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< span id = "tt" > < / span > < h1 > tt< a class = "headerlink" href = "#tt" title = "永久链接至标题" > ¶< / a > < / h1 >
< blockquote >
< div > 方法执行数据的时空隧道，记录下指定方法每次调用的入参和返回信息，并能对这些不同的时间下调用进行观测< / div > < / blockquote >
< p > < code class = "docutils literal notranslate" > < span class = "pre" > watch< / span > < / code > 虽然很方便和灵活，但需要提前想清楚观察表达式的拼写，这对排查问题而言要求太高，因为很多时候我们并不清楚问题出自于何方，只能靠蛛丝马迹进行猜测。< / p >
< p > 这个时候如果能记录下当时方法调用的所有入参和返回值、抛出的异常会对整个问题的思考与判断非常有帮助。< / p >
< p > 于是乎， < / p >
< div class = "section" id = "" >
< span id = "id1" > < / span > < h2 > 记录方法的调用< a class = "headerlink" href = "#" title = "永久链接至标题" > ¶< / a > < / h2 >
< ul >
< li > < p class = "first" > 基本用法< / p >
< p > 对于一个最基本的使用来说，就是记录下当前方法的每次调用环境现场。< / p >
< div class = "highlight-java notranslate" > < div class = "highlight" > < pre > < span > < / span > < span class = "n" > $< / span > < span class = "n" > tt< / span > < span class = "o" > -< / span > < span class = "n" > t< / span > < span class = "o" > -< / span > < span class = "n" > n< / span > < span class = "mi" > 3< / span > < span class = "o" > *< / span > < span class = "n" > Test< / span > < span class = "n" > print< / span >
< span class = "n" > Press< / span > < span class = "n" > Ctrl< / span > < span class = "o" > +< / span > < span class = "n" > D< / span > < span class = "n" > or< / span > < span class = "n" > Ctrl< / span > < span class = "o" > +< / span > < span class = "n" > X< / span > < span class = "n" > to< / span > < span class = "n" > abort< / span > < span class = "o" > .< / span >
< span class = "nf" > Affect< / span > < span class = "o" > (< / span > < span class = "n" > class< / span > < span class = "o" > -< / span > < span class = "n" > cnt< / span > < span class = "o" > :< / span > < span class = "mi" > 1< / span > < span class = "o" > ,< / span > < span class = "n" > method< / span > < span class = "o" > -< / span > < span class = "n" > cnt< / span > < span class = "o" > :< / span > < span class = "mi" > 1< / span > < span class = "o" > )< / span > < span class = "n" > cost< / span > < span class = "n" > in< / span > < span class = "mi" > 115< / span > < span class = "n" > ms< / span > < span class = "o" > .< / span >
< span class = "o" > +----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+< / span >
< span class = "o" > |< / span > < span class = "n" > INDEX< / span > < span class = "o" > |< / span > < span class = "n" > TIMESTAMP< / span > < span class = "o" > |< / span > < span class = "n" > COST< / span > < span class = "o" > (< / span > < span class = "n" > ms< / span > < span class = "o" > )< / span > < span class = "o" > |< / span > < span class = "n" > IS< / span > < span class = "o" > -< / span > < span class = "n" > RET< / span > < span class = "o" > |< / span > < span class = "n" > IS< / span > < span class = "o" > -< / span > < span class = "n" > EXP< / span > < span class = "o" > |< / span > < span class = "n" > OBJECT< / span > < span class = "o" > |< / span > < span class = "n" > CLASS< / span > < span class = "o" > |< / span > < span class = "n" > METHOD< / span > < span class = "o" > |< / span >
< span class = "o" > +----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+< / span >
< span class = "o" > |< / span > < span class = "mi" > 1007< / span > < span class = "o" > |< / span > < span class = "mi" > 2015< / span > < span class = "o" > -< / span > < span class = "mo" > 07< / span > < span class = "o" > -< / span > < span class = "mi" > 26< / span > < span class = "mi" > 12< / span > < span class = "o" > :< / span > < span class = "mi" > 23< / span > < span class = "o" > :< / span > < span class = "mi" > 21< / span > < span class = "o" > |< / span > < span class = "mi" > 138< / span > < span class = "o" > |< / span > < span class = "kc" > true< / span > < span class = "o" > |< / span > < span class = "kc" > false< / span > < span class = "o" > |< / span > < span class = "mh" > 0x42cc13a0< / span > < span class = "o" > |< / span > < span class = "n" > GaOgnlUtilsTest< / span > < span class = "o" > |< / span > < span class = "n" > print< / span > < span class = "o" > |< / span >
