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package retrieval
import (
"fmt"
"hash/fnv"
"strings"
clientmodel "github.com/prometheus/client_golang/model"
"github.com/prometheus/prometheus/config"
)
// Relabel returns a relabeled copy of the given label set. The relabel configurations
// are applied in order of input.
// If a label set is dropped, nil is returned.
func Relabel(labels clientmodel.LabelSet, cfgs ...*config.RelabelConfig) (clientmodel.LabelSet, error) {
out := clientmodel.LabelSet{}
for ln, lv := range labels {
out[ln] = lv
}
var err error
for _, cfg := range cfgs {
if out, err = relabel(out, cfg); err != nil {
return nil, err
}
if out == nil {
return nil, nil
}
}
return out, nil
}
func relabel(labels clientmodel.LabelSet, cfg *config.RelabelConfig) (clientmodel.LabelSet, error) {
values := make([]string, 0, len(cfg.SourceLabels))
for _, ln := range cfg.SourceLabels {
values = append(values, string(labels[ln]))
}
val := strings.Join(values, cfg.Separator)
switch cfg.Action {
case config.RelabelDrop:
if cfg.Regex.MatchString(val) {
return nil, nil
}
case config.RelabelKeep:
if !cfg.Regex.MatchString(val) {
return nil, nil
}
case config.RelabelReplace:
// If there is no match no replacement must take place.
if !cfg.Regex.MatchString(val) {
break
}
res := cfg.Regex.ReplaceAllString(val, cfg.Replacement)
if res == "" {
delete(labels, cfg.TargetLabel)
} else {
labels[cfg.TargetLabel] = clientmodel.LabelValue(res)
}
case config.RelabelHashMod:
hasher := fnv.New64a()
hasher.Write([]byte(val))
mod := hasher.Sum64() % cfg.Modulus
labels[cfg.TargetLabel] = clientmodel.LabelValue(fmt.Sprintf("%d", mod))
default:
panic(fmt.Errorf("retrieval.relabel: unknown relabel action type %q", cfg.Action))
}
return labels, nil
}
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