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JBoss Clustering An Overview

Bela Ban (bela@jboss.com)Lead JGroups, Manager Clustering Group

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Topics• What is clustering?• JBoss/JEMS Clustering Components

JGroups, JBoss Cache, HA-JNDI, SLSBs, SFSBs, HTTP session replication, Entity beans, EJB3 and POJO Clustering

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Why JBoss Clustering?• Transparent

No stub re-compiling! Client doesn’t know about clustering

aspect Cluster is maintained automatically Modular/stack approach

• Open source No extra cost to activate clustering Fairly robust 24/7 production support

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Clustering Terminology• Scalability

I want to handle x times the number of concurrent access than what I have now

• High availability Services are accessible with reasonable (and predictable)

response times at any time E.g., 99.999 (5 Nines in Telco)

• Load balancing A way to obtain high availability and better performance by

dispatching incoming requests to different servers Session affinity (or stickiness)

• Failover Process can continue when it is re-directed to a “backup” node

because the original one fails State needs to be available on backup

• Fault tolerance A service that guarantees strictly correct behavior despite

system failure

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Clustering Overview

Load Balancer

State Replication

Failover

R1

R1

R2

R2

R3

R3

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JBoss Thin Client Clustering• Front end load balancer

Software• Apache httpd and JBossWeb

Apache with mod_jk/mod_proxy JBossWeb (Tomcat on steroids)

Hardware• F5 Big IP

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JBoss Fat Client Clustering• Client uses smart proxy retrieved from JNDI• HA smart proxy

Based on Remoting (EJB3.0) or RMI (EJB2.1) Has load balancing policy, e.g., Round-Robin Has failover capability (sticky), e.g., detect call

failure• HA smart proxy has logic inside• Logic is pluggable, users can provide their

own Failover policy Load balancing, e.g. based on load or weight

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Running JBoss Cluster – Basic Steps• Use JBoss’ “all” configuration

run.bat -c all ./run.sh -c all

• The “all” configuration contains everything needed for clustering: It has all the libraries for clustering

• JGroups.jar, jboss-cache.jar Clustered beans (cluster-service.xml) HA-JNDI HTTP session replications (tc5-cluster-

service.xml) Farming HA-JMS

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Clustering divided in 3 parts• Client-cluster communication

Formerly HA-RMI, no HA-Remoting Load balancing and failover logic for fat

clients• State replication (inside cluster)

JBoss Cache• HTTP session, SFSBs, DistributedState

• Cluster communication (inside cluster) Method calls across all cluster nodes

• Cache invalidation, HA-JNDI, Farming

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Clustering Stack

JGroups

JBossCache

DRM

HA

-JN

DI

HTT

P

SFS

B

Ent

ity

Hibernate

Distributed RPC,

Membership

Mes

sagi

ng

HAServices

DRM

Farm

ing

HA-Singleton

HA

-R

emot

ing

Dis

tribu

ted

Sta

te

jBpm

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What is JGroups?• A reliable group messaging library• Reliable messaging

Sequence ordering• FIFO or total ordering

Flow control Acknowledgement Fragmentation

• Manage group membership Join Leave Shun

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What is JBoss Cache?• An in-memory, replicated,

transactional, persistent, and fine-grained cache system

• Uses JGroups as the messaging layer• Ideal for state replication

Transactional Persistent (and passivation) Fine-grained field-level replication Sub-partitioning, Buddy Replication

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HA-JNDI• Clustered JNDI

Node 1

HA-JNDI

JNDI

Node 2

JNDI

Node 3

HA-JNDI

JNDI

HA-JNDI

Partition "Main"

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• Local proxies Local proxies have direct reference to container localInvoke() creates invocation in container

• Remote proxies Remote proxies create invocation on client (method, args,

ObjectName) Communicate via Remoting framework

HA Smart Proxies

Client JVM

Dispatcher

Server JVM

011101

Typed Interface

Remote Proxy

RemotingConnector

AOP ContainerInvocation

Port 3873Client

dynamicInvoke(Invocation)

localInvoke(Method, args)

Local clientTyped

Interface

Local Proxy

JBoss Remoting

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JBoss Remoting

• JBoss Remoting is a framework with a single, simple API for making network based invocations and other network related services.

• Client – the external API access point for client code.• Client/Server Invoker – protocol specific implementation. For example,

SocketClientInvoker and SocketServerInvoker.• Invocation Handler – end target interface implemented by user that

receives the invocation from the client.

