As documented in the Administrator's Guide, Orbix Java provides two client side load balancing strategies for replicated servers:

1. per-client ORB (default) - once a client side proxy binding has been established to a server replica, all  subsequent requests from that client ORB to that server will reuse the same client side proxy binding. This results in all requests from a client ORB going the same server replica. 
2. per_request_lb - for each request the client ORB retrieves an IOR from the locator and the request is forwarded to the server replica specified by that IOR.

It is also possible to turn off the client side proxy binding reuse (described in point 1) by setting the com.iona.corba.IT_CORBA.CLIENT_LOAD_BALANCING_POLICY_ID policy. If the client side proxy binding is not reused, then each time a CORBA proxy is created, the ORB retrieves an IOR from the locator that specifies a server replica. All subsequent requests made on that CORBA proxy will be sent to the same server replica.

To understand how com.iona.corba.IT_CORBA.CLIENT_LOAD_BALANCING_POLICY_ID is used we need to understand when an ORB reuses a client side proxy binding. When a client application invokes the first operation on a CORBA Proxy, the ORB takes the following details into account as it determines whether or not it can reuse an existing client side proxy binding:

• Associated ORB instance—the identity of the ORB instance on the client side with which the object reference is associated.

• Endpoint ID—from the IOR profile currently used by the object.

• IOR Components—from the IOR profile currently used by the object.

• Effective policy set—the client policies that are effective for this CORBA proxy. On the client side, it is possible to set policies at several granularity levels, down to the level of a single CORBA proxy. The effective policy set is obtained by merging CORBA proxy and ORB-level policies.

...

java.util.Properties props = System.getProperties();
props.put("org.omg.CORBA.ORBClass", "com.iona.corba.art.artimpl.ORBImpl");
props.put("org.omg.CORBA.ORBSingletonClass", "com.iona.corba.art.artimpl.ORBSingleton");

 

//retrieve IOR

org.omg.CORBA.Object default_corba_obj = ...

 

//create policy with a unique (for that proxy) string value.

 

Any any1 = orb.create_any();
any1.insert_string("one");

 

Policy policies1[] = { orb.create_policy(CLIENT_LOAD_BALANCING_POLICY_ID.value, any1) };

//set policy

 

org.omg.CORBA.Object modified_policy_obj = ObjectHelper.set_policy_overrides(default_corba_obj,
                                                                  policies1,
                                                                  SetOverrideType.ADD_OVERRIDE);

 

//narrow to interface object in the standard way.

 

SimpleObject simpleObject = SimpleObjectHelper.narrow(modified_policy_obj );

 

  ...

org.omg.CORBA.Object default_corba_obj = ...

//create policy with a unique (for that proxy) string value.

Policy policies1[] = { orb.create_policy(CLIENT_LOAD_BALANCING_POLICY_ID.value, any1) };

//set policy