feat(logs): change logs to structured json

main.go

@@ -8,7 +8,7 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"log"
+	"log/slog"
 	"net/http"
 	"net/url"
 	"os"
@@ -111,13 +111,17 @@ func main() {
 	configPath := flag.String("config", "config.toml", "path to config file")
 	flag.Parse()
 
+	slog.SetDefault(slog.New(slog.NewJSONHandler(os.Stdout, nil)))
+
 	cfg, interval, err := loadConfig(*configPath)
 	if err != nil {
-		log.Fatalf("config error: %v", err)
+		slog.Error("config load failed", "error", err)
+		os.Exit(1)
 	}
 
 	if err := os.MkdirAll(cfg.CacheDir, 0o755); err != nil {
-		log.Fatalf("cache dir: %v", err)
+		slog.Error("cache dir create failed", "error", err)
+		os.Exit(1)
 	}
 
 	agg := NewAggregator()
@@ -133,7 +137,7 @@ func main() {
 	for _, source := range cfg.Sources {
 		cached, err := loadCachedLinks(cfg.CacheDir, source)
 		if err != nil {
-			log.Printf("load cache for %s: %v", source, err)
+			slog.Error("load cache failed", "source", source, "error", err)
 		}
 		if len(cached) > 0 {
 			agg.Update(source, cached)
@@ -149,7 +153,7 @@ func main() {
 
 	mux := http.NewServeMux()
 	mux.HandleFunc("/list", func(w http.ResponseWriter, r *http.Request) {
-		log.Printf("request /list from %s [%s %s]", r.RemoteAddr, r.Method, r.UserAgent())
+		slog.Info("request", "path", "/list", "remote", r.RemoteAddr, "method", r.Method, "user_agent", r.UserAgent())
 		links := agg.List()
 		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 		for i, link := range links {
@@ -158,7 +162,7 @@ func main() {
 			}
 			_, _ = w.Write([]byte(link))
 		}
-		log.Printf("response /list to %s: %d links", r.RemoteAddr, len(links))
+		slog.Info("response", "path", "/list", "remote", r.RemoteAddr, "links", len(links))
 	})
 
 	server := &http.Server{
@@ -173,15 +177,16 @@ func main() {
 		<-ctx.Done()
 		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 		defer cancel()
-		log.Printf("server shutdown")
+		slog.Info("server shutting down")
 		if err := server.Shutdown(shutdownCtx); err != nil {
-			log.Printf("server shutdown error: %v", err)
+			slog.Error("server shutdown failed", "error", err)
 		}
 	}()
 
-	log.Printf("listening on :%d", cfg.Port)
+	slog.Info("listening", "port", cfg.Port)
 	if err := server.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
-		log.Fatalf("server error: %v", err)
+		slog.Error("server listen failed", "error", err)
+		os.Exit(1)
 	}
 }
 
@@ -194,7 +199,7 @@ func pollSource(ctx context.Context, source string, interval time.Duration, cach
 	for {
 		select {
 		case <-ctx.Done():
-			log.Printf("poller shutdown")
+			slog.Info("poller stopped", "source", source)
 			return
 		case <-ticker.C:
 			runOnce(ctx, source, cacheDir, agg, client)
@@ -205,22 +210,22 @@ func pollSource(ctx context.Context, source string, interval time.Duration, cach
 func runOnce(ctx context.Context, source string, cacheDir string, agg *Aggregator, client *http.Client) {
 	links, err := fetchSource(ctx, source, client)
 	if err != nil {
-		log.Printf("poll %s: failed - %v", source, err)
+		slog.Error("poll failed", "source", source, "error", err)
 		return
 	}
 	if len(links) == 0 {
-		log.Printf("poll %s: success - 0 links", source)
+		slog.Info("poll success", "source", source, "links", 0)
 		agg.Update(source, nil)
 		if err := writeCache(cacheDir, source, nil); err != nil {
-			log.Printf("write cache %s: %v", source, err)
+			slog.Error("write cache failed", "source", source, "error", err)
 		}
 		return
 	}
 
-	log.Printf("poll %s: success - %d links", source, len(links))
+	slog.Info("poll success", "source", source, "links", len(links))
 	agg.Update(source, links)
 	if err := writeCache(cacheDir, source, links); err != nil {
-		log.Printf("write cache %s: %v", source, err)
+		slog.Error("write cache failed", "source", source, "error", err)
 	}
 }
 
@@ -244,11 +249,11 @@ func fetchSource(ctx context.Context, source string, client *http.Client) ([]str
 		if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 			return nil, fmt.Errorf("unexpected status: %s", resp.Status)
 		}
-		log.Printf("fetch %s: HTTP %d", source, resp.StatusCode)
 		body, err := io.ReadAll(resp.Body)
 		if err != nil {
 			return nil, fmt.Errorf("read body: %w", err)
 		}
+		slog.Info("fetch complete", "source", source, "status", resp.StatusCode, "bytes", len(body))
 		return normalizeLinks(string(body)), nil
 	case "file":
 		path := u.Path
@@ -259,7 +264,7 @@ func fetchSource(ctx context.Context, source string, client *http.Client) ([]str
 		if err != nil {
 			return nil, fmt.Errorf("read file: %w", err)
 		}
-		log.Printf("fetch %s: file read %d bytes", source, len(data))
+		slog.Info("fetch complete", "source", source, "bytes", len(data))
 		return normalizeLinks(string(data)), nil
 	default:
 		return nil, fmt.Errorf("unsupported source scheme: %s", u.Scheme)