refactor: improve OTLP endpoint configuration handling

Change InitTracer to accept endpoint as parameter instead of reading
from environment variable. This improves testability and follows
separation of concerns.

Changes:
- InitTracer now takes endpoint as parameter: InitTracer(ctx, endpoint)
- Remove confusing env var manipulation in cmd/build.go
- Simplify test (no need to manipulate environment)
- Make configuration flow clearer: flag → function parameter

Benefits:
- Easier to test (no env var side effects)
- Clearer API (explicit parameter vs implicit env var)
- Consistent with other reporters (e.g., SegmentReporter)
- No circular dependency between flag default and env var

Co-authored-by: Ona <no-reply@ona.com>

Author: corneliusludmann

cmd/build.go

@@ -325,13 +325,8 @@ func getBuildOpts(cmd *cobra.Command) ([]leeway.BuildOption, cache.LocalCache, f
 	if otelEndpoint, err := cmd.Flags().GetString("otel-endpoint"); err != nil {
 		log.Fatal(err)
 	} else if otelEndpoint != "" {
-		// Set environment variable for InitTracer if not already set
-		if os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT") == "" {
-			os.Setenv("OTEL_EXPORTER_OTLP_ENDPOINT", otelEndpoint)
-		}
-
-		// Initialize tracer
-		tp, err := telemetry.InitTracer(context.Background())
+		// Initialize tracer with the provided endpoint
+		tp, err := telemetry.InitTracer(context.Background(), otelEndpoint)
 		if err != nil {
 			log.WithError(err).Warn("failed to initialize OpenTelemetry tracer")
 		} else {

pkg/leeway/telemetry/tracer.go

@@ -17,12 +17,11 @@ import (
 )
 
 // InitTracer initializes the OpenTelemetry tracer with OTLP HTTP exporter.
-// It reads the OTEL_EXPORTER_OTLP_ENDPOINT environment variable for the endpoint.
+// The endpoint parameter specifies the OTLP endpoint URL (e.g., "localhost:4318").
 // Returns the TracerProvider which must be shut down when done.
-func InitTracer(ctx context.Context) (*sdktrace.TracerProvider, error) {
-	endpoint := os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT")
+func InitTracer(ctx context.Context, endpoint string) (*sdktrace.TracerProvider, error) {
 	if endpoint == "" {
-		return nil, xerrors.Errorf("OTEL_EXPORTER_OTLP_ENDPOINT not set")
+		return nil, xerrors.Errorf("OTLP endpoint not provided")
 	}
 
 	// Create OTLP HTTP exporter

pkg/leeway/telemetry/tracer_test.go

@@ -2,7 +2,6 @@ package telemetry
 
 import (
 	"context"
-	"os"
 	"testing"
 
 	"go.opentelemetry.io/otel/trace"
@@ -168,17 +167,9 @@ func TestFormatTraceContext_Invalid(t *testing.T) {
 }
 
 func TestInitTracer_NoEndpoint(t *testing.T) {
-	// Save and restore environment
-	oldEndpoint := os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT")
-	defer func() {
-		_ = os.Setenv("OTEL_EXPORTER_OTLP_ENDPOINT", oldEndpoint)
-	}()
-
-	_ = os.Unsetenv("OTEL_EXPORTER_OTLP_ENDPOINT")
-
-	_, err := InitTracer(context.Background())
+	_, err := InitTracer(context.Background(), "")
 	if err == nil {
-		t.Error("InitTracer() should fail when OTEL_EXPORTER_OTLP_ENDPOINT is not set")
+		t.Error("InitTracer() should fail when endpoint is empty")
 	}
 }