feat(otel): address first review

otel/README.md

@@ -5,57 +5,29 @@
 package main
 
 import (
-	"context"
-	"errors"
-	"fmt"
-	"log"
-	"time"
+  "context"
 
-	"github.com/Scalingo/go-utils/otel"
+  "github.com/Scalingo/go-utils/otel"
+  "github.com/kelseyhightower/envconfig"
 )
 
 func main() {
-	ctx := context.Background()
-	// Set up OpenTelemetry SDK
-	// Method 1: Using the env
-	otelShutdown, err := otel.InitFromEnv(ctx)
-	if err != nil {
-		return
-	}
-	// Method 2: configuring it ourselves
-	// otelConfig := otel.ConfigFromEnv()
-	// otelConfig.Exporter = ...
-	// otelShutdown, err := otel.InitGlobalWrapper(ctx, otelConfig)
-
-	// Handle shutdown properly so nothing leaks.
-	defer func() {
-		err = errors.Join(err, otelShutdown(context.Background()))
-	}()
-
-	// 4. Get Global Meter and Send Metrics
-	if err := globalWrapperSendMetrics(ctx); err != nil {
-		log.Fatalf("failed to send metrics: %v", err)
-	}
-
-	fmt.Println("Metrics successfully sent!")
-}
-
-// globalWrapperSendMetrics sends an example metric
-func globalWrapperSendMetrics(ctx context.Context) error {
-	// Example of sending a counter metric
-	err := otel.SendMetric(ctx, "example.counter", 1.0, "An example counter metric")
-	if err != nil {
-		return err
-	}
-
-	// Simulating some load
-	time.Sleep(2 * time.Second)
-
-	err = otel.SendMetric(ctx, "example.counter", 2.5, "Another counter increment")
-	if err != nil {
-		return err
-	}
-
-	return nil
+  ctx := context.Background()
+
+  // Get Otel configuration from environment
+  var otelConfig otel.Config
+  err := envconfig.Process("OTEL", &otelConfig)
+  if err != nil {
+    return
+  }
+
+  // Initialize Otel
+  err := otel.New(ctx, otelConfig)
+  if err != nil {
+    return
+  }
+
+  // Handle shutdown properly so nothing leaks.
+  defer otel.Shutdown(ctx)
 }
 ```

otel/go.mod

@@ -3,12 +3,11 @@ module github.com/Scalingo/go-utils/otel
 go 1.23.4
 
 require (
-	github.com/Scalingo/go-utils/env v1.1.1
+	github.com/Scalingo/go-utils/errors/v2 v2.4.0
 	go.opentelemetry.io/otel v1.34.0
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc v1.34.0
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp v1.34.0
 	go.opentelemetry.io/otel/exporters/stdout/stdoutmetric v1.34.0
-	go.opentelemetry.io/otel/metric v1.34.0
 	go.opentelemetry.io/otel/sdk v1.34.0
 	go.opentelemetry.io/otel/sdk/metric v1.34.0
 )
@@ -19,7 +18,9 @@ require (
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.25.1 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
+	go.opentelemetry.io/otel/metric v1.34.0 // indirect
 	go.opentelemetry.io/otel/trace v1.34.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.5.0 // indirect
 	golang.org/x/net v0.34.0 // indirect
@@ -29,4 +30,5 @@ require (
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20250115164207-1a7da9e5054f // indirect
 	google.golang.org/grpc v1.69.4 // indirect
 	google.golang.org/protobuf v1.36.3 // indirect
+	gopkg.in/errgo.v1 v1.0.1 // indirect
 )

otel/go.sum

@@ -1,24 +1,38 @@
-github.com/Scalingo/go-utils/env v1.1.1 h1:N0lqjTLVTPyyTr0W2PcJUrd7EBXcBnlAweTB38vrWHY=
-github.com/Scalingo/go-utils/env v1.1.1/go.mod h1:/vSTf+LpZnO2u3IscTY5xE/yxjf+6Rv5OI8SdVQ8VLM=
+github.com/Scalingo/go-utils/errors/v2 v2.4.0 h1:vKG0Js3kzWG7+03LEvH7j8fw+picEcRhbjMm3i9Xbb8=
+github.com/Scalingo/go-utils/errors/v2 v2.4.0/go.mod h1:WU6Kzi19AlZyUfoxFkdvEeYkIa0W0f172hKPqkOeIpU=
 github.com/cenkalti/backoff/v4 v4.3.0 h1:MyRJ/UdXutAwSAT+s3wNd7MfTIcy71VQueUuFK343L8=
 github.com/cenkalti/backoff/v4 v4.3.0/go.mod h1:Y3VNntkOUPxTVeUxJ/G5vcM//AlwfmyYozVcomhLiZE=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/frankban/quicktest v1.2.2 h1:xfmOhhoH5fGPgbEAlhLpJH9p0z/0Qizio9osmvn9IUY=
+github.com/frankban/quicktest v1.2.2/go.mod h1:Qh/WofXFeiAFII1aEBu529AtJo6Zg2VHscnEsbBnJ20=
 github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
 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=
 github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
