func convertRelabelingRule()

in pkg/operator/apis/monitoring/v1/pod_config.go [463:522]
41 lines of code
12 McCabe index (conditional complexity)

func convertRelabelingRule(r RelabelingRule) (*relabel.Config, error) {
	rcfg := &relabel.Config{
		// Upstream applies ToLower when digesting the config, so we allow the same.
		Action:      relabel.Action(strings.ToLower(r.Action)),
		TargetLabel: r.TargetLabel,
		Separator:   r.Separator,
		Replacement: r.Replacement,
		Modulus:     r.Modulus,
	}
	for _, n := range r.SourceLabels {
		rcfg.SourceLabels = append(rcfg.SourceLabels, prommodel.LabelName(n))
	}
	// Instantiate the default regex Prometheus uses so that the checks below can be run
	// if no explicit value is provided.
	re := relabel.MustNewRegexp(`(.*)`)

	// We must only set the regex if its not empty. Like in other cases, the Prometheus code does
	// not setup the structs correctly and this would default to the string "null" when marshalled,
	// which is then interpreted as a regex again when read by Prometheus.
	if r.Regex != "" {
		var err error
		re, err = relabel.NewRegexp(r.Regex)
		if err != nil {
			return nil, fmt.Errorf("invalid regex %q: %w", r.Regex, err)
		}
		rcfg.Regex = re
	}

	// Validate that the protected target labels are not mutated by the provided relabeling rules.
	switch rcfg.Action {
	// Default action is "replace" per https://prometheus.io/docs/prometheus/latest/configuration/configuration/#relabel_config.
	case relabel.Replace, relabel.HashMod, "":
		// These actions write into the target label and it must not be a protected one.
		if protectedLabel[r.TargetLabel] {
			return nil, fmt.Errorf("cannot relabel with action %q onto protected label %q", r.Action, r.TargetLabel)
		}
	case relabel.LabelDrop:
		if matchesAnyProtectedLabel(re) {
			return nil, fmt.Errorf("regex %s would drop at least one of the protected labels %v", r.Regex, protectedLabels)
		}
	case relabel.LabelKeep:
		// Keep drops all labels that don't match the regex. So all protected labels must
		// match keep.
		if !matchesAllProtectedLabels(re) {
			return nil, fmt.Errorf("regex %s would drop at least one of the protected labels %s", r.Regex, protectedLabels)
		}
	case relabel.LabelMap:
		// It is difficult to prove for certain that labelmap does not override a protected label.
		// Thus we just prohibit its use for now.
		// The most feasible way to support this would probably be store all protected labels
		// in __tmp_protected_<name> via a replace rule, then apply labelmap, then replace the
		// __tmp label back onto the protected label.
		return nil, fmt.Errorf("relabeling with action %q not allowed", r.Action)
	case relabel.Keep, relabel.Drop:
		// These actions don't modify a series and are OK.
	default:
		return nil, fmt.Errorf("unknown relabeling action %q", r.Action)
	}
	return rcfg, nil
}