feat(logging): add slog-based structured logging

Introduce slog-based structured logging throughout the booking service
and
server handlers. Add configurable log level via LOG_LEVEL environment
variable. Replace legacy log usage with slog and propagate logger to
booking service for improved observability.

.golangci.yml

@@ -0,0 +1,10 @@
+version: "2"
+linters:
+  default: none
+  enable:
+    - sloglint
+  settings:
+    sloglint:
+      # Enforce using attributes only.
+      # This will raise an error for any key-value pair arguments.
+      attr-only: true

internal/config/config.go

@@ -17,6 +17,8 @@ type Config struct {
 	DatabaseUrl string `env:"DATABASE_URL, required"`
 	// Debug enables debug mode when true
 	Debug bool `env:"DEBUG, default=false"`
+	// LogLevel is the logging level (e.g., debug, info, warn, error)
+	LogLevel string `env:"LOG_LEVEL, default=info"`
 	// Origins is the list of allowed origins
 	Origins []string `env:"ORIGINS, required"`
 	// Port is the HTTP server port number

internal/cron/job_report.go

@@ -29,7 +29,7 @@ func JobMonthlyBookingReport() error {
 	}
 
 	store := booking.NewPgStore(db)
-	service, err := bookingService.NewService(store, nil, ps)
+	service, err := bookingService.NewService(nil, store, nil, ps)
 	if err != nil {
 		return fmt.Errorf("error creating booking service: %w", err)
 	}

internal/driver/logger/log.go

@@ -0,0 +1,30 @@
+package logger
+
+import (
+	"log/slog"
+	"os"
+	"strings"
+)
+
+var logLevel slog.LevelVar
+
+func getLevel(levelStr string) slog.Level {
+	switch strings.ToLower(levelStr) {
+	case "debug":
+		return slog.LevelDebug
+	case "warn":
+		return slog.LevelWarn
+	case "error":
+		return slog.LevelError
+	default:
+		return slog.LevelInfo
+	}
+}
+
+func New(levelStr string) *slog.Logger {
+	logLevel.Set(getLevel(levelStr))
+
+	return slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
+		Level: &logLevel,
+	}))
+}

internal/server/handle_bookings.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"log/slog"
 	"net/http"
 	"strconv"
 	"time"
@@ -31,6 +32,8 @@ func handleBookingListPage(bs *booking.Service, hc *config.Host) echo.HandlerFun
 			bookings = bs.All()
 		}
 
+		slog.Info("serving bookings", slog.Int("bookings_length", len(bookings)))
+
 		bvm := u.Map(bookings, func(b *booking.Line) *view.ListBookingsViewModel {
 			return &view.ListBookingsViewModel{
 				Id:       b.InvoiceNumber(hc),

internal/service/booking/service.go

@@ -1,7 +1,7 @@
 package booking
 
 import (
-	"log"
+	"log/slog"
 	"time"
 
 	"github.com/rjNemo/rentease/internal/config"
@@ -46,10 +46,12 @@ type Service struct {
 	store  Store
 	parser parserClient
 	pdf    PdfClient
+	logger *slog.Logger
 }
 
-func NewService(store Store, parser parserClient, pdf PdfClient) (*Service, error) {
+func NewService(logger *slog.Logger, store Store, parser parserClient, pdf PdfClient) (*Service, error) {
 	return &Service{
+		logger: logger.With(slog.String("component", "booking_service")),
 		store:  store,
 		parser: parser,
 		pdf:    pdf,
@@ -57,6 +59,7 @@ func NewService(store Store, parser parserClient, pdf PdfClient) (*Service, erro
 }
 
 func (bs Service) All() []*Line {
+	bs.logger.Info("fetching all bookings")
 	return bs.store.All()
 }
 
@@ -71,7 +74,7 @@ func (bs Service) Create(From time.Time, To time.Time, Name, PhoneNumber, Email,
 	b := NewBooking(From, To, Name, PhoneNumber, Email, Platform, CustomerNumber, PlatformFees, externalId)
 	err := bs.store.Create(b)
 	if err != nil {
-		log.Println(err)
+		bs.logger.Info("failed to create booking", slog.Any("err", err))
 	}
 	return b
 }
@@ -86,7 +89,7 @@ func (bs Service) Update(id int, From time.Time, To time.Time, Name string, Phon
 ) *Booking {
 	b := NewBooking(From, To, Name, PhoneNumber, Email, Platform, CustomerNumber, PlatformFees, externalId).WithId(id)
 	if err := bs.store.Update(b); err != nil {
-		log.Println(err)
+		bs.logger.Info("failed to create booking", slog.Any("err", err))
 	}
 	return b
 }
@@ -94,7 +97,7 @@ func (bs Service) Update(id int, From time.Time, To time.Time, Name string, Phon
 func (bs Service) Cancel(id int) {
 	err := bs.store.Cancel(id)
 	if err != nil {
-		log.Println(err)
+		bs.logger.Info("failed to create booking", slog.Any("err", err))
 	}
 }
 

main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/signal"
 
@@ -11,6 +12,7 @@ import (
 	"github.com/rjNemo/rentease/assets"
 	"github.com/rjNemo/rentease/internal/config"
 	"github.com/rjNemo/rentease/internal/driver/database"
+	"github.com/rjNemo/rentease/internal/driver/logger"
 	"github.com/rjNemo/rentease/internal/driver/parser"
 	"github.com/rjNemo/rentease/internal/driver/pdf"
 	bookingRepo "github.com/rjNemo/rentease/internal/repository/booking"
@@ -37,6 +39,9 @@ func run(c context.Context) error {
 		return err
 	}
 
+	appLogger := logger.New(appConfig.LogLevel)
+	slog.SetDefault(appLogger)
+
 	// init sentry
 	if err := sentry.Init(sentry.ClientOptions{
 		Dsn:              appConfig.SentryDsn,
@@ -66,7 +71,7 @@ func run(c context.Context) error {
 
 	parsingClient := parser.NewBookingAgentParser()
 
-	bookingService, err := booking.NewService(bookingStore, parsingClient, pc)
+	bookingService, err := booking.NewService(appLogger, bookingStore, parsingClient, pc)
 	if err != nil {
 		return fmt.Errorf("error creating booking service: %w", err)
 	}