src/wallet/db.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 "db.h"
   7
   8 #include "addrman.h"
   9 #include "fs.h"
  10 #include "hash.h"
  11 #include "protocol.h"
  12 #include "util.h"
  13 #include "utilstrencodings.h"
  14
  15 #include <stdint.h>
  16
  17 #ifndef WIN32
  18 #include <sys/stat.h>
  19 #endif
  20
  21 #include <boost/foreach.hpp>
  22 #include <boost/thread.hpp>
  23
  24 //
  25 // CDB
  26 //
  27
  28 CDBEnv bitdb;
  29
  30 void CDBEnv::EnvShutdown()
  31 {
  32     if (!fDbEnvInit)
  33         return;
  34
  35     fDbEnvInit = false;
  36     int ret = dbenv->close(0);
  37     if (ret != 0)
  38         LogPrintf("CDBEnv::EnvShutdown: Error %d shutting down database environment: %s\n", ret, DbEnv::strerror(ret));
  39     if (!fMockDb)
  40         DbEnv((u_int32_t)0).remove(strPath.c_str(), 0);
  41 }
  42
  43 void CDBEnv::Reset()
  44 {
  45     delete dbenv;
  46     dbenv = new DbEnv(DB_CXX_NO_EXCEPTIONS);
  47     fDbEnvInit = false;
  48     fMockDb = false;
  49 }
  50
  51 CDBEnv::CDBEnv() : dbenv(NULL)
  52 {
  53     Reset();
  54 }
  55
  56 CDBEnv::~CDBEnv()
  57 {
  58     EnvShutdown();
  59     delete dbenv;
  60     dbenv = NULL;
  61 }
  62
  63 void CDBEnv::Close()
  64 {
  65     EnvShutdown();
  66 }
  67
  68 bool CDBEnv::Open(const fs::path& pathIn)
  69 {
  70     if (fDbEnvInit)
  71         return true;
  72
  73     boost::this_thread::interruption_point();
  74
  75     strPath = pathIn.string();
  76     fs::path pathLogDir = pathIn / "database";
  77     TryCreateDirectory(pathLogDir);
  78     fs::path pathErrorFile = pathIn / "db.log";
  79     LogPrintf("CDBEnv::Open: LogDir=%s ErrorFile=%s\n", pathLogDir.string(), pathErrorFile.string());
  80
  81     unsigned int nEnvFlags = 0;
  82     if (GetBoolArg("-privdb", DEFAULT_WALLET_PRIVDB))
  83         nEnvFlags |= DB_PRIVATE;
  84
  85     dbenv->set_lg_dir(pathLogDir.string().c_str());
  86     dbenv->set_cachesize(0, 0x100000, 1); // 1 MiB should be enough for just the wallet
  87     dbenv->set_lg_bsize(0x10000);
  88     dbenv->set_lg_max(1048576);
  89     dbenv->set_lk_max_locks(40000);
  90     dbenv->set_lk_max_objects(40000);
  91     dbenv->set_errfile(fsbridge::fopen(pathErrorFile, "a")); /// debug
  92     dbenv->set_flags(DB_AUTO_COMMIT, 1);
  93     dbenv->set_flags(DB_TXN_WRITE_NOSYNC, 1);
  94     dbenv->log_set_config(DB_LOG_AUTO_REMOVE, 1);
  95     int ret = dbenv->open(strPath.c_str(),
  96                          DB_CREATE |
  97                              DB_INIT_LOCK |
  98                              DB_INIT_LOG |
  99                              DB_INIT_MPOOL |
 100                              DB_INIT_TXN |
 101                              DB_THREAD |
 102                              DB_RECOVER |
 103                              nEnvFlags,
 104                          S_IRUSR | S_IWUSR);
 105     if (ret != 0)
 106         return error("CDBEnv::Open: Error %d opening database environment: %s\n", ret, DbEnv::strerror(ret));
 107
 108     fDbEnvInit = true;
 109     fMockDb = false;
 110     return true;
 111 }
 112
 113 void CDBEnv::MakeMock()
 114 {
 115     if (fDbEnvInit)
 116         throw std::runtime_error("CDBEnv::MakeMock: Already initialized");
 117
 118     boost::this_thread::interruption_point();
 119
 120     LogPrint(BCLog::DB, "CDBEnv::MakeMock\n");
 121
 122     dbenv->set_cachesize(1, 0, 1);
 123     dbenv->set_lg_bsize(10485760 * 4);
 124     dbenv->set_lg_max(10485760);
 125     dbenv->set_lk_max_locks(10000);
 126     dbenv->set_lk_max_objects(10000);
 127     dbenv->set_flags(DB_AUTO_COMMIT, 1);
 128     dbenv->log_set_config(DB_LOG_IN_MEMORY, 1);
 129     int ret = dbenv->open(NULL,
 130                          DB_CREATE |
 131                              DB_INIT_LOCK |
 132                              DB_INIT_LOG |
 133                              DB_INIT_MPOOL |
 134                              DB_INIT_TXN |
