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update doc
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@ -33,13 +33,16 @@ Many times what we are interested is the exact trace result when the method call
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`trace` is handy to help discovering and locating the performance flaws in your system, but pls. note Arthas can only trace the first level method call each time.
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After version 3.3.0, you can use the Dynamic Trace feature to add new matching classes/methods, see the following example.
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### Usage
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#### Start Demo
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Start `arthas-demo` in [Quick Start](quick-start.md).
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#### trace method
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#### Trace method
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```bash
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$ trace demo.MathGame run
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@ -55,7 +58,7 @@ Affect(class-cnt:1 , method-cnt:1) cost in 28 ms.
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```
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#### trace times limit
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#### Trace times limit
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If the method invoked many times, use `-n` options to specify trace times. For example, the command will exit when received a trace result.
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@ -125,7 +128,7 @@ Affect(class-cnt:1 , method-cnt:1) cost in 41 ms.
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* The total time cost may not equal to the sum of the time costs each sub method call takes, this is because Arthas instrumented code takes time too.
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#### trace multiple classes or multiple methods
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#### Trace multiple classes or multiple methods
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The trace command will only trace the subcalls in the method to the trace, and will not trace down multiple layers. Because traces are expensive, multi-layer traces can lead to a lot of classes and methods that ultimately have to be traced.
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@ -133,4 +136,53 @@ You can use the regular expression to match multiple classes and methods on the
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```bash
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Trace -E com.test.ClassA|org.test.ClassB method1|method2|method3
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```
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```
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#### Dynamic trace
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> Supported since version 3.3.0.
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Open terminal 1, trace the `run` method, and you can see the printout `listenerId: 1` .
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```bash
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[arthas@59161]$ trace demo.MathGame run
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Press Q or Ctrl+C to abort.
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Affect(class count: 1 , method count: 1) cost in 112 ms, listenerId: 1
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`---ts=2020-07-09 16:48:11;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
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`---[1.389634ms] demo.MathGame:run()
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`---[0.123934ms] demo.MathGame:primeFactors() #24 [throws Exception]
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`---ts=2020-07-09 16:48:12;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
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`---[3.716391ms] demo.MathGame:run()
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+---[3.182813ms] demo.MathGame:primeFactors() #24
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`---[0.167786ms] demo.MathGame:print() #25
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```
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Now to drill down into the sub method `primeFactors`, you can open a new terminal 2 and use the `telnet localhost 3658` connects to the arthas, then trace `primeFactors` with the specify `listenerId`.
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```bash
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[arthas@59161]$ trace demo.MathGame primeFactors --listenerId 1
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Press Q or Ctrl+C to abort.
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Affect(class count: 1 , method count: 1) cost in 34 ms, listenerId: 1
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```
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At Terminal 2 prints the results, indicating that a method has been enhanced: `Affect(class count: 1 , method count: 1)`, but no more results are printed.
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At terminal 1, you can see that the trace result has increased by one layer:
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```bash
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`---ts=2020-07-09 16:49:29;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
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`---[0.492551ms] demo.MathGame:run()
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`---[0.113929ms] demo.MathGame:primeFactors() #24 [throws Exception]
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`---[0.061462ms] demo.MathGame:primeFactors()
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`---[0.001018ms] throw:java.lang.IllegalArgumentException() #46
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`---ts=2020-07-09 16:49:30;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
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`---[0.409446ms] demo.MathGame:run()
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+---[0.232606ms] demo.MathGame:primeFactors() #24
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| `---[0.1294ms] demo.MathGame:primeFactors()
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`---[0.084025ms] demo.MathGame:print() #25
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```
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Dynamic trace by specifying `listenerId`, you can go deeper and deeper. In addition, commands such as `watch`/`tt`/`monitor` also support similar functionality.
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@ -34,6 +34,11 @@ trace
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`trace` 能方便的帮助你定位和发现因 RT 高而导致的性能问题缺陷，但其每次只能跟踪一级方法的调用链路。
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参考：[Trace命令的实现原理](https://github.com/alibaba/arthas/issues/597)
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3.3.0 版本后，可以使用动态Trace功能，不断增加新的匹配类，参考下面的示例。
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### 使用参考
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@ -137,3 +142,52 @@ trace命令只会trace匹配到的函数里的子调用，并不会向下trace
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```bash
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trace -E com.test.ClassA|org.test.ClassB method1|method2|method3
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```
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### 动态trace
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3.3.0 版本后支持。
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打开终端1，trace `run`函数，可以看到打印出 `listenerId: 1`：
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```bash
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[arthas@59161]$ trace demo.MathGame run
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Press Q or Ctrl+C to abort.
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Affect(class count: 1 , method count: 1) cost in 112 ms, listenerId: 1
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`---ts=2020-07-09 16:48:11;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
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`---[1.389634ms] demo.MathGame:run()
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`---[0.123934ms] demo.MathGame:primeFactors() #24 [throws Exception]
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`---ts=2020-07-09 16:48:12;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
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`---[3.716391ms] demo.MathGame:run()
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+---[3.182813ms] demo.MathGame:primeFactors() #24
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`---[0.167786ms] demo.MathGame:print() #25
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```
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现在想要深入子函数`primeFactors`，可以打开一个新终端2，使用`telnet localhost 3658`连接上arthas，再trace `primeFactors`时，指定`listenerId`。
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```bash
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[arthas@59161]$ trace demo.MathGame primeFactors --listenerId 1
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Press Q or Ctrl+C to abort.
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Affect(class count: 1 , method count: 1) cost in 34 ms, listenerId: 1
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```
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这时终端2打印的结果，说明已经增强了一个函数：`Affect(class count: 1 , method count: 1)`，但不再打印更多的结果。
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再查看终端1，可以发现trace的结果增加了一层，打印了`primeFactors`函数里的内容：
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```bash
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`---ts=2020-07-09 16:49:29;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
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`---[0.492551ms] demo.MathGame:run()
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`---[0.113929ms] demo.MathGame:primeFactors() #24 [throws Exception]
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`---[0.061462ms] demo.MathGame:primeFactors()
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`---[0.001018ms] throw:java.lang.IllegalArgumentException() #46
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`---ts=2020-07-09 16:49:30;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
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`---[0.409446ms] demo.MathGame:run()
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+---[0.232606ms] demo.MathGame:primeFactors() #24
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| `---[0.1294ms] demo.MathGame:primeFactors()
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`---[0.084025ms] demo.MathGame:print() #25
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```
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通过指定`listenerId`的方式动态trace，可以不断深入。另外 `watch`/`tt`/`monitor`等命令也支持类似的功能。
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