如何分析Thread Dump
当Java Web程序运行变慢，或者发生故障时，需要使用Thread Dumps. 如果你觉得ThreadDumps非常复杂，这篇文章很可能帮助你。将会分析Java中的线程，线程如何创建的，如何管理线程，怎么从运行中的程序中dump 线程，最后怎么分析他们得到阻塞和存在瓶颈的线程。本文是在应用程序调试下得到的结果。
Java和线程 一个web server使用几十到几百条线程去处理大量的并发用户。如果多条线程使用共享的资源，无法避免线程之间对数据的竞争，有时候还会发生死锁。
线程竞争是web程序上不同的线程去访问共享资源，一条线程等待另外线程释放锁。例如，在记录log的时候，线程记录log时，必须先获得锁，然后去再访问共享资源。
死锁是一种特殊的线程竞争，两个或多个线程要完成自己的任务，都要必须要等待其他的线程完成他们的任务。
线程竞争会带来各种不同的问题，为了分析这些问题，需要使用Thread Dump。Thread Dump记录了每个线程真正的状态。
Java线程的背景
线程同步
多条线程之间可以同时执行，为了确保多线程在使用共享资源上面的通用性，使用线程同步保证在同一时间只能有一条线程可以访问共享资源。 线程同步在Java中可以使用监视器。每个Java对象都有一个监视器，这个监视器只能被一个线程拥有。当一个线程要获得另外线程拥有的监视器时，需要进入等待队列直到线程释放监视器。
线程的状态 为了分析Thread Dump ，需要先了解线程的状态。线程的状态是在java.lang.Thread.State中。
NEW:线程被创建但是还没有被执行RUNNABLE:线程正在占用cpu并且在执行任务BLOCKED:线程为了获得监视器需要等待其他线程释放锁WAITING:调用了wait，join，park方法使线程等待-无限期等待TIMED_WAITING:调用了sleep，wait，join，park方法使线程等待--有限期等待
线程类型java中线程可以分为两种： 1. 后台线程
2. 非后台线程
当没有其他的非后台线程运行时后台线程将会终止。即使你不创建线程，java应用默认也会创建很多线程。这些大多数都是后台线程，主要为了执行gc或者jmx等类型的任务
从 'static void main(String[] args)’方法中开启的线程叫做非后台线程，当这些线程停止时，其他的所有后台线程也会停止()
获得一个Thread Dump
将会介绍三种常用的方法。请注意还会有其他很多方法可以获取Thread Dump。一个Thread dump仅仅可以显示测量时的线程状态。所以为了查看线程状态的变化，建议5到10次，每次间隔5秒。
使用jstack获得Thread Ｄｕｍｐ通过使用ｊｐｓ命令来获得当前正在运行的Ｊａｖａ程序的ＰＩＤ
[user@linux ~]$ jps -v 25780 RemoteTestRunner -Dfile.encoding=UTF-825590 sub.rmi.registry.RegistryImpl 2999 -Dapplication.home=/home1/user/java/jdk.1.6.0_24 -Xms8m26300 sun.tools.jps.Jps -mlvV -Dapplication.home=/home1/user/java/jdk.1.6.0_24 -Xms8m使用ＰＩＤ作为ｊｓｔａｃｋ的参数获得Ｔｈｒｅａｄ Ｄｕｍｐ[user@linux ~]$ jstack -f 5824
"pool-1-thread-13" prio=6 tid=0x000000000729a000 nid=0x2fb4 runnable [0x0000000007f0f000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:129) at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:264) at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306) at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158) - locked <0x0000000780b7e688> (a java.io.InputStreamReader) at java.io.InputStreamReader.read(InputStreamReader.java:167) at java.io.BufferedReader.fill(BufferedReader.java:136) at java.io.BufferedReader.readLine(BufferedReader.java:299) - locked <0x0000000780b7e688> (a java.io.InputStreamReader) at java.io.BufferedReader.readLine(BufferedReader.java:362)
"BLOCKED_TEST pool-1-thread-1" prio=6 tid=0x0000000006904800 nid=0x28f4 runnable [0x000000000785f000] java.lang.Thread.State: RUNNABLE at java.io.FileOutputStream.writeBytes(Native Method) at java.io.FileOutputStream.write(FileOutputStream.java:282) at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:65) at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:123) - locked <0x0000000780a31778> (a java.io.BufferedOutputStream) at java.io.PrintStream.write(PrintStream.java:432) - locked <0x0000000780a04118> (a java.io.PrintStream) at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:202) at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:272) at sun.nio.cs.StreamEncoder.flushBuffer(StreamEncoder.java:85) - locked <0x0000000780a040c0> (a java.io.OutputStreamWriter) at java.io.OutputStreamWriter.flushBuffer(OutputStreamWriter.java:168) at java.io.PrintStream.newLine(PrintStream.java:496) - locked <0x0000000780a04118> (a java.io.PrintStream) at java.io.PrintStream.println(PrintStream.java:687) - locked <0x0000000780a04118> (a java.io.PrintStream) at com.nbp.theplatform.threaddump.ThreadBlockedState.monitorLock(ThreadBlockedState.java:44) - locked <0x0000000780a000b0> (a com.nbp.theplatform.threaddump.ThreadBlockedState) at com.nbp.theplatform.threaddump.ThreadBlockedState$1.run(ThreadBlockedState.java:7) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) Locked ownable synchronizers: - <0x0000000780a31758> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)"BLOCKED_TEST pool-1-thread-2" prio=6 tid=0x0000000007673800 nid=0x260c waiting for monitor entry [0x0000000008abf000] java.lang.Thread.State: BLOCKED (on object monitor) at com.nbp.theplatform.threaddump.ThreadBlockedState.monitorLock(ThreadBlockedState.java:43) - waiting to lock <0x0000000780a000b0> (a com.nbp.theplatform.threaddump.ThreadBlockedState) at com.nbp.theplatform.threaddump.ThreadBlockedState$2.run(ThreadBlockedState.java:26) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) Locked ownable synchronizers: - <0x0000000780b0c6a0> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)"BLOCKED_TEST pool-1-thread-3" prio=6 tid=0x00000000074f5800 nid=0x1994 waiting for monitor entry [0x0000000008bbf000] java.lang.Thread.State: BLOCKED (on object monitor) at com.nbp.theplatform.threaddump.ThreadBlockedState.monitorLock(ThreadBlockedState.java:42) - waiting to lock <0x0000000780a000b0> (a com.nbp.theplatform.threaddump.ThreadBlockedState) at com.nbp.theplatform.threaddump.ThreadBlockedState$3.run(ThreadBlockedState.java:34) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) Locked ownable synchronizers: - <0x0000000780b0e1b8> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
"DEADLOCK_TEST-1" daemon prio=6 tid=0x000000000690f800 nid=0x1820 waiting for monitor entry [0x000000000805f000] java.lang.Thread.State: BLOCKED (on object monitor) at com.nbp.theplatform.threaddump.ThreadDeadLockState$DeadlockThread.goMonitorDeadlock(ThreadDeadLockState.java:197) - waiting to lock <0x00000007d58f5e60> (a com.nbp.theplatform.threaddump.ThreadDeadLockState$Monitor) at com.nbp.theplatform.threaddump.ThreadDeadLockState$DeadlockThread.monitorOurLock(ThreadDeadLockState.java:182) - locked <0x00000007d58f5e48> (a com.nbp.theplatform.threaddump.ThreadDeadLockState$Monitor) at com.nbp.theplatform.threaddump.ThreadDeadLockState$DeadlockThread.run(ThreadDeadLockState.java:135) Locked ownable synchronizers: - None"DEADLOCK_TEST-2" daemon prio=6 tid=0x0000000006858800 nid=0x17b8 waiting for monitor entry [0x000000000815f000] java.lang.Thread.State: BLOCKED (on object monitor) at com.nbp.theplatform.threaddump.ThreadDeadLockState$DeadlockThread.goMonitorDeadlock(ThreadDeadLockState.java:197) - waiting to lock <0x00000007d58f5e78> (a com.nbp.theplatform.threaddump.ThreadDeadLockState$Monitor) at com.nbp.theplatform.threaddump.ThreadDeadLockState$DeadlockThread.monitorOurLock(ThreadDeadLockState.java:182) - locked <0x00000007d58f5e60> (a com.nbp.theplatform.threaddump.ThreadDeadLockState$Monitor) at com.nbp.theplatform.threaddump.ThreadDeadLockState$DeadlockThread.run(ThreadDeadLockState.java:135) Locked ownable synchronizers: - None"DEADLOCK_TEST-3" daemon prio=6 tid=0x0000000006859000 nid=0x25dc waiting for monitor entry [0x000000000825f000] java.lang.Thread.State: BLOCKED (on object monitor) at com.nbp.theplatform.threaddump.ThreadDeadLockState$DeadlockThread.goMonitorDeadlock(ThreadDeadLockState.java:197) - waiting to lock <0x00000007d58f5e48> (a com.nbp.theplatform.threaddump.ThreadDeadLockState$Monitor) at com.nbp.theplatform.threaddump.ThreadDeadLockState$DeadlockThread.monitorOurLock(ThreadDeadLockState.java:182) - locked <0x00000007d58f5e78> (a com.nbp.theplatform.threaddump.ThreadDeadLockState$Monitor) at com.nbp.theplatform.threaddump.ThreadDeadLockState$DeadlockThread.run(ThreadDeadLockState.java:135) Locked ownable synchronizers: - None
"socketReadThread" prio=6 tid=0x0000000006a0d800 nid=0x1b40 runnable [0x00000000089ef000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:129) at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:264) at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306) at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158) - locked <0x00000007d78a2230> (a java.io.InputStreamReader) at sun.nio.cs.StreamDecoder.read0(StreamDecoder.java:107) - locked <0x00000007d78a2230> (a java.io.InputStreamReader) at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:93) at java.io.InputStreamReader.read(InputStreamReader.java:151) at com.nbp.theplatform.threaddump.ThreadSocketReadState$1.run(ThreadSocketReadState.java:27) at java.lang.Thread.run(Thread.java:662)
"IoWaitThread" prio=6 tid=0x0000000007334800 nid=0x2b3c waiting on condition [0x000000000893f000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000007d5c45850> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:1987) at java.util.concurrent.LinkedBlockingDeque.takeFirst(LinkedBlockingDeque.java:440) at java.util.concurrent.LinkedBlockingDeque.take(LinkedBlockingDeque.java:629) at com.nbp.theplatform.threaddump.ThreadIoWaitState$IoWaitHandler2.run(ThreadIoWaitState.java:89) at java.lang.Thread.run(Thread.java:662)
[user@linux ~]$ ps -mo pid.lwp.stime.time.cpu -C java PID LWP STIME TIME %CPU10029 - Dec07 00:02:02 99.5 - 10039 Dec07 00:00:00 0.1 - 10040 Dec07 00:00:00 95.5
"NioProcessor-2" prio=10 tid=0x0a8d2800 nid=0x2737 runnable [0x49aa5000]java.lang.Thread.State: RUNNABLE at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method) at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:210) at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:65) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:69) - locked <0x74c52678> (a sun.nio.ch.Util$1) - locked <0x74c52668> (a java.util.Collections$UnmodifiableSet) - locked <0x74c501b0> (a sun.nio.ch.EPollSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:80) at external.org.apache.mina.transport.socket.nio.NioProcessor.select(NioProcessor.java:65) at external.org.apache.mina.common.AbstractPollingIoProcessor$Worker.run(AbstractPollingIoProcessor.java:708) at external.org.apache.mina.util.NamePreservingRunnable.run(NamePreservingRunnable.java:51) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662)
" DB-Processor-13" daemon prio=5 tid=0x003edf98 nid=0xca waiting for monitor entry [0x000000000825f000]java.lang.Thread.State: BLOCKED (on object monitor) at beans.ConnectionPool.getConnection(ConnectionPool.java:102) - waiting to lock <0xe0375410> (a beans.ConnectionPool) at beans.cus.ServiceCnt.getTodayCount(ServiceCnt.java:111) at beans.cus.ServiceCnt.insertCount(ServiceCnt.java:43)"DB-Processor-14" daemon prio=5 tid=0x003edf98 nid=0xca waiting for monitor entry [0x000000000825f020]java.lang.Thread.State: BLOCKED (on object monitor) at beans.ConnectionPool.getConnection(ConnectionPool.java:102) - waiting to lock <0xe0375410> (a beans.ConnectionPool) at beans.cus.ServiceCnt.getTodayCount(ServiceCnt.java:111) at beans.cus.ServiceCnt.insertCount(ServiceCnt.java:43)" DB-Processor-3" daemon prio=5 tid=0x00928248 nid=0x8b waiting for monitor entry [0x000000000825d080]java.lang.Thread.State: RUNNABLE at oracle.jdbc.driver.OracleConnection.isClosed(OracleConnection.java:570) - waiting to lock <0xe03ba2e0> (a oracle.jdbc.driver.OracleConnection) at beans.ConnectionPool.getConnection(ConnectionPool.java:112) - locked <0xe0386580> (a java.util.Vector) - locked <0xe0375410> (a beans.ConnectionPool) at beans.cus.Cue_1700c.GetNationList(Cue_1700c.java:66) at org.apache.jsp.cue_1700c_jsp._jspService(cue_1700c_jsp.java:120)
public Thread(Runnable target, String name);public Thread(ThreadGroup group, String name);public Thread(ThreadGroup group, Runnable target, String name);public Thread(ThreadGroup group, Runnable target, String name, long stackSize);
import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.ThreadFactory;import java.util.concurrent.atomic.AtomicInteger; public class MyThreadFactory implements ThreadFactory { private static final ConcurrentHashMap<String, AtomicInteger> POOL_NUMBER = new ConcurrentHashMap<String, AtomicInteger>(); private final ThreadGroup group; private final AtomicInteger threadNumber = new AtomicInteger(1); private final String namePrefix; public MyThreadFactory(String threadPoolName) { if (threadPoolName == null) { throw new NullPointerException("threadPoolName"); } POOL_NUMBER.putIfAbsent(threadPoolName, new AtomicInteger()); SecurityManager securityManager = System.getSecurityManager(); group = (securityManager != null) ? securityManager.getThreadGroup() : Thread.currentThread().getThreadGroup(); AtomicInteger poolCount = POOL_NUMBER.get(threadPoolName); if (poolCount == null) { namePrefix = threadPoolName + " pool-00-thread-"; } else { namePrefix = threadPoolName + " pool-" + poolCount.getAndIncrement() + "-thread-"; } } public Thread newThread(Runnable runnable) { Thread thread = new Thread(group, runnable, namePrefix + threadNumber.getAndIncrement(), 0); if (thread.isDaemon()) { thread.setDaemon(false); } if (thread.getPriority() != Thread.NORM_PRIORITY) { thread.setPriority(Thread.NORM_PRIORITY); } return thread; }}ThreadMXBean mxBean = ManagementFactory.getThreadMXBean();long[] threadIds = mxBean.getAllThreadIds();ThreadInfo[] threadInfos = mxBean.getThreadInfo(threadIds); for (ThreadInfo threadInfo : threadInfos) { System.out.println( threadInfo.getThreadName()); System.out.println( threadInfo.getBlockedCount()); System.out.println( threadInfo.getBlockedTime()); System.out.println( threadInfo.getWaitedCount()); System.out.println( threadInfo.getWaitedTime());}