Fix busy binary reinstall and add per-node log viewing.

Co-authored-by: Cursor <cursoragent@cursor.com>

cmd/node/main.go

@@ -2,10 +2,12 @@ package main
 
 import (
 	"encoding/json"
+	"io"
 	"log"
 	"net/http"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -18,6 +20,7 @@ type Agent struct {
 	secret    string
 	version   string
 	dataDir   string
+	logPath   string
 	startedAt time.Time
 	mu        sync.RWMutex
 	config    map[string]any
@@ -34,11 +37,19 @@ func main() {
 	dataDir := env("DATA_DIR", "/var/lib/vpn-node")
 	_ = os.MkdirAll(dataDir, 0o755)
 
+	logPath := filepath.Join(dataDir, "agent.log")
+	logFile, err := os.OpenFile(logPath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o644)
+	if err == nil {
+		log.SetOutput(io.MultiWriter(os.Stderr, logFile))
+		defer logFile.Close()
+	}
+
 	a := &Agent{
 		name:      name,
 		secret:    secret,
 		version:   version,
 		dataDir:   dataDir,
+		logPath:   logPath,
 		startedAt: time.Now().UTC(),
 		config:    map[string]any{},
 	}
@@ -48,6 +59,7 @@ func main() {
 	mux.HandleFunc("/health", a.auth(a.health))
 	mux.HandleFunc("/api/v1/config", a.auth(a.configHandler))
 	mux.HandleFunc("/api/v1/status", a.auth(a.status))
+	mux.HandleFunc("/api/v1/logs", a.auth(a.logs))
 
 	addr := ":" + port
 	log.Printf("vpn-node %s listening on %s name=%s", version, addr, name)
@@ -130,6 +142,34 @@ func (a *Agent) status(w http.ResponseWriter, _ *http.Request) {
 	})
 }
 
+func (a *Agent) logs(w http.ResponseWriter, r *http.Request) {
+	lines := 300
+	if v := r.URL.Query().Get("lines"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil && n > 0 && n <= 5000 {
+			lines = n
+		}
+	}
+	content, err := tailFile(a.logPath, lines)
+	if err != nil {
+		writeJSON(w, map[string]any{"ok": true, "logs": "(no agent.log yet)"})
+		return
+	}
+	writeJSON(w, map[string]any{"ok": true, "logs": content})
+}
+
+func tailFile(path string, maxLines int) (string, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return "", err
+	}
+	text := string(b)
+	parts := strings.Split(text, "\n")
+	if len(parts) > maxLines {
+		parts = parts[len(parts)-maxLines:]
+	}
+	return strings.Join(parts, "\n"), nil
+}
+
 func (a *Agent) configHandler(w http.ResponseWriter, r *http.Request) {
 	switch r.Method {
 	case http.MethodGet:
@@ -146,6 +186,7 @@ func (a *Agent) configHandler(w http.ResponseWriter, r *http.Request) {
 		a.config = cfg
 		a.mu.Unlock()
 		_ = a.saveConfig(filepath.Join(a.dataDir, "config.json"))
+		log.Printf("config updated: installed=%v enabled=%v", stringList(cfg, "protocols_installed"), stringList(cfg, "protocols_enabled"))
 		writeJSON(w, map[string]any{"ok": true})
 	default:
 		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)