src/miner.cpp

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2016 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #include "miner.h"
   7
   8 #include "amount.h"
   9 #include "chain.h"
  10 #include "chainparams.h"
  11 #include "coins.h"
  12 #include "consensus/consensus.h"
  13 #include "consensus/tx_verify.h"
  14 #include "consensus/merkle.h"
  15 #include "consensus/validation.h"
  16 #include "hash.h"
  17 #include "validation.h"
  18 #include "net.h"
  19 #include "policy/feerate.h"
  20 #include "policy/policy.h"
  21 #include "pow.h"
  22 #include "primitives/transaction.h"
  23 #include "script/standard.h"
  24 #include "timedata.h"
  25 #include "txmempool.h"
  26 #include "util.h"
  27 #include "utilmoneystr.h"
  28 #include "validationinterface.h"
  29
  30 #include <algorithm>
  31 #include <queue>
  32 #include <utility>
  33
  34 //////////////////////////////////////////////////////////////////////////////
  35 //
  36 // BitcoinMiner
  37 //
  38
  39 //
  40 // Unconfirmed transactions in the memory pool often depend on other
  41 // transactions in the memory pool. When we select transactions from the
  42 // pool, we select by highest fee rate of a transaction combined with all
  43 // its ancestors.
  44
  45 uint64_t nLastBlockTx = 0;
  46 uint64_t nLastBlockSize = 0;
  47 uint64_t nLastBlockWeight = 0;
  48
  49 int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
  50 {
  51     int64_t nOldTime = pblock->nTime;
  52     int64_t nNewTime = std::max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
  53
  54     if (nOldTime < nNewTime)
  55         pblock->nTime = nNewTime;
  56
  57     // Updating time can change work required on testnet:
  58     if (consensusParams.fPowAllowMinDifficultyBlocks)
  59         pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);
  60
  61     return nNewTime - nOldTime;
  62 }
  63
  64 BlockAssembler::Options::Options() {
  65     blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
  66     nBlockMaxWeight = DEFAULT_BLOCK_MAX_WEIGHT;
  67     nBlockMaxSize = DEFAULT_BLOCK_MAX_SIZE;
  68 }
  69
  70 BlockAssembler::BlockAssembler(const CChainParams& params, const Options& options) : chainparams(params)
  71 {
  72     blockMinFeeRate = options.blockMinFeeRate;
  73     // Limit weight to between 4K and MAX_BLOCK_WEIGHT-4K for sanity:
  74     nBlockMaxWeight = std::max<size_t>(4000, std::min<size_t>(MAX_BLOCK_WEIGHT - 4000, options.nBlockMaxWeight));
  75     // Limit size to between 1K and MAX_BLOCK_SERIALIZED_SIZE-1K for sanity:
  76     nBlockMaxSize = std::max<size_t>(1000, std::min<size_t>(MAX_BLOCK_SERIALIZED_SIZE - 1000, options.nBlockMaxSize));
  77     // Whether we need to account for byte usage (in addition to weight usage)
  78     fNeedSizeAccounting = (nBlockMaxSize < MAX_BLOCK_SERIALIZED_SIZE - 1000);
  79 }
  80
  81 static BlockAssembler::Options DefaultOptions(const CChainParams& params)
  82 {
  83     // Block resource limits
  84     // If neither -blockmaxsize or -blockmaxweight is given, limit to DEFAULT_BLOCK_MAX_*
  85     // If only one is given, only restrict the specified resource.
  86     // If both are given, restrict both.
