storage system on a P2P Network". Engineering @ Facebook's Notes. Retrieved June 17, 2014.
- "The Apache Cassandra Project". Forest Hill, MD, USA: The Apache Software Foundation. Retrieved June 17, 2014.
- "Project Wiki". Forest Hill, MD, USA: The Apache Software Foundation. Archived from the original on June 14, 2014. Retrieved June 17, 2014.
- Hewitt, Eben (December 1, 2010). "Adopting Apache Cassandra". infoq.com. InfoQ, C4Media Inc. Retrieved June 17, 2014.
- Lakshman, Avinash; Malik, Prashant (August 15, 2009). "Cassandra - A Decentralized Structured Storage System" (PDF). cs.cornell.edu. The authors are from Facebook. Retrieved June 17, 2014.
- Ellis, Jonathan (July 29, 2009). "What Every Developer Should Know About Database Scalability". slideshare.net. Retrieved June 17, 2014. From the OSCON 2009 talk on RDBMS vs. Dynamo, Bigtable, and Cassandra.
- "Cassandra-RPM - Red Hat Package Manager (RPM) build for the Apache Cassandra project". code.google.com. Menlo Park, CA, USA: Google Project Hosting. Retrieved June 17, 2014.
- Roth, Gregor (October 14, 2012). "Cassandra by example - the path of read and write requests". slideshare.net. Retrieved June 17, 2014.
- Mansoor, Umer (November 4, 2012). "A collection of Cassandra tutorials". Retrieved February 8, 2015.
- Bushik, Sergey (October 22, 2012). "A vendor-independent comparison of NoSQL databases: Cassandra, HBase, MongoDB, Riak". NetworkWorld. Framingham, MA, USA and Staines, Middlesex, UK: IDG. Archived from the original on May 28, 2014. Retrieved June 17, 2014.