opentracing Inject函数分析

李恒道

与https://bbs.tampermonkey.net.cn/thread-4904-1-1.html逻辑基本一致
主要调用carrier的Set函数存储Span数据

func (t *TextMapPropagator) Inject(spanContext MockSpanContext, carrier interface{}) error {
    writer, ok := carrier.(opentracing.TextMapWriter)
    if !ok {
        return opentracing.ErrInvalidCarrier
    }
    // Ids:
    writer.Set(mockTextMapIdsPrefix+"traceid", strconv.Itoa(spanContext.TraceID))
    writer.Set(mockTextMapIdsPrefix+"spanid", strconv.Itoa(spanContext.SpanID))
    writer.Set(mockTextMapIdsPrefix+"sampled", fmt.Sprint(spanContext.Sampled))
    // Baggage:
    for baggageKey, baggageVal := range spanContext.Baggage {
        safeVal := baggageVal
        if t.HTTPHeaders {
            safeVal = url.QueryEscape(baggageVal)
        }
        writer.Set(mockTextMapBaggagePrefix+baggageKey, safeVal)
    }
    return nil
}