fix(proxy): use filesystem config watcher

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

configwatcher_test.go

@@ -4,12 +4,13 @@ import (
 	"os"
 	"path/filepath"
 	"testing"
+	"time"
 )
 
 func TestConfigWatcher_New_Good(t *testing.T) {
 	dir := t.TempDir()
 	path := filepath.Join(dir, "config.json")
-	if err := os.WriteFile(path, []byte(`{"mode":"nicehash"}`), 0o644); err != nil {
+	if err := os.WriteFile(path, []byte(`{"mode":"nicehash","workers":"false","bind":[{"host":"127.0.0.1","port":3333}],"pools":[{"url":"pool.example:3333","enabled":true}]}`), 0o644); err != nil {
 		t.Fatalf("write config file: %v", err)
 	}
 
@@ -21,3 +22,42 @@ func TestConfigWatcher_New_Good(t *testing.T) {
 		t.Fatal("expected last modification time to be initialised from the file")
 	}
 }
+
+func TestConfigWatcher_Start_Good(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()
+
+	updated := []byte(`{"mode":"simple","workers":"user","bind":[{"host":"127.0.0.1","port":3333}],"pools":[{"url":"pool.example:3333","enabled":true}]}`)
+	if err := os.WriteFile(path, updated, 0o644); err != nil {
+		t.Fatalf("write updated config file: %v", err)
+	}
+
+	select {
+	case cfg := <-updates:
+		if cfg == nil {
+			t.Fatal("expected config update")
+		}
+		if got := cfg.Mode; got != "simple" {
+			t.Fatalf("expected updated mode, got %q", got)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("expected watcher to reload updated config")
+	}
+}

core_impl.go

@@ -11,10 +11,13 @@ import (
 	"math"
 	"net"
 	"os"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"sync"
 	"time"
+
+	"github.com/fsnotify/fsnotify"
 )
 
 // Result is the success/error carrier used by constructors and loaders.
@@ -375,23 +378,65 @@ func (w *ConfigWatcher) Start() {
 	if w == nil || w.path == "" || w.onChange == nil {
 		return
 	}
+	w.mu.Lock()
+	if w.watcher != nil {
+		w.mu.Unlock()
+		return
+	}
+	fsWatcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		w.mu.Unlock()
+		return
+	}
+	w.watcher = fsWatcher
+	w.mu.Unlock()
+
+	watchPath := filepath.Clean(w.path)
+	watchDir := filepath.Dir(watchPath)
+	if watchDir == "" {
+		watchDir = "."
+	}
+	if err := fsWatcher.Add(watchDir); err != nil {
+		_ = fsWatcher.Close()
+		w.mu.Lock()
+		if w.watcher == fsWatcher {
+			w.watcher = nil
+		}
+		w.mu.Unlock()
+		return
+	}
+
 	go func() {
-		ticker := time.NewTicker(time.Second)
-		defer ticker.Stop()
+		defer func() {
+			_ = fsWatcher.Close()
+			w.mu.Lock()
+			if w.watcher == fsWatcher {
+				w.watcher = nil
+			}
+			w.mu.Unlock()
+		}()
 		for {
 			select {
-			case <-ticker.C:
-				info, err := os.Stat(w.path)
-				if err != nil {
+			case event, ok := <-fsWatcher.Events:
+				if !ok {
+					return
+				}
+				if filepath.Clean(event.Name) != watchPath {
 					continue
 				}
-				mod := info.ModTime()
-				if mod.After(w.lastMod) {
-					w.lastMod = mod
-					config, result := LoadConfig(w.path)
-					if result.OK && config != nil {
-						w.onChange(config)
+				if event.Op&(fsnotify.Write|fsnotify.Create|fsnotify.Rename|fsnotify.Remove|fsnotify.Chmod) == 0 {
+					continue
+				}
+				config, result := LoadConfig(w.path)
+				if result.OK && config != nil {
+					if info, err := os.Stat(w.path); err == nil {
+						w.lastMod = info.ModTime()
 					}
+					w.onChange(config)
+				}
+			case _, ok := <-fsWatcher.Errors:
+				if !ok {
+					return
 				}
 			case <-w.done:
 				return
@@ -405,6 +450,12 @@ func (w *ConfigWatcher) Stop() {
 	if w == nil {
 		return
 	}
+	w.mu.Lock()
+	if w.watcher != nil {
+		_ = w.watcher.Close()
+		w.watcher = nil
+	}
+	w.mu.Unlock()
 	select {
 	case <-w.done:
 	default:

go.mod

@@ -1,3 +1,7 @@
 module dappco.re/go/proxy
 
 go 1.26.0
+
+require github.com/fsnotify/fsnotify v1.7.0
+
+require golang.org/x/sys v0.4.0 // indirect

go.sum

@@ -0,0 +1,4 @@
+github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
+github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
+golang.org/x/sys v0.4.0 h1:Zr2JFtRQNX3BCZ8YtxRE9hNJYC8J6I1MVbMg6owUp18=
+golang.org/x/sys v0.4.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

proxy.go

@@ -8,6 +8,7 @@
 package proxy
 
 import (
+	"github.com/fsnotify/fsnotify"
 	"net/http"
 	"sync"
 	"sync/atomic"
@@ -120,6 +121,8 @@ type ConfigWatcher struct {
 	onChange func(*Config)
 	lastMod  time.Time
 	done     chan struct{}
+	mu       sync.Mutex
+	watcher  *fsnotify.Watcher
 }
 
 // RateLimiter throttles new connections per source IP.