experimental/stats: Add metrics registry

experimental/stats/metricregistry.go

@@ -0,0 +1,230 @@
+/*
+ *
+ * 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
+
+import (
+	"maps"
+	"testing"
+
+	"google.golang.org/grpc/grpclog"
+)
+
+var logger = grpclog.Component("metrics-registry")
+
+// DefaultMetrics are the default metrics registered through global metrics
+// registry. This is written to at initialization time only, and is read only
+// after initialization.
+var DefaultMetrics = NewMetrics()
+
+// MetricDescriptor is the data for a registered metric.
+type MetricDescriptor struct {
+	// The name of this metric. This name must be unique across the whole binary
+	// (including any per call metrics). See
+	// https://github.com/grpc/proposal/blob/master/A79-non-per-call-metrics-architecture.md#metric-instrument-naming-conventions
+	// for metric naming conventions.
+	Name Metric
+	// The description of this metric.
+	Description string
+	// The unit (e.g. entries, seconds) of this metric.
+	Unit string
+	// The required label keys for this metric. These are intended to
+	// metrics emitted from a stats handler.
+	Labels []string
+	// The optional label keys for this metric. These are intended to attached
+	// to metrics emitted from a stats handler if configured.
+	OptionalLabels []string
+	// Whether this metric is on by default.
+	Default bool
+	// The type of metric. This is set by the metric registry, and not intended
+	// to be set by a component registering a metric.
+	Type MetricType
+}
+
+// MetricType is the type of metric.
+type MetricType int
+
+const (
+	MetricTypeIntCount MetricType = iota
+	MetricTypeFloatCount
+	MetricTypeIntHisto
+	MetricTypeFloatHisto
+	MetricTypeIntGauge
+)
+
+// Int64CountHandle is a typed handle for a int count metric. This handle
+// is passed at the recording point in order to know which metric to record
+// on.
+type Int64CountHandle MetricDescriptor
+
+// Record records the int64 count value on the metrics recorder provided.
+func (h *Int64CountHandle) Record(recorder MetricsRecorder, incr int64, labels ...string) {
+	recorder.RecordInt64Count(h, incr, labels...)
+}
+
+// Float64CountHandle is a typed handle for a float count metric. This handle is
+// passed at the recording point in order to know which metric to record on.
+type Float64CountHandle MetricDescriptor
+
+// Record records the float64 count value on the metrics recorder provided.
+func (h *Float64CountHandle) Record(recorder MetricsRecorder, incr float64, labels ...string) {
+	recorder.RecordFloat64Count(h, incr, labels...)
+}
+
+// Int64HistoHandle is a typed handle for an int histogram metric. This handle
+// is passed at the recording point in order to know which metric to record on.
+type Int64HistoHandle MetricDescriptor
+
+// Record records the int64 histo value on the metrics recorder provided.
+func (h *Int64HistoHandle) Record(recorder MetricsRecorder, incr int64, labels ...string) {
+	recorder.RecordInt64Histo(h, incr, labels...)
+}
+
+// Float64HistoHandle is a typed handle for a float histogram metric. This
+// handle is passed at the recording point in order to know which metric to
+// record on.
+type Float64HistoHandle MetricDescriptor
+
+// Record records the float64 histo value on the metrics recorder provided.
+func (h *Float64HistoHandle) Record(recorder MetricsRecorder, incr float64, labels ...string) {
+	recorder.RecordFloat64Histo(h, incr, labels...)
+}
+
+// Int64GaugeHandle is a typed handle for an int gauge metric. This handle is
+// passed at the recording point in order to know which metric to record on.
+type Int64GaugeHandle MetricDescriptor
+
+// Record records the int64 histo value on the metrics recorder provided.
+func (h *Int64GaugeHandle) Record(recorder MetricsRecorder, incr int64, labels ...string) {
+	recorder.RecordInt64Gauge(h, incr, labels...)
+}
+
+// registeredMetrics are the registered metric descriptor names.
+var registeredMetrics = make(map[Metric]bool)
+
+// metricsRegistry contains all of the registered metrics.
+//
+// This is written to only at init time, and read only after that.
+var metricsRegistry = make(map[Metric]*MetricDescriptor)
+
+// DescriptorForMetric returns the MetricDescriptor from the global registry.
