how I stop this blocking of thread?

Hi Amit,

As you can see in the stack trace posted in the question description, the thread being parked is from the thread pool related to the blocking queue. Threads that are "parked" coming from pools are simply waiting for a task to be assigned. Also, they really consume 0% CPU so I don't think this should be a problem. sun.misc.Unsafe.park(...) is basically like Thread.wait, but it uses os code, so it is not exposed to us.

It is possible though that you have a concurrency issue making it so your queue is blocking itself forever.

Hello Amit!

 Looks like you captured the application once it has become very sick. You should have used '-F' (i.e. Force) option to capture the thread dump. When you use the '-F' option, all threads will be showing up only in two states: 

1. BLOCKED

2. NATIVE

 You might want to capture thread dump before it becomes very sick. 

 Leaving that point aside, still I could see two issues in your application:
 
 a. 636 threads are in BLOCKED state that are originating from 'java.util.concurrent.ThreadPoolExecutor'
 
- sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise)
- java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame)
- java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await() @bci=42, line=2039 (Compiled frame)
- java.util.concurrent.LinkedBlockingQueue.take() @bci=29, line=442 (Compiled frame)
- java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1074 (Compiled frame)
- java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1134 (Compiled frame)
- java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=624 (Compiled frame)
- java.lang.Thread.run() @bci=11, line=748 (Compiled frame)

 b. 146 threads are in BLOCKED state that are originating from 'java.util.concurrent.ScheduledThreadPoolExecutor'
 
- sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise)
- java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame)
- java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await() @bci=42, line=2039 (Compiled frame)
- java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=100, line=1088 (Compiled frame)
- java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame)
- java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1074 (Compiled frame)
- java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1134 (Compiled frame)
- java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=624 (Compiled frame)
- java.lang.Thread.run() @bci=11, line=748 (Compiled frame)

Primary reason for this is: There are way too many threads in the pool that then the demand for the work load. You might have to configure lower value to the min thread pool size.