< span class = "o" > +----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+< / span >
< span class = "o" > |< / span > < span class = "mi" > 1008< / span > < span class = "o" > |< / span > < span class = "mi" > 2015< / span > < span class = "o" > -< / span > < span class = "mo" > 07< / span > < span class = "o" > -< / span > < span class = "mi" > 26< / span > < span class = "mi" > 12< / span > < span class = "o" > :< / span > < span class = "mi" > 23< / span > < span class = "o" > :< / span > < span class = "mi" > 22< / span > < span class = "o" > |< / span > < span class = "mi" > 143< / span > < span class = "o" > |< / span > < span class = "kc" > true< / span > < span class = "o" > |< / span > < span class = "kc" > false< / span > < span class = "o" > |< / span > < span class = "mh" > 0x42cc13a0< / span > < span class = "o" > |< / span > < span class = "n" > GaOgnlUtilsTest< / span > < span class = "o" > |< / span > < span class = "n" > print< / span > < span class = "o" > |< / span >
< span class = "o" > +----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+< / span >
< span class = "o" > |< / span > < span class = "mi" > 1009< / span > < span class = "o" > |< / span > < span class = "mi" > 2015< / span > < span class = "o" > -< / span > < span class = "mo" > 07< / span > < span class = "o" > -< / span > < span class = "mi" > 26< / span > < span class = "mi" > 12< / span > < span class = "o" > :< / span > < span class = "mi" > 23< / span > < span class = "o" > :< / span > < span class = "mi" > 23< / span > < span class = "o" > |< / span > < span class = "mi" > 130< / span > < span class = "o" > |< / span > < span class = "kc" > true< / span > < span class = "o" > |< / span > < span class = "kc" > false< / span > < span class = "o" > |< / span > < span class = "mh" > 0x42cc13a0< / span > < span class = "o" > |< / span > < span class = "n" > GaOgnlUtilsTest< / span > < span class = "o" > |< / span > < span class = "n" > print< / span > < span class = "o" > |< / span >
< span class = "o" > +----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+< / span >
< span class = "n" > $< / span >
< / pre > < / div >
< / div >
< / li >
< li > < p class = "first" > 命令参数解析< / p >
< ul >
< li > < p class = "first" > < code class = "docutils literal notranslate" > < span class = "pre" > -t< / span > < / code > < / p >
< p > tt 命令有很多个主参数，< code class = "docutils literal notranslate" > < span class = "pre" > -t< / span > < / code > 就是其中之一。这个参数的表明希望记录下类 < code class = "docutils literal notranslate" > < span class = "pre" > *Test< / span > < / code > 的 < code class = "docutils literal notranslate" > < span class = "pre" > print< / span > < / code > 方法的每次执行情况。< / p >
< / li >
< li > < p class = "first" > < code class = "docutils literal notranslate" > < span class = "pre" > -n< / span > < span class = "pre" > 3< / span > < / code > < / p >
< p > 当你执行一个调用量不高的方法时可能你还能有足够的时间用 < code class = "docutils literal notranslate" > < span class = "pre" > CTRL+C< / span > < / code > 中断 tt 命令记录的过程，但如果遇到调用量非常大的方法，瞬间就能将你的 JVM 内存撑爆。< / p >
< p > 此时你可以通过 < code class = "docutils literal notranslate" > < span class = "pre" > -n< / span > < / code > 参数指定你需要记录的次数，当达到记录次数时 Arthas 会主动中断tt命令的记录过程， < / p >
< / li >
< / ul >
< / li >
< li > < p class = "first" > 表格字段说明< / p >
< / li >
< / ul >
< table border = "1" class = "docutils" >
< thead >
< tr >
< th > 表格字段< / th >
< th > 字段解释< / th >
< / tr >
< / thead >
< tbody >
< tr >
< td > INDEX< / td >
< td > 时间片段记录编号， ， ， < / td >
< / tr >
< tr >
< td > TIMESTAMP< / td >
< td > 方法执行的本机时间，记录了这个时间片段所发生的本机时间< / td >
< / tr >
< tr >
< td > COST(ms)< / td >
< td > 方法执行的耗时< / td >
< / tr >
< tr >
< td > IS-RET< / td >
< td > 方法是否以正常返回的形式结束< / td >
< / tr >
< tr >
< td > IS-EXP< / td >
< td > 方法是否以抛异常的形式结束< / td >
