Add instrument registry

internal/instrumentregistry/instrument_registry.go

@@ -0,0 +1,236 @@
+/*
+ *
+ * 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 instrumentregistry
+
+import "log"
+
+// InstrumentDescriptor is a data of a registered instrument (metric).
+type InstrumentDescriptor struct {
+	// Name is the name of this metric.
+	Name string
+	// Description is the description of this metric.
+	Description string
+	// Unit is the unit of this metric.
+	Unit string
+	// Labels are the required label keys for this metric.
+	Labels []string
+	// OptionalLabels are the optional label keys for this
+	// metric.
+	OptionalLabels []string
+	// Default is whether this metric is on by default.
+	Default bool
+}
+
+// All of these globals are written to at initialization time only, and are read
+// only after initialization.
+// Int64CountInsts is information about registered int 64 count instruments in
+// order of registration.
+var Int64CountInsts []InstrumentDescriptor
+
+// Float64CountInsts is information about registered float 64 count instruments
+// in order of registration.
+var Float64CountInsts []InstrumentDescriptor
+
+// Int64HistoInsts is information about registered int 64 histo instruments in
+// order of registration.
+var Int64HistoInsts []InstrumentDescriptor
+
+// Float64HistoInsts is information about registered float 64 histo instruments
+// in order of registration.
+var Float64HistoInsts []InstrumentDescriptor
+
+// Int64GaugeInsts is information about registered int 64 gauge instruments in
+// order of registration.
+var Int64GaugeInsts []InstrumentDescriptor
+
+// registeredInsts are the registered instrument descriptor names.
+var registeredInsts = make(map[string]bool)
+
+// DefaultNonPerCallMetrics are the instruments registered that are on by
+// default.
+var DefaultNonPerCallMetrics = make(map[string]bool)
+
+// ClearInstrumentRegistry clears the instrument registry for testing purposes
+// only.
+func ClearInstrumentRegistryForTesting() {
+	Int64CountInsts = nil
+	Float64CountInsts = nil
+	Int64HistoInsts = nil
+	Float64HistoInsts = nil
+	Int64GaugeInsts = nil
+	registeredInsts = make(map[string]bool)
+	DefaultNonPerCallMetrics = make(map[string]bool)
+}
+
+// Label represents a string attribute/label to attach to metrics.
+type Label struct {
+	// Key is the key of the label.
+	Key string
+	// Value is the value of the label.
+	Value string
+}
+
+func registerInst(name string, def bool) {
+	if registeredInsts[name] {
+		log.Panicf("instrument %v already registered", name)
+	}
+	registeredInsts[name] = true
+	if def {
+		DefaultNonPerCallMetrics[name] = true
+	}
+}
+
+// Int64CountHandle is a typed handle for a int count instrument. This handle is
+// passed at the recording point in order to know which instrument to record on.
+type Int64CountHandle struct {
+	Index int
+}
+
+// RegisterInt64Count registers the int count instrument description onto the
+// global registry. It returns a typed handle to use when 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 instruments are
+// registered with the same name, this function will panic.
+func RegisterInt64Count(name string, desc string, unit string, labels []string, optionalLabels []string, def bool) Int64CountHandle {
+	registerInst(name, def)
+	Int64CountInsts = append(Int64CountInsts, InstrumentDescriptor{
+		Name:           name,
+		Description:    desc,
+		Unit:           unit,
+		Labels:         labels,
+		OptionalLabels: optionalLabels,
+		Default:        def,
+	})
+	return Int64CountHandle{
+		Index: len(Int64CountInsts) - 1,
+	}
+}
+
+// Float64CountHandle is a typed handle for a float count instrument. This handle
+// is passed at the recording point in order to know which instrument to record
+// on.
+type Float64CountHandle struct {
+	Index int
+}
+
+// RegisterFloat64Count registers the float count instrument description onto the
+// global registry. It returns a typed handle to use when 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 instruments are
+// registered with the same name, this function will panic.
+func RegisterFloat64Count(name string, desc string, unit string, labels []string, optionalLabels []string, def bool) Float64CountHandle {
+	registerInst(name, def)
+	Float64CountInsts = append(Float64CountInsts, InstrumentDescriptor{
+		Name:           name,
+		Description:    desc,
+		Unit:           unit,
+		Labels:         labels,
+		OptionalLabels: optionalLabels,
+		Default:        def,
+	})
+	return Float64CountHandle{
+		Index: len(Float64CountInsts) - 1,
+	}
+}
+
+// Int64HistoHandle is a typed handle for a int histogram instrument. This handle
+// is passed at the recording point in order to know which instrument to record
+// on.
+type Int64HistoHandle struct {
+	Index int
+}
+
+// RegisterInt64Histo registers the int histogram instrument description onto the
+// global registry. It returns a typed handle to use when 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 instruments are
+// registered with the same name, this function will panic.
+func RegisterInt64Histo(name string, desc string, unit string, labels []string, optionalLabels []string, def bool) Int64HistoHandle {
+	registerInst(name, def)
+	Int64HistoInsts = append(Int64HistoInsts, InstrumentDescriptor{
+		Name:           name,
+		Description:    desc,
+		Unit:           unit,
+		Labels:         labels,
+		OptionalLabels: optionalLabels,
+		Default:        def,
+	})
+	return Int64HistoHandle{
+		Index: len(Int64HistoInsts) - 1,
+	}
+}
+
+// Float64HistoHandle is a typed handle for a float histogram instrument. This
+// handle is passed at the recording point in order to know which instrument to
+// record on.
+type Float64HistoHandle struct {
+	Index int
+}
+
+// RegisterFloat64Histo registers the float histogram instrument description
+// onto the global registry. It returns a typed handle to use when 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 instruments are
+// registered with the same name, this function will panic.
+func RegisterFloat64Histo(name string, desc string, unit string, labels []string, optionalLabels []string, def bool) Float64HistoHandle {
+	registerInst(name, def)
+	Float64HistoInsts = append(Float64HistoInsts, InstrumentDescriptor{
+		Name:           name,
+		Description:    desc,
+		Unit:           unit,
+		Labels:         labels,
+		OptionalLabels: optionalLabels,
+		Default:        def,
+	})
+	return Float64HistoHandle{
+		Index: len(Float64HistoInsts) - 1,
+	}
+}
+
+// Int64GaugeHandle is a typed handle for a int gauge instrument. This handle is
+// passed at the recording point in order to know which instrument to record on.
+type Int64GaugeHandle struct {
+	Index int
+}
+
+// RegisterInt64Gauge registers the int gauge instrument description onto the
+// global registry. It returns a typed handle to use when 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 instruments are
+// registered with the same name, this function will panic.
+func RegisterInt64Gauge(name string, desc string, unit string, labels []string, optionalLabels []string, def bool) Int64GaugeHandle {
+	registerInst(name, def)
+	Int64GaugeInsts = append(Int64GaugeInsts, InstrumentDescriptor{
+		Name:           name,
+		Description:    desc,
+		Unit:           unit,
+		Labels:         labels,
+		OptionalLabels: optionalLabels,
+		Default:        def,
+	})
+	return Int64GaugeHandle{
+		Index: len(Int64GaugeInsts) - 1,
+	}
+}