Do not use . in labels in the flatten function of converter.go

[kyasbal]

I'm using slog-loki just for my personal project. I've tried the newer version with updating the client of loki before merging #5 .

I found slog-loki might need to convert label names in different way.

slog-loki/converter.go

Lines 39 to 55 in 7da5375

	func flatten(prefix string, src map[string]any, dest model.LabelSet) {
	if len(prefix) > 0 {
	prefix += "."
	}
	for k, v := range src {
	switch child := v.(type) {
	case map[string]any:
	flatten(prefix+k, child, dest)
	case []any:
	for i := 0; i < len(child); i++ {
	dest[model.LabelName(prefix+k+"."+strconv.Itoa(i))] = model.LabelValue(fmt.Sprintf("%v", child[i]))
	}
	default:
	dest[model.LabelName(prefix+k)] = model.LabelValue(fmt.Sprintf("%v", v))
	}
	}
	}

The function is using . to express enclosed slog.Attrs. But this seems not to be allowed in loki[1].

I tweaked that to use _ in my usecase and it's easy to send a PR for this fix. But this solution might be not the ideal that the auhor of this library think of.

[1]https://grafana.com/docs/loki/latest/get-started/labels/#format

[samber]

Hi @kyasbal and thanks for the bug report.

I would suggest __ separators (double _), to prevent collision with user defined _.

Using : would be even better IMO, but Prometheus recommends not using it. Moreover it looks like it is only available for __name__ label name...

[samber]

added in v3.1.0