Java EE - find session size

Question

Is there a way to programmatically track the size of a specific session on a Java EE application server, or do I need to resort to tools for application developers for applications to do this?

Two scenarios:

• Tracking from the application (a kind of interface like JMX)
• A track from the outside (outside) is a common code that works on all application servers.

Answer 1

There is no standard way to do this. In fact, there is really no special way to weigh an object, considering it not just primitives. One way is to serialize the object into an array of bytes and accept it as an indicator of size.

An option would be to use a profiler such as YourKit , which takes a pretty good hit when calculating the saved link size.

Maybe the provider API is for this, since most SessionManager should serialize session data for replication and storage.

Answer 2

There are two approaches:

• If your session is Serializable (as it should be), there are some tools that calculate the length of the serialized version of the Session object. e.g. LambdaProbe for Apache Tomcat

• If your session is not Serializable, then this is more complicated. The solution we took is to follow the sizeofagent method. It uses the [Instrumentation.getObjectSize ()] method ( http://java.sun.com/j2se/1.5.0/docs/api/java/lang/instrument/Instrumentation.html#getObjectSize(java.lang.Object)) . It requires you to run the JVM with a special agent:

  java -javaagent: sizeofag.jar