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<div class="section" id="tt">
<span id="tt"></span><h1>tt<a class="headerlink" href="#tt" title="Permalink to this headline">¶</a></h1>
<p>Check the <tt class="docutils literal">parameters</tt>, <tt class="docutils literal">return values</tt> and <tt class="docutils literal">exceptions</tt> of the methods at different times.</p>
<p><tt class="docutils literal">watch</tt> is a powerful command but due to its feasibility and complexity, it’s quite hard to locate the issue effectively.</p>
<p>In such difficulties, <tt class="docutils literal">tt</tt> comes into play.</p>
<p>With the help of <tt class="docutils literal">tt</tt> (<em>TimeTunnel</em>), you can check the contexts of the methods at different times in execution history.</p>
<div class="section" id="usage">
<span id="usage"></span><h2>Usage<a class="headerlink" href="#usage" title="Permalink to this headline">¶</a></h2>
<div class="section" id="start-demo">
<span id="start-demo"></span><h3>Start Demo<a class="headerlink" href="#start-demo" title="Permalink to this headline">¶</a></h3>
<p>Start <tt class="docutils literal">arthas-demo</tt> in <a class="reference internal" href="quick-start.html"><span class="doc">Quick Start</span></a>.</p>
</div>
<div class="section" id="record-method-calls">
<span id="record-method-calls"></span><h3>Record method calls<a class="headerlink" href="#record-method-calls" title="Permalink to this headline">¶</a></h3>
<div class="highlight-bash notranslate"><div class="highlight hljs"><pre class="bash">$ tt -t demo.MathGame primeFactors
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 66 ms.
INDEX TIMESTAMP COST(ms) IS-RET IS-EXP OBJECT CLASS METHOD
-------------------------------------------------------------------------------------------------------------------------------------
1000 2018-12-04 11:15:38 1.096236 false true 0x4b67cf4d MathGame primeFactors
1001 2018-12-04 11:15:39 0.191848 false true 0x4b67cf4d MathGame primeFactors
1002 2018-12-04 11:15:40 0.069523 false true 0x4b67cf4d MathGame primeFactors
1003 2018-12-04 11:15:41 0.186073 false true 0x4b67cf4d MathGame primeFactors
1004 2018-12-04 11:15:42 17.76437 true false 0x4b67cf4d MathGame primeFactors
</pre></div>
</div>
<ul>
<li><p class="first"><tt class="docutils literal">-t</tt></p>
<p>record the calling context of the method <tt class="docutils literal">demo.MathGame primeFactors</tt></p>
</li>
<li><p class="first"><tt class="docutils literal">-n 3</tt></p>
<p>limit the number of the records (avoid overflow for too many records; with <tt class="docutils literal">-n</tt> option, Arthas can automatically stop recording once the records reach the specified limit)</p>
</li>
<li><p class="first">Property</p>
</li>
</ul>
<table border="1" class="docutils">
<thead>
<tr>
<th>Name</th>
<th>Specification</th>
</tr>
</thead>
<tbody>
<tr>
<td>INDEX</td>
<td>the index for each call based on time</td>
</tr>
<tr>
<td>TIMESTAMP</td>
<td>time to invoke the method</td>
</tr>
<tr>
<td>COST(ms)</td>
<td>time cost of the method call</td>
</tr>
<tr>
<td>IS-RET</td>
<td>whether method exits with normal return</td>
</tr>
<tr>
<td>IS-EXP</td>
<td>whether method failed with exceptions</td>
</tr>
<tr>
<td>OBJECT</td>
<td><code>hashCode()</code> of the object invoking the method</td>
</tr>
<tr>
<td>CLASS</td>
<td>class name of the object invoking the method</td>
</tr>
<tr>
<td>METHOD</td>
<td>method being invoked</td>
</tr>
</tbody>
</table><ul class="simple">
<li>Condition expression</li>
</ul>
<p>Tips:</p>
<ol class="simple">
<li><tt class="docutils literal">tt -t *Test print params[0].length==1</tt> with different amounts of parameters;</li>
<li><tt class="docutils literal">tt -t *Test print 'params[1] instanceof Integer'</tt> with different types of parameters;</li>
<li><tt class="docutils literal">tt -t *Test print params[0].mobile=="13989838402"</tt> with specified parameter.</li>
</ol>
<p>Advanced:</p>
<div class="toctree-wrapper compound">
<ul>
<li class="toctree-l1"><a class="reference internal" href="advice-class.html">Critical fields in expression</a></li>
<li class="toctree-l1"><a class="reference external" href="https://github.com/alibaba/arthas/issues/71">Special usage</a></li>
<li class="toctree-l1"><a class="reference external" href="https://commons.apache.org/proper/commons-ognl/language-guide.html">OGNL official guide</a></li>
</ul>
</div>
</div>
<div class="section" id="list-all-records">
<span id="list-all-records"></span><h3>List all records<a class="headerlink" href="#list-all-records" title="Permalink to this headline">¶</a></h3>
<div class="highlight-bash notranslate"><div class="highlight hljs"><pre class="bash">$ tt -l
INDEX TIMESTAMP COST(ms) IS-RET IS-EXP OBJECT CLASS METHOD
-------------------------------------------------------------------------------------------------------------------------------------
1000 2018-12-04 11:15:38 1.096236 false true 0x4b67cf4d MathGame primeFactors
1001 2018-12-04 11:15:39 0.191848 false true 0x4b67cf4d MathGame primeFactors
1002 2018-12-04 11:15:40 0.069523 false true 0x4b67cf4d MathGame primeFactors
1003 2018-12-04 11:15:41 0.186073 false true 0x4b67cf4d MathGame primeFactors
1004 2018-12-04 11:15:42 17.76437 true false 0x4b67cf4d MathGame primeFactors
9
1005 2018-12-04 11:15:43 0.4776 false true 0x4b67cf4d MathGame primeFactors
Affect(row-cnt:6) cost in 4 ms.
