Terracotta

Context – Database abuse Database used to store Durable and Temporary data The database can become a bottleneck when too many requests SPOB SPOF

Database used to store Durable and Temporary data

The database can become a bottleneck when too many requests

SPOB

SPOF

Goals High availability High performances Linear scalability A possible solution : data grids It is a cluster of machines that handles in memory a large quantity of shared data

High availability

High performances

Linear scalability

A possible solution : data grids

It is a cluster of machines that handles in memory a large quantity of shared data

Terracotta (Server) Clustering at the JVM level 1 active TC server Server TC : Shared data Clients list Spread the updates Manage locks Garbage Collector

Clustering at the JVM level

1 active TC server

Server TC :

Shared data

Clients list

Spread the updates

Manage locks

Garbage Collector

Terracotta (Client) From the code No specific storage structure, only use Java classes Recommanded to use "synchronized" keyword Configuration file (XML) To configure the objects to share (roots) To configure locks To configure distributed methods ...

From the code

No specific storage structure, only use Java classes

Recommanded to use "synchronized" keyword

Configuration file (XML)

To configure the objects to share (roots)

To configure locks

To configure distributed methods

...

Useful for Relieving Database Overload Distributed Caching Hibernate second level cache HTTP Session Simplifying Application Architecture and avoid clustering by hand Virtual Heap for Large Datasets Clustering OSS Frameworks Master / Worker POJO Clustering Linear Scalability by connected JVMs

Relieving Database Overload

Distributed Caching

Hibernate second level cache

HTTP Session

Simplifying Application Architecture and avoid clustering by hand

Virtual Heap for Large Datasets

Clustering OSS Frameworks

Master / Worker

POJO Clustering

Linear Scalability by connected JVMs

HTTP Sessions

Demo Sample Terracotta application

Clustering a Wicket Application Wicket stores objects into the session Page, PageMap... These objects would need to be declared in the Terracotta configuration Already done in a wicket-module for Terracotta <clients> <modules> <module name= &quot;clustered-wicket-1.3&quot; version= &quot;2.6.2&quot; /> </modules> </clients> <instrumented-classes> <!--Include all classes for DSO instrumentation--> <include> <class-expression> *..* </class-expression> </include> </instrumented-classes> <!--Tell DSO which applications in your web container is using DSO--> <web-applications> <web-application> Gallery </web-application> </web-applications>

Wicket stores objects into the session

Page, PageMap...

These objects would need to be declared in the Terracotta configuration

Already done in a wicket-module for Terracotta

Sharing Data Wicket, as a Java application, will use objects for the business layer Instead of coming from the database, those objects can be in memory Should be declared in the tc-config file Classes using it (Pages), should declare it in the tc-config file public class SharedAlbum extends Observable implements Serializable { private List<String> images; private String defaultImage; private String host; private String album; private boolean slideShow = false ; }

Wicket, as a Java application, will use objects for the business layer

Instead of coming from the database, those objects can be in memory

Should be declared in the tc-config file

Classes using it (Pages), should declare it in the tc-config file

Demo Sharing information Wicket application vs Swing client

Ajax component Using of a checkbox to activate / deactivate a slideshow Wicket has built in integration for Ajax behaviours By clicking on the checkbox, The « Album » object state will be update on the server with the value of the checkbox The update object is shared / clustered via Terracotta add( new AjaxCheckBox( &quot;slideshow&quot; , new PropertyModel( this , &quot;slideshow&quot; )) { @Override protected void onUpdate(AjaxRequestTarget target) { album.updateSlideShowStatus( slideshow ); } }); <input type= &quot;checkbox&quot; wicket:id= &quot;slideshow&quot; value= &quot;true&quot; > Slideshow </input>

Using of a checkbox to activate / deactivate a slideshow

Wicket has built in integration for Ajax behaviours

By clicking on the checkbox, The « Album » object state will be update on the server with the value of the checkbox

The update object is shared / clustered via Terracotta

Demo Sharing information -Ajax checkbox

Why a cache ? Temporal Locality Non-uniform distribution EhCache Hibernate 2 nd level cache Terracotta

Why a cache ?

Temporal Locality

Non-uniform distribution

EhCache

Hibernate 2 nd level cache

Terracotta

Temporal Locality

Non Uniform Distribution

Non Uniform Distribution top 4 pages account for >50% of total hits top 17 pages account for >80% of total hits (14% of total pages) spend small amount of memory to cache top 14% of pages -> remove 80% of load

Cache limitations Amdahl' Law If the thing you’re caching is not your bottleneck, it won’t matter Memory cache uses memory which your app might need Concurrency access to cache can be a bottleneck

Amdahl' Law

If the thing you’re caching is not your bottleneck, it won’t matter

Memory

cache uses memory which your app might need

Concurrency

access to cache can be a bottleneck

Reduce LAtency

EhCache First created in 2003 by Greg Luck Most widely used Java cache Apache 2.0 licence JSR 107 Java cach implementation

First created in 2003 by Greg Luck

Most widely used Java cache

Apache 2.0 licence

JSR 107 Java cach implementation

EhCache Architecture

Hibernate 2 nd Level Cache

Using Terracotta EhCache 1.7.0 can be as drop in replacement Side effect on a single node, keeping state Monitoring and profiling capabilities Distributed transparently

EhCache 1.7.0 can be as drop in replacement

Side effect on a single node, keeping state

Monitoring and profiling capabilities

Distributed transparently

Using Terracotta

Enhancement to Hibernate More efficient in-memory and total count eviction (3.1.1) Better visibility of memory conditions Improved Query Caching Improved performance of core Terracotta (lock manager and memory manager)

More efficient in-memory and total count eviction (3.1.1)

Better visibility of memory conditions

Improved Query Caching

Improved performance of core Terracotta (lock manager and memory manager)