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Calculate the minimum tx fee when creating transactions.

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This commit is contained in:
Josh Rickmar 2013-12-03 19:22:47 -05:00
parent 378af40329
commit 48a685e85e
3 changed files with 265 additions and 125 deletions
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27
cmdmgr.go
View file

@ -566,15 +566,9 @@ func SendFrom(frontend chan []byte, icmd btcjson.Cmd) {
cmd.ToAddress: cmd.Amount,
}
// Get fee to add to tx.
// TODO(jrick): this needs to be fee per kB.
TxFee.Lock()
fee := TxFee.i
TxFee.Unlock()
// Create transaction, replying with an error if the creation
// was not successful.
createdTx, err := a.txToPairs(pairs, fee, cmd.MinConf)
createdTx, err := a.txToPairs(pairs, cmd.MinConf)
switch {
case err == ErrNonPositiveAmount:
e := &btcjson.Error{
@ -664,15 +658,9 @@ func SendMany(frontend chan []byte, icmd btcjson.Cmd) {
return
}
// Get fee to add to tx.
// TODO(jrick): this needs to be fee per kB.
TxFee.Lock()
fee := TxFee.i
TxFee.Unlock()
// Create transaction, replying with an error if the creation
// was not successful.
createdTx, err := a.txToPairs(cmd.Amounts, fee, cmd.MinConf)
createdTx, err := a.txToPairs(cmd.Amounts, cmd.MinConf)
switch {
case err == ErrNonPositiveAmount:
e := &btcjson.Error{
@ -840,7 +828,7 @@ func handleSendRawTxReply(frontend chan []byte, icmd btcjson.Cmd,
return true
}
// SetTxFee sets the global transaction fee added to transactions.
// SetTxFee sets the transaction fee per kilobyte added to transactions.
func SetTxFee(frontend chan []byte, icmd btcjson.Cmd) {
// Type assert icmd to access parameters.
cmd, ok := icmd.(*btcjson.SetTxFeeCmd)
@ -860,12 +848,9 @@ func SetTxFee(frontend chan []byte, icmd btcjson.Cmd) {
}
// Set global tx fee.
//
// TODO(jrick): this must be a fee per kB.
// TODO(jrick): need to notify all frontends of new tx fee.
TxFee.Lock()
TxFee.i = cmd.Amount
TxFee.Unlock()
TxFeeIncrement.Lock()
TxFeeIncrement.i = cmd.Amount
TxFeeIncrement.Unlock()
// A boolean true result is returned upon success.
ReplySuccess(frontend, cmd.Id(), true)

213
createtx.go
View file

@ -46,14 +46,18 @@ var ErrNonPositiveAmount = errors.New("amount is not positive")
// negative.
var ErrNegativeFee = errors.New("fee is negative")
// TxFee represents the global transaction fee added to newly-created
// transactions and sent as a reward to the block miner. i is measured
// in satoshis.
var TxFee = struct {
// minTxFee is the default minimum transation fee (0.0001 BTC,
// measured in satoshis) added to transactions requiring a fee.
const minTxFee = 10000
// TxFeeIncrement represents the global transaction fee per KB of Tx
// added to newly-created transactions and sent as a reward to the block
// miner. i is measured in satoshis.
var TxFeeIncrement = struct {
sync.Mutex
i int64
}{
i: 10000, // This is a fee of 0.0001 BTC.
i: minTxFee,
}
// CreatedTx is a type holding information regarding a newly-created
@ -64,7 +68,7 @@ type CreatedTx struct {
time time.Time
inputs []*tx.Utxo
outputs []tx.Pair
btcout int64
btcspent int64
fee int64
changeAddr string
changeUtxo *tx.Utxo
@ -152,11 +156,11 @@ func selectInputs(s tx.UtxoStore, amt uint64, minconf int) (inputs []*tx.Utxo, b
// address, changeUtxo will point to a unconfirmed (height = -1, zeroed
// block hash) Utxo. ErrInsufficientFunds is returned if there are not
// enough eligible unspent outputs to create the transaction.
