20 lines
3.9 KiB
HTML
20 lines
3.9 KiB
HTML
<html><head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>7. Current Span</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-sleuth.html" title="Spring Cloud Sleuth"><link rel="up" href="multi_spring-cloud-sleuth.html" title="Spring Cloud Sleuth"><link rel="prev" href="multi__current_tracing_component.html" title="6. Current Tracing Component"><link rel="next" href="multi__instrumentation.html" title="8. Instrumentation"></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">7. Current Span</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi__current_tracing_component.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="multi__instrumentation.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_current_span" href="#_current_span"></a>7. Current Span</h1></div></div></div><p>Brave supports a "current span" concept which represents the in-flight
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operation. <code class="literal">Tracer.currentSpan()</code> can be used to add custom tags to a
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span and <code class="literal">Tracer.nextSpan()</code> can be used to create a child of whatever
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is in-flight.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_setting_a_span_in_scope_manually" href="#_setting_a_span_in_scope_manually"></a>7.1 Setting a span in scope manually</h2></div></div></div><p>When writing new instrumentation, it is important to place a span you
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created in scope as the current span. Not only does this allow users to
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access it with <code class="literal">Tracer.currentSpan()</code>, but it also allows customizations
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like SLF4J MDC to see the current trace IDs.</p><p><code class="literal">Tracer.withSpanInScope(Span)</code> facilitates this and is most conveniently
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employed via the try-with-resources idiom. Whenever external code might
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be invoked (such as proceeding an interceptor or otherwise), place the
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span in scope like this.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">try</span> (SpanInScope ws = tracer.withSpanInScope(span)) {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> inboundRequest.invoke();
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} <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">finally</span> { <span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// note the scope is independent of the span</span>
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span.finish();
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}</pre><p>In edge cases, you may need to clear the current span temporarily. For
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example, launching a task that should not be associated with the current
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request. To do this, simply pass null to <code class="literal">withSpanInScope</code>.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">try</span> (SpanInScope cleared = tracer.withSpanInScope(null)) {
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startBackgroundThread();
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}</pre></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="multi__current_tracing_component.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="multi__instrumentation.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">6. Current Tracing Component </td><td width="20%" align="center"><a accesskey="h" href="multi_spring-cloud-sleuth.html">Home</a></td><td width="40%" align="right" valign="top"> 8. Instrumentation</td></tr></table></div></body></html> |