</pre></div>
</div>
</div>
<div class="section" id="searching-for-records">
<span id="searching-for-records"></span><h3>Searching for records<a class="headerlink" href="#searching-for-records" title="Permalink to this headline">¶</a></h3>
<div class="highlight-bash notranslate"><div class="highlight hljs"><pre class="bash">$ tt -s 'method.name=="primeFactors"'
INDEX TIMESTAMP COST(ms) IS-RET IS-EXP OBJECT CLASS METHOD
-------------------------------------------------------------------------------------------------------------------------------------
1000 2018-12-04 11:15:38 1.096236 false true 0x4b67cf4d MathGame primeFactors
1001 2018-12-04 11:15:39 0.191848 false true 0x4b67cf4d MathGame primeFactors
1002 2018-12-04 11:15:40 0.069523 false true 0x4b67cf4d MathGame primeFactors
1003 2018-12-04 11:15:41 0.186073 false true 0x4b67cf4d MathGame primeFactors
1004 2018-12-04 11:15:42 17.76437 true false 0x4b67cf4d MathGame primeFactors
9
1005 2018-12-04 11:15:43 0.4776 false true 0x4b67cf4d MathGame primeFactors
Affect(row-cnt:6) cost in 607 ms.
</pre></div>
</div>
<p>Advanced:</p>
<div class="toctree-wrapper compound">
<ul>
<li class="toctree-l1"><a class="reference internal" href="advice-class.html">Critical fields in expression</a></li>
</ul>
</div>
</div>
<div class="section" id="check-context-of-the-call">
<span id="check-context-of-the-call"></span><h3>Check context of the call<a class="headerlink" href="#check-context-of-the-call" title="Permalink to this headline">¶</a></h3>
<p>Using <tt class="docutils literal">tt -i <index></tt> to check a specific calling details.</p>
<div class="highlight-bash notranslate"><div class="highlight hljs"><pre class="bash">$ tt -i 1003
INDEX 1003
GMT-CREATE 2018-12-04 11:15:41
COST(ms) 0.186073
OBJECT 0x4b67cf4d
CLASS demo.MathGame
METHOD primeFactors
IS-RETURN false
IS-EXCEPTION true
PARAMETERS[0] @Integer[-564322413]
THROW-EXCEPTION java.lang.IllegalArgumentException: number is: -564322413, need >= 2
at demo.MathGame.primeFactors(MathGame.java:46)
at demo.MathGame.run(MathGame.java:24)
at demo.MathGame.main(MathGame.java:16)
Affect(row-cnt:1) cost in 11 ms.
</pre></div>
</div>
</div>
</div>
<div class="section" id="replay-record">
<span id="replay-record"></span><h2>Replay record<a class="headerlink" href="#replay-record" title="Permalink to this headline">¶</a></h2>
<p>Since Arthas stores the context of the call, you can even <em>replay</em> the method calling afterwards with extra option <tt class="docutils literal">-p</tt> to replay the issue for advanced troubleshooting.</p>
<div class="highlight-bash notranslate"><div class="highlight hljs"><pre class="bash">$ tt -i 1004 -p
RE-INDEX 1004
GMT-REPLAY 2018-12-04 11:26:00
OBJECT 0x4b67cf4d
CLASS demo.MathGame
METHOD primeFactors
PARAMETERS[0] @Integer[946738738]
IS-RETURN true
IS-EXCEPTION false
RETURN-OBJ @ArrayList[
@Integer[2],
@Integer[11],
@Integer[17],
@Integer[2531387],
]
Time fragment[1004] successfully replayed.
Affect(row-cnt:1) cost in 14 ms.
</pre></div>
</div>
<p>F.Y.I</p>
<ol>
<li><p class="first"><strong>Loss</strong> of the <tt class="docutils literal">ThreadLocal</tt></p>
<p>Arthas save params into an array, then invoke the method with the params again. The method execute in another thread, so the <tt class="docutils literal">ThreadLocal</tt> <strong>lost</strong>.</p>
</li>
<li><p class="first">params may be modified</p>
<p>Arthas save params into an array, they are object references. The Objects may be modified by other code.</p>
</li>
</ol>
</div>
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