The new face of Cassandra

Michaël Figuière@mfiguiere

©2012 DataStax

Speaker

Michaël Figuière

@mfiguiere

2

©2012 DataStax

Ring Architecture

CassandraNode

Node

NodeNode

Node

Node

3

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Ring Architecture

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Node

Node Replica

Replica

NodeReplica

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Linear Scalability

5

Client Writes/s by Node Count - Replication Factor = 3

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Client / Server Communication

Client

Client

Client

Client

Node?

Node

6

Replica

Replica

Replica

Node

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Client / Server Communication

Client

Client

Client

Client

Node

Node

Coordinator node:Forwards all R/W requeststo corresponding replicas

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Replica

Replica

ReplicaNode

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3 replicas

A A A

Time

8

Tunable Consistency

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Write and wait for acknowledge from one node

Write ‘B’

B A A

9

Time

A A A

Tunable Consistency

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R + W < N

Read waiting for one node to answer

B A A

10

B A A

A A A

Write and wait for acknowledge from one node

Time

Tunable Consistency

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R + W = N

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B B A

B A

A A A

B

Write and wait for acknowledges from two nodes

Read waiting for one node to answer

Tunable ConsistencyTime

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Tunable Consistency

R + W > N

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B A

B A

A A A

B

B

Write and wait for acknowledges from two nodes

Read waiting for two nodes to answer

Time

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Tunable Consistency

R = W = QUORUM

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B A

B A

A A A

B

B

Time

QUORUM = (N / 2) + 1

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Request Path

1

2

2

2

3

3

3

4

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Client

Client

Client

Client

Node

Node

Node

Replica

Replica

Replica

Coordinator node

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Multi-Datacenter

Node6

Node1

Node4

Node5

Node2

Node3

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Node 1

Node 2

Datacenter A

Node 3

Node 4

Datacenter B

Node 5

Node 6

Datacenter C

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Column Family Data Model

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123 main

address

jb@ds.com

email

Jonathan

name

TX

statejbellis

45 2nd st

address

dh@ds.com

email

Daria

name

CA

statedhutch

eg@ds.com

email

Eric

nameegilmore

Row Key Columns = List of K/V pairs sorted by Key

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Column Family Data Model

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datastax dhutch egilmore mzcassiejbellis

egilmoredhutch

datastax mzcassieegilmore

Row Key Columns = List of K/V pairs sorted by Key

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Storage Engine

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Memtable

CommitLog SSTable SSTableSSTableSSTable

Memtable

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CQL3 Denormalized Model

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Data duplicated over several tables

CQL3 Query Language comes with a new Data Model abstraction made of denormalized, statically defined tables

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CQL3 Data Model

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gmason

user_id

1735

tweet_id

phenry

author

Give me liberty or give me death

body

PartitionKey

gmason 1742 gwashington I chopped down the cherry tree

ahamilton 1767 jadams A government of laws, not men

ahamilton 1794 gwashington I chopped down the cherry tree

ClusteringKey

Timeline Table

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CQL3 Data Model

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gmason

user_id

1735

tweet_id

phenry

author

Give me liberty or give me death

body

gmason 1742 gwashington I chopped down the cherry tree

ahamilton 1767 jadams A government of laws, not men

ahamilton 1794 gwashington I chopped down the cherry tree

Timeline Table

CREATE TABLE timeline ( user_id varchar, tweet_id timeuuid, author varchar, body varchar, PRIMARY KEY (user_id, tweet_id));

CQL

©2012 DataStax

CQL3 Data Model

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gmason

user_id tweet_id

phenry

author

Give me liberty or give me death

body

gmason gwashington I chopped down the cherry tree

ahamilton jadams A government of laws, not men

ahamilton gwashington I chopped down the cherry tree

gwashington

[1735, author]

I chopped down the...

[1735, body]

phenry

[1742, author]

Give me liberty or give...

[1742, body]gmason

gwashington

[1767, author]

I chopped down the...

[1767, body]

jadams

[1794, author]

A government of laws...

[1794, body]ahamilton

Timeline Table

Timeline Physical Layout

1735

1742

1767

1794

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Current Drivers Architecture

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Thrift API

Thrift RPC

CQL API

Thrift RPC

DB API

* This is a simplified view of drivers architecture. Details vary from one language to another.

OO API

Client Library CQL Driver

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New Drivers Architecture

24

DB API

CQL Native Protocol

CQL API OO API

* This is a simplified view of drivers architecture. Details vary from one language to another.

Next Generation Driver

©2012 DataStax

DataStax Java Driver• Reference Implementation

• Asynchronous architecture based on Netty

• Prepared Statements Support

• Automatic Fail-over

• Node Discovery

• Cassandra Tracing Support

• Tunable policies• LoadBalancingPolicy• ReconnectionPolicy• RetryPolicy

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Connect and Write

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Cluster cluster = new Cluster.Builder() .addContactPoints("10.0.0.1", "10.0.0.2") .build();

Session session = cluster.connect("myKeyspace");

session.execute( "INSERT INTO user (user_id, name, email) VALUES (12345, 'johndoe', 'john@doe.com')");

©2012 DataStax

Read

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ResultSet rs = session.execute("SELECT * FROM test");

List<Row> rows = rs.fetchAll(); for (Row row : rows) {

String userId = row.getString("user_id"); String name = row.getString("name"); String email = row.getString("email");}

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Asynchronous Read

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ResultSet.Future future = session.executeAsync("SELECT * FROM test");

for (Row row : future.get()) {

String userId = row.getString("user_id"); String name = row.getString("name"); String email = row.getString("email");}

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Object Mapping

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public enum Gender {

@EnumValue("m") MALE, @EnumValue("f") FEMALE;}

@Table(name = "user")public class User { @PartitionKey @Column(name = "user_id") private String userId; private String name; private String email; private Gender gender;}

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Inheritance

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@InheritanceValue("tv")public class TV extends Product {

private float size;}

@Table(name = "catalog")@Inheritance( subClasses = {Phone.class, TV.class}, column = "product_type")public abstract class Product {

@Column(name = "product_id") private String productId; private float price; private String vendor; private String model;

}

https://github.com/datastax/java-driver

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@mfiguiere

blog.datastax.com

Stay Tuned!