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Ryan Baxter
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<title>53. Span lifecycle</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 VII. Spring Cloud Sleuth"><link rel="prev" href="multi__instrumentation.html" title="52. Instrumentation"><link rel="next" href="multi__naming_spans.html" title="54. Naming spans"></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">53. Span lifecycle</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi__instrumentation.html">Prev</a> </td><th width="60%" align="center">Part VII. Spring Cloud Sleuth</th><td width="20%" align="right"> <a accesskey="n" href="multi__naming_spans.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="_span_lifecycle" href="#_span_lifecycle"></a>53. Span lifecycle</h2></div></div></div><p>You can do the following operations on the Span by means of <span class="strong"><strong>brave.Tracer</strong></span>:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><a class="link" href="multi__span_lifecycle.html#creating-and-finishing-spans" title="53.1 Creating and finishing spans">start</a> - when you start a span its name is assigned and start timestamp is recorded.</li><li class="listitem"><a class="link" href="multi__span_lifecycle.html#creating-and-finishing-spans" title="53.1 Creating and finishing spans">close</a> - the span gets finished (the end time of the span is recorded) and if
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the span is <span class="strong"><strong>sampled</strong></span> then it will be eligible for collection to e.g. Zipkin.</li><li class="listitem"><a class="link" href="multi__span_lifecycle.html#continuing-spans" title="53.2 Continuing spans">continue</a> - a new instance of span will be created whereas it will be a copy of the
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one that it continues.</li><li class="listitem"><a class="link" href="multi__span_lifecycle.html#continuing-spans" title="53.2 Continuing spans">detach</a> - the span doesn’t get stopped or closed. It only gets removed from the current thread.</li><li class="listitem"><a class="link" href="multi__span_lifecycle.html#creating-spans-with-explicit-parent" title="53.3 Creating spans with an explicit parent">create with explicit parent</a> - you can create a new span and set an explicit parent to it</li></ul></div><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>Spring Cloud Sleuth creates the instance of <code class="literal">Tracer</code> for you. In order to use it,
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all you need is to just autowire it.</p></td></tr></table></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-and-finishing-spans" href="#creating-and-finishing-spans"></a>53.1 Creating and finishing spans</h2></div></div></div><p>You can manually create spans by using the <span class="strong"><strong>Tracer</strong></span>.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// Start a span. If there was a span present in this thread it will become</span>
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<title>54. Span lifecycle</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 VIII. Spring Cloud Sleuth"><link rel="prev" href="multi__instrumentation.html" title="53. Instrumentation"><link rel="next" href="multi__naming_spans.html" title="55. Naming spans"></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">54. Span lifecycle</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi__instrumentation.html">Prev</a> </td><th width="60%" align="center">Part VIII. Spring Cloud Sleuth</th><td width="20%" align="right"> <a accesskey="n" href="multi__naming_spans.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="_span_lifecycle" href="#_span_lifecycle"></a>54. Span lifecycle</h2></div></div></div><p>You can do the following operations on the Span by means of <span class="strong"><strong>brave.Tracer</strong></span>:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><a class="link" href="multi__span_lifecycle.html#creating-and-finishing-spans" title="54.1 Creating and finishing spans">start</a> - when you start a span its name is assigned and start timestamp is recorded.</li><li class="listitem"><a class="link" href="multi__span_lifecycle.html#creating-and-finishing-spans" title="54.1 Creating and finishing spans">close</a> - the span gets finished (the end time of the span is recorded) and if
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the span is <span class="strong"><strong>sampled</strong></span> then it will be eligible for collection to e.g. Zipkin.</li><li class="listitem"><a class="link" href="multi__span_lifecycle.html#continuing-spans" title="54.2 Continuing spans">continue</a> - a new instance of span will be created whereas it will be a copy of the
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one that it continues.</li><li class="listitem"><a class="link" href="multi__span_lifecycle.html#continuing-spans" title="54.2 Continuing spans">detach</a> - the span doesn’t get stopped or closed. It only gets removed from the current thread.</li><li class="listitem"><a class="link" href="multi__span_lifecycle.html#creating-spans-with-explicit-parent" title="54.3 Creating spans with an explicit parent">create with explicit parent</a> - you can create a new span and set an explicit parent to it</li></ul></div><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>Spring Cloud Sleuth creates the instance of <code class="literal">Tracer</code> for you. In order to use it,
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all you need is to just autowire it.</p></td></tr></table></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-and-finishing-spans" href="#creating-and-finishing-spans"></a>54.1 Creating and finishing spans</h2></div></div></div><p>You can manually create spans by using the <span class="strong"><strong>Tracer</strong></span>.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// Start a span. If there was a span present in this thread it will become</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// the `newSpan`'s parent.</span>
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Span newSpan = <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">this</span>.tracer.nextSpan().name(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"calculateTax"</span>);