< / tr >
< tr >
< td > OBJECT< / td >
< td > 执行对象的< code > hashCode()< / code > ， ， ， < / td >
< / tr >
< tr >
< td > CLASS< / td >
< td > 执行的类名< / td >
< / tr >
< tr >
< td > METHOD< / td >
< td > 执行的方法名< / td >
< / tr >
< / tbody >
< / table > < ul >
< li > < p class = "first" > 条件表达式< / p >
< p > 不知道大家是否有在使用过程中遇到以下困惑< / p >
< ul class = "simple" >
< li > Arthas 似乎很难区分出重载的方法< / li >
< li > 我只需要观察特定参数，但是 tt 却全部都给我记录了下来< / li >
< / ul >
< p > 条件表达式也是用 < code class = "docutils literal notranslate" > < span class = "pre" > < / span > < / code > 来编写，核心的判断对象依然是 < code class = "docutils literal notranslate" > < span class = "pre" > Advice< / span > < / code > 对象。除了 < code class = "docutils literal notranslate" > < span class = "pre" > tt< / span > < / code > 命令之外，< code class = "docutils literal notranslate" > < span class = "pre" > watch< / span > < / code > 、< code class = "docutils literal notranslate" > < span class = "pre" > trace< / span > < / code > 、< code class = "docutils literal notranslate" > < span class = "pre" > stack< / span > < / code > 命令也都支持条件表达式。< / p >
< / li >
< li > < p class = "first" > 解决方法重载< / p >
< p > < code class = "docutils literal notranslate" > < span class = "pre" > tt< / span > < span class = "pre" > -t< / span > < span class = "pre" > *Test< / span > < span class = "pre" > print< / span > < span class = "pre" > params[0].length==1< / span > < / code > < / p >
< p > 通过制定参数个数的形式解决不同的方法签名，如果参数个数一样，你还可以这样写< / p >
< p > < code class = "docutils literal notranslate" > < span class = "pre" > tt< / span > < span class = "pre" > -t< / span > < span class = "pre" > *Test< / span > < span class = "pre" > print< / span > < span class = "pre" > 'params[1]< / span > < span class = "pre" > instanceof< / span > < span class = "pre" > Integer'< / span > < / code > < / p >
< / li >
< li > < p class = "first" > 解决指定参数< / p >
< p > < code class = "docutils literal notranslate" > < span class = "pre" > tt< / span > < span class = "pre" > -t< / span > < span class = "pre" > *Test< / span > < span class = "pre" > print< / span > < span class = "pre" > params[0].mobile==" 13989838402" < / span > < / code > < / p >
< / li >
< li > < p class = "first" > 构成条件表达式的 < code class = "docutils literal notranslate" > < span class = "pre" > Advice< / span > < / code > 对象< / p >
< p > 前边看到了很多条件表达式中，都适用了 < code class = "docutils literal notranslate" > < span class = "pre" > params[0]< / span > < / code > ，有关这个变量的介绍，请参考< a class = "reference internal" href = "advice-class.html" > < span class = "doc" > 表达式核心变量< / span > < / a > < / p >
< / li >
< / ul >
< / div >
< div class = "section" id = "" >
< span id = "id2" > < / span > < h2 > 检索调用记录< a class = "headerlink" href = "#" title = "永久链接至标题" > ¶< / a > < / h2 >
< p > 当你用 < code class = "docutils literal notranslate" > < span class = "pre" > tt< / span > < / code > 记录了一大片的时间片段之后，你希望能从中筛选出自己需要的时间片段，这个时候你就需要对现有记录进行检索。< / p >
< p > 假设我们有这些记录< / p >
< div class = "highlight-default notranslate" > < div class = "highlight" > < pre > < span > < / span > $ tt -l
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| INDEX | TIMESTAMP | COST(ms) | IS-RET | IS-EXP | OBJECT | CLASS | METHOD |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1000 | 2015-07-26 01:16:27 | 130 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1001 | 2015-07-26 01:16:27 | 0 | false | true | 0x42cc13a0 | GaOgnlUtilsTest | printAddress |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1002 | 2015-07-26 01:16:28 | 119 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1003 | 2015-07-26 01:16:28 | 0 | false | true | 0x42cc13a0 | GaOgnlUtilsTest | printAddress |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1004 | 2015-07-26 12:21:56 | 130 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1005 | 2015-07-26 12:21:57 | 138 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1006 | 2015-07-26 12:21:58 | 130 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
Affect(row-cnt:7) cost in 2 ms.
