fix(rpc): optimize eth_getBalance endpoint (#1169)

* optimize get balance endpoint

* add comment

* add changelog

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

CHANGELOG.md

@@ -46,6 +46,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### Improvements
 
 * (feemarket) [\#1165](https://github.com/evmos/ethermint/pull/1165) Add hint in specs about different gas terminology for gas in Cosmos and Ethereum.
+* (rpc) [\#1169](https://github.com/evmos/ethermint/pull/1169) Remove unnecessary queries from `getBlockNumber` function
 
 ## [v0.17.0] - 2022-06-27
 

rpc/backend/backend.go

@@ -61,6 +61,7 @@ type EVMBackend interface {
 	CurrentHeader() *ethtypes.Header
 	HeaderByNumber(blockNum types.BlockNumber) (*ethtypes.Header, error)
 	HeaderByHash(blockHash common.Hash) (*ethtypes.Header, error)
+	GetBlockNumberByHash(blockHash common.Hash) (*big.Int, error)
 	PendingTransactions() ([]*sdk.Tx, error)
 	GetTransactionCount(address common.Address, blockNum types.BlockNumber) (*hexutil.Uint64, error)
 	SendTransaction(args evmtypes.TransactionArgs) (common.Hash, error)

rpc/backend/evm_backend.go

@@ -369,6 +369,18 @@ func (b *Backend) HeaderByNumber(blockNum types.BlockNumber) (*ethtypes.Header,
 	return ethHeader, nil
 }
 
+// GetBlockNumberByHash returns the block height of given block hash
+func (b *Backend) GetBlockNumberByHash(blockHash common.Hash) (*big.Int, error) {
+	resBlock, err := b.GetTendermintBlockByHash(blockHash)
+	if err != nil {
+		return nil, err
+	}
+	if resBlock == nil {
+		return nil, errors.Errorf("block not found for hash %s", blockHash.Hex())
+	}
+	return big.NewInt(resBlock.Block.Height), nil
+}
+
 // HeaderByHash returns the block header identified by hash.
 func (b *Backend) HeaderByHash(blockHash common.Hash) (*ethtypes.Header, error) {
 	resBlock, err := b.GetTendermintBlockByHash(blockHash)

rpc/namespaces/ethereum/eth/api.go

@@ -1138,11 +1138,11 @@ func (e *PublicAPI) getBlockNumber(blockNrOrHash rpctypes.BlockNumberOrHash) (rp
 	case blockNrOrHash.BlockHash == nil && blockNrOrHash.BlockNumber == nil:
 		return rpctypes.EthEarliestBlockNumber, fmt.Errorf("types BlockHash and BlockNumber cannot be both nil")
 	case blockNrOrHash.BlockHash != nil:
-		blockHeader, err := e.backend.HeaderByHash(*blockNrOrHash.BlockHash)
+		blockNumber, err := e.backend.GetBlockNumberByHash(*blockNrOrHash.BlockHash)
 		if err != nil {
 			return rpctypes.EthEarliestBlockNumber, err
 		}
-		return rpctypes.NewBlockNumber(blockHeader.Number), nil
+		return rpctypes.NewBlockNumber(blockNumber), nil
 	case blockNrOrHash.BlockNumber != nil:
 		return *blockNrOrHash.BlockNumber, nil
 	default: