settlement: add available balance metric (#1172)

pkg/settlement/swap/chequebook/chequebook.go

@@ -50,7 +50,7 @@ type Service interface {
 	// Address returns the address of the used chequebook contract.
 	Address() common.Address
 	// Issue a new cheque for the beneficiary with an cumulativePayout amount higher than the last.
-	Issue(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc SendChequeFunc) error
+	Issue(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc SendChequeFunc) (*big.Int, error)
 	// LastCheque returns the last cheque we issued for the beneficiary.
 	LastCheque(beneficiary common.Address) (*SignedCheque, error)
 	// LastCheque returns the last cheques for all beneficiaries.
@@ -204,21 +204,21 @@ func lastIssuedChequeKey(beneficiary common.Address) string {
 	return fmt.Sprintf("chequebook_last_issued_cheque_%x", beneficiary)
 }
 
-func (s *service) reserveTotalIssued(ctx context.Context, amount *big.Int) error {
+func (s *service) reserveTotalIssued(ctx context.Context, amount *big.Int) (*big.Int, error) {
 	s.lock.Lock()
 	defer s.lock.Unlock()
 
 	availableBalance, err := s.AvailableBalance(ctx)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	if amount.Cmp(big.NewInt(0).Sub(availableBalance, s.totalIssuedReserved)) > 0 {
-		return ErrOutOfFunds
+		return nil, ErrOutOfFunds
 	}
 
 	s.totalIssuedReserved = s.totalIssuedReserved.Add(s.totalIssuedReserved, amount)
-	return nil
+	return big.NewInt(0).Sub(availableBalance, amount), nil
 }
 
 func (s *service) unreserveTotalIssued(amount *big.Int) {
@@ -227,12 +227,14 @@ func (s *service) unreserveTotalIssued(amount *big.Int) {
 	s.totalIssuedReserved = s.totalIssuedReserved.Sub(s.totalIssuedReserved, amount)
 }
 
-// Issue issues a new cheque and passes it to sendChequeFunc
-// if sendChequeFunc succeeds the cheque is considered sent and saved
-func (s *service) Issue(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc SendChequeFunc) error {
-	err := s.reserveTotalIssued(ctx, amount)
+// Issue issues a new cheque and passes it to sendChequeFunc.
+// The cheque is considered sent and saved when sendChequeFunc succeeds.
+// The available balance which is available after sending the cheque is passed
+// to the caller for it to be communicated over metrics.
+func (s *service) Issue(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc SendChequeFunc) (*big.Int, error) {
+	availableBalance, err := s.reserveTotalIssued(ctx, amount)
 	if err != nil {
-		return err
+		return nil, err
 	}
 	defer s.unreserveTotalIssued(amount)
 
@@ -240,7 +242,7 @@ func (s *service) Issue(ctx context.Context, beneficiary common.Address, amount
 	lastCheque, err := s.LastCheque(beneficiary)
 	if err != nil {
 		if err != ErrNoCheque {
-			return err
+			return nil, err
 		}
 		cumulativePayout = big.NewInt(0)
 	} else {
@@ -263,7 +265,7 @@ func (s *service) Issue(ctx context.Context, beneficiary common.Address, amount
 		Beneficiary:      beneficiary,
 	})
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	// actually send the check before saving to avoid double payment
@@ -272,12 +274,12 @@ func (s *service) Issue(ctx context.Context, beneficiary common.Address, amount
 		Signature: sig,
 	})
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	err = s.store.Put(lastIssuedChequeKey(beneficiary), cheque)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	s.lock.Lock()
@@ -285,10 +287,10 @@ func (s *service) Issue(ctx context.Context, beneficiary common.Address, amount
 
 	totalIssued, err := s.totalIssued()
 	if err != nil {
-		return err
+		return nil, err
 	}
 	totalIssued = totalIssued.Add(totalIssued, amount)
-	return s.store.Put(totalIssuedKey, totalIssued)
+	return availableBalance, s.store.Put(totalIssuedKey, totalIssued)
 }
 
 // returns the total amount in cheques issued so far

pkg/settlement/swap/chequebook/chequebook_test.go

@@ -292,7 +292,7 @@ func TestChequebookIssue(t *testing.T) {
 		return sig, nil
 	}
 
