OpenCensus：通过 POST 请求跟踪传播

Question

在 Java 中，我试图通过 HTTP POST 请求 (org.apache.http.client.methods.HttpPost) 传播 TraceContext。我将上下文参数传递给标题如下：

    try (Scope scope = tracer.spanBuilder("firstSpan").startScopedSpan()) {

        SpanContext spanContext = tracer.getCurrentSpan().getContext();
        
        StringBuilder builder =
                new StringBuilder()
                    .append(spanContext.getTraceId().toLowerBase16())
                    .append(SPAN_ID_DELIMITER)
                    .append(UnsignedLongs.toString(spanIdToLong(spanContext.getSpanId())))
                    .append(TRACE_OPTION_DELIMITER)
                    .append(spanContext.getTraceOptions().isSampled() ? SAMPLED : NOT_SAMPLED);

        httpPost.addHeader(HEADER_NAME, builder.toString());

        HttpResponse response = reportSession.getHttpClient().execute(httpPost,reportSession.getHttpContext());

请求由 Servlet（在单独的 JAR 中）处理，我在其中检索参数并尝试打开一个新的 Span：

    String headerStr = req.getHeader(HEADER_NAME);

    TraceId traceId = TraceId.fromLowerBase16(headerStr.subSequence(0, TRACE_ID_SIZE));

    int traceOptionsPos = headerStr.indexOf(TRACE_OPTION_DELIMITER, TRACE_ID_SIZE);
    CharSequence spanIdStr = headerStr.subSequence(SPAN_ID_START_POS, traceOptionsPos < 0 ? headerStr.length() : traceOptionsPos);

    SpanId spanId = longToSpanId(UnsignedLongs.parseUnsignedLong(spanIdStr.toString(), 10));
    TraceOptions traceOptions = OPTIONS_NOT_SAMPLED;

    if (traceOptionsPos > 0) {
        String traceOptionsStr = headerStr.substring(traceOptionsPos + TRACE_OPTION_DELIMITER_SIZE);
        if ((UnsignedInts.parseUnsignedInt(traceOptionsStr, 10) & CLOUD_TRACE_IS_SAMPLED) != 0) {
            traceOptions = OPTIONS_SAMPLED;
        }
    }

    SpanContext context = SpanContext.create(traceId, spanId, traceOptions, TRACESTATE_DEFAULT);

    try (Scope scope = tracer.spanBuilderWithRemoteParent("newSpan", context).setSpanKind(Kind.SERVER).startScopedSpan())  {
       // execute Servlet code
    }

但是在 Google Cloud 平台中，我唯一能看到的 Span 是“firstSpan”，而监视器中不存在“newSpan”...有人可以帮我吗？

谢谢