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<title>11. Managing Spans with Annotations</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__naming_spans.html" title="10. Naming spans"><link rel="next" href="multi__sending_spans_to_zipkin.html" title="12. Sending Spans to Zipkin"></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">11. Managing Spans with Annotations</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi__naming_spans.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="multi__sending_spans_to_zipkin.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_managing_spans_with_annotations" href="#_managing_spans_with_annotations"></a>11. Managing Spans with Annotations</h1></div></div></div><p>You can manage spans with a variety of annotations.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_rationale" href="#_rationale"></a>11.1 Rationale</h2></div></div></div><p>There are a number of good reasons to manage spans with annotations, including:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">API-agnostic means to collaborate with a span. Use of annotations lets users add to a span with no library dependency on a span api.
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<title>11. Managing Spans with Annotations</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__naming_spans.html" title="10. Naming spans"><link rel="next" href="multi__customizations.html" title="12. Customizations"></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">11. Managing Spans with Annotations</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi__naming_spans.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="multi__customizations.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_managing_spans_with_annotations" href="#_managing_spans_with_annotations"></a>11. Managing Spans with Annotations</h1></div></div></div><p>You can manage spans with a variety of annotations.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_rationale" href="#_rationale"></a>11.1 Rationale</h2></div></div></div><p>There are a number of good reasons to manage spans with annotations, including:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">API-agnostic means to collaborate with a span. Use of annotations lets users add to a span with no library dependency on a span api.
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Doing so lets Sleuth change its core API to create less impact to user code.</li><li class="listitem">Reduced surface area for basic span operations. Without this feature, you must use the span api, which has lifecycle commands that could be used incorrectly.
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By only exposing scope, tag, and log functionality, you can collaborate without accidentally breaking span lifecycle.</li><li class="listitem">Collaboration with runtime generated code. With libraries such as Spring Data and Feign, the implementations of interfaces are generated at runtime.
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Consequently, span wrapping of objects was tedious.
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@@ -39,42 +39,4 @@ Its class name has to be passed as the value of the <code class="literal">resolv
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}</pre><p>No custom implementation of a <code class="literal">TagValueExpressionResolver</code> leads to evaluation of the SPEL expression, and a tag with a value of <code class="literal">4 characters</code> is set on the span.
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If you want to use some other expression resolution mechanism, you can create your own implementation of the bean.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_using_the_literal_tostring_literal_method" href="#_using_the_literal_tostring_literal_method"></a>11.4.3 Using the <code class="literal">toString()</code> method</h3></div></div></div><p>Consider the following annotated method:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@NewSpan</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> getAnnotationForArgumentToString(<em><span class="hl-annotation" style="color: gray">@SpanTag("test")</span></em> Long param) {
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}</pre><p>Running the preceding method with a value of <code class="literal">15</code> leads to setting a tag with a String value of <code class="literal">"15"</code>.</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="__literal_tracefilter_literal" href="#__literal_tracefilter_literal"></a>11.5 <code class="literal">TraceFilter</code></h2></div></div></div><p>You can also modify the behavior of the <code class="literal">TraceFilter</code>, which is the component that is responsible for processing the input HTTP request and adding tags basing on the HTTP response.
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You can customize the tags or modify the response headers by registering your own instance of the <code class="literal">TraceFilter</code> bean.</p><p>In the following example, we register the <code class="literal">TraceFilter</code> bean, add the <code class="literal">ZIPKIN-TRACE-ID</code> response header containing the current Span’s trace id, and add a tag with key <code class="literal">custom</code> and a value <code class="literal">tag</code> to the span.</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@Component</span></em>
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<em><span class="hl-annotation" style="color: gray">@Order(TraceFilter.ORDER + 1)</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> MyFilter <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">extends</span> GenericFilterBean {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">final</span> Tracer tracer;
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MyFilter(Tracer tracer) {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">this</span>.tracer = tracer;
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}
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<em><span class="hl-annotation" style="color: gray">@Override</span></em> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> doFilter(ServletRequest request, ServletResponse response,
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FilterChain chain) <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">throws</span> IOException, ServletException {
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Span currentSpan = <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">this</span>.tracer.currentSpan();
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then(currentSpan).isNotNull();
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// for readability we're returning trace id in a hex form</span>
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((HttpServletResponse) response)
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.addHeader(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"ZIPKIN-TRACE-ID"</span>,
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currentSpan.context().traceIdString());
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-comment">// we can also add some custom tags</span>
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currentSpan.tag(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"custom"</span>, <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"tag"</span>);
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chain.doFilter(request, response);
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}
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}</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_custom_service_name" href="#_custom_service_name"></a>11.6 Custom service name</h2></div></div></div><p>By default, Sleuth assumes that, when you send a span to Zipkin, you want the span’s service name to be equal to the value of the <code class="literal">spring.application.name</code> property.
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That is not always the case, though.
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There are situations in which you want to explicitly provide a different service name for all spans coming from your application.
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To achieve that, you can pass the following property to your application to override that value (the example is for a service named <code class="literal">myService</code>):</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">spring.zipkin.service.name</span>: myService</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_customization_of_reported_spans" href="#_customization_of_reported_spans"></a>11.7 Customization of Reported Spans</h2></div></div></div><p>Before reporting spans (for example, to Zipkin) you may want to modify that span in some way.
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You can do so by using the <code class="literal">SpanAdjuster</code> interface.</p><p>In Sleuth, we generat spans with a fixed name.
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Some users want to modify the name depending on values of tags.
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You can implement the <code class="literal">SpanAdjuster</code> interface to alter that name.</p><p>The following example shows how to register two beans that implement <code class="literal">SpanAdjuster</code>:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@Bean</span></em> SpanAdjuster adjusterOne() {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> span -> span.toBuilder().name(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"foo"</span>).build();
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}
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<em><span class="hl-annotation" style="color: gray">@Bean</span></em> SpanAdjuster adjusterTwo() {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> span -> span.toBuilder().name(span.name() + <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">" bar"</span>).build();
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}</pre><p>The preceding example results in changing the name of the reported span to <code class="literal">foo bar</code>, just before it gets reported (for example, to Zipkin).</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_host_locator" href="#_host_locator"></a>11.8 Host Locator</h2></div></div></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>This section is about defining <span class="strong"><strong>host</strong></span> from service discovery.
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It is <span class="strong"><strong>NOT</strong></span> about finding Zipkin through service discovery.</p></td></tr></table></div><p>To define the host that corresponds to a particular span, we need to resolve the host name and port.
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The default approach is to take these values from server properties.
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If those are not set, we try to retrieve the host name from the network interfaces.</p><p>If you have the discovery client enabled and prefer to retrieve the host address from the registered instance in a service registry, you have to set the <code class="literal">spring.zipkin.locator.discovery.enabled</code> property (it is applicable for both HTTP-based and Stream-based span reporting), as follows:</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">spring.zipkin.locator.discovery.enabled</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">true</span></pre></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="multi__naming_spans.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="multi__sending_spans_to_zipkin.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">10. Naming spans </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"> 12. Sending Spans to Zipkin</td></tr></table></div></body></html>
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}</pre><p>Running the preceding method with a value of <code class="literal">15</code> leads to setting a tag with a String value of <code class="literal">"15"</code>.</p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="multi__naming_spans.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="multi__customizations.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">10. Naming spans </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"> 12. Customizations</td></tr></table></div></body></html>
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