Cassandra for Java Developers @ Paris JUG

Cassandra for Java DevelopersDataStax Java Driver & DevCenter

Copyright @ 2015 ParisJug. Licence CC - Creative Commons 2.0 France – Paternité - Pas d'Utilisation Commerciale - Partage des Conditions Initiales à l'Identique

About Me

Alexandre DutraDriver and Tools Software Engineer @

@alexdut

linkedin.com/in/alexandredutra

github.com/adutra

alexandre.dutra@datastax.com

Agenda

1. Java Driver Architecture• Native Protocol• Node Discovery• Load Balancing• Failover & Fault Tolerance

Agenda

2. Java Driver In Practice• Asynchronous queries• Prepared Statements• Query Builder• Object Mapping API

Agenda

2. Java Driver In Practice• Asynchronous queries• Prepared Statements• Query Builder• Object Mapping API

3. DevCenter• Connection Manager• CQL Editor• Query Tracing• Visual DDL

I. Java Driver Architecture

Native Protocol - Basics

Client Coord

Node Replica

Replica

ReplicaNode

Coordinator node:Forwards all R/W requeststo corresponding replicas

Native Protocol

Native Protocol - Request Pipelining

Client

WithoutRequest Pipelining

Cassandra

Native Protocol - Request Pipelining

Client

WithRequest Pipelining

Cassandra

StreamID

Native Protocol - Notifications

Client

WithoutNotifications

WithNotifications

NodeNode

Client

NodeNode

Node Discovery

Contact point will reply with cluster topology, peer addresses etc.

Contact Point Node

Client

Contact Point

Cluster.init()

Control connection

Session.init()

Regular connections

Discovered node

Load Balancing

ClientThread

Driver

Cassandra 2.0N connections per node

Load Balancing

ClientThread

Driver

Cassandra 2.1+ 1 single connection per node

Load Balancing

ClientThread

1Driver

Load balancing picks up a node

Load Balancing - Round Robin

NodeNode

Client

3 etc.

Load Balancing - DC Aware Round Robin

Client

Datacenter A

Local nodes are tried first

Datacenter B

Load Balancing - DC Aware Round Robin

Client

Datacenter A

Datacenter B

If no local node is available, the request is sent to a remote node.

Load Balancing - Available Policies

RoundRobinPolicy

LoadBalancingPolicy

DCAwareRoundRobinPolicy

Load Balancing - Available Policies

TokenAwarePolicy

WhiteListPolicy

LatencyAwarePolicy

RoundRobinPolicy

LoadBalancingPolicy

Load Balancing - Token Awareness

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

ReplicaNode

Client

Replica

Load Balancing - Default Policy

TokenAwarePolicy

Token awareness

DC awareness

Automatic Failover

ClientThread

Driver

Load balancing tries next node

Fault Tolerance

• UnavailableException

• Consistency level not met

• ReadTimeoutException

• WriteTimeoutException

• Coordinator times out

X⚠️

Client

Fault Tolerance

• UnavailableException

• Consistency level not met

• ReadTimeoutException

• WriteTimeoutException

• Coordinator times out

X⚠️

Client

• NoHostAvailableException

• Cluster is down

• Network connectivity issue

Client X

Reconnect

Retry - Available Policies

LoggingRetryPolicyDefaultRetryPolicy

RetryPolicy

DowngradingConsistencyRetryPolicy

FallthroughRetryPolicy

Reconnection - Available Policies

ExponentialReconnectionPolicy

ReconnectionPolicy

ConstantReconnectionPolicy

(default)

II. Java Driver In Practice

Java Driver - Maven Artifact

<dependency> <groupId>com.datastax.cassandra</groupId> <artifactId>cassandra-‐driver-‐core</artifactId> <version>2.1.4</version>

</dependency>

Available in Maven Central (OSGi bundle).

Supports Apache Cassandra 1.2 to 2.1

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

• http://www.datastax.com/documentation/developer/java-driver/2.1

Bootstrapping

1) Ready… (configure)

Cluster cluster = Cluster.builder() .addContactPoints("10.1.2.5", "cassandra_node3") .build();

2) Steady… (connect)

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

3) Go! (execute)

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

The rest of the nodes will be discovered by the driver

Cluster and Session are thread-safe. Singletons should be created at startup!

Live Coding!

• https://www.github.com/adutra/cassandra-java-driver-demo

Object Mapping API

• Map Objects to Statements and ResultSets to Objects

• Avoid boilerplate for common use cases

• Do NOT hide Cassandra from the developer

• No “clever tricks” à la Hibernate

• Not JPA compatible, but JPA-ish API

Object Mapping API - Maven Artifact

<dependency> <groupId>com.datastax.cassandra</groupId> <artifactId>cassandra-‐driver-‐mapping</artifactId> <version>2.1.4</version>

</dependency>

Additional artifact for object mapping

Available since Driver 2.1.0

Basic Object Mapping

CREATE TYPE address ( street text, city text, zip int ); CREATE TABLE users ( login text PRIMARY KEY, name text, age int, address frozen<address> );

@UDT(name = "address") public class Address { private String street; private String city; private int zip; // getters and setters omitted... } @Table(name = "users") public class User { @PartitionKey private String login; private String name; private Integer age; @Frozen private Address address; // getters and setters omitted... }

III. DevCenter

DevCenter

• Easy-to-use visual query tool for Cassandra and DSE• Current version: 1.2.2

• 1.3 coming soon• Features

• Create and manage connections• Create and run CQL queries + results visualization• Syntax highlighting & validation• Content assist• Query Tracing Support• Visual DDL assistants (coming soon)

DevCenter

• Audience• Developers (prototyping)• Ops (administration)• Students (learn CQL)

• Technology• Standalone Eclipse RCP application• Linux, Mac, Windows

• datastax.com/download

Questions?

We’re Hiring!

@DataStaxCareers

blog.datastax.com

github.com/datastax

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