Exploring Terracotta

Alex Miller (@puredanger)

Agenda

• Architecture and scale

• Examinator reference application

• What do people use it for?

• How does it work?

• Terracotta 3.0

Applications in Three Tiers

Server

Database

Client

How do we scale?

Server

Database

Client

Server

Client

Server

Client

But what about failover?

Option 1: Servers share state

Server

Database

Client

Server

Client

Server

Client

How?

• RMI

• JMS

• Custom (JGroups, etc)

Option 2: Database (“stateless”)

Server

Database

Client

Server

Client

Server

Client

Stateless == “State in the database”

• Database load

• Serialization to and from the database

• Network bandwidth

• Object / relational mapping due to impedance mismatch

Option 3: Terracotta!

Server

Client

Terracotta

Server

Client

Terracotta

Server

Client

Terracotta

DatabaseTerracotta

Server

Instance

Terracotta

Server

Instance

Why is this better?

• Hub and spoke vs peer to peer

• Avoid object / relational translation

• Avoid serialization

• Reduce database overload

• Programming model you already know

• Focus on your app, not scalability and high availability

Agenda

• Architecture and scale

• Examinator reference application

• What do people use it for?

• How does it work?

• Terracotta 3.0

Examinator

• Terracotta reference web application

• Online exams

• “Session” use case

• http://reference.terracotta.org

Examinator stack

• Spring-based stack

• MVC

• Web Flow

• Security

• Transactions

• Open source

• Tomcat / Jetty

• Hibernate / JPA

• Site Mesh

• Freemarker

View

Model

Controller

Service

DAO

Domain

Spring Web FlowSpring MVCSitemesh

JPAHibernate

Freemarker

Spring Security

What state should go in Terracotta?

Memory Terracotta Database

Data Lifetime

Appro

priate

ness

Examinator Terracotta Usage

• User registration codes

• Password reset codes

• Exam cache

• Session clustering

• Spring security (via session)

• Spring web flow (via session)

• Exam in progress session - answers, choice ordering, marked to review

Demo

Agenda

• Architecture and scale

• Examinator reference application

• What do people use it for?

• How does it work?

• Terracotta 3.0

Business Use Cases

• Distributed cache

• Clustered HTTP sessions

• Batch processing

• Grid

• Messaging and events

Terracotta Elements

• Replicated sessions

• Async processor

• Cache evictor

• ConcurrentStringMap

• Queues

• Master-worker

• TC Cache

Who Uses It?

• e-Commerce

• Online gaming

• Financial services

• Travel & leisure

• Social networking

Agenda

• Architecture and scale

• Examinator reference application

• What do people use it for?

• How does it work?

• Terracotta 3.0

Core Concepts

• Roots

• Instrumented Classes

• Locks

• Integration Modules

Clustered Heap

App App app = new App();app.run();

Clustered Heap

EmployeeManager employeeMgr = new EmployeeManager();

Object lock = new Object();Map<String,Employee> =

new HashMap<String,Employee>();

EmployeeManager

HashMap employees

Object lock

App

Clustered Heap

EmployeeManager

HashMap employees

Object lock

Employee

App

"U99411"

Employee.ACTIVE == 1

"Gandalf"

Employee employee = new Employee(

“U99411”, “Gandalf”, Employee.ACTIVE);

Clustered Heap

EmployeeManager

HashMap employees

Object lock

"U99411" Employee

App

"U99411"

Employee.ACTIVE == 1

"Gandalf"

employeeMgr.addEmployee(employee);

synchronized(lock) { employees.put(e.getId(), e);}

Clustered Heap

EmployeeManager

HashMap employees

Object lock

"U99411"

"U23526"

Employee

Employee

App

"U99411"

Employee.ACTIVE == 1

"Gandalf"

"U23526"

Employee.ACTIVE = 1

"U99411"

Let’s look at how to do that...

Agenda

• Architecture and scale

• Examinator reference application

• What do people use it for?

• How does it work?

• Terracotta 3.0

Terracotta 3.0

• Server Array Striping - server scalability

• Operations Center / Developer Console - new dashboard, DGC stats

• Cluster events API - topology, data locality

• Application groups - sharing data across heterogeneous applications

• Platform support - Oracle WebLogic 10.2, 10.3 and RHEL 5.0

Thanks!

• Terracotta Open Source JVM clustering:

• http://www.terracotta.org

• Apress: “The Definitive Guide to Terracotta”

• by Ari Zilka, Alex Miller, Geert Bevin, Jonas Boner, Orion Letizi, Taylor Gautier

• Alex Miller

• @puredanger

• http://tech.puredanger.com