🔧 feat: add OpenTelemetry instrumentation to persistence layer

- Added persistence telemetry configuration option (telemetry.persistence.enabled)
- Created PersistenceTelemetryConfig struct for fine-grained control
- Added GetPersistenceTelemetryEnabled() helper method
- Implemented telemetry span creation in SQLite repository
- Added OpenTelemetry instrumentation to key repository methods:
  - CreateUser: Tracks user creation with error recording
  - GetUserByUsername: Tracks queries with username attribute
- Maintained backward compatibility - telemetry is optional and disabled by default
- Updated all tests to pass config parameter to repository constructor
- Added proper error recording and span attributes for observability

Benefits:
- Performance monitoring of database operations
- Flamegraph generation capability for persistence layer
- Distributed tracing across service boundaries
- Configurable instrumentation for production vs development

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

cmd/server/main.go

@@ -12,14 +12,14 @@
 //	@license.name	MIT
 //	@license.url	https://opensource.org/licenses/MIT
 
-//	@host		localhost:8080
-//	@BasePath	/api
-//	@schemes	http https
+//	@host						localhost:8080
+//	@BasePath					/api
+//	@schemes					http https
 //
 //	@securityDefinitions.apikey	ApiKeyAuth
-//	@in				header
-//	@name			Authorization
-//	@description	JWT authentication using Bearer token. Format: Bearer <token>
+//	@in							header
+//	@name						Authorization
+//	@description				JWT authentication using Bearer token. Format: Bearer <token>
 
 package main
 

pkg/config/config.go

@@ -43,11 +43,17 @@ type LoggingConfig struct {
 
 // TelemetryConfig holds OpenTelemetry-related configuration
 type TelemetryConfig struct {
-	Enabled      bool          `mapstructure:"enabled"`
-	OTLPEndpoint string        `mapstructure:"otlp_endpoint"`
-	ServiceName  string        `mapstructure:"service_name"`
-	Insecure     bool          `mapstructure:"insecure"`
-	Sampler      SamplerConfig `mapstructure:"sampler"`
+	Enabled      bool                       `mapstructure:"enabled"`
+	OTLPEndpoint string                     `mapstructure:"otlp_endpoint"`
+	ServiceName  string                     `mapstructure:"service_name"`
+	Insecure     bool                       `mapstructure:"insecure"`
+	Sampler      SamplerConfig              `mapstructure:"sampler"`
+	Persistence  PersistenceTelemetryConfig `mapstructure:"persistence"`
+}
+
+// PersistenceTelemetryConfig holds persistence layer telemetry configuration
+type PersistenceTelemetryConfig struct {
+	Enabled bool `mapstructure:"enabled"`
 }
 
 // APIConfig holds API version configuration
@@ -107,6 +113,7 @@ func LoadConfig() (*Config, error) {
 	v.SetDefault("telemetry.insecure", true)
 	v.SetDefault("telemetry.sampler.type", "parentbased_always_on")
 	v.SetDefault("telemetry.sampler.ratio", 1.0)
+	v.SetDefault("telemetry.persistence.enabled", false)
 
 	// API defaults
 	v.SetDefault("api.v2_enabled", false)
@@ -215,6 +222,11 @@ func (c *Config) GetServiceName() string {
 	return c.Telemetry.ServiceName
 }
 
+// GetPersistenceTelemetryEnabled returns whether persistence layer telemetry is enabled
+func (c *Config) GetPersistenceTelemetryEnabled() bool {
+	return c.Telemetry.Enabled && c.Telemetry.Persistence.Enabled
+}
+
 // GetTelemetryInsecure returns whether to use insecure connection
 func (c *Config) GetTelemetryInsecure() bool {
 	return c.Telemetry.Insecure

pkg/server/server.go

@@ -77,7 +77,7 @@ func initializeUserServices(cfg *config.Config) (user.UserRepository, user.UserS
 	dbPath := "file::memory:?cache=shared"
 
 	// Create user repository
-	repo, err := user.NewSQLiteRepository(dbPath)
+	repo, err := user.NewSQLiteRepository(dbPath, cfg)
 	if err != nil {
 		return nil, nil, fmt.Errorf("failed to create user repository: %w", err)
 	}

pkg/user/sqlite_repository.go

@@ -9,6 +9,10 @@ import (
 	"path/filepath"
 	"time"
 
+	"dance-lessons-coach/pkg/config"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
 	"gorm.io/driver/sqlite"
 	"gorm.io/gorm"
 	"gorm.io/gorm/logger"
@@ -16,14 +20,18 @@ import (
 
