void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
{
pblock->vtx.emplace_back(iter->GetSharedTx());
pblocktemplate->vTxFees.push_back(iter->GetFee());
pblocktemplate->vTxSigOpsCost.push_back(iter->GetSigOpCost());
nBlockWeight += iter->GetTxWeight();
++nBlockTx;
nBlockSigOpsCost += iter->GetSigOpCost();
nFees += iter->GetFee();
inBlock.insert(iter);
bool fPrintPriority = gArgs.GetBoolArg("-printpriority", DEFAULT_PRINTPRIORITY);
if (fPrintPriority) {
LogPrintf("fee %s txid %s\n",
CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
iter->GetTx().GetHash().ToString());
}
}
// This transaction selection algorithm orders the mempool based
// on feerate of a transaction including all unconfirmed ancestors.
// Since we don't remove transactions from the mempool as we select them
// for block inclusion, we need an alternate method of updating the feerate
// of a transaction with its not-yet-selected ancestors as we go.
// This is accomplished by walking the in-mempool descendants of selected
// transactions and storing a temporary modified state in mapModifiedTxs.
// Each time through the loop, we compare the best transaction in
// mapModifiedTxs with the next transaction in the mempool to decide what
// transaction package to work on next.
void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated)
{
// mapModifiedTx will store sorted packages after they are modified
// because some of their txs are already in the block
indexed_modified_transaction_set mapModifiedTx;
// Keep track of entries that failed inclusion, to avoid duplicate work
CTxMemPool::setEntries failedTx;
// Start by adding all descendants of previously added txs to mapModifiedTx
// and modifying them for their already included ancestors
UpdatePackagesForAdded(inBlock, mapModifiedTx);
CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = mempool.mapTx.get<ancestor_score>().begin();
CTxMemPool::txiter iter;
// Limit the number of attempts to add transactions to the block when it is
// close to full; this is just a simple heuristic to finish quickly if the
// mempool has a lot of entries.
const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
int64_t nConsecutiveFailed = 0;
while (mi != mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty())
{
// First try to find a new transaction in mapTx to evaluate.
if (mi != mempool.mapTx.get<ancestor_score>().end() &&
SkipMapTxEntry(mempool.mapTx.project<0>(mi), mapModifiedTx, failedTx)) {
++mi;
continue;
}
// Now that mi is not stale, determine which transaction to evaluate:
// the next entry from mapTx, or the best from mapModifiedTx?
bool fUsingModified = false;
modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
if (mi == mempool.mapTx.get<ancestor_score>().end()) {
// We're out of entries in mapTx; use the entry from mapModifiedTx
iter = modit->iter;
fUsingModified = true;
} else {
// Try to compare the mapTx entry to the mapModifiedTx entry
iter = mempool.mapTx.project<0>(mi);
if (modit != mapModifiedTx.get<ancestor_score>().end() &&
CompareModifiedEntry()(*modit, CTxMemPoolModifiedEntry(iter))) {
// The best entry in mapModifiedTx has higher score
// than the one from mapTx.
// Switch which transaction (package) to consider
iter = modit->iter;
fUsingModified = true;
} else {
// Either no entry in mapModifiedTx, or it's worse than mapTx.
// Increment mi for the next loop iteration.
++mi;
}
}
// We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
// contain anything that is inBlock.
assert(!inBlock.count(iter));
uint64_t packageSize = iter->GetSizeWithAncestors();
CAmount packageFees = iter->GetModFeesWithAncestors();
int64_t packageSigOpsCost = iter->GetSigOpCostWithAncestors();
if (fUsingModified) {
packageSize = modit->nSizeWithAncestors;
packageFees = modit->nModFeesWithAncestors;
packageSigOpsCost = modit->nSigOpCostWithAncestors;
}
if (packageFees < blockMinFeeRate.GetFee(packageSize)) {
// Everything else we might consider has a lower fee rate
return;
}
if (!TestPackage(packageSize, packageSigOpsCost)) {
if (fUsingModified) {
// Since we always look at the best entry in mapModifiedTx,
// we must erase failed entries so that we can consider the
// next best entry on the next loop iteration
mapModifiedTx.get<ancestor_score>().erase(modit);
failedTx.insert(iter);
}
++nConsecutiveFailed;
if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight >
nBlockMaxWeight - 4000) {
// Give up if we're close to full and haven't succeeded in a while
break;
}
continue;
}
CTxMemPool::setEntries ancestors;
uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
std::string dummy;
mempool.CalculateMemPoolAncestors(*iter, ancestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
onlyUnconfirmed(ancestors);
ancestors.insert(iter);
// Test if all tx's are Final
if (!TestPackageTransactions(ancestors)) {
if (fUsingModified) {
mapModifiedTx.get<ancestor_score>().erase(modit);
failedTx.insert(iter);
}
continue;
}
// This transaction will make it in; reset the failed counter.
nConsecutiveFailed = 0;
// Package can be added. Sort the entries in a valid order.
std::vector<CTxMemPool::txiter> sortedEntries;
SortForBlock(ancestors, iter, sortedEntries);
for (size_t i=0; i<sortedEntries.size(); ++i) {
AddToBlock(sortedEntries[i]);
// Erase from the modified set, if present
mapModifiedTx.erase(sortedEntries[i]);
}
++nPackagesSelected;
// Update transactions that depend on each of these
nDescendantsUpdated += UpdatePackagesForAdded(ancestors, mapModifiedTx);
}
}