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Non-atomic flushing using the blockchain as replay journal

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This commit is contained in:
Pieter Wuille 2017-04-19 09:34:30 -07:00
parent b3a279cd58
commit 013a56aa1a
7 changed files with 186 additions and 16 deletions
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9
src/coins.cpp
View File

@ -13,6 +13,7 @@
bool CCoinsView::GetCoin(const COutPoint &outpoint, Coin &coin) const { return false; }
bool CCoinsView::HaveCoin(const COutPoint &outpoint) const { return false; }
uint256 CCoinsView::GetBestBlock() const { return uint256(); }
std::vector<uint256> CCoinsView::GetHeadBlocks() const { return std::vector<uint256>(); }
bool CCoinsView::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return false; }
CCoinsViewCursor *CCoinsView::Cursor() const { return 0; }
@ -21,6 +22,7 @@ CCoinsViewBacked::CCoinsViewBacked(CCoinsView *viewIn) : base(viewIn) { }
bool CCoinsViewBacked::GetCoin(const COutPoint &outpoint, Coin &coin) const { return base->GetCoin(outpoint, coin); }
bool CCoinsViewBacked::HaveCoin(const COutPoint &outpoint) const { return base->HaveCoin(outpoint); }
uint256 CCoinsViewBacked::GetBestBlock() const { return base->GetBestBlock(); }
std::vector<uint256> CCoinsViewBacked::GetHeadBlocks() const { return base->GetHeadBlocks(); }
void CCoinsViewBacked::SetBackend(CCoinsView &viewIn) { base = &viewIn; }
bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return base->BatchWrite(mapCoins, hashBlock); }
CCoinsViewCursor *CCoinsViewBacked::Cursor() const { return base->Cursor(); }
@ -81,13 +83,14 @@ void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possi
cachedCoinsUsage += it->second.coin.DynamicMemoryUsage();
}
void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight) {
void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight, bool check) {
bool fCoinbase = tx.IsCoinBase();
const uint256& txid = tx.GetHash();
for (size_t i = 0; i < tx.vout.size(); ++i) {
// Pass fCoinbase as the possible_overwrite flag to AddCoin, in order to correctly
bool overwrite = check ? cache.HaveCoin(COutPoint(txid, i)) : fCoinbase;
// Always set the possible_overwrite flag to AddCoin for coinbase txn, in order to correctly
// deal with the pre-BIP30 occurrences of duplicate coinbase transactions.
cache.AddCoin(COutPoint(txid, i), Coin(tx.vout[i], nHeight, fCoinbase), fCoinbase);
cache.AddCoin(COutPoint(txid, i), Coin(tx.vout[i], nHeight, fCoinbase), overwrite);
}
}

13
src/coins.h
View File

@ -155,6 +155,12 @@ public:
//! Retrieve the block hash whose state this CCoinsView currently represents
virtual uint256 GetBestBlock() const;
//! Retrieve the range of blocks that may have been only partially written.
//! If the database is in a consistent state, the result is the empty vector.
//! Otherwise, a two-element vector is returned consisting of the new and
//! the old block hash, in that order.
virtual std::vector<uint256> GetHeadBlocks() const;
//! Do a bulk modification (multiple Coin changes + BestBlock change).
//! The passed mapCoins can be modified.
virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
@ -181,6 +187,7 @@ public:
bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
bool HaveCoin(const COutPoint &outpoint) const override;
uint256 GetBestBlock() const override;
std::vector<uint256> GetHeadBlocks() const override;
void SetBackend(CCoinsView &viewIn);
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
CCoinsViewCursor *Cursor() const override;
@ -289,10 +296,12 @@ private:
};
//! Utility function to add all of a transaction's outputs to a cache.
// It assumes that overwrites are only possible for coinbase transactions,
// When check is false, this assumes that overwrites are only possible for coinbase transactions.
// When check is true, the underlying view may be queried to determine whether an addition is
// an overwrite.
// TODO: pass in a boolean to limit these possible overwrites to known
// (pre-BIP34) cases.
void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight);
void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool check = false);
//! Utility function to find any unspent output with a given txid.
const Coin& AccessByTxid(const CCoinsViewCache& cache, const uint256& txid);