 // SQLiteRepository implements UserRepository using SQLite
 type SQLiteRepository struct {
-	db     *gorm.DB
-	dbPath string
+	db         *gorm.DB
+	dbPath     string
+	config     *config.Config
+	spanPrefix string
 }
 
 // NewSQLiteRepository creates a new SQLite repository
-func NewSQLiteRepository(dbPath string) (*SQLiteRepository, error) {
+func NewSQLiteRepository(dbPath string, config *config.Config) (*SQLiteRepository, error) {
 	repo := &SQLiteRepository{
-		dbPath: dbPath,
+		dbPath:     dbPath,
+		config:     config,
+		spanPrefix: "user.repo.",
 	}
 
 	if err := repo.initializeDatabase(); err != nil {
@@ -70,8 +78,17 @@ func (r *SQLiteRepository) initializeDatabase() error {
 
 // CreateUser creates a new user in the database
 func (r *SQLiteRepository) CreateUser(ctx context.Context, user *User) error {
+	// Create telemetry span
+	ctx, span := r.createSpan(ctx, "create_user")
+	if span != nil {
+		defer span.End()
+	}
+
 	result := r.db.WithContext(ctx).Create(user)
 	if result.Error != nil {
+		if span != nil {
+			span.RecordError(result.Error)
+		}
 		return fmt.Errorf("failed to create user: %w", result.Error)
 	}
 	return nil
@@ -79,12 +96,22 @@ func (r *SQLiteRepository) CreateUser(ctx context.Context, user *User) error {
 
 // GetUserByUsername retrieves a user by username
 func (r *SQLiteRepository) GetUserByUsername(ctx context.Context, username string) (*User, error) {
+	// Create telemetry span
+	ctx, span := r.createSpan(ctx, "get_user_by_username")
+	if span != nil {
+		defer span.End()
+		span.SetAttributes(attribute.String("username", username))
+	}
+
 	var user User
 	result := r.db.WithContext(ctx).Where("username = ?", username).First(&user)
 	if result.Error != nil {
 		if errors.Is(result.Error, gorm.ErrRecordNotFound) {
 			return nil, nil
 		}
+		if span != nil {
+			span.RecordError(result.Error)
+		}
 		return nil, fmt.Errorf("failed to get user by username: %w", result.Error)
 	}
 	return &user, nil
@@ -172,3 +199,15 @@ func (r *SQLiteRepository) Close() error {
 	}
 	return sqlDB.Close()
 }
+
+// createSpan creates a new telemetry span if persistence telemetry is enabled
+func (r *SQLiteRepository) createSpan(ctx context.Context, operation string) (context.Context, trace.Span) {
+	if r.config == nil || !r.config.GetPersistenceTelemetryEnabled() {
+		return ctx, trace.SpanFromContext(ctx)
+	}
+
+	// Create a new span with the operation name
+	spanName := r.spanPrefix + operation
+	tr := otel.Tracer("user-repository")
+	return tr.Start(ctx, spanName)
+}

pkg/user/user_test.go

@@ -6,17 +6,31 @@ import (
 	"testing"
 	"time"
 
+	"dance-lessons-coach/pkg/config"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+// createTestConfig creates a test configuration with telemetry disabled
+func createTestConfig() *config.Config {
+	return &config.Config{
+		Telemetry: config.TelemetryConfig{
+			Enabled: false,
+			Persistence: config.PersistenceTelemetryConfig{
+				Enabled: false,
+			},
+		},
+	}
+}
+
 func TestSQLiteRepository(t *testing.T) {
 	t.Run("CRUD operations", func(t *testing.T) {
 		// Create a temporary database
 		dbPath := "test_db.sqlite"
 		defer os.Remove(dbPath)
 
-		repo, err := NewSQLiteRepository(dbPath)
+		cfg := createTestConfig()
+		repo, err := NewSQLiteRepository(dbPath, cfg)
 		require.NoError(t, err)
 		defer repo.Close()
 
@@ -92,7 +106,8 @@ func TestAuthService(t *testing.T) {
 		dbPath := "test_auth_db.sqlite"
 		defer os.Remove(dbPath)
 
-		repo, err := NewSQLiteRepository(dbPath)
+		cfg := createTestConfig()
+		repo, err := NewSQLiteRepository(dbPath, cfg)
 		require.NoError(t, err)
 		defer repo.Close()
 
@@ -162,7 +177,8 @@ func TestPasswordResetService(t *testing.T) {
 		dbPath := "test_reset_db.sqlite"
 		defer os.Remove(dbPath)
 
-		repo, err := NewSQLiteRepository(dbPath)
+		cfg := createTestConfig()
+		repo, err := NewSQLiteRepository(dbPath, cfg)
 		require.NoError(t, err)
 		defer repo.Close()