 github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=
 github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
+github.com/google/go-cmp v0.2.1-0.20190312032427-6f77996f0c42/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/grpc-ecosystem/grpc-gateway/v2 v2.25.1 h1:VNqngBF40hVlDloBruUehVYC3ArSgIyScOAyMRqBxRg=
 github.com/grpc-ecosystem/grpc-gateway/v2 v2.25.1/go.mod h1:RBRO7fro65R6tjKzYgLAFo0t1QEXY1Dp+i/bvpRiqiQ=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rogpeppe/go-internal v1.13.1 h1:KvO1DLK/DRN07sQ1LQKScxyZJuNnedQ5/wKSR38lUII=
+github.com/rogpeppe/go-internal v1.13.1/go.mod h1:uMEvuHeurkdAXX61udpOXGD/AzZDWNMNyH2VO9fmH0o=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 go.opentelemetry.io/auto/sdk v1.1.0 h1:cH53jehLUN6UFLY71z+NDOiNJqDdPRaXzTel0sJySYA=
@@ -55,5 +69,7 @@ google.golang.org/grpc v1.69.4 h1:MF5TftSMkd8GLw/m0KM6V8CMOCY6NZ1NQDPGFgbTt4A=
 google.golang.org/grpc v1.69.4/go.mod h1:vyjdE6jLBI76dgpDojsFGNaHlxdjXN9ghpnd2o7JGZ4=
 google.golang.org/protobuf v1.36.3 h1:82DV7MYdb8anAVi3qge1wSnMDrnKK7ebr+I0hHRN1BU=
 google.golang.org/protobuf v1.36.3/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
+gopkg.in/errgo.v1 v1.0.1 h1:oQFRXzZ7CkBGdm1XZm/EbQYaYNNEElNBOd09M6cqNso=
+gopkg.in/errgo.v1 v1.0.1/go.mod h1:3NjfXwocQRYAPTq4/fzX+CwUhPRcR/azYRhj8G+LqMo=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

otel/otel.go

@@ -2,118 +2,102 @@ package otel
 
 import (
 	"context"
-	"errors"
-	"fmt"
 	"sync"
 	"time"
 
 	otelsdk "go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp"
 	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
-	"go.opentelemetry.io/otel/metric"
 	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
 	"go.opentelemetry.io/otel/sdk/resource"
 	semconv "go.opentelemetry.io/otel/semconv/v1.26.0"
+
+	"github.com/Scalingo/go-utils/errors/v2"
 )
 
-// Config defines the Otel Wrapper configuration for metrics
 type Config struct {
-	ServiceName               string
-	Debug                     bool
-	ExporterType              string
-	ExporterEndpoint          string
-	ExporterTimeout           string
-	ExporterCertificate       string
-	ExporterClientCertificate string
-	ExporterClientKey         string
-	CollectionInterval        time.Duration
-	MetricsReader             sdkmetric.Reader
-	MetricsExporter           sdkmetric.Exporter
+	ServiceName        string        `required:"true" split_words:"true"`
+	Debug              bool          `default:"false"`
+	ExporterType       string        `default:"http" split_words:"true"`
+	CollectionInterval time.Duration `default:"10s" split_words:"true"`
 }
 
-// OtelWrapper encapsulates OpenTelemetry MetricProvider and utilities
-type OtelWrapper struct {
+// OtelProviders encapsulates OpenTelemetry providers and utilities
+type OtelProviders struct {
 	meterProvider *sdkmetric.MeterProvider
-	globalMeter   metric.Meter
+	shutdownFunc  func(context.Context) error
 	config        Config
 }
 
 var (
-	globalWrapper *OtelWrapper
-
-	// singletonShutdown holds the shutdown function once the meter provider is initialized.
-	singletonShutdown func(context.Context) error
+	globalProvider *OtelProviders
 
 	// once ensures that initialization happens only once.
 	globalOnce sync.Once
-
-	// initErr captures any error encountered during initialization.
-	initErr error
 )
 
-// InitSingleton initializes the MeterProvider as a singleton.
-// Subsequent calls to this function will return the same shutdown function and error.
+// Initializes the OtelWrapper as a singleton.
 // The configuration is used only on the first call.
-func InitGlobalWrapper(ctx context.Context, cfg Config) (func(context.Context) error, error) {
+func New(ctx context.Context, cfg Config) error {
+	var err error
 	globalOnce.Do(func() {
-		singletonShutdown, initErr = New(ctx, cfg)
+		globalProvider, err = setupProviders(ctx, cfg)
 	})
-	return singletonShutdown, initErr
+	return err
 }
 
-func New(ctx context.Context, cfg Config) (shutdown func(context.Context) error, err error) {