  87     BlockAssembler::Options options;
  88     options.nBlockMaxWeight = DEFAULT_BLOCK_MAX_WEIGHT;
  89     options.nBlockMaxSize = DEFAULT_BLOCK_MAX_SIZE;
  90     bool fWeightSet = false;
  91     if (gArgs.IsArgSet("-blockmaxweight")) {
  92         options.nBlockMaxWeight = gArgs.GetArg("-blockmaxweight", DEFAULT_BLOCK_MAX_WEIGHT);
  93         options.nBlockMaxSize = MAX_BLOCK_SERIALIZED_SIZE;
  94         fWeightSet = true;
  95     }
  96     if (gArgs.IsArgSet("-blockmaxsize")) {
  97         options.nBlockMaxSize = gArgs.GetArg("-blockmaxsize", DEFAULT_BLOCK_MAX_SIZE);
  98         if (!fWeightSet) {
  99             options.nBlockMaxWeight = options.nBlockMaxSize * WITNESS_SCALE_FACTOR;
 100         }
 101     }
 102     if (gArgs.IsArgSet("-blockmintxfee")) {
 103         CAmount n = 0;
 104         ParseMoney(gArgs.GetArg("-blockmintxfee", ""), n);
 105         options.blockMinFeeRate = CFeeRate(n);
 106     } else {
 107         options.blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
 108     }
 109     return options;
 110 }
 111
 112 BlockAssembler::BlockAssembler(const CChainParams& params) : BlockAssembler(params, DefaultOptions(params)) {}
 113
 114 void BlockAssembler::resetBlock()
 115 {
 116     inBlock.clear();
 117
 118     // Reserve space for coinbase tx
 119     nBlockSize = 1000;
 120     nBlockWeight = 4000;
 121     nBlockSigOpsCost = 400;
 122     fIncludeWitness = false;
 123
 124     // These counters do not include coinbase tx
 125     nBlockTx = 0;
 126     nFees = 0;
 127 }
 128
 129 std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx)
 130 {
 131     int64_t nTimeStart = GetTimeMicros();
 132
 133     resetBlock();
 134
 135     pblocktemplate.reset(new CBlockTemplate());
 136
 137     if(!pblocktemplate.get())
 138         return nullptr;
 139     pblock = &pblocktemplate->block; // pointer for convenience
 140
 141     // Add dummy coinbase tx as first transaction
 142     pblock->vtx.emplace_back();
 143     pblocktemplate->vTxFees.push_back(-1); // updated at end
 144     pblocktemplate->vTxSigOpsCost.push_back(-1); // updated at end
 145
 146     LOCK2(cs_main, mempool.cs);
 147     CBlockIndex* pindexPrev = chainActive.Tip();
 148     nHeight = pindexPrev->nHeight + 1;
 149
 150     pblock->nVersion = ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
 151     // -regtest only: allow overriding block.nVersion with
 152     // -blockversion=N to test forking scenarios
 153     if (chainparams.MineBlocksOnDemand())
 154         pblock->nVersion = gArgs.GetArg("-blockversion", pblock->nVersion);
 155
 156     pblock->nTime = GetAdjustedTime();
 157     const int64_t nMedianTimePast = pindexPrev->GetMedianTimePast();
 158
 159     nLockTimeCutoff = (STANDARD_LOCKTIME_VERIFY_FLAGS & LOCKTIME_MEDIAN_TIME_PAST)
 160                        ? nMedianTimePast
 161                        : pblock->GetBlockTime();
 162
 163     // Decide whether to include witness transactions
 164     // This is only needed in case the witness softfork activation is reverted
 165     // (which would require a very deep reorganization) or when
 166     // -promiscuousmempoolflags is used.
 167     // TODO: replace this with a call to main to assess validity of a mempool
 168     // transaction (which in most cases can be a no-op).
 169     fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus()) && fMineWitnessTx;
 170
 171     int nPackagesSelected = 0;
 172     int nDescendantsUpdated = 0;
 173     addPackageTxs(nPackagesSelected, nDescendantsUpdated);
 174
 175     int64_t nTime1 = GetTimeMicros();
 176
 177     nLastBlockTx = nBlockTx;
 178     nLastBlockSize = nBlockSize;
 179     nLastBlockWeight = nBlockWeight;
 180
 181     // Create coinbase transaction.
