Введение в apache cassandra
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© 2014 Grid Dynamics
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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