htlcswitch: fix error when calculating the switch's 10 second stats

This commit fixes an error within the logic previously used to compute
the switch’s 10 seconds stats. The prior error would reset the number
of sat sent and received each 10 seconds to zero, rather than running a
delta over the accumulate amount.

htlcswitch.go

@@ -235,8 +235,12 @@ func (h *htlcSwitch) htlcForwarder() {
 	// (src, htlcKey).
 
 	// TODO(roasbeef): cleared vs settled distinction
-	var numUpdates uint64
-	var satSent, satRecv btcutil.Amount
+	var (
+		deltaNumUpdates, totalNumUpdates uint64
+
+		deltaSatSent, deltaSatRecv btcutil.Amount
+		totalSatSent, totalSatRecv btcutil.Amount
+	)
 	logTicker := time.NewTicker(10 * time.Second)
 out:
 	for {
@@ -289,7 +293,7 @@ out:
 			htlcPkt.err <- fmt.Errorf("Insufficient capacity")
 		case pkt := <-h.htlcPlex:
 			// TODO(roasbeef): properly account with cleared vs settled
-			numUpdates++
+			deltaNumUpdates++
 
 			hswcLog.Tracef("plex packet: %v", newLogClosure(func() string {
 				return spew.Sdump(pkt)
@@ -395,7 +399,7 @@ out:
 				hswcLog.Tracef("Decrementing link %v bandwidth to %v",
 					circuit.clear.chanPoint, n)
 
-				satRecv += pkt.amt
+				deltaSatRecv += pkt.amt
 
 			// We've just received a settle message which means we
 			// can finalize the payment circuit by forwarding the
@@ -413,7 +417,7 @@ out:
 				if !ok {
 					hswcLog.Debugf("No existing circuit "+
 						"for %x to settle", rHash[:])
-					satSent += pkt.amt
+					deltaSatSent += pkt.amt
 					continue
 				}
 
@@ -436,7 +440,7 @@ out:
 				hswcLog.Tracef("Incrementing link %v bandwidth to %v",
 					circuit.settle.chanPoint, n)
 
-				satSent += pkt.amt
+				deltaSatSent += pkt.amt
 
 				delete(h.paymentCircuits, cKey)
 
@@ -478,18 +482,35 @@ out:
 				delete(h.paymentCircuits, pkt.payHash)
 			}
 		case <-logTicker.C:
-			if numUpdates == 0 {
+			if deltaNumUpdates == 0 {
 				continue
 			}
 
+			oldSatSent := totalSatRecv
+			oldSatRecv := totalSatRecv
+			oldNumUpdates := totalNumUpdates
+
+			newSatSent := oldSatRecv + deltaSatSent
+			newSatRecv := totalSatRecv + deltaSatRecv
+			newNumUpdates := totalNumUpdates + deltaNumUpdates
+
+			satSent := newSatSent - oldSatSent
+			satRecv := newSatRecv - oldSatRecv
+			numUpdates := newNumUpdates - oldNumUpdates
 			hswcLog.Infof("Sent %v satoshis, received %v satoshis in "+
 				"the last 10 seconds (%v tx/sec)",
 				satSent.ToUnit(btcutil.AmountSatoshi),
 				satRecv.ToUnit(btcutil.AmountSatoshi),
-				float64(numUpdates)/10)
-			satSent = 0
-			satRecv = 0
-			numUpdates = 0
+				numUpdates)
+
+			totalSatSent += deltaSatSent
+			deltaSatSent = 0
+
+			totalSatRecv += deltaSatRecv
+			deltaSatRecv = 0
+
+			totalNumUpdates += deltaNumUpdates
+			deltaNumUpdates = 0
 		case <-h.quit:
 			break out
 		}