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<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>48.&nbsp;Sampling</title><link rel="stylesheet" type="text/css" href="css/manual-multipage.css"><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="multi_spring-cloud.html" title="Spring Cloud"><link rel="up" href="multi__spring_cloud_sleuth.html" title="Part&nbsp;VII.&nbsp;Spring Cloud Sleuth"><link rel="prev" href="multi__features_2.html" title="47.&nbsp;Features"><link rel="next" href="multi__propagation.html" title="49.&nbsp;Propagation"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">48.&nbsp;Sampling</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi__features_2.html">Prev</a>&nbsp;</td><th width="60%" align="center">Part&nbsp;VII.&nbsp;Spring Cloud Sleuth</th><td width="20%" align="right">&nbsp;<a accesskey="n" href="multi__propagation.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="_sampling" href="#_sampling"></a>48.&nbsp;Sampling</h2></div></div></div><p>Sampling may be employed to reduce the data collected and reported out
<title>49.&nbsp;Sampling</title><link rel="stylesheet" type="text/css" href="css/manual-multipage.css"><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="multi_spring-cloud.html" title="Spring Cloud"><link rel="up" href="multi__spring_cloud_sleuth.html" title="Part&nbsp;VIII.&nbsp;Spring Cloud Sleuth"><link rel="prev" href="multi__features_2.html" title="48.&nbsp;Features"><link rel="next" href="multi__propagation.html" title="50.&nbsp;Propagation"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">49.&nbsp;Sampling</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi__features_2.html">Prev</a>&nbsp;</td><th width="60%" align="center">Part&nbsp;VIII.&nbsp;Spring Cloud Sleuth</th><td width="20%" align="right">&nbsp;<a accesskey="n" href="multi__propagation.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="_sampling" href="#_sampling"></a>49.&nbsp;Sampling</h2></div></div></div><p>Sampling may be employed to reduce the data collected and reported out
of process. When a span isn&#8217;t sampled, it adds no overhead (noop).</p><p>Sampling is an up-front decision, meaning that the decision to report
data is made at the first operation in a trace, and that decision is
propagated downstream.</p><p>By default, there&#8217;s a global sampler that applies a single rate to all
traced operations. <code class="literal">Tracer.Builder.sampler</code> is how you indicate this,
and it defaults to trace every request.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_declarative_sampling" href="#_declarative_sampling"></a>48.1&nbsp;Declarative sampling</h2></div></div></div><p>Some need to sample based on the type or annotations of a java method.</p><p>Most users will use a framework interceptor which automates this sort of
and it defaults to trace every request.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_declarative_sampling" href="#_declarative_sampling"></a>49.1&nbsp;Declarative sampling</h2></div></div></div><p>Some need to sample based on the type or annotations of a java method.</p><p>Most users will use a framework interceptor which automates this sort of
policy. Here&#8217;s how they might work internally.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// derives a sample rate from an annotation on a java method</span>
DeclarativeSampler&lt;Traced&gt; sampler = DeclarativeSampler.create(Traced::sampleRate);
@@ -17,7 +17,7 @@ DeclarativeSampler&lt;Traced&gt; sampler = DeclarativeSampler.create(Traced::sam
} <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">finally</span> {
span.finish();
}
}</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_custom_sampling" href="#_custom_sampling"></a>48.2&nbsp;Custom sampling</h2></div></div></div><p>You may want to apply different policies depending on what the operation
}</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_custom_sampling" href="#_custom_sampling"></a>49.2&nbsp;Custom sampling</h2></div></div></div><p>You may want to apply different policies depending on what the operation
is. For example, you might not want to trace requests to static resources
such as images, or you might want to trace all requests to a new api.</p><p>Most users will use a framework interceptor which automates this sort of
policy. Here&#8217;s how they might work internally.</p><pre class="programlisting">Span newTrace(Request input) {
@@ -28,7 +28,7 @@ policy. Here&#8217;s how they might work internally.</p><pre class="programlisti
flags = SamplingFlags.NOT_SAMPLED;
}
<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> tracer.newTrace(flags);
}</pre><p>Note: the above is the basis for the built-in <a class="link" href="https://github.com/openzipkin/sleuth/tree/master/instrumentation/http" target="_top">http sampler</a></p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_sampling_in_spring_cloud_sleuth" href="#_sampling_in_spring_cloud_sleuth"></a>48.3&nbsp;Sampling in Spring Cloud Sleuth</h2></div></div></div><p>Spring Cloud Sleuth by default sets all spans to non-exportable.
}</pre><p>Note: the above is the basis for the built-in <a class="link" href="https://github.com/openzipkin/sleuth/tree/master/instrumentation/http" target="_top">http sampler</a></p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_sampling_in_spring_cloud_sleuth" href="#_sampling_in_spring_cloud_sleuth"></a>49.3&nbsp;Sampling in Spring Cloud Sleuth</h2></div></div></div><p>Spring Cloud Sleuth by default sets all spans to non-exportable.
That means that you will see traces in logs, but not in any remote store.
For testing the default is often enough, and it probably is all you need
if you are only using the logs (e.g. with an ELK aggregator). If you are
@@ -42,4 +42,4 @@ value needs to be a double from <code class="literal">0.0</code> to <code class=
<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> Sampler.ALWAYS_SAMPLE;
}</pre><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Tip"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="images/tip.png"></td><th align="left">Tip</th></tr><tr><td align="left" valign="top"><p>You can set the HTTP header <code class="literal">X-B3-Flags</code> to <code class="literal">1</code> or when doing messaging you can
set <code class="literal">spanFlags</code> header to <code class="literal">1</code>. Then the current span will be forced to be exportable
regardless of the sampling decision.</p></td></tr></table></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="multi__features_2.html">Prev</a>&nbsp;</td><td width="20%" align="center"><a accesskey="u" href="multi__spring_cloud_sleuth.html">Up</a></td><td width="40%" align="right">&nbsp;<a accesskey="n" href="multi__propagation.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">47.&nbsp;Features&nbsp;</td><td width="20%" align="center"><a accesskey="h" href="multi_spring-cloud.html">Home</a></td><td width="40%" align="right" valign="top">&nbsp;49.&nbsp;Propagation</td></tr></table></div></body></html>
regardless of the sampling decision.</p></td></tr></table></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="multi__features_2.html">Prev</a>&nbsp;</td><td width="20%" align="center"><a accesskey="u" href="multi__spring_cloud_sleuth.html">Up</a></td><td width="40%" align="right">&nbsp;<a accesskey="n" href="multi__propagation.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">48.&nbsp;Features&nbsp;</td><td width="20%" align="center"><a accesskey="h" href="multi_spring-cloud.html">Home</a></td><td width="40%" align="right" valign="top">&nbsp;50.&nbsp;Propagation</td></tr></table></div></body></html>