10
src/init.cpp
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@ -336,6 +336,9 @@ std::string HelpMessage(HelpMessageMode mode)
#endif
}
strUsage += HelpMessageOpt("-datadir=<dir>", _("Specify data directory"));
if (showDebug) {
strUsage += HelpMessageOpt("-dbbatchsize", strprintf("Maximum database write batch size in bytes (default: %u)", nDefaultDbBatchSize));
}
strUsage += HelpMessageOpt("-dbcache=<n>", strprintf(_("Set database cache size in megabytes (%d to %d, default: %d)"), nMinDbCache, nMaxDbCache, nDefaultDbCache));
if (showDebug)
strUsage += HelpMessageOpt("-feefilter", strprintf("Tell other nodes to filter invs to us by our mempool min fee (default: %u)", DEFAULT_FEEFILTER));
@ -1426,6 +1429,13 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
break;
}
if (!ReplayBlocks(chainparams, pcoinsdbview)) {
strLoadError = _("Unable to replay blocks. You will need to rebuild the database using -reindex-chainstate.");
break;
}
pcoinsTip->SetBestBlock(pcoinsdbview->GetBestBlock()); // TODO: only initialize pcoinsTip after ReplayBlocks
LoadChainTip(chainparams);
if (!fReindex && chainActive.Tip() != NULL) {
uiInterface.InitMessage(_("Rewinding blocks..."));
if (!RewindBlockIndex(chainparams)) {

48
src/txdb.cpp
View File

@ -21,6 +21,7 @@ static const char DB_TXINDEX = 't';
static const char DB_BLOCK_INDEX = 'b';
static const char DB_BEST_BLOCK = 'B';
static const char DB_HEAD_BLOCKS = 'H';
static const char DB_FLAG = 'F';
static const char DB_REINDEX_FLAG = 'R';
static const char DB_LAST_BLOCK = 'l';
@ -68,10 +69,45 @@ uint256 CCoinsViewDB::GetBestBlock() const {
return hashBestChain;
}
std::vector<uint256> CCoinsViewDB::GetHeadBlocks() const {
std::vector<uint256> vhashHeadBlocks;
if (!db.Read(DB_HEAD_BLOCKS, vhashHeadBlocks)) {
return std::vector<uint256>();
}
return vhashHeadBlocks;
}
bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) {
CDBBatch batch(db);
size_t count = 0;
size_t changed = 0;
size_t batch_size = (size_t)GetArg("-dbbatchsize", nDefaultDbBatchSize);
uint256 old_tip = GetBestBlock();
if (old_tip.IsNull()) {
// We may be in the middle of replaying.
std::vector<uint256> old_heads = GetHeadBlocks();
if (old_heads.size() == 2) {
assert(old_heads[0] == hashBlock);
old_tip = old_heads[1];
}
}
if (hashBlock.IsNull()) {
// Initial flush, nothing to write.
assert(mapCoins.empty());
assert(old_tip.IsNull());
return true;
}
// In the first batch, mark the database as being in the middle of a
// transition from old_tip to hashBlock.
// A vector is used for future extensibility, as we may want to support
// interrupting after partial writes from multiple independent reorgs.
batch.Erase(DB_BEST_BLOCK);
batch.Write(DB_HEAD_BLOCKS, std::vector<uint256>{hashBlock, old_tip});
for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
if (it->second.flags & CCoinsCacheEntry::DIRTY) {
CoinEntry entry(&it->first);
@ -84,10 +120,18 @@ bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) {
count++;
CCoinsMap::iterator itOld = it++;
mapCoins.erase(itOld);
if (batch.SizeEstimate() > batch_size) {
LogPrint(BCLog::COINDB, "Writing partial batch of %.2f MiB\n", batch.SizeEstimate() * (1.0 / 1048576.0));
db.WriteBatch(batch);
batch.Clear();
}
}
if (!hashBlock.IsNull())
batch.Write(DB_BEST_BLOCK, hashBlock);
// In the last batch, mark the database as consistent with hashBlock again.
batch.Erase(DB_HEAD_BLOCKS);
batch.Write(DB_BEST_BLOCK, hashBlock);
LogPrint(BCLog::COINDB, "Writing final batch of %.2f MiB\n", batch.SizeEstimate() * (1.0 / 1048576.0));
bool ret = db.WriteBatch(batch);
LogPrint(BCLog::COINDB, "Committed %u changed transaction outputs (out of %u) to coin database...\n", (unsigned int)changed, (unsigned int)count);
return ret;

3
src/txdb.h
View File

@ -25,6 +25,8 @@ static constexpr int DB_PEAK_USAGE_FACTOR = 2;
static constexpr int MAX_BLOCK_COINSDB_USAGE = 10 * DB_PEAK_USAGE_FACTOR;
//! -dbcache default (MiB)
static const int64_t nDefaultDbCache = 450;
//! -dbbatchsize default (bytes)
static const int64_t nDefaultDbBatchSize = 16 << 20;
//! max. -dbcache (MiB)
static const int64_t nMaxDbCache = sizeof(void*) > 4 ? 16384 : 1024;
//! min. -dbcache (MiB)
@ -74,6 +76,7 @@ public:
bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
bool HaveCoin(const COutPoint &outpoint) const override;
uint256 GetBestBlock() const override;
std::vector<uint256> GetHeadBlocks() const override;
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
CCoinsViewCursor *Cursor() const override;