 182     CMutableTransaction coinbaseTx;
 183     coinbaseTx.vin.resize(1);
 184     coinbaseTx.vin[0].prevout.SetNull();
 185     coinbaseTx.vout.resize(1);
 186     coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;
 187     coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
 188     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
 189     pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
 190     pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
 191     pblocktemplate->vTxFees[0] = -nFees;
 192
 193     uint64_t nSerializeSize = GetSerializeSize(*pblock, SER_NETWORK, PROTOCOL_VERSION);
 194     LogPrintf("CreateNewBlock(): total size: %u block weight: %u txs: %u fees: %ld sigops %d\n", nSerializeSize, GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
 195
 196     // Fill in header
 197     pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
 198     UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
 199     pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
 200     pblock->nNonce         = 0;
 201     pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);
 202
 203     CValidationState state;
 204     if (!TestBlockValidity(state, chainparams, *pblock, pindexPrev, false, false)) {
 205         throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, FormatStateMessage(state)));
 206     }
 207     int64_t nTime2 = GetTimeMicros();
 208
 209     LogPrint(BCLog::BENCH, "CreateNewBlock() packages: %.2fms (%d packages, %d updated descendants), validity: %.2fms (total %.2fms)\n", 0.001 * (nTime1 - nTimeStart), nPackagesSelected, nDescendantsUpdated, 0.001 * (nTime2 - nTime1), 0.001 * (nTime2 - nTimeStart));
 210
 211     return std::move(pblocktemplate);
 212 }
 213
 214 void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries& testSet)
 215 {
 216     for (CTxMemPool::setEntries::iterator iit = testSet.begin(); iit != testSet.end(); ) {
 217         // Only test txs not already in the block
 218         if (inBlock.count(*iit)) {
 219             testSet.erase(iit++);
 220         }
 221         else {
 222             iit++;
 223         }
 224     }
 225 }
 226
 227 bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost) const
 228 {
 229     // TODO: switch to weight-based accounting for packages instead of vsize-based accounting.
 230     if (nBlockWeight + WITNESS_SCALE_FACTOR * packageSize >= nBlockMaxWeight)
 231         return false;
 232     if (nBlockSigOpsCost + packageSigOpsCost >= MAX_BLOCK_SIGOPS_COST)
 233         return false;
 234     return true;
 235 }
 236
 237 // Perform transaction-level checks before adding to block:
 238 // - transaction finality (locktime)
 239 // - premature witness (in case segwit transactions are added to mempool before
 240 //   segwit activation)
 241 // - serialized size (in case -blockmaxsize is in use)
 242 bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
 243 {
 244     uint64_t nPotentialBlockSize = nBlockSize; // only used with fNeedSizeAccounting
 245     for (const CTxMemPool::txiter it : package) {
 246         if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
 247             return false;
 248         if (!fIncludeWitness && it->GetTx().HasWitness())
 249             return false;
 250         if (fNeedSizeAccounting) {
 251             uint64_t nTxSize = ::GetSerializeSize(it->GetTx(), SER_NETWORK, PROTOCOL_VERSION);
 252             if (nPotentialBlockSize + nTxSize >= nBlockMaxSize) {
 253                 return false;
 254             }
 255             nPotentialBlockSize += nTxSize;
 256         }
 257     }
 258     return true;
 259 }
 260
 261 void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
 262 {
 263     pblock->vtx.emplace_back(iter->GetSharedTx());
 264     pblocktemplate->vTxFees.push_back(iter->GetFee());
 265     pblocktemplate->vTxSigOpsCost.push_back(iter->GetSigOpCost());
 266     if (fNeedSizeAccounting) {
 267         nBlockSize += ::GetSerializeSize(iter->GetTx(), SER_NETWORK, PROTOCOL_VERSION);
 268     }
 269     nBlockWeight += iter->GetTxWeight();
 270     ++nBlockTx;
 271     nBlockSigOpsCost += iter->GetSigOpCost();
 272     nFees += iter->GetFee();
 273     inBlock.insert(iter);
 274
 275     bool fPrintPriority = gArgs.GetBoolArg("-printpriority", DEFAULT_PRINTPRIORITY);
 276     if (fPrintPriority) {
 277         LogPrintf("fee %s txid %s\n",
 278                   CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
 279                   iter->GetTx().GetHash().ToString());
 280     }
 281 }
 282
 283 int BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded,
 284         indexed_modified_transaction_set &mapModifiedTx)
 285 {
 286     int nDescendantsUpdated = 0;
 287     for (const CTxMemPool::txiter it : alreadyAdded) {
 288         CTxMemPool::setEntries descendants;
 289         mempool.CalculateDescendants(it, descendants);
 290         // Insert all descendants (not yet in block) into the modified set
 291         for (CTxMemPool::txiter desc : descendants) {
 292             if (alreadyAdded.count(desc))
 293                 continue;
 294             ++nDescendantsUpdated;
 295             modtxiter mit = mapModifiedTx.find(desc);
 296             if (mit == mapModifiedTx.end()) {
 297                 CTxMemPoolModifiedEntry modEntry(desc);
 298                 modEntry.nSizeWithAncestors -= it->GetTxSize();
 299                 modEntry.nModFeesWithAncestors -= it->GetModifiedFee();
 300                 modEntry.nSigOpCostWithAncestors -= it->GetSigOpCost();
 301                 mapModifiedTx.insert(modEntry);
 302             } else {
 303                 mapModifiedTx.modify(mit, update_for_parent_inclusion(it));
 304             }
 305         }
 306     }
 307     return nDescendantsUpdated;
 308 }
 309
 310 // Skip entries in mapTx that are already in a block or are present
 311 // in mapModifiedTx (which implies that the mapTx ancestor state is
 312 // stale due to ancestor inclusion in the block)
 313 // Also skip transactions that we've already failed to add. This can happen if
 314 // we consider a transaction in mapModifiedTx and it fails: we can then
 315 // potentially consider it again while walking mapTx.  It's currently
 316 // guaranteed to fail again, but as a belt-and-suspenders check we put it in
 317 // failedTx and avoid re-evaluation, since the re-evaluation would be using
 318 // cached size/sigops/fee values that are not actually correct.
