fix: clear registry on config reload to pick up new bucket settings

main.go

@@ -178,7 +178,7 @@ func serveHTTP(mux http.Handler, listenAddress string, logger *slog.Logger) {
 	os.Exit(1)
 }
 
-func sighupConfigReloader(fileName string, mapper *mapper.MetricMapper, logger *slog.Logger) {
+func sighupConfigReloader(fileName string, mapper *mapper.MetricMapper, registry exporter.Registry, logger *slog.Logger) {
 	signals := make(chan os.Signal, 1)
 	signal.Notify(signals, syscall.SIGHUP)
 
@@ -190,16 +190,19 @@ func sighupConfigReloader(fileName string, mapper *mapper.MetricMapper, logger *
 
 		logger.Info("Received signal, attempting reload", "signal", s)
 
-		reloadConfig(fileName, mapper, logger)
+		reloadConfig(fileName, mapper, registry, logger)
 	}
 }
 
-func reloadConfig(fileName string, mapper *mapper.MetricMapper, logger *slog.Logger) {
+func reloadConfig(fileName string, mapper *mapper.MetricMapper, registry exporter.Registry, logger *slog.Logger) {
 	err := mapper.InitFromFile(fileName)
 	if err != nil {
 		logger.Info("Error reloading config", "error", err)
 		configLoads.WithLabelValues("failure").Inc()
 	} else {
+		// Reset registry so that metrics with updated bucket/quantile settings
+		// are re-registered with the new configuration.
+		registry.Reset()
 		logger.Info("Config reloaded successfully")
 		configLoads.WithLabelValues("success").Inc()
 	}
@@ -327,6 +330,7 @@ func main() {
 	}
 
 	exporter := exporter.NewExporter(prometheus.DefaultRegisterer, thisMapper, logger, eventsActions, eventsUnmapped, errorEventStats, eventStats, conflictingEventStats, metricsCount)
+	exporterRegistry := exporter.Registry
 
 	if *checkConfig {
 		logger.Info("Configuration check successful, exiting")
@@ -519,7 +523,7 @@ func main() {
 					return
 				}
 				logger.Info("Received lifecycle api reload, attempting reload")
-				reloadConfig(*mappingConfig, thisMapper, logger)
+				reloadConfig(*mappingConfig, thisMapper, exporterRegistry, logger)
 			}
 		})
 		mux.HandleFunc("/-/quit", func(w http.ResponseWriter, r *http.Request) {
@@ -548,7 +552,7 @@ func main() {
 
 	go serveHTTP(mux, *listenAddress, logger)
 
-	go sighupConfigReloader(*mappingConfig, thisMapper, logger)
+	go sighupConfigReloader(*mappingConfig, thisMapper, exporterRegistry, logger)
 	go exporter.Listen(events)
 
 	signals := make(chan os.Signal, 1)

pkg/exporter/exporter.go

@@ -37,6 +37,9 @@ type Registry interface {
 	GetHistogram(metricName string, labels prometheus.Labels, help string, mapping *mapper.MetricMapping, metricsCount *prometheus.GaugeVec) (prometheus.Observer, error)
 	GetSummary(metricName string, labels prometheus.Labels, help string, mapping *mapper.MetricMapping, metricsCount *prometheus.GaugeVec) (prometheus.Observer, error)
 	RemoveStaleMetrics()
+	// Reset clears all cached metrics, forcing re-registration on next use.
+	// This is needed after config reload to pick up new bucket/quantile settings.
+	Reset()
 }
 
 type Exporter struct {

pkg/registry/registry.go

@@ -378,6 +378,10 @@ func (r *Registry) GetSummary(metricName string, labels prometheus.Labels, help
 	return observer, nil
 }
 
+func (r *Registry) Reset() {
+	r.Metrics = make(map[string]metrics.Metric)
+}
+
 func (r *Registry) RemoveStaleMetrics() {
 	now := clock.Now()
 	// delete timeseries with expired ttl

pkg/registry/registry_test.go

@@ -0,0 +1,75 @@
+// Copyright 2013 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package registry
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/statsd_exporter/pkg/mapper"
+	"github.com/prometheus/statsd_exporter/pkg/metrics"
+)
+
+func TestRegistryReset(t *testing.T) {
+	reg := prometheus.NewRegistry()
+	m := &mapper.MetricMapper{}
+	r := NewRegistry(reg, m)
+
+	// Use Store directly with correct signature
+	metric := metrics.Metric{
+		MetricType: metrics.CounterMetricType,
+		Vectors:    make(map[metrics.NameHash]*metrics.Vector),
+		Metrics:    make(map[metrics.ValueHash]*metrics.RegisteredMetric),
+	}
+	r.Metrics["test_metric"] = metric
+
+	if len(r.Metrics) != 1 {
+		t.Fatalf("expected 1 metric, got %d", len(r.Metrics))
+	}
+
+	// Reset should clear all metrics
+	r.Reset()
+
+	if len(r.Metrics) != 0 {
+		t.Fatalf("expected 0 metrics after reset, got %d", len(r.Metrics))
+	}
+}
+
+func TestRegistryResetAfterStore(t *testing.T) {
+	reg := prometheus.NewRegistry()
+	m := &mapper.MetricMapper{}
+	r := NewRegistry(reg, m)
+
+	// Simulate storing metrics with different types
+	r.Metrics["metric1"] = metrics.Metric{
+		MetricType: metrics.CounterMetricType,
+		Vectors:    make(map[metrics.NameHash]*metrics.Vector),
+		Metrics:    make(map[metrics.ValueHash]*metrics.RegisteredMetric),
+	}
+	r.Metrics["metric2"] = metrics.Metric{
+		MetricType: metrics.GaugeMetricType,
+		Vectors:    make(map[metrics.NameHash]*metrics.Vector),
+		Metrics:    make(map[metrics.ValueHash]*metrics.RegisteredMetric),
+	}
+
+	if len(r.Metrics) != 2 {
+		t.Fatalf("expected 2 metrics, got %d", len(r.Metrics))
+	}
+
+	r.Reset()
+
+	if len(r.Metrics) != 0 {
+		t.Fatalf("expected 0 metrics after reset, got %d", len(r.Metrics))
+	}
+}