In a "Random Variable" element set true the "Per Thread(User)" option, and launch test plan in distributed mode (Remote Start).

ERROR - jmeter.threads.JMeterThread: Test failed! java.lang.NullPointerException

	at org.apache.jmeter.config.RandomVariableConfig.iterationStart(RandomVariableConfig.java:90)

	at org.apache.jmeter.control.GenericController.fireIterationStart(GenericController.java:318)

	at org.apache.jmeter.control.GenericController.fireIterEvents(GenericController.java:308)

	at org.apache.jmeter.control.GenericController.next(GenericController.java:128)

	at org.apache.jmeter.control.GenericController.nextIsAController(GenericController.java:182)

	at org.apache.jmeter.control.GenericController.next(GenericController.java:146)

	at org.apache.jmeter.control.GenericController.nextIsAController(GenericController.java:185)

	at org.apache.jmeter.control.GenericController.next(GenericController.java:146)

	at org.apache.jmeter.control.GenericController.nextIsAController(GenericController.java:182)

	at org.apache.jmeter.control.GenericController.next(GenericController.java:146)

	at org.apache.jmeter.control.GenericController.nextIsAController(GenericController.java:182)

	at org.apache.jmeter.control.GenericController.next(GenericController.java:146)

	at org.apache.jmeter.control.LoopController.next(LoopController.java:109)

	at org.apache.jmeter.threads.ThreadGroup.next(ThreadGroup.java:129)

	at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:242)

	at java.lang.Thread.run(Unknown Source)

The method:

public void iterationStart(LoopIterationEvent iterEvent) {
        Random randGen=null;
        if (getPerThread()){
            randGen = (Random) perThreadRandom.get();          <------ At line 90, the perThreadRandom object IS NULL.
        } else {
            synchronized(this){
                if (globalRandom == null){
                    init();
                    globalRandom = new Random(getRandomSeedAsLong());
                }
                randGen=globalRandom;
            }
        }
        if (n <=0){
            return;
        }
       long nextRand = minimum + randGen.nextInt(n);
       // Cannot use getThreadContext() as we are not cloned per thread
       JMeterVariables variables = JMeterContextService.getContext().getVariables();
       variables.put(getVariableName(), formatNumber(nextRand));
    }

The declaration:

private transient ThreadLocal perThreadRandom = new ThreadLocal() {
            protected Object initialValue() {
                init();
                return new Random(getRandomSeedAsLong());
            }};


¿Why transient? Javadoc says that ThreadLocal instances are typically private static fields in classes that wish to associate state with a thread. However, in this case not in possible, because init() and getRandomSeedAsLong() are non-static methods in the class. I comment out these calls, set static the declaration and work fine.

References: http://java.sun.com/j2se/1.5.0/docs/api/java/lang/ThreadLocal.html
I use: java version "1.6.0_14"