Apache Cassandra - A gentle introduction

A gentle introduction by @przemur from

Tuesday, October 22, 13

PERFORMANCE


http://www.datastax.com/wp-content/uploads/2013/02/WP-Benchmarking-Top-NoSQL-Databases.pdf




http://techblog.netflix.com/2011/11/benchmarking-cassandra-scalability-on.html




http://www.networkworld.com/news/tech/2012/102212-nosql-263595.html




http://www.cubrid.org/blog/dev-platform/nosql-benchmarking/




A TAXONOMY OF DISTRIBUTED DATABASES


ID FIRST LAST

1 John Smith

2 Mike Kowalski

:name_1 -> “John Smith”:name_2 -> “Mike Kowalski”

Employee

Name: John SmithID: 1Employee

Name: Mike KowalskiID: 2

Company Employee:1:Name Employee:2:Name

ACME John Smith Mike Kowalski

John Smith

Mike Kowalski

works with


ID FIRST LAST

1 John Smith

2 Mike Kowalski


Employee





John Smith

Mike Kowalski

works with

Relational (MySQL, Oracle, ...)


ID FIRST LAST

1 John Smith

2 Mike Kowalski


Employee





John Smith

Mike Kowalski

works with


Key-Value(Redis, Riak, Dynamo, ...)


ID FIRST LAST

1 John Smith

2 Mike Kowalski


Employee





John Smith

Mike Kowalski

works with



Document (MongoDB, Couchbase, ...)


ID FIRST LAST

1 John Smith

2 Mike Kowalski


Employee





John Smith

Mike Kowalski

works with




Graph (Neo4j, ...)


ID FIRST LAST

1 John Smith

2 Mike Kowalski


Employee





John Smith

Mike Kowalski

works with



Wide Column(BigTable, Cassandra, HBase, ...)


Graph (Neo4j, ...)


Consistency

Availability Partition tolerance

“Pick any two”(and have acceptable latency)


Consistency



RDBMSs


Consistency



RDBMSs Immediate Consistency: HBase, ...


Consistency




Eventual Consistency: Cassandra, Riak, ...


Consistency




Eventual Consistency: Cassandra, Riak, ...

+ Configurable (MongoDB, Cassandra - to

some extent, ...)


OH REALLY?• Cassandra vs. Consistency:

http://aphyr.com/posts/294-call-me-maybe-cassandra

• CAP criticism:

http://aphyr.com/posts/292-call-me-maybe-nuodb

http://www.julianbrowne.com/article/viewer/brewers-cap-theorem

http://www.percona.com/live/mysql-conference-2013/sites/default/files/slides/aslett%20cap%20theorem.pdf
















KEY IDEAS


•Dynamo partitioning + BigTable model

• simple architecture, minimal administration

•no single point of failure

•closer to the metal (e.g. no HDFS)

• low latency


CASSANDRA’S DATA MODEL


Keyspace

Column Family

Row (Partition) Key

Column Name

Value


Keyspace

Column Family

Row (Partition) Key

Column Name

Value

“Database”


Keyspace

Column Family

Row (Partition) Key

Column Name

Value

“Database”

“Table”


Keyspace

Column Family

Row (Partition) Key

Column Name

Value

“Database”

“Table”

“Primary ID”


Keyspace

Column Family

Row (Partition) Key

Column Name

Value

“Database”

“Table”

“Primary ID”

Sorted “Column”


Keyspace

Column Family

Row (Partition) Key

Column Name

Value

“Database”

“Table”

“Primary ID”

Sorted “Column”

“Value”


PARTITIONING


TWO PARTITIONERS OUT OF THE BOX

• Byte Ordered Partitioner

• Random Partitioner

http://www.datastax.com/docs/1.0/cluster_architecture/partitioning




TWO PARTITIONERS OUT OF THE BOX

• Byte Ordered Partitioner

• Random Partitioner

Forget it:•hot spots•uneven distribution•load balancing





1aaa

2bbb

4zzz

3xxx


1aaa

2bbb

4zzz

3xxx

Initial token


1aaa

2bbb

4zzz

3xxx

Initial token

Range: [aaa,bbb)


1aaa

2bbb

4zzz

3xxx

Range: [aaa,bbb)


1aaa

2bbb

4zzz

3xxx


Row Key Hash ...

abc ...

klm ...

xyz ... 1aaa

2bbb

4zzz

3xxx


Row Key Hash ...

abc ...

klm ...

xyz ... 1aaa

2bbb

4zzz

3xxx

abc


Row Key Hash ...

abc ...

klm ...

xyz ... 1aaa

2bbb

4zzz

3xxx

abc

klm


Row Key Hash ...

abc ...

klm ...

xyz ... 1aaa

2bbb

4zzz

3xxx

abc

klmxyz


WHAT ABOUT THE REPLICATION!?