+//
+// Returns nil if MetricDescriptor not present.
+func DescriptorForMetric(metric Metric) *MetricDescriptor {
+	return metricsRegistry[metric]
+}
+
+func registerMetric(name Metric, def bool) {
+	if registeredMetrics[name] {
+		logger.Fatalf("metric %v already registered", name)
+	}
+	registeredMetrics[name] = true
+	if def {
+		DefaultMetrics = DefaultMetrics.Add(name)
+	}
+}
+
+// RegisterInt64Count registers the metric description onto the global registry.
+// It returns a typed handle to use to recording data.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe. If multiple metrics are
+// registered with the same name, this function will panic.
+func RegisterInt64Count(descriptor MetricDescriptor) *Int64CountHandle {
+	registerMetric(descriptor.Name, descriptor.Default)
+	descriptor.Type = MetricTypeIntCount
+	descPtr := &descriptor
+	metricsRegistry[descriptor.Name] = descPtr
+	return (*Int64CountHandle)(descPtr)
+}
+
+// RegisterFloat64Count registers the metric description onto the global
+// registry. It returns a typed handle to use to recording data.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe. If multiple metrics are
+// registered with the same name, this function will panic.
+func RegisterFloat64Count(descriptor MetricDescriptor) *Float64CountHandle {
+	registerMetric(descriptor.Name, descriptor.Default)
+	descriptor.Type = MetricTypeFloatCount
+	descPtr := &descriptor
+	metricsRegistry[descriptor.Name] = descPtr
+	return (*Float64CountHandle)(descPtr)
+}
+
+// RegisterInt64Histo registers the metric description onto the global registry.
+// It returns a typed handle to use to recording data.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe. If multiple metrics are
+// registered with the same name, this function will panic.
+func RegisterInt64Histo(descriptor MetricDescriptor) *Int64HistoHandle {
+	registerMetric(descriptor.Name, descriptor.Default)
+	descriptor.Type = MetricTypeIntHisto
+	descPtr := &descriptor
+	metricsRegistry[descriptor.Name] = descPtr
+	return (*Int64HistoHandle)(descPtr)
+}
+
+// RegisterFloat64Histo registers the metric description onto the global
+// registry. It returns a typed handle to use to recording data.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe. If multiple metrics are
+// registered with the same name, this function will panic.
+func RegisterFloat64Histo(descriptor MetricDescriptor) *Float64HistoHandle {
+	registerMetric(descriptor.Name, descriptor.Default)
+	descriptor.Type = MetricTypeFloatHisto
+	descPtr := &descriptor
+	metricsRegistry[descriptor.Name] = descPtr
+	return (*Float64HistoHandle)(descPtr)
+}
+
+// RegisterInt64Gauge registers the metric description onto the global registry.
+// It returns a typed handle to use to recording data.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe. If multiple metrics are
+// registered with the same name, this function will panic.
+func RegisterInt64Gauge(descriptor MetricDescriptor) *Int64GaugeHandle {
+	registerMetric(descriptor.Name, descriptor.Default)
+	descriptor.Type = MetricTypeIntGauge
+	descPtr := &descriptor
+	metricsRegistry[descriptor.Name] = descPtr
+	return (*Int64GaugeHandle)(descPtr)
+}
+
+// snapshotMetricsRegistryForTesting snapshots the global data of the metrics
+// registry. Registers a cleanup function on the provided testing.T that sets
+// the metrics registry to its original state. Only called in testing functions.
+func snapshotMetricsRegistryForTesting(t *testing.T) {
+	oldDefaultMetrics := DefaultMetrics
+	oldRegisteredMetrics := registeredMetrics
+	oldMetricsRegistry := metricsRegistry
+
+	registeredMetrics = make(map[Metric]bool)
+	metricsRegistry = make(map[Metric]*MetricDescriptor)
+	maps.Copy(registeredMetrics, registeredMetrics)
+	maps.Copy(metricsRegistry, metricsRegistry)
+
+	t.Cleanup(func() {
+		DefaultMetrics = oldDefaultMetrics
+		registeredMetrics = oldRegisteredMetrics
+		metricsRegistry = oldMetricsRegistry
+	})
+}