 135                              DB_THREAD |
 136                              DB_PRIVATE,
 137                          S_IRUSR | S_IWUSR);
 138     if (ret > 0)
 139         throw std::runtime_error(strprintf("CDBEnv::MakeMock: Error %d opening database environment.", ret));
 140
 141     fDbEnvInit = true;
 142     fMockDb = true;
 143 }
 144
 145 CDBEnv::VerifyResult CDBEnv::Verify(const std::string& strFile, recoverFunc_type recoverFunc, std::string& out_backup_filename)
 146 {
 147     LOCK(cs_db);
 148     assert(mapFileUseCount.count(strFile) == 0);
 149
 150     Db db(dbenv, 0);
 151     int result = db.verify(strFile.c_str(), NULL, NULL, 0);
 152     if (result == 0)
 153         return VERIFY_OK;
 154     else if (recoverFunc == NULL)
 155         return RECOVER_FAIL;
 156
 157     // Try to recover:
 158     bool fRecovered = (*recoverFunc)(strFile, out_backup_filename);
 159     return (fRecovered ? RECOVER_OK : RECOVER_FAIL);
 160 }
 161
 162 bool CDB::Recover(const std::string& filename, void *callbackDataIn, bool (*recoverKVcallback)(void* callbackData, CDataStream ssKey, CDataStream ssValue), std::string& newFilename)
 163 {
 164     // Recovery procedure:
 165     // move wallet file to walletfilename.timestamp.bak
 166     // Call Salvage with fAggressive=true to
 167     // get as much data as possible.
 168     // Rewrite salvaged data to fresh wallet file
 169     // Set -rescan so any missing transactions will be
 170     // found.
 171     int64_t now = GetTime();
 172     newFilename = strprintf("%s.%d.bak", filename, now);
 173
 174     int result = bitdb.dbenv->dbrename(NULL, filename.c_str(), NULL,
 175                                        newFilename.c_str(), DB_AUTO_COMMIT);
 176     if (result == 0)
 177         LogPrintf("Renamed %s to %s\n", filename, newFilename);
 178     else
 179     {
 180         LogPrintf("Failed to rename %s to %s\n", filename, newFilename);
 181         return false;
 182     }
 183
 184     std::vector<CDBEnv::KeyValPair> salvagedData;
 185     bool fSuccess = bitdb.Salvage(newFilename, true, salvagedData);
 186     if (salvagedData.empty())
 187     {
 188         LogPrintf("Salvage(aggressive) found no records in %s.\n", newFilename);
 189         return false;
 190     }
 191     LogPrintf("Salvage(aggressive) found %u records\n", salvagedData.size());
 192
 193     std::unique_ptr<Db> pdbCopy(new Db(bitdb.dbenv, 0));
 194     int ret = pdbCopy->open(NULL,               // Txn pointer
 195                             filename.c_str(),   // Filename
 196                             "main",             // Logical db name
 197                             DB_BTREE,           // Database type
 198                             DB_CREATE,          // Flags
 199                             0);
 200     if (ret > 0)
 201     {
 202         LogPrintf("Cannot create database file %s\n", filename);
 203         return false;
 204     }
 205
 206     DbTxn* ptxn = bitdb.TxnBegin();
 207     for (CDBEnv::KeyValPair& row : salvagedData)
 208     {
 209         if (recoverKVcallback)
 210         {
 211             CDataStream ssKey(row.first, SER_DISK, CLIENT_VERSION);
 212             CDataStream ssValue(row.second, SER_DISK, CLIENT_VERSION);
 213             if (!(*recoverKVcallback)(callbackDataIn, ssKey, ssValue))
 214                 continue;
 215         }
 216         Dbt datKey(&row.first[0], row.first.size());
 217         Dbt datValue(&row.second[0], row.second.size());
 218         int ret2 = pdbCopy->put(ptxn, &datKey, &datValue, DB_NOOVERWRITE);
 219         if (ret2 > 0)
 220             fSuccess = false;
 221     }
 222     ptxn->commit(0);
 223     pdbCopy->close(0);
 224
 225     return fSuccess;
 226 }
 227
 228 bool CDB::VerifyEnvironment(const std::string& walletFile, const fs::path& dataDir, std::string& errorStr)
 229 {
 230     LogPrintf("Using BerkeleyDB version %s\n", DbEnv::version(0, 0, 0));
