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 @

3

@alexdut

linkedin.com/in/alexandredutra

github.com/adutra

[email protected]


Agenda

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

4


Agenda


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

5

TDD!


Agenda


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

6

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

TDD!

Demo!

I. Java Driver Architecture


Native Protocol - Basics

8

Client Coord

Node Replica

Replica

ReplicaNode

Coordinator node:Forwards all R/W requeststo corresponding replicas

Native Protocol


Native Protocol - Request Pipelining

9

Client

WithoutRequest Pipelining

Cassandra


Native Protocol - Request Pipelining

10

Client

WithRequest Pipelining

Cassandra

1

2

1

3

2

3

StreamID


Native Protocol - Notifications

11

Client

WithoutNotifications

WithNotifications

NodeNode

Node

Client

NodeNode

Node

Poll

Push


Node Discovery

12

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

Node

Node

Contact Point Node

Client

Contact Point

Contact Point

Cluster.init()

Control connection

Session.init()

Regular connections

Discovered node


Load Balancing

13

Node

Node

Node

ClientThread

Node

Driver

Cassandra 2.0N connections per node


Load Balancing

14

Node

Node

Node

ClientThread

Node

Driver

Cassandra 2.1+ 1 single connection per node


Load Balancing

15

ClientThread

Node

Node

Node

Node

6

23

45

1Driver

Load balancing picks up a node


Load Balancing - Round Robin

16

Node

Node

NodeNode

Client

Node

Node

1

2

3 etc.


Load Balancing - DC Aware Round Robin

17

Node

Node

Node

Client

Datacenter A

Local nodes are tried first

Node

Node

Node

Datacenter B


Load Balancing - DC Aware Round Robin

18

Node

Node

Node

Client

Datacenter A

Node

Node

Node

Datacenter B

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


Load Balancing - Available Policies

19

RoundRobinPolicy

LoadBalancingPolicy

DCAwareRoundRobinPolicy


Load Balancing - Available Policies

20

TokenAwarePolicy

WhiteListPolicy

LatencyAwarePolicy

RoundRobinPolicy

LoadBalancingPolicy



Load Balancing - Token Awareness

21

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

Node

Node

ReplicaNode

Client

Replica

Replica


Load Balancing - Default Policy

22

TokenAwarePolicy


Token awareness

DC awareness


Automatic Failover

23

ClientThread

Node

Node

Node

Node

7

2

4

53

1

Driver

6

X

Load balancing tries next node


Fault Tolerance

24

• UnavailableException

• Consistency level not met

• ReadTimeoutException

• WriteTimeoutException

• Coordinator times out

Retry

X⚠️

Client


Fault Tolerance

25

• UnavailableException

• Consistency level not met

• ReadTimeoutException

• WriteTimeoutException

• Coordinator times out

Retry

X⚠️

Client

• NoHostAvailableException

• Cluster is down

• Network connectivity issue

Client X

Reconnect


Retry - Available Policies

26

LoggingRetryPolicyDefaultRetryPolicy

RetryPolicy

DowngradingConsistencyRetryPolicy

FallthroughRetryPolicy


Reconnection - Available Policies

27

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

29


Bootstrapping

30

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', '[email protected]')");

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

31


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

32


Object Mapping API - Maven Artifact

33

<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

34

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)

36


DevCenter

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

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

• datastax.com/download

37

Questions?

We’re Hiring!

@DataStaxCareers

blog.datastax.com

github.com/datastax


Paris JUG Sponsors

40

Cassandra for Java Developers @ Paris JUG

Technology

Transcript of Cassandra for Java Developers @ Paris JUG