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Merge pull request #89 from unicornultrafoundation/fix/revert_estimat…
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…e_gas

Revert "[WIP] Optimize EstimateGas API"
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@lewtran
lewtran authored Jan 31, 2024
2 parents 886fdbc + 3c7c817 commit d285ed7
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Showing 2 changed files with 51 additions and 78 deletions.
127 changes: 50 additions & 77 deletions ethapi/api.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1032,17 +1032,11 @@ func DoCall(ctx context.Context, b Backend, args TransactionArgs, blockNrOrHash
if state == nil || err != nil {
return nil, err
}

return doCall(ctx, b, args, state, header, overrides, timeout, globalGasCap)
}

func doCall(ctx context.Context, b Backend, args TransactionArgs, state *state.StateDB, header *evmcore.EvmHeader,
overrides *StateOverride, timeout time.Duration, globalGasCap uint64) (*evmcore.ExecutionResult, error) {
if err := overrides.Apply(state); err != nil {
return nil, err
}
// Setup context so it may be cancelled the call has completed
// or, in case of unmetered gas, set up a context with a timeout.
// or, in case of unmetered gas, setup a context with a timeout.
var cancel context.CancelFunc
if timeout > 0 {
ctx, cancel = context.WithTimeout(ctx, timeout)
Expand Down Expand Up @@ -1136,30 +1130,13 @@ func (s *PublicBlockChainAPI) Call(ctx context.Context, args TransactionArgs, bl
return result.Return(), result.Err
}

// executeEstimate is a helper that executes the transaction under a given gas limit and returns
// true if the transaction fails for a reason that might be related to not enough gas. A non-nil
// error means execution failed due to reasons unrelated to the gas limit.
func executeEstimate(ctx context.Context, b Backend, args TransactionArgs, state *state.StateDB, header *evmcore.EvmHeader, gasCap uint64, gasLimit uint64) (bool, *evmcore.ExecutionResult, error) {
args.Gas = (*hexutil.Uint64)(&gasLimit)
result, err := doCall(ctx, b, args, state, header, nil, 0, gasCap)
if err != nil {
if errors.Is(err, evmcore.ErrIntrinsicGas) {
return true, nil, nil // Special case, raise gas limit
}
return true, nil, err // Bail out
}
return result.Failed(), result, nil
}

// DoEstimateGas returns the lowest possible gas limit that allows the transaction to run
// successfully at block `blockNrOrHash`. It returns error if the transaction would revert, or if
// there are unexpected failures. The gas limit is capped by both `args.Gas` (if non-nil &
// non-zero) and `gasCap` (if non-zero).
func DoEstimateGas(ctx context.Context, b Backend, args TransactionArgs, blockNrOrHash rpc.BlockNumberOrHash, overrides *StateOverride, gasCap uint64) (hexutil.Uint64, error) {
// Binary search the gas limit, as it may need to be higher than the amount used
// DoEstimateGas - binary search the gas requirement, as it may be higher than the amount used
func DoEstimateGas(ctx context.Context, b Backend, args TransactionArgs, blockNrOrHash rpc.BlockNumberOrHash, gasCap uint64) (hexutil.Uint64, error) {
// Binary search the gas requirement, as it may be higher than the amount used
var (
lo uint64 // lowest-known gas limit where tx execution fails
hi uint64 // lowest-known gas limit where tx execution succeeds
lo uint64 = params.TxGas - 1
hi uint64
cap uint64
)
// Use zero address if sender unspecified.
if args.From == nil {
Expand All @@ -1182,22 +1159,17 @@ func DoEstimateGas(ctx context.Context, b Backend, args TransactionArgs, blockNr
} else {
feeCap = common.Big0
}

state, header, err := b.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
if state == nil || err != nil {
return 0, err
}
if err := overrides.Apply(state); err != nil {
return 0, err
}

// Recap the highest gas limit with account's available balance.
if feeCap.BitLen() != 0 {
state, _, err := b.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
if state == nil || err != nil {
return 0, err
}
balance := state.GetBalance(*args.From) // from can't be nil
available := new(big.Int).Set(balance)
if args.Value != nil {
if args.Value.ToInt().Cmp(available) >= 0 {
return 0, evmcore.ErrInsufficientFundsForTransfer
return 0, errors.New("insufficient funds for transfer")
}
available.Sub(available, args.Value.ToInt())
}
Expand All @@ -1219,42 +1191,30 @@ func DoEstimateGas(ctx context.Context, b Backend, args TransactionArgs, blockNr
log.Warn("Caller gas above allowance, capping", "requested", hi, "cap", gasCap)
hi = gasCap
}
cap = hi

// We first execute the transaction at the highest allowable gas limit, since if this fails we
// can return error immediately.
failed, result, err := executeEstimate(ctx, b, args, state.Copy(), header, gasCap, hi)
if err != nil {
return 0, err
}
if failed {
if result != nil && result.Err != vm.ErrOutOfGas {
if len(result.Revert()) > 0 {
return 0, newRevertError(result)
// Create a helper to check if a gas allowance results in an executable transaction
executable := func(gas uint64) (bool, *evmcore.ExecutionResult, error) {
args.Gas = (*hexutil.Uint64)(&gas)

result, err := DoCall(ctx, b, args, blockNrOrHash, nil, 0, gasCap)
if err != nil {
if errors.Is(err, evmcore.ErrIntrinsicGas) {
return true, nil, nil // Special case, raise gas limit
}
return 0, result.Err
return true, nil, err // Bail out
}
return 0, fmt.Errorf("gas required exceeds allowance (%d)", hi)
return result.Failed(), result, nil
}
// For almost any transaction, the gas consumed by the unconstrained execution above
// lower-bounds the gas limit required for it to succeed. One exception is those txs that
// explicitly check gas remaining in order to successfully execute within a given limit, but we
// probably don't want to return a lowest possible gas limit for these cases anyway.
lo = result.UsedGas - 1

// Binary search for the smallest gas limit that allows the tx to execute successfully.
// Execute the binary search and hone in on an executable gas limit
for lo+1 < hi {
mid := (hi + lo) / 2
if mid > lo*2 {
// Most txs don't need much higher gas limit than their gas used, and most txs don't
// require near the full block limit of gas, so the selection of where to bisect the
// range here is skewed to favor the low side.
mid = lo * 2
}
failed, _, err = executeEstimate(ctx, b, args, state.Copy(), header, gasCap, mid)
failed, _, err := executable(mid)

// If the error is not nil(consensus error), it means the provided message
// call or transaction will never be accepted no matter how much gas it is
// assigned. Return the error directly, don't struggle any more.
if err != nil {
// This should not happen under normal conditions since if we make it this far the
// transaction had run without error at least once before.
log.Error("execution error in estimate gas", "err", err)
return 0, err
}
if failed {
Expand All @@ -1263,21 +1223,34 @@ func DoEstimateGas(ctx context.Context, b Backend, args TransactionArgs, blockNr
hi = mid
}
}
// Reject the transaction as invalid if it still fails at the highest allowance
if hi == cap {
failed, result, err := executable(hi)
if err != nil {
return 0, err
}
if failed {
if result != nil && result.Err != vm.ErrOutOfGas {
if len(result.Revert()) > 0 {
return 0, newRevertError(result)
}
return 0, result.Err
}
// Otherwise, the specified gas cap is too low
return 0, fmt.Errorf("gas required exceeds allowance (%d)", cap)
}
}
return hexutil.Uint64(hi), nil
}

// EstimateGas returns the lowest possible gas limit that allows the transaction to run
// successfully at block `blockNrOrHash`, or the latest block if `blockNrOrHash` is unspecified. It
// returns error if the transaction would revert or if there are unexpected failures. The returned
// value is capped by both `args.Gas` (if non-nil & non-zero) and the backend's RPCGasCap
// configuration (if non-zero).
func (s *PublicBlockChainAPI) EstimateGas(ctx context.Context, args TransactionArgs, blockNrOrHash *rpc.BlockNumberOrHash,
overrides *StateOverride) (hexutil.Uint64, error) {
// EstimateGas returns an estimate of the amount of gas needed to execute the
// given transaction against the current pending block.
func (s *PublicBlockChainAPI) EstimateGas(ctx context.Context, args TransactionArgs, blockNrOrHash *rpc.BlockNumberOrHash) (hexutil.Uint64, error) {
bNrOrHash := rpc.BlockNumberOrHashWithNumber(rpc.LatestBlockNumber)
if blockNrOrHash != nil {
bNrOrHash = *blockNrOrHash
}
return DoEstimateGas(ctx, s.b, args, bNrOrHash, overrides, s.b.RPCGasCap())
return DoEstimateGas(ctx, s.b, args, bNrOrHash, s.b.RPCGasCap())
}

// ExecutionResult groups all structured logs emitted by the EVM
Expand Down
2 changes: 1 addition & 1 deletion ethapi/transaction_args.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -148,7 +148,7 @@ func (args *TransactionArgs) setDefaults(ctx context.Context, b Backend) error {
AccessList: args.AccessList,
}
pendingBlockNr := rpc.BlockNumberOrHashWithNumber(rpc.PendingBlockNumber)
estimated, err := DoEstimateGas(ctx, b, callArgs, pendingBlockNr, nil, b.RPCGasCap())
estimated, err := DoEstimateGas(ctx, b, callArgs, pendingBlockNr, b.RPCGasCap())
if err != nil {
return err
}
Expand Down

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