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[db] Migration for txindex data to new, separate database.

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This commit is contained in:
Jim Posen 2017-12-11 16:58:25 -08:00
parent 0cb8303241
commit c88bcec93f
2 changed files with 143 additions and 0 deletions
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139
src/txdb.cpp
View file

@ -22,6 +22,7 @@ static const char DB_COIN = 'C';
static const char DB_COINS = 'c';
static const char DB_BLOCK_FILES = 'f';
static const char DB_TXINDEX = 't';
static const char DB_TXINDEX_BLOCK = 'T';
static const char DB_BLOCK_INDEX = 'b';
static const char DB_BEST_BLOCK = 'B';
@ -456,3 +457,141 @@ bool TxIndexDB::WriteBestBlock(const CBlockLocator& locator)
{
return Write(DB_BEST_BLOCK, locator);
}
/*
* Safely persist a transfer of data from the old txindex database to the new one, and compact the
* range of keys updated. This is used internally by MigrateData.
*/
static void WriteTxIndexMigrationBatches(TxIndexDB& newdb, CBlockTreeDB& olddb,
CDBBatch& batch_newdb, CDBBatch& batch_olddb,
const std::pair<unsigned char, uint256>& begin_key,
const std::pair<unsigned char, uint256>& end_key)
{
// Sync new DB changes to disk before deleting from old DB.
newdb.WriteBatch(batch_newdb, /*fSync=*/ true);
olddb.WriteBatch(batch_olddb);
olddb.CompactRange(begin_key, end_key);
batch_newdb.Clear();
batch_olddb.Clear();
}
bool TxIndexDB::MigrateData(CBlockTreeDB& block_tree_db, const CBlockLocator& best_locator)
{
// The prior implementation of txindex was always in sync with block index
// and presence was indicated with a boolean DB flag. If the flag is set,
// this means the txindex from a previous version is valid and in sync with
// the chain tip. The first step of the migration is to unset the flag and
// write the chain hash to a separate key, DB_TXINDEX_BLOCK. After that, the
// index entries are copied over in batches to the new database. Finally,
// DB_TXINDEX_BLOCK is erased from the old database and the block hash is
// written to the new database.
//
// Unsetting the boolean flag ensures that if the node is downgraded to a
// previous version, it will not see a corrupted, partially migrated index
// -- it will see that the txindex is disabled. When the node is upgraded
// again, the migration will pick up where it left off and sync to the block
// with hash DB_TXINDEX_BLOCK.
bool f_legacy_flag = false;
block_tree_db.ReadFlag("txindex", f_legacy_flag);
if (f_legacy_flag) {
if (!block_tree_db.Write(DB_TXINDEX_BLOCK, best_locator)) {
return error("%s: cannot write block indicator", __func__);
}
if (!block_tree_db.WriteFlag("txindex", false)) {
return error("%s: cannot write block index db flag", __func__);
}
}
CBlockLocator locator;
if (!block_tree_db.Read(DB_TXINDEX_BLOCK, locator)) {
return true;
}
int64_t count = 0;
LogPrintf("Upgrading txindex database... [0%%]\n");
uiInterface.ShowProgress(_("Upgrading txindex database"), 0, true);
int report_done = 0;
const size_t batch_size = 1 << 24; // 16 MiB
CDBBatch batch_newdb(*this);
CDBBatch batch_olddb(block_tree_db);
std::pair<unsigned char, uint256> key;
std::pair<unsigned char, uint256> begin_key{DB_TXINDEX, uint256()};
std::pair<unsigned char, uint256> prev_key = begin_key;
bool interrupted = false;
std::unique_ptr<CDBIterator> cursor(block_tree_db.NewIterator());
for (cursor->Seek(begin_key); cursor->Valid(); cursor->Next()) {
boost::this_thread::interruption_point();
if (ShutdownRequested()) {
interrupted = true;
break;
}
if (!cursor->GetKey(key)) {
return error("%s: cannot get key from valid cursor", __func__);
}
if (key.first != DB_TXINDEX) {
break;
}
// Log progress every 10%.
if (++count % 256 == 0) {
// Since txids are uniformly random and traversed in increasing order, the high 16 bits
// of the hash can be used to estimate the current progress.
const uint256& txid = key.second;
uint32_t high_nibble =
(static_cast<uint32_t>(*(txid.begin() + 0)) << 8) +
(static_cast<uint32_t>(*(txid.begin() + 1)) << 0);
int percentage_done = (int)(high_nibble * 100.0 / 65536.0 + 0.5);
uiInterface.ShowProgress(_("Upgrading txindex database"), percentage_done, true);
if (report_done < percentage_done/10) {
LogPrintf("Upgrading txindex database... [%d%%]\n", percentage_done);
report_done = percentage_done/10;
}
}
CDiskTxPos value;
if (!cursor->GetValue(value)) {
return error("%s: cannot parse txindex record", __func__);
}
batch_newdb.Write(key, value);
batch_olddb.Erase(key);
if (batch_newdb.SizeEstimate() > batch_size || batch_olddb.SizeEstimate() > batch_size) {
// NOTE: it's OK to delete the key pointed at by the current DB cursor while iterating
// because LevelDB iterators are guaranteed to provide a consistent view of the
// underlying data, like a lightweight snapshot.
WriteTxIndexMigrationBatches(*this, block_tree_db,
batch_newdb, batch_olddb,
prev_key, key);
prev_key = key;
}
}
// If these final DB batches complete the migration, write the best block
// hash marker to the new database and delete from the old one. This signals
// that the former is fully caught up to that point in the blockchain and
// that all txindex entries have been removed from the latter.
if (!interrupted) {
batch_olddb.Erase(DB_TXINDEX_BLOCK);
batch_newdb.Write(DB_BEST_BLOCK, locator);
}
WriteTxIndexMigrationBatches(*this, block_tree_db,
batch_newdb, batch_olddb,
begin_key, key);
if (interrupted) {
LogPrintf("[CANCELLED].\n");
return false;
}
uiInterface.ShowProgress("", 100, false);
LogPrintf("[DONE].\n");
return true;
}

4
src/txdb.h
View file

@ -151,6 +151,10 @@ public:
/// Write block locator of the chain that the txindex is in sync with.
bool WriteBestBlock(const CBlockLocator& locator);
/// Migrate txindex data from the block tree DB, where it may be for older nodes that have not
/// been upgraded yet to the new database.
bool MigrateData(CBlockTreeDB& block_tree_db, const CBlockLocator& best_locator);
};
#endif // BITCOIN_TXDB_H