feat(otlp/metrics): add in memory exporter and noop meter provider

go.mod

@@ -21,7 +21,6 @@ require (
 	github.com/go-sql-driver/mysql v1.8.1
 	github.com/golang-jwt/jwt/v5 v5.2.1
 	github.com/google/uuid v1.6.0
-	github.com/grafana/otel-profiling-go v0.5.1
 	github.com/hashicorp/go-retryablehttp v0.7.7
 	github.com/invopop/jsonschema v0.12.0
 	github.com/jackc/pgx/v5 v5.7.1
@@ -67,7 +66,8 @@ require (
 	go.temporal.io/api v1.39.0
 	go.temporal.io/sdk v1.29.1
 	go.temporal.io/sdk/contrib/opentelemetry v0.6.0
-	go.uber.org/fx v1.23.0
+	go.uber.org/dig v1.18.0
+	go.uber.org/fx v1.22.2
 	go.uber.org/mock v0.4.0
 	go.uber.org/zap v1.27.0
 )
@@ -198,7 +198,6 @@ require (
 	github.com/yusufpapurcu/wmi v1.2.4 // indirect
 	go.opentelemetry.io/otel/log v0.6.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.3.1 // indirect
-	go.uber.org/dig v1.18.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
 	golang.org/x/crypto v0.28.0 // indirect
 	golang.org/x/exp v0.0.0-20240909161429-701f63a606c0 // indirect

