An Introduction To Cassandra

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An Introduction To Cassandra

Eric [email protected]

@jericevans

OpenSQL CampNovember 14, 2009

Eric Evans [email protected] @jericevans An Introduction To Cassandra


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A prophetess in Troy during the Trojan War. Her predictions werealways true, but never believed.



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A massively scalable, decentralized, structured data store (akadatabase).



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Outline

1 Project History

2 Description

3 People



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4 new committers added

Dozens of contributors

60+ people on IRC

Hundreds of closed issues (bugs, features, etc)

2 major releases, 1 point release

0.5.0 RSN



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Outline

1 Project History

2 Description

3 People



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Cassandra is...

O(1) DHT

Eventual consistency

Tunable trade-offs, consistency vs. latency



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But...

Values are structured, indexed

Columns / column families

Slicing w/ predicates (queries)



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Column families



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Supercolumn families



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Querying

By column

By column for multiple keys

Slice by names, or ranges of names

returning columnsreturning super columns

Slice for multiple keys

Range of keys

Slice on a key range RSN



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Column comparators

TimeUUID

LexicalUUID

UTF8

Long

Bytes

...



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Updating

Insert column (by key)

Batch insert (multi-column but still by key)

Remove (by key)

Remove key range RSN



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Consistency

CAP Theorem: choose any two of Consistency, Availability, orPartition tolerance.

Zero

One

Quorum ((N / 2) + 1)

All



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Client API

Thrift (12 different languages!)

Ruby

http://github.com/fauna/cassandra/tree/masterhttp://github.com/NZKoz/cassandra object/tree/master

Python

http://github.com/digg/lazyboy/tree/masterhttp://github.com/driftx/Telephus/tree/master (Twisted)

Scala

http://github.com/viktorklang/Cassidy/tree/masterhttp://github.com/nodeta/scalandra/tree/master



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Performance vs MySQL w/ 50GB

MySQL

300ms write350ms read

Cassandra

0.12ms write15ms read



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Writes



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About writes...

No reads

No seeks

Sequential disk access

Atomic within a column family

Fast

Any node

Always writeable (hinted hand-off)



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Reads



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About reads...

Any node

Read repair

Usual caching conventions apply



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Outline

1 Project History

2 Description

3 People



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Droppin’ Names

Facebook

Digg

IBM Research

Rackspace

Twitter



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http://incubator.apache.org/cassandra

#cassandra / irc.freenode.net


An Introduction To Cassandra

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