OpenTelemetry笔记(6)-AttributesExtractor

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概念

AttributesExtractor 是对 Span 的 setAttribute 方法进行业务的一种抽象封装

业务属性跟踪方式

使用 Span 的 setAttribute

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private static void doLogic()
{
    User user=new User();
    user.setId(1L);
    user.setName("curryzxh");
    user.setPhone("10010");
    UserService service=new UserService();
    Span.current().setAttribute(AttributeKey.longKey("uid"),user.getId());
    Span.current().setAttribute(AttributeKey.stringKey("name"),user.getName());
    boolean bSave=service.saveUser(user);
    Span.current().setAttribute(AttributeKey.booleanKey("result"),bSave);
}

使用 AttributesExtractor

AttributesExtractor 是 instrumentation 中非常重要的概念，每个组件基本都需要自定义实现 AttributesExtractor

接口定义

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public interface AttributesExtractor<REQUEST, RESPONSE> {

  void onStart(AttributesBuilder attributes, REQUEST request);


  void onEnd(
      AttributesBuilder attributes,
      REQUEST request,
      @Nullable RESPONSE response,
      @Nullable Throwable error);

  default <T> void set(AttributesBuilder attributes, AttributeKey<T> key, @Nullable T value) {
    if (value != null) {
      attributes.put(key, value);
    }
  }

接口实现

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public class UserAttributesExtractor implements AttributesExtractor<User,Boolean> {

    @Override
    public void onStart(AttributesBuilder attributes, User user) {
        set(attributes, AttributeKey.longKey("uid"),user.getId());
        set(attributes, AttributeKey.stringKey("name"),user.getName());
    }

    @Override
    public void onEnd(AttributesBuilder attributes, User user, @Nullable Boolean aBoolean, @Nullable Throwable error) {
         set(attributes,AttributeKey.booleanKey("result"),aBoolean);
    }
}

调用方式

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public class UserService {

    UserAttributesExtractor extractor=new UserAttributesExtractor();

    public Boolean saveUser(User user) {
        AttributesBuilder attributes = Attributes.builder();

        extractor.onStart(attributes, user);

        Boolean bSave = internalSaveUser(user);
        extractor.onEnd(attributes, user, bSave, null);
        Span.current().setAllAttributes(attributes.build());
        return bSave;
    }

    private Boolean internalSaveUser(User user)
    {
        //todo
        return true;
    }
}

使用 AttributesExtractor 实现 AOP

切面对象定义

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final class JoinPointRequest {
  private final JoinPoint joinPoint;
  private final Method method;
  private final WithSpan annotation;

  JoinPointRequest(JoinPoint joinPoint) {
    this.joinPoint = joinPoint;
    MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
    this.method = methodSignature.getMethod();
    this.annotation = this.method.getDeclaredAnnotation(WithSpan.class);
  }

  Method method() {
    return method;
  }

  WithSpan annotation() {
    return annotation;
  }

  Object[] args() {
    return joinPoint.getArgs();
  }
}

AttributesExtractor 接口实现

其有 3 个入参

  • MethodExtractor：获取对象要调用的方法
  • ParameterAttributeNamesExtractor：获取方法调用的参数名称
  • MethodArgumentsExtractor：获取方法的参数值
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public final class MethodSpanAttributesExtractor<REQUEST, RESPONSE>
    implements AttributesExtractor<REQUEST, RESPONSE> {

  private final MethodExtractor<REQUEST> methodExtractor;
  private final MethodArgumentsExtractor<REQUEST> methodArgumentsExtractor;
  private final ParameterAttributeNamesExtractor parameterAttributeNamesExtractor;

  public static <REQUEST, RESPONSE> MethodSpanAttributesExtractor<REQUEST, RESPONSE> newInstance(
      MethodExtractor<REQUEST> methodExtractor,
      ParameterAttributeNamesExtractor parameterAttributeNamesExtractor,
      MethodArgumentsExtractor<REQUEST> methodArgumentsExtractor) {

    return new MethodSpanAttributesExtractor<>(
        methodExtractor,
        parameterAttributeNamesExtractor,
        methodArgumentsExtractor);
  }

  @Override
  public void onStart(AttributesBuilder attributes, REQUEST request) {
    Method method = methodExtractor.extract(request);
    AttributeBindings bindings = cache.computeIfAbsent(method, this::bind);
    if (!bindings.isEmpty()) {
      Object[] args = methodArgumentsExtractor.extract(request);
      bindings.apply(attributes::put, args);
    }
  }

  @Override
  public void onEnd(
      AttributesBuilder attributes,
      REQUEST request,
      @Nullable RESPONSE response,
      @Nullable Throwable error) {}

调用示例

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MethodSpanAttributesExtractor.newInstance(
                    JoinPointRequest::method,
                    new WithSpanAspectParameterAttributeNamesExtractor(),
                    JoinPointRequest::args))