linux-x86/sample/scripting/scriptpad/src/scripts/memmonitor.js

/*
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 *
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 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
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 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */

// this checker function runs asynchronously
function memoryChecker(memoryBean, threshold, interval) {
    while (true) {
        var memUsage = memoryBean.HeapMemoryUsage;
        var usage = memUsage.get("used") / (1024 * 1024);

        println("usage: " + usage);

        if (usage > threshold) {
            alert("Hey! heap usage threshold exceeded!");
            // after first alert just return.
            return;
        }

        java.lang.Thread.sleep(interval);
    }
}

// add "Tools->Memory Monitor" menu item
if (this.application != undefined) {
    this.application.addTool("Memory Monitor",
        function () {
            // show threshold box with default of 50 MB
            var threshold = prompt("Threshold (mb)", 50);

            // show interval box with default of 1000 millisec.
            var interval = prompt("Sample Interval (ms):", 1000);
            var memoryBean = mbean("java.lang:type=Memory");

            // ".future" makes the function to be called
            // asynchronously in a separate thread.
            memoryChecker.future(memoryBean, threshold, interval);
        });
}