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">try</span> (Tracer.SpanInScope ws = <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">this</span>.tracer.withSpanInScope(newSpan.start())) {
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@@ -20,7 +20,7 @@ Span newSpan = <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">
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}</pre><p>In this example we could see how to create a new instance of span. Assuming that there already
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was a span present in this thread then it would become the parent of that span.</p><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Important"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="images/important.png"></td><th align="left">Important</th></tr><tr><td align="left" valign="top"><p>Always clean after you create a span! Don’t forget to finish a span if you want to send it to Zipkin.</p></td></tr></table></div><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Important"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="images/important.png"></td><th align="left">Important</th></tr><tr><td align="left" valign="top"><p>If your span contains a name greater than 50 chars, then that name will
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be truncated to 50 chars. Your names have to be explicit and concrete. Big names lead to
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latency issues and sometimes even thrown exceptions.</p></td></tr></table></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="continuing-spans" href="#continuing-spans"></a>53.2 Continuing spans</h2></div></div></div><p>Sometimes you don’t want to create a new span but you want to continue one. Example of such a
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latency issues and sometimes even thrown exceptions.</p></td></tr></table></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="continuing-spans" href="#continuing-spans"></a>54.2 Continuing spans</h2></div></div></div><p>Sometimes you don’t want to create a new span but you want to continue one. Example of such a
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situation might be (of course it all depends on the use-case):</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><span class="strong"><strong>AOP</strong></span> - If there was already a span created before an aspect was reached then you might not want to create a new span.</li><li class="listitem"><span class="strong"><strong>Hystrix</strong></span> - executing a Hystrix command is most likely a logical part of the current processing. It’s in fact
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only a technical implementation detail that you wouldn’t necessarily want to reflect in tracing as a separate being.</li></ul></div><p>To continue a span you can use <span class="strong"><strong>brave.Tracer</strong></span>.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// let's assume that we're in a thread Y and we've received</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// the `initialSpan` from thread X</span>
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@@ -36,7 +36,7 @@ Span continuedSpan = <span xmlns:d="http://docbook.org/ns/docbook" class="hl-key
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// Once done remember to flush the span. That means that</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// it will get reported but the span itself is not yet finished</span>
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continuedSpan.flush();
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}</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-spans-with-explicit-parent" href="#creating-spans-with-explicit-parent"></a>53.3 Creating spans with an explicit parent</h2></div></div></div><p>There is a possibility that you want to start a new span and provide an explicit parent of that span.
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}</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-spans-with-explicit-parent" href="#creating-spans-with-explicit-parent"></a>54.3 Creating spans with an explicit parent</h2></div></div></div><p>There is a possibility that you want to start a new span and provide an explicit parent of that span.
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Let’s assume that the parent of a span is in one thread and you want to start a new span in another thread.
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In Brave, whenever you call <code class="literal">nextSpan()</code>, it’s creating one in reference
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to the span being currently in scope. It’s enough to just put
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@@ -60,4 +60,4 @@ Span newSpan = null;
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newSpan.finish();
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}
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}</pre><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Important"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="images/important.png"></td><th align="left">Important</th></tr><tr><td align="left" valign="top"><p>After having created such a span remember to finish it, otherwise it will not get
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reported to e.g. Zipkin</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__instrumentation.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="multi__spring_cloud_sleuth.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="multi__naming_spans.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">52. Instrumentation </td><td width="20%" align="center"><a accesskey="h" href="multi_spring-cloud.html">Home</a></td><td width="40%" align="right" valign="top"> 54. Naming spans</td></tr></table></div></body></html>
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reported to e.g. Zipkin</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__instrumentation.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="multi__spring_cloud_sleuth.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="multi__naming_spans.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">53. Instrumentation </td><td width="20%" align="center"><a accesskey="h" href="multi_spring-cloud.html">Home</a></td><td width="40%" align="right" valign="top"> 55. Naming spans</td></tr></table></div></body></html>
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