 319 bool BlockAssembler::SkipMapTxEntry(CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx, CTxMemPool::setEntries &failedTx)
 320 {
 321     assert (it != mempool.mapTx.end());
 322     return mapModifiedTx.count(it) || inBlock.count(it) || failedTx.count(it);
 323 }
 324
 325 void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, CTxMemPool::txiter entry, std::vector<CTxMemPool::txiter>& sortedEntries)
 326 {
 327     // Sort package by ancestor count
 328     // If a transaction A depends on transaction B, then A's ancestor count
 329     // must be greater than B's.  So this is sufficient to validly order the
 330     // transactions for block inclusion.
 331     sortedEntries.clear();
 332     sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());
 333     std::sort(sortedEntries.begin(), sortedEntries.end(), CompareTxIterByAncestorCount());
 334 }
 335
 336 // This transaction selection algorithm orders the mempool based
 337 // on feerate of a transaction including all unconfirmed ancestors.
 338 // Since we don't remove transactions from the mempool as we select them
 339 // for block inclusion, we need an alternate method of updating the feerate
 340 // of a transaction with its not-yet-selected ancestors as we go.
 341 // This is accomplished by walking the in-mempool descendants of selected
 342 // transactions and storing a temporary modified state in mapModifiedTxs.
 343 // Each time through the loop, we compare the best transaction in
 344 // mapModifiedTxs with the next transaction in the mempool to decide what
 345 // transaction package to work on next.
 346 void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated)
 347 {
 348     // mapModifiedTx will store sorted packages after they are modified
 349     // because some of their txs are already in the block
 350     indexed_modified_transaction_set mapModifiedTx;
 351     // Keep track of entries that failed inclusion, to avoid duplicate work
 352     CTxMemPool::setEntries failedTx;
 353
 354     // Start by adding all descendants of previously added txs to mapModifiedTx
 355     // and modifying them for their already included ancestors
 356     UpdatePackagesForAdded(inBlock, mapModifiedTx);
 357
 358     CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = mempool.mapTx.get<ancestor_score>().begin();
 359     CTxMemPool::txiter iter;
 360
 361     // Limit the number of attempts to add transactions to the block when it is
 362     // close to full; this is just a simple heuristic to finish quickly if the
 363     // mempool has a lot of entries.
 364     const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
 365     int64_t nConsecutiveFailed = 0;
 366
 367     while (mi != mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty())
 368     {
 369         // First try to find a new transaction in mapTx to evaluate.
 370         if (mi != mempool.mapTx.get<ancestor_score>().end() &&
 371                 SkipMapTxEntry(mempool.mapTx.project<0>(mi), mapModifiedTx, failedTx)) {
 372             ++mi;
 373             continue;
 374         }
 375
 376         // Now that mi is not stale, determine which transaction to evaluate:
 377         // the next entry from mapTx, or the best from mapModifiedTx?
