core,pm: handle zero/nil gas price from gas price monitor

CHANGELOG_PENDING.md

@@ -8,8 +8,12 @@
 
 - \#1810 Display "n/a" in CLI when max gas price isn't specified (@kyriediculous)
 
+#### Orchestrator
+
+- \#1830 handle "zero" or "nil" gas price from gas price monitor (@kyriediculous)
+
 ### Features ⚒
 
 #### Broadcaster
 
-- \#1823 Mark more transcoder errors as NonRetryable (@jailuthra)
+- \#1823 Mark more transcoder errors as NonRetryable (@jailuthra)

core/orchestrator.go

@@ -289,7 +289,10 @@ func (orch *orchestrator) priceInfo(sender ethcommon.Address) (*big.Rat, error)
 			return nil, err
 		}
 
-		overhead = overhead.Add(overhead, new(big.Rat).Inv(txCostMultiplier))
+		if txCostMultiplier.Cmp(big.NewRat(0, 1)) > 0 {
+			overhead = overhead.Add(overhead, new(big.Rat).Inv(txCostMultiplier))
+		}
+
 	}
 	// pricePerPixel = basePrice * overhead
 	fixedPrice, err := common.PriceToFixed(new(big.Rat).Mul(basePrice, overhead))

pm/recipient.go

@@ -215,8 +215,11 @@ func (r *recipient) TicketParams(sender ethcommon.Address, price *big.Rat) (*Tic
 }
 
 func (r *recipient) txCost() *big.Int {
+	gasPrice := big.NewInt(0)
 	// Fetch current gasprice from cache through gasPrice monitor
-	gasPrice := r.gpm.GasPrice()
+	if gp := r.gpm.GasPrice(); gp != nil {
+		gasPrice = gp
+	}
 	// Return txCost = redeemGas * gasPrice
 	return new(big.Int).Mul(big.NewInt(int64(r.cfg.RedeemGas)), gasPrice)
 }
@@ -286,7 +289,11 @@ func (r *recipient) TxCostMultiplier(sender ethcommon.Address) (*big.Rat, error)
 	// defaultTxCostMultiplier = defaultFaceValue / txCost
 	// Replacing defaultFaceValue with min(defaultFaceValue, MaxFloat(sender))
 	// Will scale the TxCostMultiplier according to the effective faceValue
-	return new(big.Rat).SetFrac(faceValue, r.txCost()), nil
+	txCost := r.txCost()
+	if txCost.Cmp(big.NewInt(0)) <= 0 {
+		return big.NewRat(0, 1), nil
+	}
+	return new(big.Rat).SetFrac(faceValue, txCost), nil
 }
 
 func (r *recipient) rand(seed *big.Int, sender ethcommon.Address, faceValue *big.Int, winProb *big.Int, expirationBlock *big.Int, price *big.Rat, ticketExpirationParams *TicketExpirationParams) *big.Int {

pm/recipient_test.go

@@ -589,6 +589,27 @@ func TestTxCostMultiplier_InsufficientReserve_ReturnsError(t *testing.T) {
 	assert.EqualError(t, err, errInsufficientSenderReserve.Error())
 }
 
+func TestTxCostMultiplier_ZeroTxCost_Returns_Zero(t *testing.T) {
+	sender, b, v, gm, sm, tm, cfg, _ := newRecipientFixtureOrFatal(t)
+	gm.gasPrice = big.NewInt(0)
+	recipient := RandAddress()
+	secret := [32]byte{3}
+	r := NewRecipientWithSecret(recipient, b, v, gm, sm, tm, secret, cfg)
+
+	mul, err := r.TxCostMultiplier(sender)
+	assert.Nil(t, err)
+	assert.Equal(t, big.NewRat(0, 1), mul)
+}
+
+func TestTxCost_NilGasPrice_ReturnsZero(t *testing.T) {
+	_, b, v, gm, sm, tm, cfg, _ := newRecipientFixtureOrFatal(t)
+	gm.gasPrice = nil
+	secret := [32]byte{3}
+	r := NewRecipientWithSecret(RandAddress(), b, v, gm, sm, tm, secret, cfg)
+	txCost := r.(*recipient).txCost()
+	assert.Equal(t, big.NewInt(0), txCost)
+}
+
 func TestSenderNoncesCleanupLoop(t *testing.T) {
 	assert := assert.New(t)