snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

internal/stats/labels.go

@@ -0,0 +1,74 @@
+/*
+ *
+ * Copyright 2024 gRPC 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 stats provides internal stats related functionality.
+package stats
+
+import (
+	"context"
+	"maps"
+)
+
+// LabelCallback is a function that is executed when telemetry
+// label keys are updated.
+type LabelCallback func(map[string]string)
+type telemetryLabelCallbackKey struct{}
+
+// UpdateLabels executes registered telemetry callbacks with the update labels. Labels
+// are copied before being processed by any callbacks to ensure mutations are not
+// shared among derived contexts.
+//
+// It is the responsibility of the registrant to handle conflicts or label resets.
+func UpdateLabels(ctx context.Context, update map[string]string) {
+	executeTelemetryLabelCallbacks(ctx, update)
+}
+
+// RegisterTelemetryLabelCallback registers a callback function that is executed whenever
+// telemetry labels are updated.
+func RegisterTelemetryLabelCallback(ctx context.Context, callback LabelCallback) context.Context {
+	if callback == nil {
+		return ctx
+	}
+
+	callbacks, ok := ctx.Value(telemetryLabelCallbackKey{}).([]LabelCallback)
+	if !ok {
+		return context.WithValue(ctx, telemetryLabelCallbackKey{}, []LabelCallback{callback})
+	}
+	return context.WithValue(ctx, telemetryLabelCallbackKey{}, append(append([]LabelCallback(nil), callbacks...), callback))
+
+}
+
+// executeTelemetryLabelCallback runs the registered callbacks in the order they were
+// registered on the context with the provided labels. If no callbacks are registered
+// it does nothing.
+//
+// To ensure callbacks do not mutate the state of the provided label map it is copied
+// before execution.
+func executeTelemetryLabelCallbacks(ctx context.Context, labels map[string]string) {
+	callbacks, ok := ctx.Value(telemetryLabelCallbackKey{}).([]LabelCallback)
+	if !ok {
+		return
+	}
+
+	labelsCopy := map[string]string{}
+	maps.Copy(labelsCopy, labels)
+	for _, callback := range callbacks {
+		callback(labelsCopy)
+	}
+
+}