check the forge address balance before starting the node

cli/node/cfg.buidler.toml

@@ -51,6 +51,7 @@ ForgerAddress = "0x05c23b938a85ab26A36E6314a0D02080E9ca6BeD" # Non-Boot Coordina
 # ForgerAddressPrivateKey = "0x30f5fddb34cd4166adb2c6003fa6b18f380fd2341376be42cf1c7937004ac7a3"
 # ForgerAddress = "0xb4124ceb3451635dacedd11767f004d8a28c6ee7" # Boot Coordinator
 # ForgerAddressPrivateKey = "0xa8a54b2d8197bc0b19bb8a084031be71835580a01e70a45a13babd16c9bc1563"
+MinimumForgeAddressBalance = 0
 ConfirmBlocks = 10
 L1BatchTimeoutPerc = 0.6
 StartSlotBlocksDelay = 2

config/config.go

@@ -48,6 +48,10 @@ type ForgeBatchGasCost struct {
 type Coordinator struct {
 	// ForgerAddress is the address under which this coordinator is forging
 	ForgerAddress ethCommon.Address `validate:"required"`
+	// MinimumForgeAddressBalance is the minimum balance the forger address
+	// needs to start the coordinator in wei. Of set to 0, the coordinator
+	// will not check the balance before starting.
+	MinimumForgeAddressBalance *big.Int
 	// FeeAccount is the Hermez account that the coordinator uses to receive fees
 	FeeAccount struct {
 		// Address is the ethereum address of the account to receive fees

node/node.go

@@ -137,6 +137,23 @@ func NewNode(mode Mode, cfg *config.Node) (*Node, error) {
 		keyStore = ethKeystore.NewKeyStore(cfg.Coordinator.EthClient.Keystore.Path,
 			scryptN, scryptP)
 
+		balance, err := ethClient.BalanceAt(context.TODO(), cfg.Coordinator.ForgerAddress, nil)
+		if err != nil {
+			return nil, tracerr.Wrap(err)
+		}
+
+		minForgeBalance := cfg.Coordinator.MinimumForgeAddressBalance
+		if minForgeBalance != nil && balance.Cmp(minForgeBalance) == -1 {
+			return nil, tracerr.Wrap(fmt.Errorf(
+				"forger account balance is less than cfg.Coordinator.MinimumForgeAddressBalance: %v < %v",
+				balance.Int64(), minForgeBalance))
+		}
+		log.Infow("forger ethereum account balance",
+			"addr", cfg.Coordinator.ForgerAddress,
+			"balance", balance.Int64(),
+			"minForgeBalance", minForgeBalance.Int64(),
+		)
+
 		// Unlock Coordinator ForgerAddr in the keystore to make calls
 		// to ForgeBatch in the smart contract
 		if !keyStore.HasAddress(cfg.Coordinator.ForgerAddress) {