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fix: build tx packages similar to Bitcoin Core
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The previous implementation build packages with a global view of the
available transactions. This is different from how Bitcoin Core inserts
packages into a block template. For smoother feerate distribution plots,
the package building algorithm changed to only account for local
packages (i.e. transactions next to each other in the block). This also
simplifies the package building.
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@0xB10C
0xB10C committed Nov 22, 2023
1 parent c04f08e commit ba2c36d
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Showing 3 changed files with 57 additions and 101 deletions.
29 changes: 8 additions & 21 deletions daemon/src/model.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,3 @@
use std::cell::RefCell;
use std::collections::{HashMap, HashSet};

use bitcoin::hash_types::Txid;
Expand All @@ -17,6 +16,14 @@ impl TxInfo {
pub fn feerate(&self) -> f32 {
self.fee.to_sat() as f32 / self.tx.vsize() as f32
}

pub fn prev_output_txids(&self) -> HashSet<Txid> {
self.tx
.input
.iter()
.map(|input| input.previous_output.txid)
.collect()
}
}

pub struct TxPackage {
Expand All @@ -38,26 +45,6 @@ impl TxPackage {
}
}

#[derive(PartialEq, Eq, Clone)]
pub struct TxPackageForPackageConstruction {
pub txns: RefCell<Vec<TxInfo>>,
}

impl TxPackageForPackageConstruction {
pub fn min_tx_pos(&self) -> i32 {
self.txns
.borrow()
.iter()
.map(|tx_info| tx_info.pos)
.min()
.unwrap_or(-1)
}

pub fn txids(&self) -> HashSet<Txid> {
self.txns.borrow().iter().map(|t| t.txid).collect()
}
}

pub struct BlockTxData {
pub txids: HashSet<Txid>,
pub txid_to_txinfo_map: HashMap<Txid, TxInfo>,
Expand Down
128 changes: 49 additions & 79 deletions daemon/src/processing.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,7 @@ use std::cell::RefCell;
use std::collections::{HashMap, HashSet, VecDeque};

use crate::metrics;
use crate::model::{
BlockTxData, TemplateTxData, TxInfo, TxPackage, TxPackageForPackageConstruction,
};
use crate::model::{BlockTxData, TemplateTxData, TxInfo, TxPackage};

use miningpool_observer_shared::bitcoincore_rpc::json::{
GetBlockTemplateResult, GetBlockTxFeesResult,
Expand Down Expand Up @@ -323,79 +321,59 @@ fn get_pool_info_or_default(
}
}

/// Builds a vector of transaction packages
/// Builds a vector of transaction packages. These Packages are similar to what
/// Bitcoin Core (currently) puts into blocks.
pub fn build_packages(txns: &[TxInfo]) -> Vec<TxPackage> {
let mut packages_construction: Vec<TxPackageForPackageConstruction> = vec![];
let mut seen_outpoints: HashSet<Txid> = HashSet::new();

for tx_info in txns.iter() {
let outpoints_spend: HashSet<Txid> = tx_info
.tx
.input
.iter()
.map(|i| i.previous_output.txid)
.collect();

let mut parent_packages: Vec<&TxPackageForPackageConstruction> = vec![];
for outpoint in outpoints_spend {
if seen_outpoints.contains(&outpoint) {
'_p_finder: for package in packages_construction.iter() {
if package.txids().contains(&outpoint) {
parent_packages.push(package);
break '_p_finder;
}
}
}
}

match parent_packages.len() {
0 => {
packages_construction.push(TxPackageForPackageConstruction {
txns: RefCell::new(vec![tx_info.clone()]),
let txids_in_txns: HashSet<Txid> = txns.iter().map(|ti| ti.tx.txid()).collect();
let mut packages: Vec<TxPackage> = vec![];

// Bitcoin Core places transactions that belong to a package next to each other.
// We consider locality when building packages.
// Bitcoin Core currently uses the best ancestor set as a package. See
// https://gist.github.com/murchandamus/5cb413fe9f26dbce57abfd344ebbfaf2#file-asb-vs-csb-png

let mut package_txns: Vec<TxInfo> = vec![];
// by iterating in reverse order, we know about the children first
// This is helpful, as children reference their parents and we can directly link them
for tx_info in txns.iter().rev() {
if package_txns.is_empty() {
package_txns.push(tx_info.clone());
} else {
let parent_txids: HashSet<Txid> =
package_txns.iter().fold(HashSet::new(), |mut txids, tx| {
txids.extend(&tx.prev_output_txids());
txids
});
}
1 => {
parent_packages
.first()
.unwrap() // We can unwrap here as we know there is a first (as there is exactly 1)
.txns
.borrow_mut()
.push(tx_info.clone());
}
_ => {
let min_tx_pos_package = parent_packages
.iter()
.min_by_key(|p| p.min_tx_pos())
.unwrap(); // We can unwrap here as we know there is more than one item, which yields a min item.

