生成Java线程转储而不重新启动。 [英] Generate a Java thread dump without restarting.

问题描述

我想创建一个跟踪内存使用情况和cpu使用情况的线程。

I'd like to create a thread that keeps track of the memory usage and cpu usage.

如果应用程序达到高级别，我想生成一个堆转储或线程转储。

If the application reaches a high level, I want to generate an heap dump or a thread dump.

有没有办法在不重新启动的情况下生成线程转储运行时？

Is there a way to generate a Thread dump runtime without restarting?

推荐答案

以下是我们如何以编程方式执行此操作： http://pastebin.com/uS5jYpd4

Here's how we do it programmatically: http://pastebin.com/uS5jYpd4

我们使用 JMX ThreadMXBean 和 ThreadInfo 类：

ThreadMXBean mxBean = ManagementFactory.getThreadMXBean();
ThreadInfo[] threadInfos = mxBean.getThreadInfo(mxBean.getAllThreadIds(), 0);
...

您还可以执行 kill -QUIT pid 在~unix下将堆栈转储到标准输出。还有jstack来转储JVM的堆栈。

You can also do a kill -QUIT pid under ~unix to dump the stacks to the standard-out. There is also jstack to dump the stack of a JVM.

如果应用程序的负载平均值高于某个阈值，我们还有一个转储堆栈的自动化：

We also have an automation which dumps the stack if the load average of the application is above some threshold:

private long lastCpuTimeMillis;
private long lastPollTimeMillis;

public void checkLoadAverage() {
    long now = System.currentTimeMillis();
    long currentCpuMillis = getTotalCpuTimeMillis();
    double loadAvg = calcLoadAveragePercentage(now, currentCpuMillis);
    if (loadAvg > LOAD_AVERAGE_DUMP_THRESHOLD) {
        try {
            dumpStack("Load average percentage is " + loadAvg);
        } catch (IOException e) {
            // Oh well, we tried
        }
    }
    lastCpuTimeMillis = currentCpuMillis;
    lastPollTimeMillis = now;
}

private long getTotalCpuTimeMillis() {
    long total = 0;
    for (long id : threadMxBean.getAllThreadIds()) {
        long cpuTime = threadMxBean.getThreadCpuTime(id);
        if (cpuTime > 0) {
            total += cpuTime;
        }
    }
    // since is in nano-seconds
    long currentCpuMillis = total / 1000000;
    return currentCpuMillis;
}

private double calcLoadAveragePercentage(long now, long currentCpuMillis) {
    long timeDiff = now - lastPollTimeMillis;
    if (timeDiff == 0) {
        timeDiff = 1;
    }
    long cpuDiff = currentCpuMillis - lastCpuTimeMillis;
    double loadAvg = (double) cpuDiff / (double) timeDiff;
    return loadAvg;
}

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