go.sum

@@ -130,7 +130,6 @@ github.com/go-faster/errors v0.7.1/go.mod h1:5ySTjWFiphBs07IKuiL69nxdfd5+fzh1u7F
 github.com/go-kit/log v0.1.0/go.mod h1:zbhenjAZHb184qTLMA9ZjW7ThYL0H2mk7Q6pNt4vbaY=
 github.com/go-logfmt/logfmt v0.5.0/go.mod h1:wCYkCAKZfumFQihp8CzCvQ3paCTfi41vtzG1KdI/P7A=
 github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
-github.com/go-logr/logr v1.3.0/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/logr v1.4.2 h1:6pFjapn8bFcIbiKo3XT4j/BhANplGihG6tvd+8rYgrY=
 github.com/go-logr/logr v1.4.2/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
@@ -187,8 +186,6 @@ github.com/gorilla/securecookie v1.1.1/go.mod h1:ra0sb63/xPlUeL+yeDciTfxMRAA+MP+
 github.com/gorilla/securecookie v1.1.2 h1:YCIWL56dvtr73r6715mJs5ZvhtnY73hBvEF8kXD8ePA=
 github.com/gorilla/securecookie v1.1.2/go.mod h1:NfCASbcHqRSY+3a8tlWJwsQap2VX5pwzwo4h3eOamfo=
 github.com/gorilla/sessions v1.2.1/go.mod h1:dk2InVEVJ0sfLlnXv9EAgkf6ecYs/i80K/zI+bUmuGM=
-github.com/grafana/otel-profiling-go v0.5.1 h1:stVPKAFZSa7eGiqbYuG25VcqYksR6iWvF3YH66t4qL8=
-github.com/grafana/otel-profiling-go v0.5.1/go.mod h1:ftN/t5A/4gQI19/8MoWurBEtC6gFw8Dns1sJZ9W4Tls=
 github.com/grpc-ecosystem/go-grpc-middleware v1.4.0 h1:UH//fgunKIs4JdUbpDl1VZCDaL56wXCB/5+wF6uHfaI=
 github.com/grpc-ecosystem/go-grpc-middleware v1.4.0/go.mod h1:g5qyo/la0ALbONm6Vbp88Yd8NsDy6rZz+RcrMPxvld8=
 github.com/grpc-ecosystem/grpc-gateway/v2 v2.22.0 h1:asbCHRVmodnJTuQ3qamDwqVOIjwqUPTYmYuemVOx+Ys=
@@ -372,7 +369,6 @@ github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/tidwall/pretty v1.0.0/go.mod h1:XNkn88O1ChpSDQmQeStsy+sBenx6DDtFZJxhVysOjyk=
@@ -437,7 +433,6 @@ go.opentelemetry.io/contrib/instrumentation/runtime v0.56.0 h1:s7wHG+t8bEoH7ibWk
 go.opentelemetry.io/contrib/instrumentation/runtime v0.56.0/go.mod h1:Q8Hsv3d9DwryfIl+ebj4mY81IYVRSPy4QfxroVZwqLo=
 go.opentelemetry.io/contrib/propagators/b3 v1.31.0 h1:PQPXYscmwbCp76QDvO4hMngF2j8Bx/OTV86laEl8uqo=
 go.opentelemetry.io/contrib/propagators/b3 v1.31.0/go.mod h1:jbqfV8wDdqSDrAYxVpXQnpM0XFMq2FtDesblJ7blOwQ=
-go.opentelemetry.io/otel v1.21.0/go.mod h1:QZzNPQPm1zLX4gZK4cMi+71eaorMSGT3A4znnUvNNEo=
 go.opentelemetry.io/otel v1.31.0 h1:NsJcKPIW0D0H3NgzPDHmo0WW6SptzPdqg/L1zsIm2hY=
 go.opentelemetry.io/otel v1.31.0/go.mod h1:O0C14Yl9FgkjqcCZAsE053C13OaddMYr/hz6clDkEJE=
 go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc v1.31.0 h1:FZ6ei8GFW7kyPYdxJaV2rgI6M+4tvZzhYsQ2wgyVC08=
@@ -456,15 +451,12 @@ go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.31.0 h1:UGZ1QwZWY67Z6Bm
 go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.31.0/go.mod h1:fcwWuDuaObkkChiDlhEpSq9+X1C0omv+s5mBtToAQ64=
 go.opentelemetry.io/otel/log v0.6.0 h1:nH66tr+dmEgW5y+F9LanGJUBYPrRgP4g2EkmPE3LeK8=
 go.opentelemetry.io/otel/log v0.6.0/go.mod h1:KdySypjQHhP069JX0z/t26VHwa8vSwzgaKmXtIB3fJM=
-go.opentelemetry.io/otel/metric v1.21.0/go.mod h1:o1p3CA8nNHW8j5yuQLdc1eeqEaPfzug24uvsyIEJRWM=
 go.opentelemetry.io/otel/metric v1.31.0 h1:FSErL0ATQAmYHUIzSezZibnyVlft1ybhy4ozRPcF2fE=
 go.opentelemetry.io/otel/metric v1.31.0/go.mod h1:C3dEloVbLuYoX41KpmAhOqNriGbA+qqH6PQ5E5mUfnY=
-go.opentelemetry.io/otel/sdk v1.21.0/go.mod h1:Nna6Yv7PWTdgJHVRD9hIYywQBRx7pbox6nwBnZIxl/E=
 go.opentelemetry.io/otel/sdk v1.31.0 h1:xLY3abVHYZ5HSfOg3l2E5LUj2Cwva5Y7yGxnSW9H5Gk=
 go.opentelemetry.io/otel/sdk v1.31.0/go.mod h1:TfRbMdhvxIIr/B2N2LQW2S5v9m3gOQ/08KsbbO5BPT0=
 go.opentelemetry.io/otel/sdk/metric v1.31.0 h1:i9hxxLJF/9kkvfHppyLL55aW7iIJz4JjxTeYusH7zMc=
 go.opentelemetry.io/otel/sdk/metric v1.31.0/go.mod h1:CRInTMVvNhUKgSAMbKyTMxqOBC0zgyxzW55lZzX43Y8=
-go.opentelemetry.io/otel/trace v1.21.0/go.mod h1:LGbsEB0f9LGjN+OZaQQ26sohbOmiMR+BaslueVtS/qQ=
 go.opentelemetry.io/otel/trace v1.31.0 h1:ffjsj1aRouKewfr85U2aGagJ46+MvodynlQ1HYdmJys=
 go.opentelemetry.io/otel/trace v1.31.0/go.mod h1:TXZkRk7SM2ZQLtR6eoAWQFIHPvzQ06FJAsO1tJg480A=
 go.opentelemetry.io/proto/otlp v1.3.1 h1:TrMUixzpM0yuc/znrFTP9MMRh8trP93mkCiDVeXrui0=
@@ -478,8 +470,8 @@ go.temporal.io/sdk/contrib/opentelemetry v0.6.0/go.mod h1:Lem8VrE2ks8P+FYcRM3Uph
 go.uber.org/atomic v1.7.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
 go.uber.org/dig v1.18.0 h1:imUL1UiY0Mg4bqbFfsRQO5G4CGRBec/ZujWTvSVp3pw=
 go.uber.org/dig v1.18.0/go.mod h1:Us0rSJiThwCv2GteUN0Q7OKvU7n5J4dxZ9JKUXozFdE=
-go.uber.org/fx v1.23.0 h1:lIr/gYWQGfTwGcSXWXu4vP5Ws6iqnNEIY+F/aFzCKTg=
-go.uber.org/fx v1.23.0/go.mod h1:o/D9n+2mLP6v1EG+qsdT1O8wKopYAsqZasju97SDFCU=
+go.uber.org/fx v1.22.2 h1:iPW+OPxv0G8w75OemJ1RAnTUrF55zOJlXlo1TbJ0Buw=
+go.uber.org/fx v1.22.2/go.mod h1:o/D9n+2mLP6v1EG+qsdT1O8wKopYAsqZasju97SDFCU=
 go.uber.org/goleak v1.1.10/go.mod h1:8a7PlsEVH3e/a/GLqe5IIrQx6GzcnRmZEufDUTk4A7A=
 go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
 go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
@@ -560,7 +552,6 @@ golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.14.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
 golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

