High thread count in java thread dump

Question

My java web application running on wildfly-9.0.1.Final sometimes it consumes very high memory and CPU. I got the thread dump for this time and found more than 7K thread with an identical thread with below stack trace.

pool-47940-thread-1 - priority:5 - threadId:0x000000029ad3f800 - nativeId:0xfad0 - state:WAITING
stackTrace:
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000007a7d1fbe0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Locked ownable synchronize

I analyze thread dump using this

Here is a screenshot for the same.

I used below code in my application many times

ExecutorService executor = Executors.newFixedThreadPool(3);
//business logic
// This will make the executor accept no new threads and finish all existing threads in the queue
executor.shutdown();
// Wait until all threads are finish
while (!executor.isTerminated()) {

}

Is ablow code cause any issue?

Are this threads root cause for high memory and CPU usage?

Answer 1

In my above code, I used while (!executor.isTerminated()){} to wait for all task finished their job. This while loop uses CPU until all task finished, this may cause high CPU issue.

I modified my code as below. This solved my high CPU problem.

ExecutorService executor = Executors.newFixedThreadPool(3);
executor.shutdown();
executor.invokeAll(listOfTask);  // invokAll method will wait untill all task finished, No while loop here

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