SpringCloud TracingFilter

您还可以修改TracingFilter的行为，该行为负责处理输入的HTTP请求并基于HTTP响应添加标签。您可以通过注册自己的TracingFilter bean实例来自定义标签或修改响应头。

在下面的示例中，我们注册TracingFilter bean，添加包含当前Span的跟踪ID的ZIPKIN-TRACE-ID响应标头，并添加带有键custom和一个值的标签tag到跨度。

@Component
@Order(TraceWebServletAutoConfiguration.TRACING_FILTER_ORDER + 1)
class MyFilter extends GenericFilterBean {

	private final Tracer tracer;

	MyFilter(Tracer tracer) {
		this.tracer = tracer;
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		Span currentSpan = this.tracer.currentSpan();
		if (currentSpan == null) {
			chain.doFilter(request, response);
			return;
		}
		// for readability we're returning trace id in a hex form
		((HttpServletResponse) response).addHeader("ZIPKIN-TRACE-ID",
				currentSpan.context().traceIdString());
		// we can also add some custom tags
		currentSpan.tag("custom", "tag");
		chain.doFilter(request, response);
	}

}