otlp/cli.go

@@ -3,52 +3,41 @@ package otlp
 import (
 	"fmt"
 	"strings"
-	"sync"
 
 	flag "github.com/spf13/pflag"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/sdk/resource"
 	"go.uber.org/fx"
 )
 
-var (
-	onceInitOTLPFlags sync.Once
-	OnceLoadResources sync.Once
-)
-
 const (
 	OtelResourceAttributesFlag = "otel-resource-attributes"
 	OtelServiceNameFlag        = "otel-service-name"
 )
 
 func AddFlags(flags *flag.FlagSet) {
-	onceInitOTLPFlags.Do(func() {
+	if flags.Lookup(OtelServiceNameFlag) == nil {
 		flags.String(OtelServiceNameFlag, "", "OpenTelemetry service name")
 		flags.StringSlice(OtelResourceAttributesFlag, []string{}, "Additional OTLP resource attributes")
-	})
+	}
 }
 
 func LoadResource(serviceName string, resourceAttributes []string) fx.Option {
-	options := make([]fx.Option, 0)
-	OnceLoadResources.Do(func() {
-		options = append(options,
-			fx.Provide(func() (*resource.Resource, error) {
-				defaultResource := resource.Default()
-				attributes := make([]attribute.KeyValue, 0)
-				if serviceName != "" {
-					attributes = append(attributes, attribute.String("service.name", serviceName))
+	return fx.Options(
+		fx.Provide(func() (*resource.Resource, error) {
+			defaultResource := resource.Default()
+			attributes := make([]attribute.KeyValue, 0)
+			if serviceName != "" {
+				attributes = append(attributes, attribute.String("service.name", serviceName))
+			}
+			for _, ra := range resourceAttributes {
+				parts := strings.SplitN(ra, "=", 2)
+				if len(parts) < 2 {
+					return nil, fmt.Errorf("malformed otlp attribute: %s", ra)
 				}
-				for _, ra := range resourceAttributes {
-					parts := strings.SplitN(ra, "=", 2)
-					if len(parts) < 2 {
-						return nil, fmt.Errorf("malformed otlp attribute: %s", ra)
-					}
-					attributes = append(attributes, attribute.String(parts[0], parts[1]))
-				}
-				return resource.Merge(defaultResource, resource.NewSchemaless(attributes...))
-			}),
-		)
-	})
-
-	return fx.Options(options...)
+				attributes = append(attributes, attribute.String(parts[0], parts[1]))
+			}
+			return resource.Merge(defaultResource, resource.NewSchemaless(attributes...))
+		}),
+	)
 }