1aaa

2bbb

4zzz

3xxx

klmxyz

Replication Factor = 2

abc

Warning: greatly simplified.

Checkout snitch docs for more

info.


1aaa

2bbb

4zzz

3xxx

klmxyz


abc

abc



info.


1aaa

2bbb

4zzz

3xxx

klmxyz


abcklm

abc



info.


1aaa

2bbb

4zzz

3xxx

klmxyz


xyz

abcklm

abc



info.


1aaa

2bbb

4zzz

3xxx

abc

klmxyz


xyz

abcklm


1aaa

2bbb

4zzz

3xxx

abc

klmxyz


xyz

abcklm

abc


1aaa

2bbb

4zzz

3xxx

abc

klmxyz


xyz

abcklm

abc

klm


1aaa

2bbb

4zzz

3xxx

abc

klmxyz


xyz

abcklm

abc

klm xyz


1aaa

2bbb

4zzz

3xxx

abc

klmxyz


xyz

abcklm

abc

klm xyzBTW,

QUORUM = (RF/2)+1


WHAT HAPPENS WHEN A NEW NODE IS BEING ADDED ?

1aaa

2bbb

4zzz

3xxx

5???


VNODES1

aaacccggg

2bbbvvv

mmm

3xxxuuujjj

4zzzeeeddd


VNODES1

aaacccggg

2bbbvvv

mmm

3xxxuuujjj

4zzzeeeddd

5


1aaaccc

2bbbvvv

3xxxuuujjj

4zzzeeeddd

5ggg

mmm


1aaaccc

2bbbvvv

3xxxuuujjj

4zzzeeeddd

5ggg

mmm

This also greatly helps in case when a node is down.


CASSANDRA 101


INSTALLATION & CONFIGURATION


CQL3

SELECT * FROM books;

INSERT INTO

books (author, title, year) VALUES

(‘Moby-Dick’, ‘Herman Melville’, 1851);

DELETE FROM books WHERE author=‘Paulo Coelho’;


DATA MODELING PRACTICES

COMPOSITE COLUMNS


Author Book Year Number of words

George Orwell Animal Farm 1945 32451

George Orwell 1984 1949 110581

James Joyce Ulysses 1922 265192






CREATE TABLE books (author varchar,title varchar,year integer,number_of_words integer,PRIMARY KEY (author, title)

);






George Orwell [1984, Year]: 1949 [1984, Number of words]: 110581

[Animal Farm, Year]: 1945

[Animal Farm, Number of words]: 32451

James Joyce [Ulysses, Year]: 1922 [Ulysses, Number of words]: 265192

CREATE TABLE books (author varchar,title varchar,year integer,number_of_words integer,PRIMARY KEY (author, title)

);


COUNTERS

http://www.slideshare.net/kevinweil/rainbird-realtime-analytics-at-twitter-strata-2011






SETS, LISTS, MAPS


CONSOLE TIME


WHAT WE HIT?


•no DESCRIBE when calling from a client

•cache settings

• insertion performance with 100 000’s of columns

•PRIMARY KEY((a,b,c),d)

•compaction settings


I WANT TO KNOW MORE


• http://wiki.apache.org/cassandra/ArchitectureOverview

• http://www.datastax.com/documentation/cql/3.0/webhelp/index.html

• http://cassandra.apache.org/doc/cql3/CQL.html

• http://www.slideshare.net/acunu/freakin-fast-cassandra

• http://nosql.mypopescu.com/

• http://planetcassandra.org/


http://wiki.apache.org/cassandra/ArchitectureOverview

http://wiki.apache.org/cassandra/ArchitectureOverview

http://www.datastax.com/documentation/cql/3.0/webhelp/index.html




http://cassandra.apache.org/doc/cql3/CQL.html

http://cassandra.apache.org/doc/cql3/CQL.html

http://www.slideshare.net/acunu/freakin-fast-cassandra

http://www.slideshare.net/acunu/freakin-fast-cassandra

http://nosql.mypopescu.com/

http://nosql.mypopescu.com/

http://planetcassandra.org/

http://planetcassandra.org/

BY THE WAY...


HAVE YOU SEEN HIM?

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omTuesday, October 22, 13

Apache Cassandra - A gentle introduction

Technology

Transcript of Apache Cassandra - A gentle introduction