$
< / pre > < / div >
< / div >
< p > 我需要筛选出 < code class = "docutils literal notranslate" > < span class = "pre" > printAddress< / span > < / code > 方法的调用信息< / p >
< div class = "highlight-default notranslate" > < div class = "highlight" > < pre > < span > < / span > $ tt -s method.name==" printAddress"
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| INDEX | TIMESTAMP | COST(ms) | IS-RET | IS-EXP | OBJECT | CLASS | METHOD |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1001 | 2015-07-26 01:16:27 | 0 | false | true | 0x42cc13a0 | GaOgnlUtilsTest | printAddress |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1003 | 2015-07-26 01:16:28 | 0 | false | true | 0x42cc13a0 | GaOgnlUtilsTest | printAddress |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
Affect(row-cnt:2) cost in 55 ms.
$
< / pre > < / div >
< / div >
< p > 你需要一个 < code class = "docutils literal notranslate" > < span class = "pre" > -s< / span > < / code > 参数。< span style = "color:red;" > 同样的，搜索表达式的核心对象依旧是 < code class = "docutils literal notranslate" > < span class = "pre" > Advice< / span > < / code > 对象。< / span > < / p >
< / div >
< div class = "section" id = "" >
< span id = "id3" > < / span > < h2 > 查看调用信息< a class = "headerlink" href = "#" title = "永久链接至标题" > ¶< / a > < / h2 >
< p > 对于具体一个时间片的信息而言，你可以通过 < code class = "docutils literal notranslate" > < span class = "pre" > -i< / span > < / code > 参数后边跟着对应的 < code class = "docutils literal notranslate" > < span class = "pre" > INDEX< / span > < / code > 编号查看到他的详细信息。< / p >
< div class = "highlight-default notranslate" > < div class = "highlight" > < pre > < span > < / span > $
$ tt -i 1003
+-----------------+------------------------------------------------------------------------------------------------------+
| INDEX | 1003 |
+-----------------+------------------------------------------------------------------------------------------------------+
| GMT-CREATE | 2015-07-26 01:16:28 |
+-----------------+------------------------------------------------------------------------------------------------------+
| COST(ms) | 0 |
+-----------------+------------------------------------------------------------------------------------------------------+
| OBJECT | 0x42cc13a0 |
+-----------------+------------------------------------------------------------------------------------------------------+
| CLASS | GaOgnlUtilsTest |
+-----------------+------------------------------------------------------------------------------------------------------+
| METHOD | printAddress |
+-----------------+------------------------------------------------------------------------------------------------------+
| IS-RETURN | false |
+-----------------+------------------------------------------------------------------------------------------------------+
| IS-EXCEPTION | true |
+-----------------+------------------------------------------------------------------------------------------------------+
| PARAMETERS[0] | Address@53448f87 |
+-----------------+------------------------------------------------------------------------------------------------------+
| THROW-EXCEPTION | java.lang.RuntimeException: test |
| | at GaOgnlUtilsTest.printAddress(Unknown Source) |
| | at GaOgnlUtilsTest.< init> (Unknown Source) |
| | at GaOgnlUtilsTest.main(Unknown Source) |
+-----------------+------------------------------------------------------------------------------------------------------+
Affect(row-cnt:1) cost in 1 ms.