otlp/module.go

@@ -0,0 +1,27 @@
+package otlp
+
+import (
+	"github.com/spf13/cobra"
+	"go.uber.org/fx"
+)
+
+type Config struct {
+	ServiceName        string
+	ResourceAttributes []string
+}
+
+func NewFxModule(cfg Config) fx.Option {
+	return fx.Options(
+		LoadResource(cfg.ServiceName, cfg.ResourceAttributes),
+	)
+}
+
+func FXModuleFromFlags(cmd *cobra.Command) fx.Option {
+	otelServiceName, _ := cmd.Flags().GetString(OtelServiceNameFlag)
+	otelResourceAttributes, _ := cmd.Flags().GetStringSlice(OtelResourceAttributesFlag)
+
+	return NewFxModule(Config{
+		ServiceName:        otelServiceName,
+		ResourceAttributes: otelResourceAttributes,
+	})
+}

otlp/otlpmetrics/cli.go

@@ -11,11 +11,11 @@ import (
 )
 
 const (
-	OtelMetricsFlag                                   = "otel-metrics"
 	OtelMetricsExporterPushIntervalFlag               = "otel-metrics-exporter-push-interval"
 	OtelMetricsRuntimeFlag                            = "otel-metrics-runtime"
 	OtelMetricsRuntimeMinimumReadMemStatsIntervalFlag = "otel-metrics-runtime-minimum-read-mem-stats-interval"
 	OtelMetricsExporterFlag                           = "otel-metrics-exporter"
+	OtelMetricsKeepInMemoryFlag                       = "otel-metrics-keep-in-memory"
 	OtelMetricsExporterOTLPModeFlag                   = "otel-metrics-exporter-otlp-mode"
 	OtelMetricsExporterOTLPEndpointFlag               = "otel-metrics-exporter-otlp-endpoint"
 	OtelMetricsExporterOTLPInsecureFlag               = "otel-metrics-exporter-otlp-insecure"
@@ -24,44 +24,38 @@ const (
 func AddFlags(flags *flag.FlagSet) {
 	otlp.AddFlags(flags)
 
-	flags.Bool(OtelMetricsFlag, false, "Enable OpenTelemetry traces support")
 	flags.Duration(OtelMetricsExporterPushIntervalFlag, 10*time.Second, "OpenTelemetry metrics exporter push interval")
 	flags.Bool(OtelMetricsRuntimeFlag, false, "Enable OpenTelemetry runtime metrics")
 	flags.Duration(OtelMetricsRuntimeMinimumReadMemStatsIntervalFlag, 15*time.Second, "OpenTelemetry runtime metrics minimum read mem stats interval")
-	flags.String(OtelMetricsExporterFlag, "stdout", "OpenTelemetry metrics exporter")
-	flags.String(OtelMetricsExporterOTLPModeFlag, "grpc", "OpenTelemetry traces OTLP exporter mode (grpc|http)")
-	flags.String(OtelMetricsExporterOTLPEndpointFlag, "", "OpenTelemetry traces grpc endpoint")
-	flags.Bool(OtelMetricsExporterOTLPInsecureFlag, false, "OpenTelemetry traces grpc insecure")
+	flags.String(OtelMetricsExporterFlag, "", "OpenTelemetry metrics exporter")
+	flags.String(OtelMetricsExporterOTLPModeFlag, "grpc", "OpenTelemetry metrics OTLP exporter mode (grpc|http)")
+	flags.String(OtelMetricsExporterOTLPEndpointFlag, "", "OpenTelemetry metrics grpc endpoint")
+	flags.Bool(OtelMetricsExporterOTLPInsecureFlag, false, "OpenTelemetry metrics grpc insecure")
+
+	// notes(gfyrag): apps are in charge of exposing in memory metrics using whatever protocol it wants to
+	flags.Bool(OtelMetricsKeepInMemoryFlag, false, "Allow to keep metrics in memory")
 }
 
