On 20 Jan 2004 at 2:13, Jerry Pulley wrote:
> Hi, Mike.
>
> First, the infinite recursion issue: I've pasted in a simple controller
> and GUI that demonstrates the issue with next() returning null. If it
> is a bug in JMeter 1.9.1, the reason none of the component unit tests
> found it is probably that it requires the cooperation of the loop
> controller in the ThreadGroup. The component unit tests seem to focus
> on their components outside the framework. I don't know enough about
> JMeter to write a unit test that exercises the entire framework like
> that, so I just made a demo instead. Set up a ThreadGroup with the
> default properties and add a NullController. It'll dump the call stack
> at the 5th iteration; that should be enough to see what's happening
> before it blows the stack. When I traced it in a debugger the problem
> seemed to be in the LoopController - GenericController interaction.
This should probably be looked at with a currently active developer (not me currently,
unfortunately). So I'm copying this to the developer list as well.
>
> At any rate, once I saw what was going on I was able to deal with that
> issue by hacking a NullSampler with a trivial sample().
>
> That still left the question of why my triggered controller behaved as
> it did. If it had N subelements, all N executed the first time it was
> triggered, but only N-1 executed on all subsequent triggerings. My unit
> tests exercised it as far as I understand the various JMeter contracts,
> but I was missing the reinitialization behavior.
>
> Your comment about reInitialize() led me to try calling the
> GenericController version of it, and that solved the issue. Thank you
> very much. Having to return the NullSampler instead of null is keeping
> GenericController from reInitialize()ing, so for the moment I'm calling
> it directly.
>
> I used to understand JMeter ok, but things have changed since 1.7. Are
> there any good writeups on the GenericController and ThreadGroup
> algorithms?
Not really. The intent was to write the GenericController in such a way that each
method
used was self-explanatory and easily overridden to provide modified behavior. After
many
total rewrites of this controller, it's apparent the effort is still a failure and
probably the only
recourse is to sit down and write out documentation that fully explains the necessary
behavior
of a JMeter Controller. I doubt any developers are going to jump up to do this,
however :-) It
really is the type of thing a newcomer might do to get initially involved in the
project, if they
were interested.
-Mike
>
> thnx,
> jp
>
> P.S. Sorry for the long post. I get so excited when things start
> working.
>
> /* NullController */
> package net.jpulley.jmeter19.controller;
>
> import org.apache.jmeter.control.GenericController;
> import org.apache.jmeter.samplers.Sampler;
>
> public class NullController extends GenericController {
> private int callCount;
>
> public Sampler next() {
> if (++callCount == 5) {
> Thread.dumpStack();
> }
> return null;
> }
> }
>
> /* NullControllerGui */
> package net.jpulley.jmeter19.controller;
>
> import java.awt.BorderLayout;
> import org.apache.jmeter.control.gui.AbstractControllerGui;
> import org.apache.jmeter.testelement.TestElement;
>
> public class NullControllerGui extends AbstractControllerGui {
> public NullControllerGui() {
> init();
> }
>
> public String getStaticLabel() {
> return "Null Controller";
> }
>
> public TestElement createTestElement() {
> NullController ctlr = new NullController();
> configureTestElement(ctlr);
> return ctlr;
> }
>
> public void modifyTestElement(TestElement element) {
> configureTestElement(element);
> }
>
> private void init() {
> setLayout( new BorderLayout() );
> setBorder( makeBorder() );
> add( makeTitlePanel(), BorderLayout.NORTH );
> }
> }
> /*end demo*/
>
> Heh, might as well put in the relevant parts of the stack trace:
>
> java.lang.Exception: Stack trace
> at java.lang.Thread.dumpStack(Thread.java:1064)
> at
> net.jpulley.jmeter19.controller.NullController.next(NullController.java:11)
> org.apache.jmeter.control.GenericController.nextIsAController(GenericController.java:190)
> org.apache.jmeter.control.GenericController.next(GenericController.java:151)
> org.apache.jmeter.control.LoopController.nextIsNull(LoopController.java:169)
> org.apache.jmeter.control.GenericController.next(GenericController.java:141)
> ...
> org.apache.jmeter.control.GenericController.nextIsAController(GenericController.java:194)
> org.apache.jmeter.control.GenericController.next(GenericController.java:151)
> org.apache.jmeter.control.LoopController.nextIsNull(LoopController.java:169)
> org.apache.jmeter.control.GenericController.next(GenericController.java:141)
> org.apache.jmeter.control.GenericController.nextIsAController(GenericController.java:194)
> org.apache.jmeter.control.GenericController.next(GenericController.java:151)
> org.apache.jmeter.control.LoopController.nextIsNull(LoopController.java:169)
> org.apache.jmeter.control.GenericController.next(GenericController.java:141)
> org.apache.jmeter.control.GenericController.nextIsAController(GenericController.java:194)
> org.apache.jmeter.control.GenericController.next(GenericController.java:151)
> at org.apache.jmeter.threads.ThreadGroup.next(ThreadGroup.java:133)
> at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:270)
> at java.lang.Thread.run(Thread.java:534)
> java.lang.StackOverflowError
>
>
> On Mon, 2004-01-19 at 10:43, [EMAIL PROTECTED] wrote:
> > The semantics of the "next()" method are supposed to be like so:
> >
> > returns Sampler - sampler is intended to be executed.
> >
> > returns null, isDone() = false: This should indicate the the controller
> > has finished a full round of iteration, and the test should move on to
> > the next controller. If the test runs another iteration, the controller
> > should be ready for everything to begin again. This is why the
> > "nextIsNull()" method calls reinitialize().
> yessss
> >
> > returns null, isDone() = true; The controller has finished entirely, and
> > should not be run again. Indeed, it is generally dropped from the test
> > entirely.
> >
> > If returning null and not setting isDone to true is causing a problem,
> > that sounds like either:
> >
> > 1. You next() method is getting into and infinite recursive loop when
> > called subsequently aftering returning a null. If you haven't explicitly
> > looked into this possibility (ie written some unit tests for it) I consider
> > this most likely.
> >
> > 2. JMeter has been changed in some way since I last looked at it
> > that has introduced a bug, because this was not a problem
> > previously. I think this is unlikely since this particular bug would be
> > very noticeable in nearly all tests.
> >
> > -Mike
> >
> [snip]
>
>
>
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Michael Stover
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