ch10.1

cmd/api/errors.go

@@ -6,7 +6,10 @@ import (
 )
 
 func (app *application) logError(r *http.Request, err error) {
-	app.logger.Print(err)
+	app.logger.PrintError(err, map[string]string{
+		"request_method": r.Method,
+		"request_url":    r.URL.String(),
+	})
 }
 
 func (app *application) errorResponse(w http.ResponseWriter, r *http.Request, status int, message any) {

cmd/api/healthcheck.go

@@ -14,7 +14,6 @@ func (app *application) healthcheckHandler(w http.ResponseWriter, r *http.Reques
 	}
 	err := app.writeJSON(w, http.StatusOK, env, nil)
 	if err != nil {
-		app.logger.Print(err)
 		app.serverErrorResponse(w, r, err)
 	}
 }

cmd/api/main.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"gitea.local.lab/Lbenedar/greenlight/internal/data"
+	"gitea.local.lab/Lbenedar/greenlight/internal/jsonlog"
 	_ "github.com/lib/pq"
 )
 
@@ -18,7 +19,7 @@ const version = "1.0.0"
 
 type application struct {
 	config config
-	logger *log.Logger
+	logger *jsonlog.Logger
 	models data.Models
 }
 
@@ -70,15 +71,15 @@ func main() {
 	flag.StringVar(&cfg.db.maxIdleTime, "db-max-idle-time", "15m", "PostgreSQL max connection idle time")
 	flag.Parse()
 
-	logger := log.New(os.Stdout, "", log.Ldate|log.Ltime)
+	logger := jsonlog.New(os.Stdout, jsonlog.LevelInfo)
 
 	db, err := openDB(cfg)
 	if err != nil {
-		logger.Fatal(err)
+		logger.PrintFatal(err, nil)
 	}
 	defer db.Close()
 
-	logger.Printf("database connection pool established")
+	logger.PrintInfo("database connection pool established", nil)
 
 	app := &application{
 		config: cfg,
@@ -89,11 +90,15 @@ func main() {
 	srv := &http.Server{
 		Addr:         fmt.Sprintf(":%d", app.config.port),
 		Handler:      app.routes(),
+		ErrorLog:     log.New(logger, "", 0),
 		IdleTimeout:  time.Minute,
 		ReadTimeout:  10 * time.Second,
 		WriteTimeout: 10 * time.Second,
 	}
-	logger.Printf("starting %s server on %s", cfg.env, srv.Addr)
+	logger.PrintInfo("starting server", map[string]string{
+		"addr": srv.Addr,
+		"env":  cfg.env,
+	})
 	err = srv.ListenAndServe()
-	logger.Fatal(err)
+	logger.PrintFatal(err, nil)
 }

internal/jsonlog/jsonlog.go

@@ -0,0 +1,97 @@
+package jsonlog
+
+import (
+	"encoding/json"
+	"io"
+	"os"
+	"runtime/debug"
+	"sync"
+	"time"
+)
+
+type Level int8
+
+const (
+	LevelInfo Level = iota
+	LevelError
+	LevelFatal
+	LevelOff
+)
+
+func (l Level) String() string {
+	switch l {
+	case LevelInfo:
+		return "INFO"
+	case LevelError:
+		return "ERROR"
+	case LevelFatal:
+		return "FATAL"
+	default:
+		return ""
+	}
+}
+
+type Logger struct {
+	out      io.Writer
+	minLevel Level
+	mu       sync.Mutex
+}
+
+func New(out io.Writer, minLevel Level) *Logger {
+	return &Logger{
+		out:      out,
+		minLevel: minLevel,
+	}
+}
+
+func (l *Logger) PrintInfo(message string, properties map[string]string) {
+	l.print(LevelInfo, message, properties)
+}
+
+func (l *Logger) PrintError(err error, properties map[string]string) {
+	l.print(LevelError, err.Error(), properties)
+}
+
+func (l *Logger) PrintFatal(err error, properties map[string]string) {
+	l.print(LevelFatal, err.Error(), properties)
+	os.Exit(1)
+}
+
+func (l *Logger) print(level Level, message string, properties map[string]string) (int, error) {
+	if level < l.minLevel {
+		return 0, nil
+	}
+
+	aux := struct {
+		Level      string            `json:"level"`
+		Time       string            `json:"time"`
+		Message    string            `json:"message"`
+		Properties map[string]string `json:"properties,omitempty"`
+		Trace      string            `json:"trace,omitempty"`
+	}{
+		Level:      level.String(),
+		Time:       time.Now().UTC().Format(time.RFC3339),
+		Message:    message,
+		Properties: properties,
+	}
+
+	if level >= LevelError {
+		aux.Trace = string(debug.Stack())
+	}
+
+	var line []byte
+
+	line, err := json.Marshal(aux)
+	if err != nil {
+		line = []byte(LevelError.String() + ": unable to marshal log message: " + err.Error())
+	}
+
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	return l.out.Write(append(line, '\n'))
+}
+
+func (l *Logger) Write(message []byte) (n int, err error) {
+	return l.print(LevelError, string(message), nil)
+}