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
Client
Server
Database

How do we scale?
Client Client Client
Server Server Server
Database

But what about failover?

Option 1: Servers share state
Client Client Client
Server Server Server
Database

How?
• RMI
• JMS
• Custom (JGroups, etc)

Option 2: Database (“stateless”)
Client Client Client
Server Server Server
Database

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!
Client Client Client
Server Server Server
Terracotta Terracotta Terracotta
Terracotta
Terracotta
Database Server
Server
Instance
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
View
• Web Flow Spring Web Flow
Model Spring MVC
• Security Sitemesh
Controller
• Transactions
Spring Security
• Open source Service Freemarker
• Tomcat / Jetty
DAO
• Hibernate / JPA JPA
Hibernate
Domain
• Site Mesh
• Freemarker

What state should go in Terracotta?
Appropriateness Memory Terracotta Database
Data Lifetime

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
App EmployeeManager employeeMgr =
new EmployeeManager();
Employee
Manager
Object lock
Object lock = new Object();
Map<String,Employee> =
new HashMap<String,Employee>();
HashMap
employees

Clustered Heap
App
Employee
\"U99411\"
Manager
Object lock
Employee.ACT
IVE == 1
Employee \"Gandalf\"
HashMap
employees
Employee employee =
new Employee(
“U99411”,
“Gandalf”,
Employee.ACTIVE);

Clustered Heap
App employeeMgr.addEmployee(employee);
Employee
\"U99411\"
Manager
Object lock
Employee.ACT
IVE == 1
\"U99411\" Employee \"Gandalf\"
HashMap
employees
synchronized(lock) {
employees.put(e.getId(), e);
}

Clustered Heap
App
Employee
\"U99411\"
Manager
Object lock
Employee.ACT
IVE == 1
\"U99411\" Employee \"Gandalf\"
HashMap
employees
\"U23526\" Employee \"U23526\"
Employee.ACT
IVE = 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