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sweep: add wallet inputs to reach dust limit

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This commit allows sweeper to sweep inputs that on its own are not able
to form a sweep transaction that meets the dust limit.

This functionality is useful for sweeping small outputs. In the future,
this will be particularly important to sweep anchors. Anchors will
typically be spent with a relatively large fee to pay for the parent tx.
It will then be necessary to attach an additional wallet utxo.
This commit is contained in:
Joost Jager
2019-12-10 16:06:45 +01:00
parent 8353b6fd6e
commit e01600fdb8
7 changed files with 299 additions and 34 deletions
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27
sweep/txgenerator.go
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@@ -38,7 +38,7 @@ type inputSet []input.Input
// dust limit are returned.
func generateInputPartitionings(sweepableInputs []txInput,
relayFeePerKW, feePerKW chainfee.SatPerKWeight,
maxInputsPerTx int) ([]inputSet, error) {
maxInputsPerTx int, wallet Wallet) ([]inputSet, error) {
// Sort input by yield. We will start constructing input sets starting
// with the highest yield inputs. This is to prevent the construction
@@ -78,7 +78,7 @@ func generateInputPartitionings(sweepableInputs []txInput,
// condition that the tx will be published with the specified
// fee rate.
txInputs := newTxInputSet(
feePerKW, relayFeePerKW, maxInputsPerTx,
wallet, feePerKW, relayFeePerKW, maxInputsPerTx,
)
// From the set of sweepable inputs, keep adding inputs to the
@@ -92,18 +92,27 @@ func generateInputPartitionings(sweepableInputs []txInput,
return sets, nil
}
// Check the current output value and add wallet utxos if
// needed to push the output value to the lower limit.
if err := txInputs.tryAddWalletInputsIfNeeded(); err != nil {
return nil, err
}
// If the output value of this block of inputs does not reach
// the dust limit, stop sweeping. Because of the sorting,
// continuing with the remaining inputs will only lead to sets
// with a even lower output value.
// with an even lower output value.
if !txInputs.dustLimitReached() {
log.Debugf("Set value %v below dust limit of %v",
txInputs.outputValue, txInputs.dustLimit)
return sets, nil
}
log.Infof("Candidate sweep set of size=%v, has yield=%v",
inputCount, txInputs.outputValue)
log.Infof("Candidate sweep set of size=%v (+%v wallet inputs), "+
"has yield=%v, weight=%v",
inputCount, len(txInputs.inputs)-inputCount,
txInputs.outputValue-txInputs.walletInputTotal,
txInputs.weightEstimate.Weight())
sets = append(sets, txInputs.inputs)
sweepableInputs = sweepableInputs[inputCount:]
@@ -119,12 +128,12 @@ func createSweepTx(inputs []input.Input, outputPkScript []byte,
inputs, txWeight := getWeightEstimate(inputs)
log.Infof("Creating sweep transaction for %v inputs (%s) "+
"using %v sat/kw", len(inputs), inputTypeSummary(inputs),
int64(feePerKw))
txFee := feePerKw.FeeForWeight(txWeight)
log.Infof("Creating sweep transaction for %v inputs (%s) "+
"using %v sat/kw, tx_fee=%v", len(inputs),
inputTypeSummary(inputs), int64(feePerKw), txFee)
// Sum up the total value contained in the inputs.
var totalSum btcutil.Amount
for _, o := range inputs {