Clustering Objects with Replica-Aware Stubs
6.3.1 Clustering Objects with Replica-Aware Stubs
If an EJB or RMI object is clustered, instances of the object are deployed on all WebLogic Server instances in the cluster. The client has a choice about which instance of the object to call. Each instance of the object is referred to as a replica. The key technology that supports object clustering in WebLogic Server is the replica-aware stub. When you compile an EJB that supports clustering as defined in its deployment descriptor, appc passes the EJBs interfaces through the rmic compiler to generate replica-aware stubs for the bean. For RMI objects, you generate replica-aware stubs explicitly using command-line options to rmic, as described in Using the WebLogic RMI Compiler in Programming RMI for Oracle WebLogic Server. A replica-aware stub appears to the caller as a normal RMI stub. Instead of representing a single object, however, the stub represents a collection of replicas. The replica-aware stub contains the logic required to locate an EJB or RMI class on any WebLogic Server instance on which the object is deployed. When you deploy a cluster-aware EJB or RMI object, its implementation is bound into the JNDI tree. As described in Section 3.2, Cluster-Wide JNDI Naming Service, clustered WebLogic Server instances have the capability to update the JNDI tree to list all server instances on which the object is available. When a client accesses a clustered object, the implementation is replaced by a replica-aware stub, which is sent to the client. The stub contains the load balancing algorithm or the call routing class used to load balance method calls to the object. On each call, the stub can employ its load algorithm to choose which replica to call. This provides load balancing across the cluster in a way that is transparent to the caller. To understand the load balancing algorithms available for RMI objects and EJBs, see Section 5.2, Load Balancing for EJBs and RMI Objects. If a failure occurs during the call, the stub intercepts the exception and retries the call on another replica. This provides a failover that is also transparent to the caller.6.3.2 Clustering Support for Different Types of EJBs
Parts
» Oracle Fusion Middleware Online Documentation Library
» Document Scope and Audience Guide to this Document
» What Are the Benefits of Clustering? What Are the Key Capabilities of a Cluster?
» Servlets and JSPs EJBs and RMI Objects
» Getting Connections with Clustered JDBC Failover and Load Balancing for JDBC Connections
» Pure-Java Versus Native Socket Reader Implementations
» Client Communication via Sockets
» How WebLogic Server Creates the Cluster-Wide JNDI Tree
» How WebLogic Server Updates the JNDI Tree Client Interaction with the Cluster-Wide JNDI Tree
» Load Balancer Configuration Requirements Load Balancers and the WebLogic Session Cookie
» Related Programming Considerations How Session Connection and Failover Works with a Load Balancer
» Round-Robin Load Balancing Weight-Based Load Balancing
» Transactional Collocation Optimization for Collocated Objects
» Methods of Configuring Clusters Load Balancing for JDBC Connections
» Using Replication Groups HTTP Session State Replication
» Connection with Load Balancing Hardware Failover with Load Balancing Hardware
» Configuration Requirements for Cross-Cluster Replication
» Configuring Session State Replication Across Clusters
» Clustering Objects with Replica-Aware Stubs
» Failover and JDBC Connections Understanding Server and Service Migration
» Migration Terminology Oracle Fusion Middleware Online Documentation Library
» Features That Use Leasing Leasing Versions
» Determining Which Type of Leasing To Use High-availability Database Leasing
» Non-database Consensus Leasing Leasing
» Preparing for Automatic Whole Server Migration
» Configuring Automatic Whole Server Migration
» Startup Process in a Cluster with Migratable Servers
» Automatic Whole Server Migration Process
» Manual Whole Server Migration Process Administration Server Role in Whole Server Migration
» Migratable Server Behavior in a Cluster Node Manager Role in Whole Server Migration
» Cluster Master Role in Whole Server Migration
» JMS-related Services JTA Transaction Recovery Service
» Custom Store Availability for JMS Services Default File Store Availability for JTA
» Best Practices for Targeting JMS when Configuring Automatic Service Migration
» Architecture Web Application Tiers
» Combined Tier Architecture De-Militarized Zone DMZ Load Balancer Proxy Plug-In
» No Collocation Optimization Firewall Restrictions
» Multi-Tier Proxy Architecture Proxy Architecture Benefits Proxy Architecture Limitations
» Proxy Plug-In Versus Load Balancer
» DMZ with Two Firewall Configuration
» Dynamic Cluster Address If you do not explicitly define a cluster address
» Configuration Roadmap Install WebLogic Server
» Starting a WebLogic Server Cluster
» Configure Node Manager Configure Load Balancing Method for EJBs and RMIs
» Sample web.xml This section contains a sample deployment descriptor file
» Accessing Applications Via the Proxy Server Ensure that applications clients will
» Configure Replication Groups Configure Migratable Targets for Pinned Services
» Migrating When the Currently Active Host is Unavailable Use this migration
» Configure Multicast Time-To-Live TTL Configure Multicast Buffer Size
» Cluster-Related Configuration Options Follow Usage and Configuration Guidelines
» Manual Migration of the JTA Transaction Recovery Service State Management in a Cluster
» Naming Considerations Administration Server Considerations
» Firewall Considerations Avoiding Problems
» Check the Server Version Numbers Check the Multicast Address Check the CLASSPATH Value
Show more