-	err = chequebookService.Issue(context.Background(), beneficiary, amount, func(cheque *chequebook.SignedCheque) error {
+	_, err = chequebookService.Issue(context.Background(), beneficiary, amount, func(cheque *chequebook.SignedCheque) error {
 		if !cheque.Equal(expectedCheque) {
 			t.Fatalf("wrong cheque. wanted %v got %v", expectedCheque, cheque)
 		}
@@ -328,7 +328,7 @@ func TestChequebookIssue(t *testing.T) {
 		return sig, nil
 	}
 
-	err = chequebookService.Issue(context.Background(), beneficiary, amount2, func(cheque *chequebook.SignedCheque) error {
+	_, err = chequebookService.Issue(context.Background(), beneficiary, amount2, func(cheque *chequebook.SignedCheque) error {
 		if !cheque.Equal(expectedCheque) {
 			t.Fatalf("wrong cheque. wanted %v got %v", expectedCheque, cheque)
 		}
@@ -364,7 +364,7 @@ func TestChequebookIssue(t *testing.T) {
 		return sig, nil
 	}
 
-	err = chequebookService.Issue(context.Background(), ownerAdress, amount, func(cheque *chequebook.SignedCheque) error {
+	_, err = chequebookService.Issue(context.Background(), ownerAdress, amount, func(cheque *chequebook.SignedCheque) error {
 		if !cheque.Equal(expectedChequeOwner) {
 			t.Fatalf("wrong cheque. wanted %v got %v", expectedChequeOwner, cheque)
 		}
@@ -430,7 +430,7 @@ func TestChequebookIssueErrorSend(t *testing.T) {
 		return sig, nil
 	}
 
-	err = chequebookService.Issue(context.Background(), beneficiary, amount, func(cheque *chequebook.SignedCheque) error {
+	_, err = chequebookService.Issue(context.Background(), beneficiary, amount, func(cheque *chequebook.SignedCheque) error {
 		return errors.New("err")
 	})
 	if err == nil {
@@ -474,7 +474,7 @@ func TestChequebookIssueOutOfFunds(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = chequebookService.Issue(context.Background(), beneficiary, amount, func(cheque *chequebook.SignedCheque) error {
+	_, err = chequebookService.Issue(context.Background(), beneficiary, amount, func(cheque *chequebook.SignedCheque) error {
 		return nil
 	})
 	if !errors.Is(err, chequebook.ErrOutOfFunds) {

pkg/settlement/swap/chequebook/mock/chequebook.go

@@ -18,7 +18,7 @@ type Service struct {
 	chequebookBalanceFunc          func(context.Context) (*big.Int, error)
 	chequebookAvailableBalanceFunc func(context.Context) (*big.Int, error)
 	chequebookAddressFunc          func() common.Address
-	chequebookIssueFunc            func(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc chequebook.SendChequeFunc) error
+	chequebookIssueFunc            func(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc chequebook.SendChequeFunc) (*big.Int, error)
 	chequebookWithdrawFunc         func(ctx context.Context, amount *big.Int) (hash common.Hash, err error)
 	chequebookDepositFunc          func(ctx context.Context, amount *big.Int) (hash common.Hash, err error)
 }
@@ -48,7 +48,7 @@ func WithChequebookDepositFunc(f func(ctx context.Context, amount *big.Int) (has
 	})
 }
 
-func WithChequebookIssueFunc(f func(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc chequebook.SendChequeFunc) error) Option {
+func WithChequebookIssueFunc(f func(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc chequebook.SendChequeFunc) (*big.Int, error)) Option {
 	return optionFunc(func(s *Service) {
 		s.chequebookIssueFunc = f
 	})
@@ -105,11 +105,11 @@ func (s *Service) Address() common.Address {
 	return common.Address{}
 }
 
