使用 extract + TextMapAdapter 实现了自定义 traceId
作者：观测云
- 2023-12-27 上海
本文字数：4583 字
阅读完需：约 15 分钟
前言
某些特定的场景，需要我们通过代码的方式实现自定义 traceId。
实现思路：通过 tracer.extract 能够构造出 SpanContext ，将构造出来的 SpanContext 作为上层节点信息，通过 asChildOf(SpanContext) 能够构造出当前的 span。
TraceId 如何参数定义
对于 tracer.extract 构建 SpanContext，内部通过 ContextInterpreter 进行解析并获取对应的 traceId 和 spanId，ContextInterpreter 部分实现代码将在下文做介绍。
传播器
ddtrace 支持几种传播协议，不同的传播协议的 traceId 的参数名不一样。<br/>就 java 而言，ddtrace 支持两种传播协议：
Datadog ：默认传播协议
B3 ：B3 传播是标头“b3”和以“x-b3-”开头的标头的规范。这些标头用于跨服务边界的跟踪上下文传播。
使用 Datadog 传播器实现自定义 traceId
开启 Datadog 传播器
-Ddd.propagation.style.extract=Datadog-Ddd.propagation.style.inject=Datadog
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机制源码介绍
ddtrace 默认采用 Datadog 作为默认的传播协议，拦截器为DatadogContextInterpreter，其部分代码如下：
public boolean accept(String key, String value) { case 'x': if ("x-datadog-trace-id".equalsIgnoreCase(key)) { classification = 0; } else if ("x-datadog-parent-id".equalsIgnoreCase(key)) { classification = 1; } else if ("x-datadog-sampling-priority".equalsIgnoreCase(key)) { classification = 3; } else if ("x-datadog-origin".equalsIgnoreCase(key)) { classification = 2;
....
switch(classification) { case 0: this.traceId = DDId.from(firstValue); break; case 1: this.spanId = DDId.from(firstValue); break; case 2: this.origin = firstValue; break; case 3: this.samplingPriority = Integer.parseInt(firstValue); break; .... }
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代码实现
/*** * 自定义traceId相关信息，实现自定义链路 * @param traceId * @param parentId * @param treeLength * @return */ @GetMapping("/customTrace") @ResponseBody public String customTrace(String traceId, String parentId, Integer treeLength) { Tracer tracer = GlobalTracer.get(); traceId = StringUtils.isEmpty(traceId) ? IdGenerationStrategy.RANDOM.generate().toString() : traceId; parentId = StringUtils.isEmpty(parentId) ? DDId.ZERO.toString() : parentId; treeLength = treeLength == null ? 3 : treeLength; for (int i = 0; i < treeLength; i++) { Map<String, String> data = new HashMap<>(); data.put("x-datadog-trace-id", traceId); data.put("x-datadog-parent-id", parentId);
SpanContext extractedContext = tracer.extract(Format.Builtin.HTTP_HEADERS, new TextMapAdapter(data)); Span serverSpan = tracer.buildSpan("opt" + i) .withTag("service_name", "someService" + i) .asChildOf(extractedContext) .start(); tracer.activateSpan(serverSpan).close(); serverSpan.finish(); parentId = serverSpan.context().toSpanId(); } return "build success!"; }
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使用 B3 传播器实现自定义 traceId
B3 有两种编码：Single Header 和 Multiple Header。
多个标头编码 X-B3-在跟踪上下文中使用每个项目的前缀标头
单个标头将上下文分隔为一个名为 b3. 提取字段时，单头变体优先于多头变体。
这是一个使用多个标头编码的示例流程，假设 HTTP 请求带有传播的跟踪：
开启 B3 传播器
-Ddd.propagation.style.extract=B3-Ddd.propagation.style.inject=B3
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机制源码介绍
public boolean accept(String key, String value) { ... char first = Character.toLowerCase(key.charAt(0)); switch (first) { case 'f': if (this.handledForwarding(key, value)) { return true; } break; case 'u': if (this.handledUserAgent(key, value)) { return true; } break; case 'x': if ((this.traceId == null || this.traceId == DDId.ZERO) && "X-B3-TraceId".equalsIgnoreCase(key)) { classification = 0; } else if ((this.spanId == null || this.spanId == DDId.ZERO) && "X-B3-SpanId".equalsIgnoreCase(key)) { classification = 1; } else if (this.samplingPriority == this.defaultSamplingPriority() && "X-B3-Sampled".equalsIgnoreCase(key)) { classification = 3; } else if (this.handledXForwarding(key, value)) { return true; } }
...