 378         bool fUsingModified = false;
 379
 380         modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
 381         if (mi == mempool.mapTx.get<ancestor_score>().end()) {
 382             // We're out of entries in mapTx; use the entry from mapModifiedTx
 383             iter = modit->iter;
 384             fUsingModified = true;
 385         } else {
 386             // Try to compare the mapTx entry to the mapModifiedTx entry
 387             iter = mempool.mapTx.project<0>(mi);
 388             if (modit != mapModifiedTx.get<ancestor_score>().end() &&
 389                     CompareModifiedEntry()(*modit, CTxMemPoolModifiedEntry(iter))) {
 390                 // The best entry in mapModifiedTx has higher score
 391                 // than the one from mapTx.
 392                 // Switch which transaction (package) to consider
 393                 iter = modit->iter;
 394                 fUsingModified = true;
 395             } else {
 396                 // Either no entry in mapModifiedTx, or it's worse than mapTx.
 397                 // Increment mi for the next loop iteration.
 398                 ++mi;
 399             }
 400         }
 401
 402         // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
 403         // contain anything that is inBlock.
 404         assert(!inBlock.count(iter));
 405
 406         uint64_t packageSize = iter->GetSizeWithAncestors();
 407         CAmount packageFees = iter->GetModFeesWithAncestors();
 408         int64_t packageSigOpsCost = iter->GetSigOpCostWithAncestors();
 409         if (fUsingModified) {
 410             packageSize = modit->nSizeWithAncestors;
 411             packageFees = modit->nModFeesWithAncestors;
 412             packageSigOpsCost = modit->nSigOpCostWithAncestors;
 413         }
 414
 415         if (packageFees < blockMinFeeRate.GetFee(packageSize)) {
 416             // Everything else we might consider has a lower fee rate
 417             return;
 418         }
 419
 420         if (!TestPackage(packageSize, packageSigOpsCost)) {
 421             if (fUsingModified) {
 422                 // Since we always look at the best entry in mapModifiedTx,
 423                 // we must erase failed entries so that we can consider the
 424                 // next best entry on the next loop iteration
 425                 mapModifiedTx.get<ancestor_score>().erase(modit);
 426                 failedTx.insert(iter);
 427             }
 428
 429             ++nConsecutiveFailed;
 430
 431             if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight >
 432                     nBlockMaxWeight - 4000) {
 433                 // Give up if we're close to full and haven't succeeded in a while
 434                 break;
 435             }
 436             continue;
 437         }
 438
 439         CTxMemPool::setEntries ancestors;
 440         uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
 441         std::string dummy;
 442         mempool.CalculateMemPoolAncestors(*iter, ancestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
 443
 444         onlyUnconfirmed(ancestors);
 445         ancestors.insert(iter);
 446
 447         // Test if all tx's are Final
 448         if (!TestPackageTransactions(ancestors)) {
 449             if (fUsingModified) {
 450                 mapModifiedTx.get<ancestor_score>().erase(modit);
 451                 failedTx.insert(iter);
 452             }
 453             continue;
 454         }
 455
 456         // This transaction will make it in; reset the failed counter.
 457         nConsecutiveFailed = 0;
 458
 459         // Package can be added. Sort the entries in a valid order.
 460         std::vector<CTxMemPool::txiter> sortedEntries;
 461         SortForBlock(ancestors, iter, sortedEntries);
 462
 463         for (size_t i=0; i<sortedEntries.size(); ++i) {
 464             AddToBlock(sortedEntries[i]);
 465             // Erase from the modified set, if present
 466             mapModifiedTx.erase(sortedEntries[i]);
 467         }
 468
 469         ++nPackagesSelected;
 470
 471         // Update transactions that depend on each of these
 472         nDescendantsUpdated += UpdatePackagesForAdded(ancestors, mapModifiedTx);
 473     }
 474 }
 475
 476 void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce)
 477 {
 478     // Update nExtraNonce
 479     static uint256 hashPrevBlock;
 480     if (hashPrevBlock != pblock->hashPrevBlock)
 481     {
 482         nExtraNonce = 0;
 483         hashPrevBlock = pblock->hashPrevBlock;
 484     }
 485     ++nExtraNonce;
 486     unsigned int nHeight = pindexPrev->nHeight+1; // Height first in coinbase required for block.version=2
 487     CMutableTransaction txCoinbase(*pblock->vtx[0]);
 488     txCoinbase.vin[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce)) + COINBASE_FLAGS;
 489     assert(txCoinbase.vin[0].scriptSig.size() <= 100);
 490
 491     pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
 492     pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
 493 }