Linux排查Java线程数异常

最新推荐文章于 2022-04-20 11:44:05 发布

原创最新推荐文章于 2022-04-20 11:44:05 发布 · 770 阅读

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#java #多线程 #jdk #linux #jvm

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本文详细介绍了在Linux系统中遇到Java应用程序线程数异常时的排查步骤，包括如何使用JDK工具（如jstack）进行线程 dump，分析线程状态，找出可能导致问题的原因，以及结合Linux命令（如ps, top, strace等）进一步定位问题。" 81516263,7770296,Tomcat启动错误：数据库连接超时问题及解决,"['数据库连接', 'Tomcat故障排查', 'MySQL管理', '服务器维护']

`1.问题调查分析`

发现在代码中使用了线程池 Executors.newFixedThreadPool(20);

我们先不讨论此处线程池使用是否正确，仅就此处修改而言，将原有 Executors.newFixedThreadPool() 替换；似乎并无不妥（这么修改，是为了遵循阿里规约）

int nThreads = Runtime.getRuntime().availableProcessors();
        ThreadPoolExecutor pools = new ThreadPoolExecutor(nThreads, nThreads, 120L, TimeUnit.SECONDS,
                new LinkedBlockingQueue<>(),
                new ThreadFactoryBuilder().setNameFormat("receive-from-python-thread-pool-%d").build(),
                new ThreadPoolExecutor.AbortPolicy());

`1.1 dump线程分析`

查找到Java程序对应的进程号

jps -l

将对应Java程序的线程栈信息转储到thread_dump.log文件

jstack ${pid_num} > thread_dump.log


"pool-165671-thread-1" #188938 prio=5 os_prio=0 tid=0x00007f1a38040000 nid=0x7f19 waiting on condition [0x00007f19065b9000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000000dbb0a178> (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 synchronizers:
        - None

"pool-164990-thread-1" #188175 prio=5 os_prio=0 tid=0x00007f1a5402c800 nid=0x7a61 waiting on condition [0x00007f18d0d5e000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000000d8c1ef78> (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 synchronizers:
        - None

原因：程序每次调用方法时，均会创建一个新的线程池来执行任务。但在执行任务后并未关闭该线程池，造成线程无法被回收，线程一直处于等待状态。因而线程数会随时间线性上升

`2.总结`

这个问题是由于线程池使用不当造成的。使用线程池是为了避免重复、频繁地创建、销毁线程，进而对多个线程进行复用。以上线程池的使用明显未达到该目的，并因为线程池未关闭而造成线程无法被回收，线程数持续增加。