String firstValue = HttpCodec.firstHeaderValue(value); if (null != firstValue) { switch (classification) { case 0: if (this.setTraceId(firstValue)) { return true; } break; case 1: this.setSpanId(firstValue); break; case 2: String mappedKey = (String)this.taggedHeaders.get(lowerCaseKey); if (null != mappedKey) { if (this.tags.isEmpty()) { this.tags = new TreeMap(); }
this.tags.put(mappedKey, HttpCodec.decode(firstValue)); } break; case 3: this.samplingPriority = this.convertSamplingPriority(firstValue); break; case 4: if (this.extractB3(firstValue)) { return true; } } }
...
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以下方法是对 Single Header 方式的处理
private boolean extractB3(String firstValue) { if (firstValue.length() == 1) { this.samplingPriority = this.convertSamplingPriority(firstValue); } else { int firstIndex = firstValue.indexOf("-"); int secondIndex = firstValue.indexOf("-", firstIndex + 1); String b3SpanId; if (firstIndex != -1) { b3SpanId = firstValue.substring(0, firstIndex); if (this.setTraceId(b3SpanId)) { return true; } }
if (secondIndex == -1) { b3SpanId = firstValue.substring(firstIndex + 1); this.setSpanId(b3SpanId); } else { b3SpanId = firstValue.substring(firstIndex + 1, secondIndex); this.setSpanId(b3SpanId); String b3SamplingId = firstValue.substring(secondIndex + 1); this.samplingPriority = this.convertSamplingPriority(b3SamplingId); } }
return false; }
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Multiple Header 代码实现
private static void b3TraceByMultiple(){ String traceId = DDId.from("6917954032704516265").toHexStringOrOriginal(); Tracer tracer = GlobalTracer.get(); String parentId = DDId.from("4025816492133344807").toHexStringOrOriginal(); for (int i = 0; i < 3; i++) { Map<String, String> data = new HashMap<>(); data.put("X-B3-TraceId", traceId); data.put("X-B3-SpanId", parentId);
SpanContext extractedContext = tracer.extract(Format.Builtin.HTTP_HEADERS, new TextMapAdapter(data)); Span serverSpan = tracer.buildSpan("opt"+i) .withTag("service","someService"+i) .asChildOf(extractedContext) .start(); serverSpan.setTag("code","200"); tracer.activateSpan(serverSpan).close(); serverSpan.finish(); parentId = DDId.from(serverSpan.context().toSpanId()).toHexStringOrOriginal(); System.out.println( traceId+"\t"+serverSpan.context().toTraceId()+"\t"+parentId); }
}
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**注意：**Multiple Header 必需传入两个 header，分别为：
X-B3-TraceId和X-B3-SpanId，从拦截器上分析，是不区分大小写的。
6001828a33d570a9 6917954032704516265 58c4b35f113ee3536001828a33d570a9 6917954032704516265 330359b7aaea9d6b6001828a33d570a9 6917954032704516265 1ac0dcd332f9262f
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Single Header 代码实现
private static void b3TraceBySingle(){ String traceId = DDId.from("6917954032704516265").toHexStringOrOriginal(); Tracer tracer = GlobalTracer.get(); String parentId = DDId.from("4025816492133344807").toHexStringOrOriginal(); for (int i = 0; i < 3; i++) { String b3 = traceId+ "-"+parentId+"-1"; Map<String, String> data = new HashMap<>(); data.put("b3",b3); SpanContext extractedContext = tracer.extract(Format.Builtin.HTTP_HEADERS, new TextMapAdapter(data)); Span serverSpan = tracer.buildSpan("opt"+i) .withTag("service","someService"+i) .asChildOf(extractedContext) .start(); serverSpan.setTag("code","200"); tracer.activateSpan(serverSpan).close(); serverSpan.finish(); parentId = DDId.from(serverSpan.context().toSpanId()).toHexStringOrOriginal(); System.out.println( traceId+"\t"+serverSpan.context().toTraceId()+"\t"+parentId); System.out.println("b3="+b3); }
}
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6001828a33d570a9 6917954032704516265 308287d022272ed9b3=6001828a33d570a9-37de92c518846627-16001828a33d570a9 6917954032704516265 5e6fbaad91daef5cb3=6001828a33d570a9-308287d022272ed9-16001828a33d570a9 6917954032704516265 2cfbc225bddf5e6db3=6001828a33d570a9-5e6fbaad91daef5c-1
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**注意：**Single Header 只需要 header 传入
b3即可，格式为traceId-parentId-Sampled
开启多种传播器
两种方式任选一种即可：
System Property :
-Ddd.propagation.style.inject=Datadog,B3-Ddd.propagation.style.extract=Datadog,B3
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Environment Variable:
DD_PROPAGATION_STYLE_INJECT=Datadog,B3DD_PROPAGATION_STYLE_EXTRACT=Datadog,B3
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