New Cassandra Drivers in Depth

Michaël Figuière@mfiguiere

©2012 DataStax

Speaker

Michaël Figuière

@mfiguiere

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©2012 DataStax

CQL: the new face of Cassandra

• CQL 3• Simpler Data Model using denormalized Tables• SQL-like query language• Schema definition

• CQL Binary Protocol• Introduced in Cassandra 1.2 (CASSANDRA-2478)• Designed for CQL 3• Opens doors for Streaming, Notifications, ...• Thrift will keep being supported by Cassandra

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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

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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

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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

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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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Request Pipelining

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Client

WithoutRequest Pipelining

Cassandra

Client CassandraWith

Request Pipelining

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Notifications

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Client

WithoutNotifications

WithNotifications

NodeNode

Node

Client

NodeNode

Node

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Asynchronous Architecture

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ClientThread

Node

Node

Node

ClientThread

ClientThread

Node

Driver

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Asynchronous Architecture

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ClientThread

Node

Node

Node

ClientThread

ClientThread

Node

1

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45

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Driver

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LoadBalancingPolicy

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public interface LoadBalancingPolicy {

HostDistance distance(Host host);

Iterator<Host> newQueryPlan(Query query);

[...]

}

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DCAwareRoundRobinPolicy

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Node

Node

NodeClient

Datacenter B

Node

Node

Node

Client

Client

Client

Client

Client

Datacenter A

Local nodes are queried first, if non are available, the request will be sent to a remote node.

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Node

Node

ReplicaNode

TokenAwarePolicy

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Client Node

NodeReplica

Replica

Nodes that own a Replica of the data being read or written by the query will be contacted first.

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RetryPolicy

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public interface RetryPolicy {

RetryDecision onReadTimeout(Query query, ConsistencyLevel cl, [...] );

RetryDecision onWriteTimeout(Query query, ConsistencyLevel cl, [...] );

RetryDecision onUnavailable(Query query, ConsistencyLevel cl, [...] );

public static class RetryDecision { public static enum Type { RETRY, RETHROW, IGNORE };

private final Type type; private final ConsistencyLevel retryCL; [...] }}

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Downgrading Consistency

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Client

If the requested Consistency Level cannot be reached (QUORUM here), a second request with a lower CL is sent automatically.

Node

Node Replica

Replica

NodeReplica

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Connect and Write

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Cluster cluster = 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')");

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Read

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

List<Row> rows = rs.all(); 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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ResultSetFuture 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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Prepared Statements

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PreparedStatement ps = session.prepare("SELECT * FROM users WHERE id = ?");

BoundStatement bs = session.execute(ps.bind("123")).one().getInt("age");

bs.setString("k");

int age = session.execute(bs).one().getInt("age");

age = session.execute(ps.bind("123")).one().getInt("age");

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Query Builder

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String query = "SELECT a,b,\"C\" FROM foo WHERE a IN (127.0.0.1,127.0.0.3) AND \"C\"='foo' ORDER BY a ASC,b DESC LIMIT 42;";

Query select = select("a", "b", quote("C")).from("foo") .where(in("a", InetAddress.getByName("127.0.0.1"), InetAddress.getByName("127.0.0.3"))) .and(eq(quote("C"), "foo")) .orderBy(asc("a"), desc("b")) .limit(42);

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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/

Betas now available!

@mfiguiere

blog.datastax.com

Stay Tuned!