promtail: documented client's batch struct and improved tenant stage …

…config pointer usage

pkg/logentry/stages/tenant.go

@@ -36,19 +36,19 @@ func validateTenantConfig(c TenantConfig) error {
 
 // newTenantStage creates a new tenant stage to override the tenant ID from extracted data
 func newTenantStage(logger log.Logger, configs interface{}) (*tenantStage, error) {
-	cfg := &TenantConfig{}
-	err := mapstructure.Decode(configs, cfg)
+	cfg := TenantConfig{}
+	err := mapstructure.Decode(configs, &cfg)
 	if err != nil {
 		return nil, err
 	}
 
-	err = validateTenantConfig(*cfg)
+	err = validateTenantConfig(cfg)
 	if err != nil {
 		return nil, err
 	}
 
 	return &tenantStage{
-		cfg:    *cfg,
+		cfg:    cfg,
 		logger: logger,
 	}, nil
 }

pkg/promtail/client/batch.go

@@ -9,6 +9,10 @@ import (
 	"github.com/prometheus/common/model"
 )
 
+// batch holds pending log streams waiting to be sent to Loki, and it's used
+// to reduce the number of push requests to Loki aggregating multiple log streams
+// and entries in a single batch request. In case of multi-tenant Promtail, log
+// streams for each tenant are stored in a dedicated batch.
 type batch struct {
 	streams   map[model.Fingerprint]*logproto.Stream
 	bytes     int