func BeginSubsegment()

in xray/segment.go [264:333]
55 lines of code
12 McCabe index (conditional complexity)

func BeginSubsegment(ctx context.Context, name string) (context.Context, *Segment) {
	// If SDK is disabled then return with an empty segment
	if SdkDisabled() {
		seg := &Segment{}
		return context.WithValue(ctx, ContextKey, seg), seg
	}

	if len(name) > 200 {
		name = name[:200]
	}

	var parent *Segment
	// first time to create facade segment
	if getTraceHeaderFromContext(ctx) != nil && GetSegment(ctx) == nil {
		_, parent = newFacadeSegment(ctx)
	} else {
		parent = GetSegment(ctx)
		if parent == nil {
			cfg := GetRecorder(ctx)
			failedMessage := fmt.Sprintf("failed to begin subsegment named '%v': segment cannot be found.", name)
			if cfg != nil && cfg.ContextMissingStrategy != nil {
				cfg.ContextMissingStrategy.ContextMissing(failedMessage)
			} else {
				globalCfg.ContextMissingStrategy().ContextMissing(failedMessage)
			}
			return ctx, nil
		}
	}

	seg := &Segment{parent: parent}
	logger.Debugf("Beginning subsegment named %s", name)

	seg.Lock()
	defer seg.Unlock()

	seg.ParentSegment = parent.ParentSegment

	// generates subsegment id based on sampling decision and AWS_XRAY_NOOP_ID env variable
	noOpID := os.Getenv("AWS_XRAY_NOOP_ID")
	if noOpID != "" && strings.ToLower(noOpID) == "false" {
		seg.ID = NewSegmentID()
	} else {
		if !seg.ParentSegment.Sampled {
			seg.ID = noOpSegmentID()
		} else {
			seg.ID = NewSegmentID()
		}
	}

	// check whether segment is dummy or not based on sampling decision
	if !seg.ParentSegment.Sampled {
		seg.Dummy = true
	}

	atomic.AddUint32(&seg.ParentSegment.totalSubSegments, 1)

	parent.Lock()
	parent.rawSubsegments = append(parent.rawSubsegments, seg)
	parent.openSegments++
	parent.Unlock()

	seg.Name = name
	seg.StartTime = float64(time.Now().UnixNano()) / float64(time.Second)
	seg.InProgress = true
	seg.Sampled = seg.ParentSegment.Sampled
	seg.TraceID = seg.ParentSegment.TraceID
	seg.ParentID = seg.ParentSegment.ID

	return context.WithValue(ctx, ContextKey, seg), seg
}