 func FXModuleFromFlags(cmd *cobra.Command) fx.Option {
-	otelMetrics, _ := cmd.Flags().GetBool(OtelMetricsFlag)
-
-	if otelMetrics {
-		otelServiceName, _ := cmd.Flags().GetString(otlp.OtelServiceNameFlag)
-		otelMetricsExporterOTLPEndpoint, _ := cmd.Flags().GetString(OtelMetricsExporterOTLPEndpointFlag)
-		otelMetricsExporterOTLPMode, _ := cmd.Flags().GetString(OtelMetricsExporterOTLPModeFlag)
-		otelMetricsExporterOTLPInsecure, _ := cmd.Flags().GetBool(OtelMetricsExporterOTLPInsecureFlag)
-		otelMetricsExporter, _ := cmd.Flags().GetString(OtelMetricsExporterFlag)
-		otelMetricsRuntime, _ := cmd.Flags().GetBool(OtelMetricsRuntimeFlag)
-		otelMetricsRuntimeMinimumReadMemStatsInterval, _ := cmd.Flags().GetDuration(OtelMetricsRuntimeMinimumReadMemStatsIntervalFlag)
-		otelMetricsExporterPushInterval, _ := cmd.Flags().GetDuration(OtelMetricsExporterPushIntervalFlag)
-		otelResourceAttributes, _ := cmd.Flags().GetStringSlice(otlp.OtelResourceAttributesFlag)
-
-		return MetricsModule(ModuleConfig{
-			ServiceName:    otelServiceName,
-			ServiceVersion: "develop",
-			OTLPConfig: &OTLPConfig{
-				Mode:     otelMetricsExporterOTLPMode,
-				Endpoint: otelMetricsExporterOTLPEndpoint,
-				Insecure: otelMetricsExporterOTLPInsecure,
-			},
-			Exporter:                    otelMetricsExporter,
-			RuntimeMetrics:              otelMetricsRuntime,
-			MinimumReadMemStatsInterval: otelMetricsRuntimeMinimumReadMemStatsInterval,
-			PushInterval:                otelMetricsExporterPushInterval,
-			ResourceAttributes:          otelResourceAttributes,
-		})
-	}
-	return fx.Options()
+	otelMetricsExporterOTLPEndpoint, _ := cmd.Flags().GetString(OtelMetricsExporterOTLPEndpointFlag)
+	otelMetricsExporterOTLPMode, _ := cmd.Flags().GetString(OtelMetricsExporterOTLPModeFlag)
+	otelMetricsExporterOTLPInsecure, _ := cmd.Flags().GetBool(OtelMetricsExporterOTLPInsecureFlag)
+	otelMetricsExporter, _ := cmd.Flags().GetString(OtelMetricsExporterFlag)
+	otelMetricsRuntime, _ := cmd.Flags().GetBool(OtelMetricsRuntimeFlag)
+	otelMetricsRuntimeMinimumReadMemStatsInterval, _ := cmd.Flags().GetDuration(OtelMetricsRuntimeMinimumReadMemStatsIntervalFlag)
+	otelMetricsExporterPushInterval, _ := cmd.Flags().GetDuration(OtelMetricsExporterPushIntervalFlag)
+	otelMetricsKeepInMemory, _ := cmd.Flags().GetBool(OtelMetricsKeepInMemoryFlag)
+
+	return MetricsModule(ModuleConfig{
+		OTLPConfig: &OTLPConfig{
+			Mode:     otelMetricsExporterOTLPMode,
+			Endpoint: otelMetricsExporterOTLPEndpoint,
+			Insecure: otelMetricsExporterOTLPInsecure,
+		},
+		Exporter:                    otelMetricsExporter,
+		RuntimeMetrics:              otelMetricsRuntime,
+		MinimumReadMemStatsInterval: otelMetricsRuntimeMinimumReadMemStatsInterval,
+		PushInterval:                otelMetricsExporterPushInterval,
+		KeepInMemory:                otelMetricsKeepInMemory,
+	})
 }

