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  1. JDK
  2. JDK-8022642

ScheduledThreadPoolExecutor with zero corePoolSize create endlessly threads

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: P3
    • Resolution: Duplicate
    • Affects Version/s: 7u4
    • Fix Version/s: 9
    • Component/s: core-libs
    • Labels:

      Backports

        Description

        FULL PRODUCT VERSION :
        java version " 1.7.0_04 "
        Java(TM) SE Runtime Environment (build 1.7.0_04-b22)
        Java HotSpot(TM) Client VM (build 23.0-b21, mixed mode)

        ADDITIONAL OS VERSION INFORMATION :
        Microsoft Windows [Version 6.1.7601]

        EXTRA RELEVANT SYSTEM CONFIGURATION :
        Not related

        A DESCRIPTION OF THE PROBLEM :
        When creating ScheduledThreadPoolExecutor with corePoolSize=0 and submiiting task using scheduleAtFixedRate then executor endlessly create tasks.
        A simple code below demonstrate the problem:

        A ScheduledThreadPoolExecutor is created with schedule=0.
        A delayed task is scheduled to far in the future (30 hours).
        After 10 seconds of running about 38K threads where created (this hang our system)

        When changing schedule to 1 then everything is run as expected


        STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
        Run the simple code below.

        EXPECTED VERSUS ACTUAL BEHAVIOR :
        EXPECTED -
        Number of created threads should be 1

        Expected output:

        Time offset 0(s)] threads count=1
        Time offset 1(s)] threads count=1
        Time offset 2(s)] threads count=1
        Time offset 3(s)] threads count=1
        Time offset 4(s)] threads count=1
        Time offset 5(s)] threads count=1
        Time offset 6(s)] threads count=1
        Time offset 7(s)] threads count=1
        Time offset 8(s)] threads count=1
        Time offset 9(s)] threads count=1
        ACTUAL -
        Thousands of threads are created per second

        Output:

        Time offset 0(s)] threads count=1
        Time offset 1(s)] threads count=3952
        Time offset 2(s)] threads count=8247
        Time offset 3(s)] threads count=12755
        Time offset 4(s)] threads count=17007
        Time offset 5(s)] threads count=21268
        Time offset 6(s)] threads count=25671
        Time offset 7(s)] threads count=30016
        Time offset 8(s)] threads count=34334
        Time offset 9(s)] threads count=38709

        REPRODUCIBILITY :
        This bug can be reproduced always.

        ---------- BEGIN SOURCE ----------
        public class STPE_EndlesslyCreateThreads {


            public static void main(String[] args) throws InterruptedException {



                final AtomicInteger threadsCounter = new AtomicInteger();

                ScheduledThreadPoolExecutor threadPoolExecutor = new ScheduledThreadPoolExecutor(0, new ThreadFactory() {
                    @Override
                    public Thread newThread(Runnable r) {

                        Thread t = new Thread(r);

                        threadsCounter.incrementAndGet();

                        return t;

                    }
                });

                threadPoolExecutor.scheduleAtFixedRate(new Runnable() {
                    @Override
                    public void run() {
                    }
                }, 30, 30, TimeUnit.HOURS);


                long now = System.currentTimeMillis();
                Thread.sleep(1);

                while ((System.currentTimeMillis()-now) < 10*1000) {

                    System.out.println( " Time offset " + (System.currentTimeMillis() - now) /1000 + " (s)] threads count= " + threadsCounter);

                    Thread.sleep(1000);
                }

                threadPoolExecutor.shutdown();
                threadPoolExecutor.awaitTermination(Long.MAX_VALUE, TimeUnit.HOURS);



            }
        }

        ---------- END SOURCE ----------

        CUSTOMER SUBMITTED WORKAROUND :
        Change corePoolSize to 1

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                Assignee:
                martin Martin Buchholz
                Reporter:
                webbuggrp Webbug Group
                Votes:
                1 Vote for this issue
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                4 Start watching this issue

                  Dates

                  Created:
                  Updated:
                  Resolved: