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thread
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===
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> 查看当前线程信息，查看线程的堆栈
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### 参数说明
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|参数名称|参数说明|
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|---:|:---|
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|*id*|线程id|
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|[n:]|指定最忙的前N个线程并打印堆栈|
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|[b]|找出当前阻塞其他线程的线程|
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|[i `<value>`]|指定cpu占比统计的采样间隔，单位为毫秒|
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> cpu占比是如何统计出来的？
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> 这里的cpu统计的是，一段采样间隔内，当前JVM里各个线程所占用的cpu时间占总cpu时间的百分比。其计算方法为：
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> 首先进行一次采样，获得所有线程的cpu的使用时间(调用的是`java.lang.management.ThreadMXBean#getThreadCpuTime`这个接口)，然后睡眠一段时间，默认100ms，可以通过`-i`参数指定，然后再采样一次，最后得出这段时间内各个线程消耗的cpu时间情况，最后算出百分比。
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> 注意： 这个统计也会产生一定的开销（JDK这个接口本身开销比较大），因此会看到as的线程占用一定的百分比，为了降低统计自身的开销带来的影响，可以把采样间隔拉长一些，比如5000毫秒。
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> 如果想看从Java进程启动开始到现在的cpu占比情况：可以使用[show-busy-java-threads](https://github.com/oldratlee/useful-scripts/blob/master/docs/java.md#-show-busy-java-threads)这个脚本
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### 使用参考
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#### 支持一键展示当前最忙的前N个线程并打印堆栈：
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```shell
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$ thread -n 3
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"as-command-execute-daemon" Id=29 cpuUsage=75% RUNNABLE
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at sun.management.ThreadImpl.dumpThreads0(Native Method)
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at sun.management.ThreadImpl.getThreadInfo(ThreadImpl.java:440)
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at com.taobao.arthas.core.command.monitor200.ThreadCommand$1.action(ThreadCommand.java:58)
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at com.taobao.arthas.core.command.handler.AbstractCommandHandler.execute(AbstractCommandHandler.java:238)
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at com.taobao.arthas.core.command.handler.DefaultCommandHandler.handleCommand(DefaultCommandHandler.java:67)
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at com.taobao.arthas.core.server.ArthasServer$4.run(ArthasServer.java:276)
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at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
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at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
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at java.lang.Thread.run(Thread.java:745)
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Number of locked synchronizers = 1
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- java.util.concurrent.ThreadPoolExecutor$Worker@6cd0b6f8
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"as-session-expire-daemon" Id=25 cpuUsage=24% TIMED_WAITING
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at java.lang.Thread.sleep(Native Method)
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at com.taobao.arthas.core.server.DefaultSessionManager$2.run(DefaultSessionManager.java:85)
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"Reference Handler" Id=2 cpuUsage=0% WAITING on java.lang.ref.Reference$Lock@69ba0f27
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at java.lang.Object.wait(Native Method)
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- waiting on java.lang.ref.Reference$Lock@69ba0f27
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at java.lang.Object.wait(Object.java:503)
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at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133)
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```
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#### 当没有参数时，显示所有线程的信息。
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```shell
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$ thread
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Threads Total: 16, NEW: 0, RUNNABLE: 7, BLOCKED: 0, WAITING: 5, TIMED_WAITING: 4, TERMINATED: 0
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ID NAME GROUP PRIORITY STATE %CPU TIME INTERRUPTE DAEMON
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30 as-command-execute-daemon system 9 RUNNABLE 72 0:0 false true
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23 as-session-expire-daemon system 9 TIMED_WAIT 27 0:0 false true
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22 Attach Listener system 9 RUNNABLE 0 0:0 false true
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11 pool-2-thread-1 main 5 TIMED_WAIT 0 0:0 false false
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12 Thread-2 main 5 RUNNABLE 0 0:0 false true
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13 pool-3-thread-1 main 5 TIMED_WAIT 0 0:0 false false
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25 as-selector-daemon system 9 RUNNABLE 0 0:0 false true
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14 Thread-3 main 5 TIMED_WAIT 0 0:0 false false
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26 pool-5-thread-1 system 5 WAITING 0 0:0 false false
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15 Thread-4 main 5 RUNNABLE 0 0:0 false false
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1 main main 5 WAITING 0 0:2 false false
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2 Reference Handler system 10 WAITING 0 0:0 false true
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3 Finalizer system 8 WAITING 0 0:0 false true
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4 Signal Dispatcher system 9 RUNNABLE 0 0:0 false true
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20 NonBlockingInputStreamThread main 5 WAITING 0 0:0 false true
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21 Thread-8 main 5 RUNNABLE 0 0:0 false true
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```
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#### thread id， 显示指定线程的运行堆栈
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```shell
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$ thread 1
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"main" Id=1 WAITING on java.util.concurrent.CountDownLatch$Sync@29fafb28
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at sun.misc.Unsafe.park(Native Method)
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- waiting on java.util.concurrent.CountDownLatch$Sync@29fafb28
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at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
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at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
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at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
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at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
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at java.util.concurrent.CountDownLatch.await(CountDownLatch.java:231)
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```
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#### thread -b, 找出当前阻塞其他线程的线程
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有时候我们发现应用卡住了， 通常是由于某个线程拿住了某个锁， 并且其他线程都在等待这把锁造成的。 为了排查这类问题， arthas提供了`thread -b`， 一键找出那个罪魁祸首。
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```bash
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$ thread -b
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"http-bio-8080-exec-4" Id=27 TIMED_WAITING
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at java.lang.Thread.sleep(Native Method)
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at test.arthas.TestThreadBlocking.doGet(TestThreadBlocking.java:22)
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- locked java.lang.Object@725be470 <---- but blocks 4 other threads!
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at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
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at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
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at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
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at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
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at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
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at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
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at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
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at test.filter.TestDurexFilter.doFilter(TestDurexFilter.java:46)
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at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
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at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
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at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
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at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
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at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
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at com.taobao.tomcat.valves.ContextLoadFilterValve$FilterChainAdapter.doFilter(ContextLoadFilterValve.java:191)
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at com.taobao.eagleeye.EagleEyeFilter.doFilter(EagleEyeFilter.java:81)
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at com.taobao.tomcat.valves.ContextLoadFilterValve.invoke(ContextLoadFilterValve.java:150)
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at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
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at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
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at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
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at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:429)
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at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1085)
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at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
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at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
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- locked org.apache.tomcat.util.net.SocketWrapper@7127ee12
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at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
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at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
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at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
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at java.lang.Thread.run(Thread.java:745)
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Number of locked synchronizers = 1
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- java.util.concurrent.ThreadPoolExecutor$Worker@31a6493e
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```
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> 注意， 目前只支持找出synchronized关键字阻塞住的线程， 如果是`java.util.concurrent.Lock`， 目前还不支持。
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#### thread -i, 指定采样时间间隔
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```bash
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$ thread -n 3 -i 1000
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"as-command-execute-daemon" Id=4759 cpuUsage=23% RUNNABLE
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at sun.management.ThreadImpl.dumpThreads0(Native Method)
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at sun.management.ThreadImpl.getThreadInfo(ThreadImpl.java:440)
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at com.taobao.arthas.core.command.monitor200.ThreadCommand.processTopBusyThreads(ThreadCommand.java:133)
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at com.taobao.arthas.core.command.monitor200.ThreadCommand.process(ThreadCommand.java:79)
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at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl.process(AnnotatedCommandImpl.java:96)
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at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl.access$100(AnnotatedCommandImpl.java:27)
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at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl$ProcessHandler.handle(AnnotatedCommandImpl.java:125)
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at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl$ProcessHandler.handle(AnnotatedCommandImpl.java:122)
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at com.taobao.arthas.core.shell.system.impl.ProcessImpl$CommandProcessTask.run(ProcessImpl.java:332)
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at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
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at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
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at java.lang.Thread.run(Thread.java:756)
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Number of locked synchronizers = 1
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- java.util.concurrent.ThreadPoolExecutor$Worker@546aeec1
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...
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```
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