feat(usage): persist replayable receipts without resetting core counters

backend/wireguard/stats.go

@@ -14,6 +14,23 @@ import (
 
 const onlineActivityThreshold = 45 * time.Second
 
+// The tracker preserves cumulative deltas across peer changes and soft restarts.
+// A new backend instance receives a new epoch when its trackers are recreated.
+func (wg *WireGuard) UsageSnapshot(ctx context.Context, kind common.StatType) (string, *common.StatResponse, error) {
+	wg.syncMu.Lock()
+	defer wg.syncMu.Unlock()
+	if kind == common.StatType_Outbounds {
+		rx, tx, err := wg.getInterfaceCounters()
+		if err != nil {
+			return "", nil, err
+		}
+		rx, tx = wg.interfaceStats.Cumulative(rx, tx)
+		return wg.usageEpoch, &common.StatResponse{Stats: stats.BuildInterfaceStats(wg.config.InterfaceName, "interface", rx, tx)}, nil
+	}
+	stats, err := wg.GetStats(ctx, &common.StatRequest{Type: kind, Reset_: false})
+	return wg.usageEpoch, stats, err
+}
+
 func (wg *WireGuard) getInterfaceCounters() (int64, int64, error) {
 	wg.mu.RLock()
 	mgr := wg.manager

backend/wireguard/wireguard.go

@@ -11,6 +11,8 @@ import (
 	"sync"
 	"time"
 
+	"github.com/google/uuid"
+
 	"github.com/pasarguard/node/common"
 	"github.com/pasarguard/node/config"
 	"github.com/pasarguard/node/pkg/stats"
@@ -65,6 +67,7 @@ type WireGuard struct {
 	lastStatsErrAt time.Time
 	newManager     newManagerFunc
 	hostRouting    func()
+	usageEpoch     string
 }
 
 // getWireGuardVersion fetches the wireguard-tools version
@@ -128,6 +131,7 @@ func newWithManagerFactory(cfg *config.Config, wgConfig *Config, users []*common
 	version := getWireGuardVersion()
 
 	wg := &WireGuard{
+		usageEpoch:     uuid.NewString(),
 		cancelFunc:     wgCancel,
 		cfg:            cfg,
 		statsTracker:   stats.New(),

backend/xray/stats.go

@@ -41,3 +41,12 @@ func (x *Xray) GetStats(ctx context.Context, request *common.StatRequest) (*comm
 		return nil, errors.New("not implemented stat type")
 	}
 }
+
+// UsageSnapshot holds the lifecycle lock across the read, binding cumulative
+// counters to precisely one core generation, even during a health restart.
+func (x *Xray) UsageSnapshot(ctx context.Context, kind common.StatType) (string, *common.StatResponse, error) {
+	x.mu.RLock()
+	defer x.mu.RUnlock()
+	stats, err := x.GetStats(ctx, &common.StatRequest{Type: kind, Reset_: false})
+	return x.usageEpoch, stats, err
+}

backend/xray/xray.go

@@ -7,6 +7,8 @@ import (
 	"sync"
 	"time"
 
+	"github.com/google/uuid"
+
 	"github.com/pasarguard/node/backend/xray/api"
 	"github.com/pasarguard/node/common"
 	"github.com/pasarguard/node/config"
@@ -21,6 +23,7 @@ type Xray struct {
 	cancelFunc context.CancelFunc
 	mu         sync.RWMutex
 	syncMu     sync.Mutex
+	usageEpoch string
 }
 
 func New(ctx context.Context, xrayConfig *Config, users []*common.User, apiPort, metricPort int, cfg *config.Config) (*Xray, error) {
@@ -42,6 +45,7 @@ func New(ctx context.Context, xrayConfig *Config, users []*common.User, apiPort,
 	xCtx, xCancel := context.WithCancel(context.Background())
 
 	xray := &Xray{
+		usageEpoch: uuid.NewString(),
 		cancelFunc: xCancel,
 		cfg:        cfg,
 		metricPort: metricPort,
@@ -132,6 +136,7 @@ func (x *Xray) restartCoreWithConfig(config *Config) error {
 	if err := x.core.Restart(config, x.cfg.Debug); err != nil {
 		return err
 	}
+	x.usageEpoch = uuid.NewString()
 	return nil
 }