fix(proxy): use mtime-based config watching

Co-Authored-By: Virgil <virgil@lethean.io>

configwatcher_test.go

@@ -48,6 +48,10 @@ func TestConfigWatcher_Start_Good(t *testing.T) {
 	if err := os.WriteFile(path, updated, 0o644); err != nil {
 		t.Fatalf("write updated config file: %v", err)
 	}
+	now := time.Now()
+	if err := os.Chtimes(path, now, now.Add(2*time.Second)); err != nil {
+		t.Fatalf("touch updated config file: %v", err)
+	}
 
 	select {
 	case cfg := <-updates:
@@ -61,3 +65,42 @@ func TestConfigWatcher_Start_Good(t *testing.T) {
 		t.Fatal("expected watcher to reload updated config")
 	}
 }
+
+func TestConfigWatcher_Start_Ugly(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.json")
+	initial := []byte(`{"mode":"nicehash","workers":"false","bind":[{"host":"127.0.0.1","port":3333}],"pools":[{"url":"pool.example:3333","enabled":true}]}`)
+	if err := os.WriteFile(path, initial, 0o644); err != nil {
+		t.Fatalf("write initial config file: %v", err)
+	}
+
+	updates := make(chan *Config, 1)
+	watcher := NewConfigWatcher(path, func(cfg *Config) {
+		select {
+		case updates <- cfg:
+		default:
+		}
+	})
+	if watcher == nil {
+		t.Fatal("expected watcher")
+	}
+	watcher.Start()
+	defer watcher.Stop()
+
+	now := time.Now()
+	if err := os.Chtimes(path, now, now.Add(2*time.Second)); err != nil {
+		t.Fatalf("touch config file: %v", err)
+	}
+
+	select {
+	case cfg := <-updates:
+		if cfg == nil {
+			t.Fatal("expected config update")
+		}
+		if got := cfg.Mode; got != "nicehash" {
+			t.Fatalf("expected unchanged mode, got %q", got)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("expected watcher to reload touched config")
+	}
+}

core_impl.go

@@ -364,9 +364,6 @@ func NewConfigWatcher(configPath string, onChange func(*Config)) *ConfigWatcher
 		onChange: onChange,
 		done:     make(chan struct{}),
 	}
-	if data, err := os.ReadFile(configPath); err == nil {
-		watcher.lastSum = sha256.Sum256(data)
-	}
 	if info, err := os.Stat(configPath); err == nil {
 		watcher.lastMod = info.ModTime()
 	}
@@ -392,28 +389,20 @@ func (w *ConfigWatcher) Start() {
 		for {
 			select {
 			case <-ticker.C:
-				data, err := os.ReadFile(w.path)
-				if err != nil {
-					continue
-				}
-				sum := sha256.Sum256(data)
-				w.mu.Lock()
-				changed := sum != w.lastSum
-				if changed {
-					w.lastSum = sum
-				}
-				w.mu.Unlock()
-				if !changed {
-					continue
-				}
 				if info, err := os.Stat(w.path); err == nil {
 					w.mu.Lock()
-					w.lastMod = info.ModTime()
+					changed := info.ModTime() != w.lastMod
+					if changed {
+						w.lastMod = info.ModTime()
+					}
 					w.mu.Unlock()
-				}
-				config, result := LoadConfig(w.path)
-				if result.OK && config != nil {
-					w.onChange(config)
+					if !changed {
+						continue
+					}
+					config, result := LoadConfig(w.path)
+					if result.OK && config != nil {
+						w.onChange(config)
+					}
 				}
 			case <-w.done:
 				return

proxy.go

@@ -110,16 +110,13 @@ type CloseEvent struct {
 	Miner *Miner
 }
 
-// ConfigWatcher polls a config file for changes.
+// ConfigWatcher polls a config file every second and reloads on modification.
 //
-//	watcher := proxy.NewConfigWatcher("config.json", func(cfg *proxy.Config) {
-//	    p.Reload(cfg)
-//	})
+//	watcher := proxy.NewConfigWatcher("config.json", func(cfg *proxy.Config) { p.Reload(cfg) })
 type ConfigWatcher struct {
 	path     string
 	onChange func(*Config)
 	lastMod  time.Time
-	lastSum  [32]byte
 	done     chan struct{}
 	mu       sync.Mutex
 	started  bool