-func (s *Service) Issue(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc chequebook.SendChequeFunc) error {
+func (s *Service) Issue(ctx context.Context, beneficiary common.Address, amount *big.Int, sendChequeFunc chequebook.SendChequeFunc) (*big.Int, error) {
 	if s.chequebookIssueFunc != nil {
 		return s.chequebookIssueFunc(ctx, beneficiary, amount, sendChequeFunc)
 	}
-	return nil
+	return big.NewInt(0), nil
 }
 
 func (s *Service) LastCheque(beneficiary common.Address) (*chequebook.SignedCheque, error) {

pkg/settlement/swap/metrics.go

@@ -10,12 +10,10 @@ import (
 )
 
 type metrics struct {
-	// all metrics fields must be exported
-	// to be able to return them by Metrics()
-	// using reflection
-	TotalReceived   prometheus.Counter
-	TotalSent       prometheus.Counter
-	ChequesRejected prometheus.Counter
+	TotalReceived    prometheus.Counter
+	TotalSent        prometheus.Counter
+	ChequesRejected  prometheus.Counter
+	AvailableBalance prometheus.Gauge
 }
 
 func newMetrics() metrics {
@@ -40,6 +38,12 @@ func newMetrics() metrics {
 			Name:      "cheques_rejected",
 			Help:      "Number of cheques rejected",
 		}),
+		AvailableBalance: prometheus.NewGauge(prometheus.GaugeOpts{
+			Namespace: m.Namespace,
+			Subsystem: subsystem,
+			Name:      "available_balance",
+			Help:      "Currently availeble chequebook balance.",
+		}),
 	}
 }
 

pkg/settlement/swap/swap.go

@@ -119,12 +119,14 @@ func (s *Service) Pay(ctx context.Context, peer swarm.Address, amount uint64) er
 		}
 		return ErrUnknownBeneficary
 	}
-	err = s.chequebook.Issue(ctx, beneficiary, big.NewInt(int64(amount)), func(signedCheque *chequebook.SignedCheque) error {
+	balance, err := s.chequebook.Issue(ctx, beneficiary, big.NewInt(int64(amount)), func(signedCheque *chequebook.SignedCheque) error {
 		return s.proto.EmitCheque(ctx, peer, signedCheque)
 	})
 	if err != nil {
 		return err
 	}
+	bal, _ := big.NewFloat(0).SetInt(balance).Float64()
+	s.metrics.AvailableBalance.Set(bal)
 	s.metrics.TotalSent.Add(float64(amount))
 	return nil
 }

pkg/settlement/swap/swap_test.go

@@ -285,7 +285,7 @@ func TestPay(t *testing.T) {
 	peer := swarm.MustParseHexAddress("abcd")
 	var chequebookCalled bool
 	chequebookService := mockchequebook.NewChequebook(
-		mockchequebook.WithChequebookIssueFunc(func(ctx context.Context, b common.Address, a *big.Int, sendChequeFunc chequebook.SendChequeFunc) error {
+		mockchequebook.WithChequebookIssueFunc(func(ctx context.Context, b common.Address, a *big.Int, sendChequeFunc chequebook.SendChequeFunc) (*big.Int, error) {
 			if b != beneficiary {
 				t.Fatalf("issuing cheque for wrong beneficiary. wanted %v, got %v", beneficiary, b)
 			}
@@ -293,7 +293,7 @@ func TestPay(t *testing.T) {
 				t.Fatalf("issuing cheque with wrong amount. wanted %d, got %d", amount, a)
 			}
 			chequebookCalled = true
-			return sendChequeFunc(&cheque)
+			return big.NewInt(0), sendChequeFunc(&cheque)
 		}),
 	)
 
@@ -355,8 +355,8 @@ func TestPayIssueError(t *testing.T) {
 	peer := swarm.MustParseHexAddress("abcd")
 	errReject := errors.New("reject")
 	chequebookService := mockchequebook.NewChequebook(
-		mockchequebook.WithChequebookIssueFunc(func(ctx context.Context, b common.Address, a *big.Int, sendChequeFunc chequebook.SendChequeFunc) error {
-			return errReject
+		mockchequebook.WithChequebookIssueFunc(func(ctx context.Context, b common.Address, a *big.Int, sendChequeFunc chequebook.SendChequeFunc) (*big.Int, error) {
+			return big.NewInt(0), errReject
 		}),
 	)