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SFSB Configuration in EJB 2 <enterprise-beans> <session> <ejb-name> ClusteredSessionBean </ejb-name> <jndi-name> ClusteredSessionBean </jndi-name> <clustered>True</clustered> <cluster-config> <partition-name>MyPartition</partition-name> <home-load-balance-policy> org.jboss.ha.framework.interfaces.RoundRobin </home-load-balance-policy> <bean-load-balance-policy> org.jboss.ha.framework.interfaces.FirstAvailable </bean-load-balance-policy> </cluster-config> </session>

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import org.jboss.ejb3.remoting.Clustered;

@Stateful@Clustered (loadBalancePolicy = FirstAvailable.class, partition = ”MyPartition”)public class ClusteredSessionBean implements ClusteredSession {}

SFSB Configuration in EJB3

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Entities

• Use JBoss Cache as Hibernate’s 2nd level cache Default cache in ejb3-entity-cache-service.xml

• jboss.cache:service=EJB3EntityTreeCache Configure in META-INF/hibernate.cfg.xml per app

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Entities<hibernate-configuration>

<session-factory>

<!-- Clustered cache with TreeCache -->

<property name="cache.provider_class">org.jboss.ejb3.entity.TreeCacheProviderHook</property>

<!– Object Name of cache to use -->

<property name="treecache.mbean.object_name">jboss.cache:service=EJB3EntityTreeCache</property>

<!-- Define cached entities and collections -->

<class-cache class="org.jboss.ejb3.tutorial.clusteredentity.bean.Customer" usage="transactional"/>

<class-cache class="org.jboss.ejb3.tutorial.clusteredentity.bean.Contact" usage="transactional"/>

<collection-cache collection="org.jboss.ejb3.tutorial.clusteredentity.bean.Customer.contacts" usage="transactional"/>

</session-factory>

</hibernate-configuration>

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Future@Entity@Replicated(mode=asynchronous,type=BuddyReplication,BackupCopies=1)public class Pojo { @id long key; @transient int cacheID;}

• Common set of annotations @Replicated, @Singleton, @N-lton, @Farmed,

@Remote• Integration into EJB3 (detach and attach

extended to replication)

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HTTP Session Replication• JBossWeb• Replication granularity

Session Modified attributes Modified fields

• Implemented using JBoss Cache

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Granularity: SESSION• Entire http session is replicated• User defines whether getAttribute()

call marks a session as dirty If attribute value is mutable, the

application can modify session state without calling setAttribute()

Operates blindly (application may not have changed the object)

After each HTTP request the entire session is serialized and replicated

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Granularity: SESSION

// … if replication triggered by getAttribute() is disabled:Pojo pojo = (Pojo)session.getAttribute(“pojo”);pojo.setName(“Ben”);session.setAttribute(“pojo”, pojo); // Done manually to replicate the session

// … if replication triggered by getAttribute() is enabled:Pojo pojo = (Pojo)session.getAttribute(“pojo”); // Session will be replicatedreturn pojo.getName(); // Pojo was not actually changed

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Granularity: ATTRIBUTE• Only attributes marked as dirty are replicated.

More efficient than session granularity User still needs to manage object relationship

• Can still configure whether getAttribute() marks the attribute as dirty

Pojo pojo = (Pojo)session.getAttribute(“pojo”);pojo.setName(“Ben”);session.setAttribute(“pojo”, pojo); // Only attribute “pojo” gets replicated!

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Granularity: FIELD• Replication is on Pojo field level where Pojo

has to be instrumented with AOP Annotation or XML

• Object relationships are maintained• Available beginning with JBoss 4.0.4

Person joe = (Person)session.getAttribute(“joe”);joe.setName(“joe”); // Only this field gets replicated.Person mary = (Person)session.getAttribute(“mary”);mary.setAge(41); // Only this field gets replicated.Address addr = new Address(“San Jose”, 95123);joe.setAddress(addr);mary.setAddress(addr); // addr only gets replicated once; shared ref is maintained

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Granularity: FIELD• When a Pojo object size is huge, e.g.,

a long List of size 100K, field level replication is efficient!

Subsription subs = (Subscription)session.getAttribute(“subscription”);// What if list is size of 100K?List mailingList = (List)subs.getMailingList(); Person joe = findSubscriber(“joe”, mailingList);joe.getAddress().setZip(94086); // Only replicates this field!!

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Clustering – Configuration• Session replication is enabled per web

application in WEB-INF/web.xml• Add <distributable/> to your webapp• JBoss specific stuff (async vs sync

replication) goes into WEB-INF/jboss-web.xml

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Links• Details on Clustering

Documentation• http://docs.jboss.com

JBoss AS chapters 16 (Clustering) & 17 (JBossCache and JGroups)

http://www.jboss.com/products/jbosscache http://www.jboss.com/products/jgroups

Webinars• http://www.jboss.com/services/

online_education Training

• http://www.jboss.com/services/training/clustering (next: Berlin March 21-24)

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Questions ?