Overview

With RMI-IIOP load balancing, IIOP client requests are distributed to different server instances or name servers. The goal is to spread the load evenly across the cluster, thus providing scalability. IIOP load balancing combined with EJB clustering and availability also provides EJB failover.

The following topics are addressed here:

• General Requirements for Configuring Load Balancing

• Load Balancing Models

General Requirements for Configuring Load Balancing

Oracle GlassFish Server provides high availability of remote EJB references and NameService objects over RMI-IIOP, provided all the following apply:

• Your deployment has a cluster of at least two instances.

• Java EE applications are deployed to all instances and clusters that participate in load balancing.

• RMI-IIOP client applications are enabled for load balancing.

GlassFish Server supports load balancing for Java applications executing in the Application Client Container (ACC). See Enabling RMI-IIOP Hardware Load Balancing and Failover.

Load Balancing Models

GlassFish Server supports two general models for load balancing:

InitialContext Load Balancing

When a client performs a JNDI lookup for an object, the Naming Service creates a InitialContext (IC) object associated with a particular server instance. From then on, all lookup requests made using that IC object are sent to the same server instance. InitialContext load balancing can be configured automatically across an entire cluster.

Per-Request Load Balancing (PRLB)

Per Request Load Balancing (PRLB) is a method for load balancing stateless EJBs that enables load-balancing for each request to an EJB instance. PRLB chooses the first node in a cluster to use on each request. PRLB is configured on a per-EJB basis.