add debug metric for tracking references (#4134)

pkg/telemetry/prometheus/debug.go

@@ -0,0 +1,40 @@
+// Copyright 2023 LiveKit, Inc.
+//
+// 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 prometheus
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+
+	"github.com/livekit/protocol/livekit"
+)
+
+var (
+	refCounts *prometheus.GaugeVec
+)
+
+func initDebugStats(nodeID string, nodeType livekit.NodeType) {
+	refCounts = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace:   livekitNamespace,
+		Subsystem:   "debug",
+		Name:        "ref_count",
+		ConstLabels: prometheus.Labels{"node_id": nodeID, "node_type": nodeType.String()},
+	}, []string{"referrer"})
+
+	prometheus.MustRegister(refCounts)
+}
+
+func AddRef(referrer string, n int) {
+	refCounts.WithLabelValues(referrer).Add(float64(n))
+}

pkg/telemetry/prometheus/node.go

@@ -105,6 +105,7 @@ func Init(nodeID string, nodeType livekit.NodeType) error {
 	webhook.InitWebhookStats(prometheus.Labels{"node_id": nodeID, "node_type": nodeType.String()})
 	initQualityStats(nodeID, nodeType)
 	initDataPacketStats(nodeID, nodeType)
+	initDebugStats(nodeID, nodeType)
 
 	var err error
 	cpuStats, err = hwstats.NewCPUStats(nil)