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聊聊 Java 自带的那些*逆天*工具

原谅我的标题党,其实这些工具的确很厉害,之前其实介绍过一点相关的,是从我一次问题排查的过程中用到的,但是最近又有碰到一次排查问题,发现其实用 idea 直接 dump thread 是不现实的,毕竟服务器环境的没法这么操作,那就得用 Java 的那些工具了

jstack & jps

譬如 jstack,这个命令其实不能更简单了
看看 help 信息

-l参数可以打出锁的额外信息,然后后面的 pid 就是进程 id 咯,机智的小伙伴会问了(就你这个小白才问这么蠢的问题🤦‍♂️),怎么看 Java 应用的进程呢
那就是 jps 了,命令也很简单,一般直接用 jps命令就好了,不过也可以 help 看一下

稍微解释下,-q是只显示进程 id,-m是输出给main 方法的参数,比如我在配置中加给参数

然后用 jps -m查看

-v加上小 v 的话就是打印 jvm 参数

还是有点东西,然后就继续介绍 jstack 了,然后我们看看 jstack 出来是啥,为了加点内容我加了个死锁

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public static void main(String[] args) throws InterruptedException {
SpringApplication.run(ThreadDumpDemoApplication.class, args);
ReentrantLock lock1 = new ReentrantLock();
ReentrantLock lock2 = new ReentrantLock();
Thread t1 = new Thread() {
@Override
public void run() {
try {
lock1.lock();
TimeUnit.SECONDS.sleep(1);
lock2.lock();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
Thread t2 = new Thread() {
@Override
public void run() {
try {
lock2.lock();
TimeUnit.SECONDS.sleep(1);
lock1.lock();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
t1.setName("mythread1");
t2.setName("mythread2");
t1.start();
t2.start();
Thread.sleep(10000);
}

然后看看出来时怎么样的

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2020-08-02 21:50:32
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.201-b09 mixed mode):

"DestroyJavaVM" #147 prio=5 os_prio=31 tid=0x00007fc9dd807000 nid=0x2603 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:
- None

"mythread2" #140 prio=5 os_prio=31 tid=0x00007fc9dd877000 nid=0x9903 waiting on condition [0x0000700006fb9000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f5d4330> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
at com.nicksxs.thread_dump_demo.ThreadDumpDemoApplication$2.run(ThreadDumpDemoApplication.java:34)

Locked ownable synchronizers:
- <0x000000076f5d4360> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

"mythread1" #139 prio=5 os_prio=31 tid=0x00007fc9de873800 nid=0x9a03 waiting on condition [0x0000700006eb6000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f5d4360> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
at com.nicksxs.thread_dump_demo.ThreadDumpDemoApplication$1.run(ThreadDumpDemoApplication.java:22)

Locked ownable synchronizers:
- <0x000000076f5d4330> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