$
< / pre > < / div >
< / div >
< / div >
< div class = "section" id = "" >
< span id = "id4" > < / span > < h2 > 重做一次调用< a class = "headerlink" href = "#" title = "永久链接至标题" > ¶< / a > < / h2 >
< p > 当你稍稍做了一些调整之后，你可能需要前端系统重新触发一次你的调用，此时得求爷爷告奶奶的需要前端配合联调的同学再次发起一次调用。而有些场景下，这个调用不是这么好触发的。< / p >
< p > < code class = "docutils literal notranslate" > < span class = "pre" > tt< / span > < / code > 命令由于保存了当时调用的所有现场信息，所以我们可以自己主动对一个 < code class = "docutils literal notranslate" > < span class = "pre" > INDEX< / span > < / code > 编号的时间片自主发起一次调用，从而解放你的沟通成本。此时你需要 < code class = "docutils literal notranslate" > < span class = "pre" > -p< / span > < / code > 参数。< / p >
< div class = "highlight-default notranslate" > < div class = "highlight" > < pre > < span > < / span > $ tt -i 1003 -p
+-----------------+---------------------------------------------------------------------------------------------------------+
| RE-INDEX | 1003 |
+-----------------+---------------------------------------------------------------------------------------------------------+
| GMT-REPLAY | 2015-07-26 17:29:51 |
+-----------------+---------------------------------------------------------------------------------------------------------+
| OBJECT | 0x42cc13a0 |
+-----------------+---------------------------------------------------------------------------------------------------------+
| CLASS | GaOgnlUtilsTest |
+-----------------+---------------------------------------------------------------------------------------------------------+
| METHOD | printAddress |
+-----------------+---------------------------------------------------------------------------------------------------------+
| PARAMETERS[0] | Address@53448f87 |
+-----------------+---------------------------------------------------------------------------------------------------------+
| IS-RETURN | false |
+-----------------+---------------------------------------------------------------------------------------------------------+
| IS-EXCEPTION | true |
+-----------------+---------------------------------------------------------------------------------------------------------+
| THROW-EXCEPTION | java.lang.RuntimeException: test |
| | at GaOgnlUtilsTest.printAddress(GaOgnlUtilsTest.java:78) |
| | at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) |
| | at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) |
| | at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) |
| | at java.lang.reflect.Method.invoke(Method.java:483) |
| | at com.github.ompc.Arthas.util.GaMethod.invoke(GaMethod.java:81) |
| | at com.github.ompc.Arthas.command.TimeTunnelCommand$6.action(TimeTunnelCommand.java:592) |
| | at com.github.ompc.Arthas.server.DefaultCommandHandler.execute(DefaultCommandHandler.java:175) |
| | at com.github.ompc.Arthas.server.DefaultCommandHandler.executeCommand(DefaultCommandHandler.java:83) |
| | at com.github.ompc.Arthas.server.GaServer$4.run(GaServer.java:329) |
| | at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) |
| | at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) |
| | at java.lang.Thread.run(Thread.java:745) |
+-----------------+---------------------------------------------------------------------------------------------------------+
replay time fragment[1003] success.
Affect(row-cnt:1) cost in 3 ms.
$
< / pre > < / div >
< / div >
< p > 你会发现结果虽然一样，但调用的路径发生了变化，有原来的程序发起变成了 Arthas 自己的内部线程发起的调用了。< / p >
< ul >
< li > < p class = "first" > 需要强调的点< / p >
< ol >
< li > < p class = "first" > < strong > ThreadLocal 信息丢失< / strong > < / p >
< p > 很多框架偷偷的将一些环境变量信息塞到了发起调用线程的 ThreadLocal 中，由于调用线程发生了变化，这些 ThreadLocal 线程信息无法通过 Arthas 保存，所以这些信息将会丢失。< / p >
< p > 一些常见的 CASE 比如：鹰眼的 TraceId 等。< / p >
< / li >
< li > < p class = "first" > < strong > 引用的对象< / strong > < / p >
< p > 需要强调的是，< code class = "docutils literal notranslate" > < span class = "pre" > tt< / span > < / code > 命令是将当前环境的对象引用保存起来，但仅仅也只能保存一个引用而已。如果方法内部对入参进行了变更，或者返回的对象经过了后续的处理，那么在 < code class = "docutils literal notranslate" > < span class = "pre" > tt< / span > < / code > 查看的时候将无法看到当时最准确的值。这也是为什么 < code class = "docutils literal notranslate" > < span class = "pre" > watch< / span > < / code > 命令存在的意义。< / p >
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