114
src/validation.cpp
View File

@ -96,7 +96,7 @@ namespace {
struct CBlockIndexWorkComparator
{
bool operator()(CBlockIndex *pa, CBlockIndex *pb) const {
bool operator()(const CBlockIndex *pa, const CBlockIndex *pb) const {
// First sort by most total work, ...
if (pa->nChainWork > pb->nChainWork) return false;
if (pa->nChainWork < pb->nChainWork) return true;
@ -1331,17 +1331,19 @@ int ApplyTxInUndo(Coin&& undo, CCoinsViewCache& view, const COutPoint& out)
return DISCONNECT_FAILED; // adding output for transaction without known metadata
}
}
view.AddCoin(out, std::move(undo), undo.fCoinBase);
// The potential_overwrite parameter to AddCoin is only allowed to be false if we know for
// sure that the coin did not already exist in the cache. As we have queried for that above
// using HaveCoin, we don't need to guess. When fClean is false, a coin already existed and
// it is an overwrite.
view.AddCoin(out, std::move(undo), !fClean);
return fClean ? DISCONNECT_OK : DISCONNECT_UNCLEAN;
}
/** Undo the effects of this block (with given index) on the UTXO set represented by coins.
* When UNCLEAN or FAILED is returned, view is left in an indeterminate state. */
* When FAILED is returned, view is left in an indeterminate state. */
static DisconnectResult DisconnectBlock(const CBlock& block, const CBlockIndex* pindex, CCoinsViewCache& view)
{
assert(pindex->GetBlockHash() == view.GetBestBlock());
bool fClean = true;
CBlockUndo blockUndo;
@ -1946,6 +1948,7 @@ bool static DisconnectTip(CValidationState& state, const CChainParams& chainpara
int64_t nStart = GetTimeMicros();
{
CCoinsViewCache view(pcoinsTip);
assert(view.GetBestBlock() == pindexDelete->GetBlockHash());
if (DisconnectBlock(block, pindexDelete, view) != DISCONNECT_OK)
return error("DisconnectTip(): DisconnectBlock %s failed", pindexDelete->GetBlockHash().ToString());
bool flushed = view.Flush();
@ -3417,20 +3420,26 @@ bool static LoadBlockIndexDB(const CChainParams& chainparams)
pblocktree->ReadFlag("txindex", fTxIndex);
LogPrintf("%s: transaction index %s\n", __func__, fTxIndex ? "enabled" : "disabled");
LoadChainTip(chainparams);
return true;
}
void LoadChainTip(const CChainParams& chainparams)
{
if (chainActive.Tip() && chainActive.Tip()->GetBlockHash() == pcoinsTip->GetBestBlock()) return;
// Load pointer to end of best chain
BlockMap::iterator it = mapBlockIndex.find(pcoinsTip->GetBestBlock());
if (it == mapBlockIndex.end())
return true;
return;
chainActive.SetTip(it->second);
PruneBlockIndexCandidates();
LogPrintf("%s: hashBestChain=%s height=%d date=%s progress=%f\n", __func__,
LogPrintf("Loaded best chain: hashBestChain=%s height=%d date=%s progress=%f\n",
chainActive.Tip()->GetBlockHash().ToString(), chainActive.Height(),
DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()),
GuessVerificationProgress(chainparams.TxData(), chainActive.Tip()));
return true;
}
CVerifyDB::CVerifyDB()
@ -3499,6 +3508,7 @@ bool CVerifyDB::VerifyDB(const CChainParams& chainparams, CCoinsView *coinsview,
}
// check level 3: check for inconsistencies during memory-only disconnect of tip blocks
if (nCheckLevel >= 3 && pindex == pindexState && (coins.DynamicMemoryUsage() + pcoinsTip->DynamicMemoryUsage()) <= nCoinCacheUsage) {
assert(coins.GetBestBlock() == pindex->GetBlockHash());
DisconnectResult res = DisconnectBlock(block, pindex, coins);
if (res == DISCONNECT_FAILED) {
return error("VerifyDB(): *** irrecoverable inconsistency in block data at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
@ -3538,6 +3548,92 @@ bool CVerifyDB::VerifyDB(const CChainParams& chainparams, CCoinsView *coinsview,
return true;
}
/** Apply the effects of a block on the utxo cache, ignoring that it may already have been applied. */
static bool RollforwardBlock(const CBlockIndex* pindex, CCoinsViewCache& inputs, const CChainParams& params)
{
// TODO: merge with ConnectBlock
CBlock block;
if (!ReadBlockFromDisk(block, pindex, params.GetConsensus())) {
return error("ReplayBlock(): ReadBlockFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
}