otlp/otlpmetrics/exporter_inmemory.go

@@ -0,0 +1,81 @@
+package otlpmetrics
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+
+	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+)
+
+type InMemoryExporter struct {
+	exp     sdkmetric.Exporter
+	metrics *metricdata.ResourceMetrics
+}
+
+func (e *InMemoryExporter) Temporality(kind sdkmetric.InstrumentKind) metricdata.Temporality {
+	if e.exp != nil {
+		return e.exp.Temporality(kind)
+	}
+
+	return sdkmetric.DefaultTemporalitySelector(kind)
+}
+
+func (e *InMemoryExporter) Aggregation(kind sdkmetric.InstrumentKind) sdkmetric.Aggregation {
+	if e.exp != nil {
+		return e.exp.Aggregation(kind)
+	}
+
+	return sdkmetric.DefaultAggregationSelector(kind)
+}
+
+func (e *InMemoryExporter) ForceFlush(ctx context.Context) error {
+	if e.exp != nil {
+		return e.exp.ForceFlush(ctx)
+	}
+
+	return nil
+}
+
+func (e *InMemoryExporter) Shutdown(ctx context.Context) error {
+	if e.exp != nil {
+		return e.exp.Shutdown(ctx)
+	}
+
+	return nil
+}
+
+func (e *InMemoryExporter) Export(ctx context.Context, data *metricdata.ResourceMetrics) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
+	// notes(gfyrag): copy as indicate by interface sdkmetric.Exporter
+	// I don't know if that's enough...
+	e.metrics = &(*data)
+
+	return e.exp.Export(ctx, data)
+}
+
+func (e *InMemoryExporter) GetMetrics() *metricdata.ResourceMetrics {
+	return e.metrics
+}
+
+func NewInMemoryExporterDecorator(exp sdkmetric.Exporter) *InMemoryExporter {
+	return &InMemoryExporter{
+		exp: exp,
+	}
+}
+
+var _ sdkmetric.Exporter = (*InMemoryExporter)(nil)
+
+func NewInMemoryExporterHandler(meterProvider *sdkmetric.MeterProvider, e *InMemoryExporter) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if err := meterProvider.ForceFlush(r.Context()); err != nil {
+			panic(err)
+		}
+
+		_ = json.NewEncoder(w).Encode(e.GetMetrics())
+	}
+}

otlp/otlpmetrics/exporter_noop.go

@@ -0,0 +1,36 @@
+package otlpmetrics
+
+import (
+	"context"
+
+	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+)
+
+type NoOpExporter struct{}
+
+func (e *NoOpExporter) Temporality(kind sdkmetric.InstrumentKind) metricdata.Temporality {
+	return sdkmetric.DefaultTemporalitySelector(kind)
+}
+
+func (e *NoOpExporter) Aggregation(kind sdkmetric.InstrumentKind) sdkmetric.Aggregation {
+	return sdkmetric.DefaultAggregationSelector(kind)
+}
+
+func (e *NoOpExporter) ForceFlush(ctx context.Context) error {
+	return nil
+}
+
+func (e *NoOpExporter) Shutdown(ctx context.Context) error {
+	return nil
+}
+
+func (e *NoOpExporter) Export(ctx context.Context, data *metricdata.ResourceMetrics) error {
+	return nil
+}
+
+func NewNoOpExporter() *NoOpExporter {
+	return &NoOpExporter{}
+}
+
+var _ sdkmetric.Exporter = (*NoOpExporter)(nil)