func (w *Account) txToPairs(pairs map[string]int64, fee int64, minconf int) (*CreatedTx, error) {
func (a *Account) txToPairs(pairs map[string]int64, minconf int) (*CreatedTx, error) {
// Recorded unspent transactions should not be modified until this
// finishes.
w.UtxoStore.RLock()
defer w.UtxoStore.RUnlock()
a.UtxoStore.RLock()
defer a.UtxoStore.RUnlock()
// Create a new transaction which will include all input scripts.
msgtx := btcwire.NewMsgTx()
@ -171,17 +175,6 @@ func (w *Account) txToPairs(pairs map[string]int64, fee int64, minconf int) (*Cr
amt += v
}
if fee < 0 {
return nil, ErrNegativeFee
}
// Select unspent outputs to be used in transaction.
inputs, btcout, err := selectInputs(w.UtxoStore.s, uint64(amt+fee),
minconf)
if err != nil {
return nil, err
}
// outputs is a tx.Pair slice representing each output that is created
// by the transaction.
outputs := make([]tx.Pair, 0, len(pairs)+1)
@ -209,31 +202,61 @@ func (w *Account) txToPairs(pairs map[string]int64, fee int64, minconf int) (*Cr
outputs = append(outputs, out)
}
// Check if there are leftover unspent outputs, and return coins back to
// a new address we own.
var changeUtxo *tx.Utxo
var changeAddr string
if btcout > uint64(amt+fee) {
// Create a new address to spend leftover outputs to.
// TODO(jrick): use the next chained address, not the next unused.
var err error
// Get current block's height and hash.
bs, err := GetCurBlock()
if err != nil {
return nil, err
}
changeAddr, err = w.NextChainedAddress(&bs)
// Make a copy of msgtx before any inputs are added. This will be
// used as a starting point when trying a fee and starting over with
// a higher fee if not enough was originally chosen.
txNoInputs := msgtx.Copy()
// These are nil/zeroed until a change address is needed, and reused
// again in case a change utxo has already been chosen.
var changeAddrHash []byte
var changeAddr string
var btcspent int64
var selectedInputs []*tx.Utxo
var finalChangeUtxo *tx.Utxo
// Get the number of satoshis to increment fee by when searching for
// the minimum tx fee needed.
var fee int64 = 0
for {
msgtx = txNoInputs.Copy()
// Select unspent outputs to be used in transaction based on the amount
// neededing to sent, and the current fee estimation.
inputs, btcin, err := selectInputs(a.UtxoStore.s, uint64(amt+fee),
minconf)
if err != nil {
return nil, err
}
// Check if there are leftover unspent outputs, and return coins back to
// a new address we own.
var changeUtxo *tx.Utxo
change := btcin - uint64(amt+fee)
if change > 0 {
// Create a new address to spend leftover outputs to.
// Get a new change address if one has not already been found.
if changeAddrHash == nil {
changeAddr, err = a.NextChainedAddress(&bs)
if err != nil {
return nil, fmt.Errorf("failed to get next address: %s", err)
}
// Spend change
change := btcout - uint64(amt+fee)
changeAddrHash, _, err := btcutil.DecodeAddress(changeAddr)
changeAddrHash, _, err = btcutil.DecodeAddress(changeAddr)
if err != nil {
return nil, fmt.Errorf("cannot decode new address: %s", err)
}
}
// Spend change.
pkScript, err := btcscript.PayToPubKeyHashScript(changeAddrHash)
if err != nil {
return nil, fmt.Errorf("cannot create txout script: %s", err)
@ -252,13 +275,6 @@ func (w *Account) txToPairs(pairs map[string]int64, fee int64, minconf int) (*Cr
Subscript: pkScript,
}
copy(changeUtxo.AddrHash[:], changeAddrHash)
// Add change to outputs.
out := tx.Pair{
Amount: int64(change),
PubkeyHash: changeAddrHash,
}
outputs = append(outputs, out)
}
// Selected unspent outputs become new transaction's inputs.
@ -266,29 +282,61 @@ func (w *Account) txToPairs(pairs map[string]int64, fee int64, minconf int) (*Cr
msgtx.AddTxIn(btcwire.NewTxIn((*btcwire.OutPoint)(&ip.Out), nil))
}
for i, ip := range inputs {
addrstr, err := btcutil.EncodeAddress(ip.AddrHash[:], w.Wallet.Net())
addrstr, err := btcutil.EncodeAddress(ip.AddrHash[:],
a.Wallet.Net())
if err != nil {
return nil, err
}
privkey, err := w.AddressKey(addrstr)
privkey, err := a.AddressKey(addrstr)
if err == wallet.ErrWalletLocked {
return nil, wallet.ErrWalletLocked
} else if err != nil {
return nil, fmt.Errorf("cannot get address key: %v", err)
}
ai, err := w.AddressInfo(addrstr)
ai, err := a.AddressInfo(addrstr)
if err != nil {
return nil, fmt.Errorf("cannot get address info: %v", err)
}
sigscript, err := btcscript.SignatureScript(msgtx, i,
ip.Subscript, btcscript.SigHashAll, privkey, ai.Compressed)
ip.Subscript, btcscript.SigHashAll, privkey,
ai.Compressed)
if err != nil {
return nil, fmt.Errorf("cannot create sigscript: %s", err)
}
msgtx.TxIn[i].SignatureScript = sigscript
}
noFeeAllowed := allowFree(bs.Height, inputs, msgtx.SerializeSize())
if minFee := minimumFee(msgtx, noFeeAllowed); fee < minFee {
fee = minFee
} else {
// Fill Tx hash of change outpoint with transaction hash.
if changeUtxo != nil {
txHash, err := msgtx.TxSha()
if err != nil {
return nil, fmt.Errorf("cannot create transaction hash: %s", err)
}
copy(changeUtxo.Out.Hash[:], txHash[:])
// Add change to outputs.
out := tx.Pair{
Amount: int64(change),
PubkeyHash: changeAddrHash,
}
outputs = append(outputs, out)
finalChangeUtxo = changeUtxo
}
selectedInputs = inputs
btcspent = int64(btcin)
break
}
}
// Validate msgtx before returning the raw transaction.
flags := btcscript.ScriptCanonicalSignatures
bip16 := time.Now().After(btcscript.Bip16Activation)
@ -296,8 +344,8 @@ func (w *Account) txToPairs(pairs map[string]int64, fee int64, minconf int) (*Cr
flags |= btcscript.ScriptBip16
}
for i, txin := range msgtx.TxIn {
engine, err := btcscript.NewScript(txin.SignatureScript, inputs[i].Subscript, i,
msgtx, flags)
engine, err := btcscript.NewScript(txin.SignatureScript,
selectedInputs[i].Subscript, i, msgtx, flags)
if err != nil {
return nil, fmt.Errorf("cannot create script engine: %s", err)
}
@ -306,26 +354,77 @@ func (w *Account) txToPairs(pairs map[string]int64, fee int64, minconf int) (*Cr
}
}
// Fill Tx hash of change outpoint with transaction hash.
if changeUtxo != nil {
txHash, err := msgtx.TxSha()
if err != nil {
return nil, fmt.Errorf("cannot create transaction hash: %s", err)
}
copy(changeUtxo.Out.Hash[:], txHash[:])
}
buf := new(bytes.Buffer)
msgtx.BtcEncode(buf, btcwire.ProtocolVersion)
info := &CreatedTx{
rawTx: buf.Bytes(),
time: time.Now(),
inputs: inputs,
inputs: selectedInputs,
outputs: outputs,
btcout: int64(btcout),
btcspent: btcspent,
fee: fee,
changeAddr: changeAddr,
changeUtxo: changeUtxo,
changeUtxo: finalChangeUtxo,
}
return info, nil
}
// minimumFee calculates the minimum fee required for a transaction.
// If allowFree is true, a fee may be zero so long as the entire
// transaction has a serialized length less than 1 kilobyte
// and none of the outputs contain a value less than 1 bitcent.
// Otherwise, the fee will be calculated using TxFeeIncrement,
// incrementing the fee for each kilobyte of transaction.
func minimumFee(tx *btcwire.MsgTx, allowFree bool) int64 {
txLen := tx.SerializeSize()
TxFeeIncrement.Lock()
incr := TxFeeIncrement.i
TxFeeIncrement.Unlock()
fee := int64(1+txLen/1000) * incr
if allowFree && txLen < 1000 {
fee = 0
}
if fee < incr {
for _, txOut := range tx.TxOut {
if txOut.Value < btcutil.SatoshiPerBitcent {
return incr
}
}
}
if fee < 0 || fee > btcutil.MaxSatoshi {
fee = btcutil.MaxSatoshi
}
return fee
}
// allowFree calculates the transaction priority and checks that the
// priority reaches a certain threshhold. If the threshhold is
// reached, a free transaction fee is allowed.
func allowFree(curHeight int32, inputs []*tx.Utxo, txSize int) bool {
const blocksPerDayEstimate = 144
const txSizeEstimate = 250
var weightedSum int64
for _, utxo := range inputs {
depth := chainDepth(utxo.Height, curHeight)
weightedSum += int64(utxo.Amt) * int64(depth)
}
priority := float64(weightedSum) / float64(txSize)
return priority > float64(btcutil.SatoshiPerBitcoin)*blocksPerDayEstimate/txSizeEstimate
}
// chainDepth returns the chaindepth of a target given the current
// blockchain height.
func chainDepth(target, current int32) int32 {
if target == -1 {
// target is not yet in a block.
return 0
}
// target is in a block.
return current - target + 1
}

64
createtx_test.go
View file

@ -9,6 +9,62 @@ import (
"testing"
)
type allowFreeTest struct {
name string
inputs []*tx.Utxo
curHeight int32
txSize int
free bool
}
var allowFreeTests = []allowFreeTest{
allowFreeTest{
name: "priority < 57,600,000",
inputs: []*tx.Utxo{
&tx.Utxo{
Amt: uint64(btcutil.SatoshiPerBitcoin),
Height: 0,
},
},
curHeight: 142, // 143 confirmations
txSize: 250,
free: false,
},
allowFreeTest{
name: "priority == 57,600,000",
inputs: []*tx.Utxo{
&tx.Utxo{
Amt: uint64(btcutil.SatoshiPerBitcoin),
Height: 0,
},
},
curHeight: 143, // 144 confirmations
txSize: 250,
free: false,
},
allowFreeTest{
name: "priority > 57,600,000",
inputs: []*tx.Utxo{
&tx.Utxo{
Amt: uint64(btcutil.SatoshiPerBitcoin),
Height: 0,
},
},
curHeight: 144, // 145 confirmations
txSize: 250,
free: true,
},
}
func TestAllowFree(t *testing.T) {
for _, test := range allowFreeTests {
calcFree := allowFree(test.curHeight, test.inputs, test.txSize)
if calcFree != test.free {
t.Errorf("Allow free test '%v' failed.", test.name)
}
}
}
func TestFakeTxs(t *testing.T) {
// First we need a wallet.
w, err := wallet.NewWallet("banana wallet", "", []byte("banana"),
@ -17,7 +73,7 @@ func TestFakeTxs(t *testing.T) {
t.Errorf("Can not create encrypted wallet: %s", err)
return
}
btcw := &Account{
a := &Account{
Wallet: w,
}
@ -50,9 +106,9 @@ func TestFakeTxs(t *testing.T) {
return
}
utxo.Subscript = tx.PkScript(ss)
utxo.Amt = 10000
utxo.Amt = 1000000
utxo.Height = 12345
btcw.UtxoStore.s = append(btcw.UtxoStore.s, utxo)
a.UtxoStore.s = append(a.UtxoStore.s, utxo)
// Fake our current block height so btcd doesn't need to be queried.
curBlock.BlockStamp.Height = 12346
@ -61,7 +117,7 @@ func TestFakeTxs(t *testing.T) {
pairs := map[string]int64{
"17XhEvq9Nahdj7Xe1nv6oRe1tEmaHUuynH": 5000,
}
_, err = btcw.txToPairs(pairs, 100, 0)
_, err = a.txToPairs(pairs, 0)
if err != nil {
t.Errorf("Tx creation failed: %s", err)
return