"http-nio-8080-Acceptor" #137 daemon prio=5 os_prio=31 tid=0x00007fc9de1ac000 nid=0x9b03 runnable [0x0000700006db3000]
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.ServerSocketChannelImpl.accept0(Native Method)
at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:422)
at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:250)
- locked <0x000000076f1e4820> (a java.lang.Object)
at org.apache.tomcat.util.net.NioEndpoint.serverSocketAccept(NioEndpoint.java:469)
at org.apache.tomcat.util.net.NioEndpoint.serverSocketAccept(NioEndpoint.java:71)
at org.apache.tomcat.util.net.Acceptor.run(Acceptor.java:95)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-ClientPoller" #136 daemon prio=5 os_prio=31 tid=0x00007fc9dd876800 nid=0x6503 runnable [0x0000700006cb0000]
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.KQueueArrayWrapper.kevent0(Native Method)
at sun.nio.ch.KQueueArrayWrapper.poll(KQueueArrayWrapper.java:198)
at sun.nio.ch.KQueueSelectorImpl.doSelect(KQueueSelectorImpl.java:117)
at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
- locked <0x000000076f2978c8> (a sun.nio.ch.Util$3)
- locked <0x000000076f2978b8> (a java.util.Collections$UnmodifiableSet)
- locked <0x000000076f297798> (a sun.nio.ch.KQueueSelectorImpl)
at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
at org.apache.tomcat.util.net.NioEndpoint$Poller.run(NioEndpoint.java:709)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-10" #135 daemon prio=5 os_prio=31 tid=0x00007fc9de1af000 nid=0x9d03 waiting on condition [0x0000700006bad000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-9" #134 daemon prio=5 os_prio=31 tid=0x00007fc9de1ab800 nid=0x6403 waiting on condition [0x0000700006aaa000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-8" #133 daemon prio=5 os_prio=31 tid=0x00007fc9de873000 nid=0x9f03 waiting on condition [0x00007000069a7000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-7" #132 daemon prio=5 os_prio=31 tid=0x00007fc9df0a1800 nid=0xa103 waiting on condition [0x00007000068a4000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-6" #131 daemon prio=5 os_prio=31 tid=0x00007fc9df242800 nid=0x6103 waiting on condition [0x00007000067a1000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-5" #130 daemon prio=5 os_prio=31 tid=0x00007fc9de872000 nid=0x5f03 waiting on condition [0x000070000669e000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-4" #129 daemon prio=5 os_prio=31 tid=0x00007fc9de1a6000 nid=0x5e03 waiting on condition [0x000070000659b000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-3" #128 daemon prio=5 os_prio=31 tid=0x00007fc9de871800 nid=0x5c03 waiting on condition [0x0000700006498000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-2" #127 daemon prio=5 os_prio=31 tid=0x00007fc9dead9000 nid=0x5b03 waiting on condition [0x0000700006395000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-exec-1" #126 daemon prio=5 os_prio=31 tid=0x00007fc9ddb00000 nid=0x5a03 waiting on condition [0x0000700006292000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f26aa00> (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 org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"http-nio-8080-BlockPoller" #125 daemon prio=5 os_prio=31 tid=0x00007fc9df242000 nid=0xa503 runnable [0x000070000618f000]
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.KQueueArrayWrapper.kevent0(Native Method)
at sun.nio.ch.KQueueArrayWrapper.poll(KQueueArrayWrapper.java:198)
at sun.nio.ch.KQueueSelectorImpl.doSelect(KQueueSelectorImpl.java:117)
at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
- locked <0x000000076f1eea30> (a sun.nio.ch.Util$3)
- locked <0x000000076f1ee198> (a java.util.Collections$UnmodifiableSet)
- locked <0x000000076f1ee010> (a sun.nio.ch.KQueueSelectorImpl)
at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
at org.apache.tomcat.util.net.NioBlockingSelector$BlockPoller.run(NioBlockingSelector.java:313)

Locked ownable synchronizers:
- None

"container-0" #124 prio=5 os_prio=31 tid=0x00007fc9df06a000 nid=0x5803 waiting on condition [0x000070000608c000]
java.lang.Thread.State: TIMED_WAITING (sleeping)
at java.lang.Thread.sleep(Native Method)
at org.apache.catalina.core.StandardServer.await(StandardServer.java:570)
at org.springframework.boot.web.embedded.tomcat.TomcatWebServer$1.run(TomcatWebServer.java:197)

Locked ownable synchronizers:
- None

"Catalina-utility-2" #123 prio=1 os_prio=31 tid=0x00007fc9de886000 nid=0xa80f waiting on condition [0x0000700005f89000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076c88ab58> (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.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1088)
at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"Catalina-utility-1" #122 prio=1 os_prio=31 tid=0x00007fc9de884000 nid=0x5667 waiting on condition [0x0000700005e86000]
java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076c88ab58> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093)
at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"RMI Scheduler(0)" #15 daemon prio=5 os_prio=31 tid=0x00007fc9de9ee000 nid=0x5503 waiting on condition [0x0000700005d83000]
java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000006c0015410> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093)
at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"Attach Listener" #13 daemon prio=9 os_prio=31 tid=0x00007fc9df149800 nid=0x3c07 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:
- None

"RMI TCP Accept-0" #11 daemon prio=5 os_prio=31 tid=0x00007fc9df100000 nid=0x4003 runnable [0x0000700005977000]
java.lang.Thread.State: RUNNABLE
at java.net.PlainSocketImpl.socketAccept(Native Method)
at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409)
at java.net.ServerSocket.implAccept(ServerSocket.java:545)
at java.net.ServerSocket.accept(ServerSocket.java:513)
at sun.management.jmxremote.LocalRMIServerSocketFactory$1.accept(LocalRMIServerSocketFactory.java:52)
at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:405)
at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:377)
at java.lang.Thread.run(Thread.java:748)

Locked ownable synchronizers:
- None

"Service Thread" #9 daemon prio=9 os_prio=31 tid=0x00007fc9df0ce800 nid=0x4103 runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:
- None

"C1 CompilerThread2" #8 daemon prio=9 os_prio=31 tid=0x00007fc9df0ce000 nid=0x4203 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:
- None

