Generate a Java thread dump without restarting.
Here's how we do it programmatically: http://pastebin.com/uS5jYpd4
We use the JMX
ThreadMXBean
and ThreadInfo
classes:
ThreadMXBean mxBean = ManagementFactory.getThreadMXBean();
ThreadInfo[] threadInfos = mxBean.getThreadInfo(mxBean.getAllThreadIds(), 0);
...
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.
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;
}
Try “kill –QUIT” Process_id e.g
kill -QUIT 2134
This will trigger the thread dump without restarting it
To dump the threads to the standard out, you may do something like this
ThreadInfo[] threads = ManagementFactory.getThreadMXBean()
.dumpAllThreads(true, true);
for (ThreadInfo info : threads) {
System.out.print(info);
}
in Java 6 using the ThreadMXBean class. But I would suggest to use real logging instead of the standard output.