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Created for BigData Community by Dmitry Yaraev

Apache CassandraWhen and Why

© 2014 Grid Dynamics

Agenda

1. When RDBMS Becomes a Bottleneck2. Concepts of NoSQL Paradigm3. Variety of NoSQL Databases4. Why Apache Cassandra?5. Essential Use Cases of Cassandra6. Bad Usage Patterns

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What Is Offered by RDBMS

● Mature technology with common standards● Easy migration from one engine to another● Data model corresponds to the real world● Structured Query Language (SQL)● ACID transactions

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Bottlenecked by RDBMS

● Horizontal scalability● Schema support and migration● Server and maintenance cost

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NoSQL :: History

● First mention in 1998● Class of distributed databases● Not Only SQL

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NoSQL :: Features

● Simple schema without relations● Good horizontal scalability● Combination of two of the following:

○ Consistency○ Availability○ Partition Tolerance

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NoSQL :: CAP Theorem

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NoSQL :: Storage Types

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Questions?

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Cassandra :: What Is It?

● Wide-column distributed data store● The latest version is 2.1.2 (released this month)● Proved itself in production (Instagram, Spotify,

eBay and many other big players on IT market)

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Cassandra :: Origin

● Originally created in Facebook● Open-sourced in 2008● Apache incubator project in early 2009● Top level Apache project in March 2010

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Cassandra :: Features

● High scalability● Tunable consistency● Cross-datacenter replication● Query language (CQL)● Drivers for a variety of languages● Lightweight transactions● Indexing

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Cassandra :: Data Types

● Primitive types● Arbitrary bytes (blob)● Collections (list, map, set)● Tuples (tuple)● User defined

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Cassandra :: Data Model

● Keyspace● ColumnFamily● Row● Column

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Cassandra :: Data Model

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Cassandra :: ColumnFamily

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Cassandra :: CQL3

● SQL-like syntax● Three types of statements

○ data definition statements○ data manipulation statements○ data look up statements

● Prepared statements

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Cassandra :: Example Queries

CREATE TABLE songs ( id uuid PRIMARY KEY, title text, album text, artist text, data blob );

SELECT * FROM songs WHERE artist = ‘Metallica’; -- RETURNS AN ERROR

CREATE INDEX ON songs(artist);

SELECT * FROM songs WHERE artist = ‘Metallica’;

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Cassandra :: Data Distribution

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Cassandra :: Replication

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Cassandra :: Eventual Consistency

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Cassandra :: Tunable Consistency

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Cassandra :: Consistency Levels

● Defines a condition for successful read/write operation

● Multiple Options○ ONE○ ALL○ QUORUM,○ LOCAL_QUORUM○ SERIAL○ …

● Can be specified per request

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Cassandra :: Consistency (Quorum)

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Cassandra :: Consistency (ONE)

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Cassandra :: Consistency (ONE)

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Cassandra :: Use Cases

● Large data sets and simple scaling● Perfectly fits for semi-structured data● Fault tolerance (no SPoF)● High write throughput

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● No good for large blobs ( > 64MB )● When there are more read operations than

writes ones and low read latency is critical● ACID transactions

Cassandra :: Limitations

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Thanks!

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