for (const CTransactionRef& tx : block.vtx) {
if (!tx->IsCoinBase()) {
for (const CTxIn &txin : tx->vin) {
inputs.SpendCoin(txin.prevout);
}
}
// Pass check = true as every addition may be an overwrite.
AddCoins(inputs, *tx, pindex->nHeight, true);
}
return true;
}
bool ReplayBlocks(const CChainParams& params, CCoinsView* view)
{
LOCK(cs_main);
CCoinsViewCache cache(view);
std::vector<uint256> hashHeads = view->GetHeadBlocks();
if (hashHeads.empty()) return true; // We're already in a consistent state.
if (hashHeads.size() != 2) return error("ReplayBlocks(): unknown inconsistent state");
uiInterface.ShowProgress(_("Replaying blocks..."), 0);
LogPrintf("Replaying blocks\n");
const CBlockIndex* pindexOld = nullptr; // Old tip during the interrupted flush.
const CBlockIndex* pindexNew; // New tip during the interrupted flush.
const CBlockIndex* pindexFork = nullptr; // Latest block common to both the old and the new tip.
if (mapBlockIndex.count(hashHeads[0]) == 0) {
return error("ReplayBlocks(): reorganization to unknown block requested");
}
pindexNew = mapBlockIndex[hashHeads[0]];
if (!hashHeads[1].IsNull()) { // The old tip is allowed to be 0, indicating it's the first flush.
if (mapBlockIndex.count(hashHeads[1]) == 0) {
return error("ReplayBlocks(): reorganization from unknown block requested");
}
pindexOld = mapBlockIndex[hashHeads[1]];
pindexFork = LastCommonAncestor(pindexOld, pindexNew);
assert(pindexFork != nullptr);
}
// Rollback along the old branch.
while (pindexOld != pindexFork) {
if (pindexOld->nHeight > 0) { // Never disconnect the genesis block.
CBlock block;
if (!ReadBlockFromDisk(block, pindexOld, params.GetConsensus())) {
return error("RollbackBlock(): ReadBlockFromDisk() failed at %d, hash=%s", pindexOld->nHeight, pindexOld->GetBlockHash().ToString());
}
LogPrintf("Rolling back %s (%i)\n", pindexOld->GetBlockHash().ToString(), pindexOld->nHeight);
DisconnectResult res = DisconnectBlock(block, pindexOld, cache);
if (res == DISCONNECT_FAILED) {
return error("RollbackBlock(): DisconnectBlock failed at %d, hash=%s", pindexOld->nHeight, pindexOld->GetBlockHash().ToString());
}
// If DISCONNECT_UNCLEAN is returned, it means a non-existing UTXO was deleted, or an existing UTXO was
// overwritten. It corresponds to cases where the block-to-be-disconnect never had all its operations
// applied to the UTXO set. However, as both writing a UTXO and deleting a UTXO are idempotent operations,
// the result is still a version of the UTXO set with the effects of that block undone.
}
pindexOld = pindexOld->pprev;
}
// Roll forward from the forking point to the new tip.
int nForkHeight = pindexFork ? pindexFork->nHeight : 0;
for (int nHeight = nForkHeight + 1; nHeight <= pindexNew->nHeight; ++nHeight) {
const CBlockIndex* pindex = pindexNew->GetAncestor(nHeight);
LogPrintf("Rolling forward %s (%i)\n", pindex->GetBlockHash().ToString(), nHeight);
if (!RollforwardBlock(pindex, cache, params)) return false;
}
cache.SetBestBlock(pindexNew->GetBlockHash());
cache.Flush();
uiInterface.ShowProgress("", 100);
return true;
}
bool RewindBlockIndex(const CChainParams& params)
{
LOCK(cs_main);

5
src/validation.h
View File

@ -260,6 +260,8 @@ bool LoadExternalBlockFile(const CChainParams& chainparams, FILE* fileIn, CDiskB
bool InitBlockIndex(const CChainParams& chainparams);
/** Load the block tree and coins database from disk */
bool LoadBlockIndex(const CChainParams& chainparams);
/** Update the chain tip based on database information. */
void LoadChainTip(const CChainParams& chainparams);
/** Unload database information */
void UnloadBlockIndex();
/** Run an instance of the script checking thread */
@ -424,6 +426,9 @@ public:
bool VerifyDB(const CChainParams& chainparams, CCoinsView *coinsview, int nCheckLevel, int nCheckDepth);
};
/** Replay blocks that aren't fully applied to the database. */
bool ReplayBlocks(const CChainParams& params, CCoinsView* view);
/** Find the last common block between the parameter chain and a locator. */
CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator);