Fix accelerator revenue impact always showing zero
The old approach compared coinbasevalue from two getblocktemplate calls, but new mempool arrivals between calls masked the displacement loss. Now uses a single template snapshot to find the marginal (lowest fee-rate) transaction that would be displaced and reports its fee as the revenue cost.
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satoshi
@@ -43,6 +43,54 @@ type AccelerateResult struct {
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FeeLostError string `json:"fee_lost_error,omitempty"`
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}
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// marginalFeeLost estimates the fee revenue lost by inserting a boosted
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// transaction into the template. It finds the lowest fee-rate transaction
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// in the current template (the one that would be displaced) and returns
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// the difference: displaced_fee - boosted_tx_real_fee. If the boosted tx
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// is already in the template or the template has room, returns 0.
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func marginalFeeLost(tpl *bitcoind.BlockTemplate, txid string, txVsize int64) int64 {
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if len(tpl.Transactions) == 0 {
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return 0
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}
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// Check if the tx is already in the template (nothing displaced).
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for _, tx := range tpl.Transactions {
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if tx.Txid == txid {
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return 0
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}
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}
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// Find the marginal transaction: lowest fee-rate in the template.
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var marginal *bitcoind.TemplateTx
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var marginalRate float64 = math.MaxFloat64
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for i := range tpl.Transactions {
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tx := &tpl.Transactions[i]
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// Weight to vsize: ceil(weight/4)
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vsize := (tx.Weight + 3) / 4
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if vsize <= 0 {
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continue
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}
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rate := float64(tx.Fee) / float64(vsize)
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if rate < marginalRate {
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marginalRate = rate
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marginal = tx
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}
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}
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if marginal == nil {
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return 0
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}
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// The displaced tx's fee is the revenue we lose. We don't add the
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// boosted tx's real fee back because the pool never had it — the tx
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// wasn't in the template before the boost.
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lost := marginal.Fee
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if lost < 0 {
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lost = 0
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}
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return lost
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}
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// Accelerate boosts a transaction to the target feerate (sat/vB).
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func (s *Service) Accelerate(ctx context.Context, txid string, targetFeerateVB float64) (*AccelerateResult, error) {
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if targetFeerateVB > MaxFeerateVB {
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@@ -68,38 +116,26 @@ func (s *Service) Accelerate(ctx context.Context, txid string, targetFeerateVB f
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targetFeerateVB, modifiedFeeSats/float64(entry.Vsize))
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}
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// Snapshot coinbasevalue BEFORE the boost to measure actual impact.
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var coinbaseBefore int64
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// Estimate revenue impact from the pre-boost template. The boosted tx
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// will displace the marginal (lowest fee-rate) transaction in the
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// template. We compute this from the single template snapshot to avoid
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// a race with new mempool arrivals between two getblocktemplate calls.
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var feeLost int64
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var tplErr string
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tplBefore, err := s.RPC.GetBlockTemplate(ctx)
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tpl, err := s.RPC.GetBlockTemplate(ctx)
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if err != nil {
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tplErr = fmt.Sprintf("getblocktemplate (before): %s", bitcoind.RPCErrorMessage(err))
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s.Log.Warn("accelerate: getblocktemplate failed (before)", "err", err)
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tplErr = fmt.Sprintf("getblocktemplate: %s", bitcoind.RPCErrorMessage(err))
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s.Log.Warn("accelerate: getblocktemplate failed", "err", err)
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} else {
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coinbaseBefore = tplBefore.CoinbaseValue
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feeLost = marginalFeeLost(tpl, txid, entry.Vsize)
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s.Log.Info("accelerate: fee impact estimated",
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"marginal_fee_lost", feeLost, "boosted_tx_fee", int64(baseFeeSats))
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}
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if err := s.RPC.PrioritiseTransaction(ctx, txid, delta); err != nil {
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return nil, fmt.Errorf("prioritisetransaction: %w", err)
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}
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// Measure coinbasevalue AFTER — the difference is the real fee lost.
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var feeLost int64
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if coinbaseBefore > 0 {
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tplAfter, err := s.RPC.GetBlockTemplate(ctx)
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if err != nil {
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tplErr = fmt.Sprintf("getblocktemplate (after): %s", bitcoind.RPCErrorMessage(err))
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s.Log.Warn("accelerate: getblocktemplate failed (after)", "err", err)
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} else {
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feeLost = coinbaseBefore - tplAfter.CoinbaseValue
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if feeLost < 0 {
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feeLost = 0 // template improved (new tx arrived between calls)
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}
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s.Log.Info("accelerate: fee impact measured",
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"before", coinbaseBefore, "after", tplAfter.CoinbaseValue, "lost", feeLost)
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}
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}
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rec := store.BoostedTx{
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Txid: txid,
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OriginalFeerate: currentFeerate,
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@@ -273,11 +273,19 @@ func (c *RPC) GetNetworkHashPS(ctx context.Context, blocks, height int) (float64
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return out, nil
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}
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// TemplateTx is one transaction inside a getblocktemplate result.
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type TemplateTx struct {
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Txid string `json:"txid"`
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Fee int64 `json:"fee"` // satoshis
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Weight int64 `json:"weight"` // weight units
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}
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// BlockTemplate is the subset of getblocktemplate we care about: the
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// coinbase value (subsidy + fees) and height of the next block.
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type BlockTemplate struct {
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CoinbaseValue int64 `json:"coinbasevalue"` // satoshis
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Height int64 `json:"height"`
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Transactions []TemplateTx `json:"transactions"`
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}
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// GetBlockTemplate fetches the next block template with segwit rules.
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@@ -69,7 +69,7 @@
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} else if (feeLostSats > 0) {
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success = `Boosted from ${from} to ${to} sat/vB. Revenue impact: -${feeLostSats.toLocaleString()} sats (${(feeLostSats / 1e8).toFixed(8)} BTC) per block mined.`;
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} else {
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success = `Boosted from ${from} to ${to} sat/vB. No revenue impact — the displaced transaction's fee was equal or lower.`;
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success = `Boosted from ${from} to ${to} sat/vB. No revenue impact — the transaction was already in the template or the mempool fits in one block.`;
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}
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txid = "";
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feerateInput = "";
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@@ -169,9 +169,9 @@
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mempool isn't full (all transactions already fit), there is <em>zero cost</em>.
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</p>
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<p>
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<strong>Revenue impact:</strong> After boosting, the server compares the block template's
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coinbase value before and after. The difference (if any) is the actual fee revenue
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lost per block mined. This is shown after each boost.
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<strong>Revenue impact:</strong> The server inspects the current block template to find
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the marginal transaction — the lowest fee-rate tx that would be displaced by the
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boosted one. Its fee is the revenue you sacrifice per block mined, shown after each boost.
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</p>
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<p>
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Your pool: {formatHashrate(poolHashrate)} /
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