How to get database connection through websphere O

问题:

i've got a websphere 6.1 cluster environment which is composed of two nodes with 2 appservers each. Let's call NodeA including Server1(2809) & Server2(2810), NodeB including Server3(2811) & Server4(2812). Meanwhile, i created a cluster-scope datasource with JNDI local_db.

Right now i want to get database connection in a java client through WAS ORB call from above environment. The specific part of java code would look like this:

        Hashtable env = new Hashtable();
        env.put(Context.INITIAL_CONTEXT_FACTORY,"com.ibm.websphere.naming.WsnInitialContextFactory");
        env.put(Context.PROVIDER_URL,"iiop://localhost:2809");  

        javax.sql.DataSource ds = (DataSource)initialContext.lookup("local_db");

        Connection cn = ds.getConnection();

1. If above java client code gets run, will the database connection retrieve request follow load-balancing rule among the four connection pools of all application servers?

2. Moreover, if my java client gets one database connection successfully and then run a big SQL Query with large result return, as for the memory space occupation, which WAS application server would take care? only server1 due to port 2809 used above or the target server who returns the database connection?

3. BTW, if i put two server members for that PROVIDER_URL, such as iiop://localhost:2809, localhost:2810, does it mean load-balancing or failover?

   Please help explain and correct me if i'm understanding wrongly!

Thanks

回答1:

Let me start with the easy ones and proceed to the rest

1. Having two provider URLs' implies failover. If you can't connect to the first naming server, it connects to the second naming server and continues till the end of that list. Notice the Fail over is for connection to the naming server (not to the resource itself)

The look up is done on the server that you connect to. THe local_db represents a datasource (and its connection pool) on that server. You will one work with the server1 (as you are connecting to that NS) and will get connection from the datasource hosted on that server.

You will never get any connection from the other servers. In others words there is no load balancing (one request uses connection from server1, another uses a connection from server 2 etc). I believe this is what you mean by load balancing in your question above.

HTH

回答2:

A DataSource is neither remotable nor serializable. Therefore, if you look up local_db from the server, it will return a javax.naming.Reference that the client uses to create a new DataSource instance with the same configuration as the one on the server. That also means that once the lookup has been performed, no JDBC method will ever send requests to the WebSphere server.