lets-go:3.3: structured logging, configuration, app struct, error

snippetbox/cmd/web/handlers.go

@@ -3,13 +3,13 @@ package main
 import (
 	"fmt"
 	"html/template"
-	"log"
+	"log/slog"
 	"net/http"
 	"strconv"
 )
 
 // home ...
-func home(w http.ResponseWriter, r *http.Request)  {
+func (app *application) home(w http.ResponseWriter, r *http.Request)  {
 	if r.URL.Path != "/" {
 		http.NotFound(w, r)
 		return
@@ -23,21 +23,21 @@ func home(w http.ResponseWriter, r *http.Request)  {
 
 	ts, err := template.ParseFiles(files...)
 	if err != nil {
-		log.Print(err.Error())
+		app.logger.Error(err.Error(), slog.String("method", r.Method), slog.String("uri", r.URL.RequestURI()))
 		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
 		return
 	}
 
 	err = ts.ExecuteTemplate(w, "base", nil)
 	if err != nil {
-		log.Print(err.Error())
+		app.logger.Error(err.Error(), slog.String("method", r.Method), slog.String("uri", r.URL.RequestURI()))
 		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
 		return
 	}
 }
 
 // snippetView ...
-func snippetView(w http.ResponseWriter, r *http.Request)  {
+func (app *application) snippetView(w http.ResponseWriter, r *http.Request)  {
 	id, err := strconv.Atoi(r.URL.Query().Get("id"))
 	if err != nil || id < 1 {
 		http.NotFound(w, r)
@@ -48,7 +48,7 @@ func snippetView(w http.ResponseWriter, r *http.Request)  {
 }
 
 // snippetCreate ...
-func snippetCreate(w http.ResponseWriter, r *http.Request)  {
+func (app *application) snippetCreate(w http.ResponseWriter, r *http.Request)  {
 	w.Header().Set("Allow", "POST")
 
 	if r.Method != http.MethodPost {

snippetbox/cmd/web/main.go

@@ -2,27 +2,55 @@ package main
 
 import (
 	"flag"
-	"log"
+	"log/slog"
 	"net/http"
+	"os"
 )
 
+// for application wide dependencies
+type application struct {
+	logger *slog.Logger
+}
+
 // main it's the snippetbox webapp
 func main() {
 	// configuration
 	addr := flag.String("addr", ":4000", "HTTP network address")
+	logfmt := flag.String("logfmt", "text", "Log output format")
+	loglevel := flag.String("loglevel", "INFO", "Log level: DEBUG, INFO, WARN, or ERROR")
 	flag.Parse()
 
+	var logger *slog.Logger
+	var handler_options slog.HandlerOptions
+
+	switch *loglevel {
+        case "DEBUG": handler_options = slog.HandlerOptions{Level: slog.LevelDebug}
+	case "INFO": handler_options = slog.HandlerOptions{Level: slog.LevelInfo}
+	case "WARN": handler_options = slog.HandlerOptions{Level: slog.LevelWarn}
+	case "ERROR": handler_options = slog.HandlerOptions{Level: slog.LevelError}
+	}
+
+	switch *logfmt {
+	case "json": logger = slog.New(slog.NewJSONHandler(os.Stdout, &handler_options))
+	default: logger = slog.New(slog.NewTextHandler(os.Stdout, &handler_options))
+	}
+
+	app := &application{
+		logger: logger,
+	}
+
 	mux := http.NewServeMux()
 
 	// setup server for static files
 	fileServer := http.FileServer(http.Dir("./ui/static"))
 	mux.Handle("/static/", http.StripPrefix("/static", fileServer))
 
-	mux.HandleFunc("/", home)
-	mux.HandleFunc("/snippet/view", snippetView)
-	mux.HandleFunc("/snippet/create", snippetCreate)
+	mux.HandleFunc("/", app.home)
+	mux.HandleFunc("/snippet/view", app.snippetView)
+	mux.HandleFunc("/snippet/create", app.snippetCreate)
 
-	log.Printf("starting a server on %s", *addr)
+	logger.Info("starting server", slog.String("addr", *addr))
 	err := http.ListenAndServe(*addr, mux)
-	log.Fatal(err)
+	logger.Error(err.Error())
+	os.Exit(1)
 }