"C2 CompilerThread1" #7 daemon prio=9 os_prio=31 tid=0x00007fc9de0a3800 nid=0x3503 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:
- None

"C2 CompilerThread0" #6 daemon prio=9 os_prio=31 tid=0x00007fc9de89b000 nid=0x3403 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:
- None

"Monitor Ctrl-Break" #5 daemon prio=5 os_prio=31 tid=0x00007fc9df0ca000 nid=0x3303 runnable [0x0000700005468000]
java.lang.Thread.State: RUNNABLE
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
at java.net.SocketInputStream.read(SocketInputStream.java:171)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
- locked <0x00000006c001b760> (a java.io.InputStreamReader)
at java.io.InputStreamReader.read(InputStreamReader.java:184)
at java.io.BufferedReader.fill(BufferedReader.java:161)
at java.io.BufferedReader.readLine(BufferedReader.java:324)
- locked <0x00000006c001b760> (a java.io.InputStreamReader)
at java.io.BufferedReader.readLine(BufferedReader.java:389)
at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)

Locked ownable synchronizers:
- None

"Signal Dispatcher" #4 daemon prio=9 os_prio=31 tid=0x00007fc9de824000 nid=0x4503 runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:
- None

"Finalizer" #3 daemon prio=8 os_prio=31 tid=0x00007fc9dd811800 nid=0x4f03 in Object.wait() [0x0000700005262000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000006c0008348> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)
- locked <0x00000006c0008348> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)

Locked ownable synchronizers:
- None

"Reference Handler" #2 daemon prio=10 os_prio=31 tid=0x00007fc9de02a000 nid=0x5003 in Object.wait() [0x000070000515f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000006c001b940> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
- locked <0x00000006c001b940> (a java.lang.ref.Reference$Lock)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)

Locked ownable synchronizers:
- None

"VM Thread" os_prio=31 tid=0x00007fc9df00b800 nid=0x2c03 runnable

"GC task thread#0 (ParallelGC)" os_prio=31 tid=0x00007fc9de805000 nid=0x1e07 runnable

"GC task thread#1 (ParallelGC)" os_prio=31 tid=0x00007fc9de003800 nid=0x2a03 runnable

"GC task thread#2 (ParallelGC)" os_prio=31 tid=0x00007fc9df002000 nid=0x5403 runnable

"GC task thread#3 (ParallelGC)" os_prio=31 tid=0x00007fc9df002800 nid=0x5203 runnable

"VM Periodic Task Thread" os_prio=31 tid=0x00007fc9df11a800 nid=0x3a03 waiting on condition

JNI global references: 1087


Found one Java-level deadlock:
=============================
"mythread2":
waiting for ownable synchronizer 0x000000076f5d4330, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),
which is held by "mythread1"
"mythread1":
waiting for ownable synchronizer 0x000000076f5d4360, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),
which is held by "mythread2"

Java stack information for the threads listed above:
===================================================
"mythread2":
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f5d4330> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
at com.nicksxs.thread_dump_demo.ThreadDumpDemoApplication$2.run(ThreadDumpDemoApplication.java:34)
"mythread1":
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x000000076f5d4360> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
at com.nicksxs.thread_dump_demo.ThreadDumpDemoApplication$1.run(ThreadDumpDemoApplication.java:22)

Found 1 deadlock.

前面的信息其实上次就看过了,后面就可以发现有个死锁了,

上面比较长,把主要的截出来,就是这边的,这点就很强大了。

jmap

惯例还是看一下帮助信息

这个相对命令比较多,不过因为现在 dump 下来我们可能会用文件模式,然后将文件下载下来使用 mat 进行分析,所以可以使用
jmap -dump:live,format=b,file=heap.bin <pid>
命令照着上面看的就是打印活着的对象,然后以二进制格式,文件名叫 heap.bin 然后最后就是进程 id,打印出来以后可以用 mat 打开

这样就可以很清晰的看到应用里的各种信息,jmap 直接在命令中还可以看很多信息,比如使用jmap -histo <pid>打印对象的实例数和对象占用的内存

jmap -finalizerinfo <pid> 打印正在等候回收的对象

小tips

对于一些应用内存已经占满了,jstack 和 jmap 可能会连不上的情况,可以使用-F参数强制打印线程或者 dump 文件,但是要注意这两者使用的用户必须与 java 进程启动用户一致,并且使用的 jdk 也要一致

请我喝杯咖啡