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Debugging JMeter Tests

(This article is part of the JMeter Series)

Useful ways to debug JMeter as far as I know:

  • insert a “Debug Sampler”

the “Debug Sampler” will emit “everything that’s known” to JMeter. That output can be displayed in the “View Results Tree Listener”:

  • have a look at the JMeter log file (which is usually dumped from where you’ve started JMeter)

  • check the output of one of the listeners such as the “View Results Tree Listener”.

  • if you need to debug regexes of a “Regular Expression Extractor” then you can have a look at the source code of the page you want to extract a value from inside the “View Results Tree Llistener” and enter the same regular expression in the “Search” field (searching is only implemented in JMeter > v2.4).

In that picture you can see JMeter matching and displaying the regex entered in the search field inside an HTML page retrieved though the “HTTP Client Sampler”.

Tomáš Pospíšek, 1.1.2011

Understanding what's going on in ExtJS

Recently I had to pre-select a Node inside a TreePanel ExtJS widget. I tried many ways but failed because most of the time when I tried to:;

that node would not yet be rendered into the browser's DOM and so the select would fail somewhere inside the extjs.js blob with something like "this ... undefined ...". What I needed was a "rendered" event, but there doesn't seem to be such an event for neither TreePanel not TreeNode or any of their superclasses. Diving into ExtJS code was not really very helpful because it's a framework that does things through layers and layers and as such is not trivial to understand quickly.

Thus, the same ole problem with JavaScript as ever: "show me all the events there are". However, surprisingly, in contrast to standard JavaScript, ExtJS has an easy standard way to accomplish this:

  Ext.util.Observable.capture( myTree, function(event) {                                                                                                        
                                         console.log("got an event in myTree");
                                         console.log(event); });

And quickly I discovered that there indeed is an obscure event that I can, out of alternatives, missuse to do what I want, which is expandnode.

Aparently, after a node is exapanded, all its children are put into the DOM and seem to be manipulable then. Thus:

         * select node with real_id - this is only called once
         * after the tree is rendered for the first time.
         * After that the listener itself is unregistered.
        function select_node(node) {
          node.eachChild( function(child) { 
            if(child.attributes.real_id == real_id ) {
              categories_panel.un('expandnode', select_node);
        myTree.on('expandnode', select_node);

Tomáš Pospíšek

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