eth,server: move max gas price logic to gas price monitor

eth/backend.go

@@ -44,8 +44,7 @@ type Backend interface {
 	ethereum.LogFilterer
 	ethereum.ChainReader
 	ChainID(ctx context.Context) (*big.Int, error)
-	MaxGasPrice() *big.Int
-	SetMaxGasPrice(gp *big.Int)
+	GasPriceMonitor() *GasPriceMonitor
 }
 
 type backend struct {
@@ -55,7 +54,6 @@ type backend struct {
 	gpm          *GasPriceMonitor
 
 	sync.RWMutex
-	maxGasPrice *big.Int
 }
 
 func NewBackend(client *ethclient.Client, signer types.Signer, gpm *GasPriceMonitor) Backend {
@@ -95,27 +93,20 @@ func (b *backend) SuggestGasPrice(ctx context.Context) (*big.Int, error) {
 
 	// Use the gas price monitor instead of the ethereum client to suggest a gas price
 	gp := b.gpm.GasPrice()
+	maxGp := b.gpm.MaxGasPrice()
 
-	if b.maxGasPrice != nil && gp.Cmp(b.maxGasPrice) > 0 {
+	if maxGp != nil && gp.Cmp(maxGp) > 0 {
 		return nil, fmt.Errorf("current gas price exceeds maximum gas price max=%v GWei current=%v GWei",
-			FromWei(b.maxGasPrice, params.GWei),
+			FromWei(maxGp, params.GWei),
 			FromWei(gp, params.GWei),
 		)
 	}
 
 	return gp, nil
 }
 
-func (b *backend) SetMaxGasPrice(gp *big.Int) {
-	b.Lock()
-	defer b.Unlock()
-	b.maxGasPrice = gp
-}
-
-func (b *backend) MaxGasPrice() *big.Int {
-	b.RLock()
-	defer b.RUnlock()
-	return b.maxGasPrice
+func (b *backend) GasPriceMonitor() *GasPriceMonitor {
+	return b.gpm
 }
 
 type txLog struct {

eth/backend_test.go

@@ -92,10 +92,3 @@ func TestSendTransaction_SendErr_DontUpdateNonce(t *testing.T) {
 
 	assert.Equal(t, nonceLockBefore.nonce, nonceLockAfter.nonce)
 }
-
-func TestBackend_SetMaxGasPrice(t *testing.T) {
-	gp := big.NewInt(10)
-	backend := &backend{}
-	backend.SetMaxGasPrice(gp)
-	assert.Equal(t, gp, backend.MaxGasPrice())
-}

eth/gaspricemonitor.go

@@ -34,6 +34,8 @@ type GasPriceMonitor struct {
 	gasPrice *big.Int
 	// minGasPrice is the minimum gas price below which polled values will be discarded
 	minGasPrice *big.Int
+	// maxGasPrice is the max acceptable gas price defined by the user
+	maxGasPrice *big.Int
 
 	// update is a channel used to send notifications to a listener
 	// when the gas price is updated
@@ -125,6 +127,18 @@ func (gpm *GasPriceMonitor) Stop() error {
 	return nil
 }
 
+func (gpm *GasPriceMonitor) SetMaxGasPrice(gp *big.Int) {
+	gpm.gasPriceMu.Lock()
+	defer gpm.gasPriceMu.Unlock()
+	gpm.maxGasPrice = gp
+}
+
+func (gpm *GasPriceMonitor) MaxGasPrice() *big.Int {
+	gpm.gasPriceMu.RLock()
+	defer gpm.gasPriceMu.RUnlock()
+	return gpm.maxGasPrice
+}
+
 func (gpm *GasPriceMonitor) fetchAndUpdateGasPrice(ctx context.Context) error {
 	gasPrice, err := gpm.gpo.SuggestGasPrice(ctx)
 	if err != nil {

eth/gaspricemonitor_test.go

@@ -204,3 +204,10 @@ func TestStop(t *testing.T) {
 	_, ok := (<-gpm.update)
 	assert.False(ok)
 }
+
+func TestSetMaxGasPrice(t *testing.T) {
+	gp := big.NewInt(10)
+	gpm := &GasPriceMonitor{}
+	gpm.SetMaxGasPrice(gp)
+	assert.Equal(t, gp, gpm.MaxGasPrice())
+}

server/webserver.go

@@ -1147,7 +1147,7 @@ func (s *LivepeerServer) cliWebServerHandlers(bindAddr string) *http.ServeMux {
 			respondWith400(w, err.Error())
 			return
 		}
-		gprice := b.MaxGasPrice()
+		gprice := b.GasPriceMonitor().MaxGasPrice()
 		if gprice == nil {
 			w.Write([]byte(""))
 		} else {
@@ -1175,7 +1175,7 @@ func (s *LivepeerServer) cliWebServerHandlers(bindAddr string) *http.ServeMux {
 			respondWith400(w, err.Error())
 			return
 		}
-		b.SetMaxGasPrice(gprice)
+		b.GasPriceMonitor().SetMaxGasPrice(gprice)
 	})
 
 	mux.Handle("/currentBlock", currentBlockHandler(s.LivepeerNode.Database))