+func setupProviders(ctx context.Context, cfg Config) (*OtelProviders, error) {
 	var shutdownFuncs []func(context.Context) error
 
 	// shutdown calls cleanup functions registered via shutdownFuncs.
 	// The errors from the calls are joined.
 	// Each registered cleanup will be invoked once.
-	shutdown = func(ctx context.Context) error {
+	shutdown := func(ctx context.Context) error {
 		var err error
 		for _, fn := range shutdownFuncs {
-			err = errors.Join(err, fn(ctx))
+			shutdownErr := fn(ctx)
+			if shutdownErr != nil {
+				err = errors.Wrapf(ctx, err, "failed to shutdown provider: %v", shutdownErr)
+			}
 		}
 		shutdownFuncs = nil
 		return err
 	}
 
 	// handleErr calls shutdown for cleanup and makes sure that all errors are returned.
-	handleErr := func(inErr error) {
-		err = errors.Join(inErr, shutdown(ctx))
+	handleErr := func(inErr error) error {
+		err := shutdown(ctx)
+		if err != nil {
+			return errors.Wrapf(ctx, inErr, "failed to shutdown otel providers: %v", err)
+		}
+		return inErr
 	}
 
 	// Set up meter provider.
 	meterProvider, err := newMeterProvider(ctx, cfg)
 	if err != nil {
-		handleErr(err)
-		return
+		return nil, handleErr(err)
 	}
 	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
 	otelsdk.SetMeterProvider(meterProvider)
 
-	globalWrapper = &OtelWrapper{
+	return &OtelProviders{
 		meterProvider: meterProvider,
-		globalMeter:   meterProvider.Meter(cfg.ServiceName),
+		shutdownFunc:  shutdown,
 		config:        cfg,
-	}
-
-	return
+	}, nil
 }
 
 func newMeterProvider(ctx context.Context, cfg Config) (*sdkmetric.MeterProvider, error) {
 	if cfg.ServiceName == "" {
-		return nil, errors.New("ServiceName is required")
-	}
-	if cfg.MetricsExporter == nil {
-		exporter, err := newMetricsExporter(ctx, cfg)
-		if err != nil {
-			return nil, fmt.Errorf("failed to load exporter", err)
-		}
-		cfg.MetricsExporter = exporter
+		return nil, errors.New(ctx, "ServiceName is required")
 	}
-	if cfg.MetricsReader == nil {
-		cfg.MetricsReader = sdkmetric.NewPeriodicReader(cfg.MetricsExporter, sdkmetric.WithInterval(cfg.CollectionInterval))
+	metricsExporter, err := newMetricsExporter(ctx, cfg)
+	if err != nil {
+		return nil, errors.Wrap(ctx, err, "failed to load exporter")
 	}
+	metricsReader := sdkmetric.NewPeriodicReader(metricsExporter, sdkmetric.WithInterval(cfg.CollectionInterval))
 
 	res, err := resource.Merge(
 		resource.Default(),
@@ -123,12 +107,12 @@ func newMeterProvider(ctx context.Context, cfg Config) (*sdkmetric.MeterProvider
 		),
 	)
 	if err != nil {
-		return nil, fmt.Errorf("failed to create resource: %w", err)
+		return nil, errors.Wrap(ctx, err, "failed to create resource")
 	}
 
 	// Initialize MeterProvider
 	provider := sdkmetric.NewMeterProvider(
-		sdkmetric.WithReader(cfg.MetricsReader),
+		sdkmetric.WithReader(metricsReader),
 		sdkmetric.WithResource(res),
 	)
 
@@ -145,27 +129,14 @@ func newMetricsExporter(ctx context.Context, cfg Config) (sdkmetric.Exporter, er
 	case "grpc":
 		return otlpmetricgrpc.New(ctx)
 	default:
-		return nil, errors.New("invalid exporter type")
-	}
-}
-
-// GetGlobalMeter returns the global Meter
-func GetGlobalMeter() metric.Meter {
-	if globalWrapper == nil {
-		panic("Global OtelWrapper is not initialized")
+		return nil, errors.New(ctx, "invalid exporter type")
 	}
-	return globalWrapper.globalMeter
 }
 
-// SendMetric wraps the meter to send a metric
-func SendMetric(ctx context.Context, name string, value float64, description string) error {
-	counter, err := GetGlobalMeter().Float64Counter(
-		name,
-		metric.WithDescription(description),
-	)
-	if err != nil {
-		return fmt.Errorf("failed to create counter: %w", err)
+// Gracefully shuts down the providers
+func Shutdown(ctx context.Context) error {
+	if err := globalProvider.shutdownFunc(ctx); err != nil {
+		return errors.Wrap(ctx, err, "failed to shutdown otel providers")
 	}
-	counter.Add(ctx, value)
 	return nil
 }