let mut new_txns: Vec<TxInfo> = vec![tx_info.clone()];
for p in parent_packages.iter() {
// the tnxs can be empty because we can have visited the package before
// as the parent packages vec can contain duplicate packages. This happens,
// for example, when transaction spends from both transactions in a package.
if !p.txns.borrow().is_empty() {
new_txns.append(&mut p.txns.borrow_mut());
}
}
new_txns.sort_by_key(|tx| tx.pos);
min_tx_pos_package.txns.replace(new_txns);
if parent_txids.contains(&tx_info.tx.txid()) {
// belongs to the same package if the tx is a parent of a tx in the package
package_txns.push(tx_info.clone());
} else if tx_info
.prev_output_txids()
.iter()
.filter(|txid| txids_in_txns.contains(*txid))
.any(|txid| parent_txids.contains(txid))
{
// belongs to the same package if the transaction shares a parent with a
// transaction already in the package (if this parent is in the `txns` set of
// transactions)
package_txns.push(tx_info.clone());
} else {
packages.push(TxPackage {
txns: package_txns.clone(),
});
package_txns.clear();
package_txns.push(tx_info.clone());
}
}
// remove empty packages (we empty packages on merge)
packages_construction.retain(|p| !p.txns.borrow().is_empty());

seen_outpoints.insert(tx_info.txid);
}

let packages: Vec<TxPackage> = packages_construction
.iter()
.map(|construction_package| TxPackage {
txns: construction_package.txns.take(),
})
.collect();
if !package_txns.is_empty() {
packages.push(TxPackage {
txns: package_txns.clone(),
});
}
packages.reverse();

let total_tx: usize = packages.iter().map(|p| p.txns.len()).sum();

assert_eq!(txns.len(), total_tx);

packages
Expand Down Expand Up @@ -1240,7 +1218,7 @@ mod tests {
//
// 'X <- Y' means Y spends X; X is the partent of Y
// A <- B <- C
let mut txns = vec![tx_a_info.clone(), tx_b_info.clone(), tx_d_info, tx_c_info];
let mut txns = vec![tx_a_info.clone(), tx_b_info.clone(), tx_c_info, tx_d_info]; // order matters
let packages = build_packages(&txns.clone());

println!("There should be exactly two packages");
Expand All @@ -1253,10 +1231,6 @@ mod tests {
println!("The package weight should be the sum of the three transaction weights");
assert_eq!(package.weight(), tx_a.weight + tx_b.weight + tx_c.weight);

println!("Transactions in the package should be sorted by position (asceding)");
assert_eq!(package.txns.first().unwrap().pos, 0);
assert_eq!(package.txns.last().unwrap().pos, 2);

// fake tx that spends from A and B
let tx_e = Transaction {
lock_time: LockTime::from_consensus(0),
Expand Down Expand Up @@ -1294,7 +1268,7 @@ mod tests {
tx: tx_e.clone(),
};

txns.push(tx_e_info);
txns.insert(3, tx_e_info); // order matters

let packages = build_packages(&txns);

Expand All @@ -1310,9 +1284,5 @@ mod tests {
package.weight(),
tx_a.weight + tx_b.weight + tx_c.weight + tx_e.weight().to_wu() as usize
);

println!("Transactions in the package should be sorted by position (asceding). The new transaction should be the last.");
assert_eq!(package.txns.first().unwrap().pos, 0);
assert_eq!(package.txns.last().unwrap().pos, 3);
}
}
1 change: 0 additions & 1 deletion www/templates/subpage/template_and_block.html
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Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,6 @@ <h4>Feerate Distribution in Template and Block</h4>
</div>
</noscript>
</div>
<span class="text-muted small">Note: The graph might contain package ordering artifacts from transaction package construction. The packages are purposefully not sorted by feerate to show custom pool prioritizations (if present).</span>
</div>

<div class="my-3 p-3 bg-white shadow-sm">
Expand Down

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