 231     LogPrintf("Using wallet %s\n", walletFile);
 232
 233     // Wallet file must be a plain filename without a directory
 234     if (walletFile != fs::basename(walletFile) + fs::extension(walletFile))
 235     {
 236         errorStr = strprintf(_("Wallet %s resides outside data directory %s"), walletFile, dataDir.string());
 237         return false;
 238     }
 239
 240     if (!bitdb.Open(dataDir))
 241     {
 242         // try moving the database env out of the way
 243         fs::path pathDatabase = dataDir / "database";
 244         fs::path pathDatabaseBak = dataDir / strprintf("database.%d.bak", GetTime());
 245         try {
 246             fs::rename(pathDatabase, pathDatabaseBak);
 247             LogPrintf("Moved old %s to %s. Retrying.\n", pathDatabase.string(), pathDatabaseBak.string());
 248         } catch (const fs::filesystem_error&) {
 249             // failure is ok (well, not really, but it's not worse than what we started with)
 250         }
 251
 252         // try again
 253         if (!bitdb.Open(dataDir)) {
 254             // if it still fails, it probably means we can't even create the database env
 255             errorStr = strprintf(_("Error initializing wallet database environment %s!"), GetDataDir());
 256             return false;
 257         }
 258     }
 259     return true;
 260 }
 261
 262 bool CDB::VerifyDatabaseFile(const std::string& walletFile, const fs::path& dataDir, std::string& warningStr, std::string& errorStr, CDBEnv::recoverFunc_type recoverFunc)
 263 {
 264     if (fs::exists(dataDir / walletFile))
 265     {
 266         std::string backup_filename;
 267         CDBEnv::VerifyResult r = bitdb.Verify(walletFile, recoverFunc, backup_filename);
 268         if (r == CDBEnv::RECOVER_OK)
 269         {
 270             warningStr = strprintf(_("Warning: Wallet file corrupt, data salvaged!"
 271                                      " Original %s saved as %s in %s; if"
 272                                      " your balance or transactions are incorrect you should"
 273                                      " restore from a backup."),
 274                                    walletFile, backup_filename, dataDir);
 275         }
 276         if (r == CDBEnv::RECOVER_FAIL)
 277         {
 278             errorStr = strprintf(_("%s corrupt, salvage failed"), walletFile);
 279             return false;
 280         }
 281     }
 282     // also return true if files does not exists
 283     return true;
 284 }
 285
 286 /* End of headers, beginning of key/value data */
 287 static const char *HEADER_END = "HEADER=END";
 288 /* End of key/value data */
 289 static const char *DATA_END = "DATA=END";
 290
 291 bool CDBEnv::Salvage(const std::string& strFile, bool fAggressive, std::vector<CDBEnv::KeyValPair>& vResult)
 292 {
 293     LOCK(cs_db);
 294     assert(mapFileUseCount.count(strFile) == 0);
 295
 296     u_int32_t flags = DB_SALVAGE;
 297     if (fAggressive)
 298         flags |= DB_AGGRESSIVE;
 299
 300     std::stringstream strDump;
 301
 302     Db db(dbenv, 0);
 303     int result = db.verify(strFile.c_str(), NULL, &strDump, flags);
 304     if (result == DB_VERIFY_BAD) {
 305         LogPrintf("CDBEnv::Salvage: Database salvage found errors, all data may not be recoverable.\n");
 306         if (!fAggressive) {
 307             LogPrintf("CDBEnv::Salvage: Rerun with aggressive mode to ignore errors and continue.\n");
 308             return false;
 309         }
 310     }
 311     if (result != 0 && result != DB_VERIFY_BAD) {
 312         LogPrintf("CDBEnv::Salvage: Database salvage failed with result %d.\n", result);
 313         return false;
 314     }
 315
 316     // Format of bdb dump is ascii lines:
 317     // header lines...
 318     // HEADER=END
 319     //  hexadecimal key
 320     //  hexadecimal value
 321     //  ... repeated
 322     // DATA=END
 323
 324     std::string strLine;
 325     while (!strDump.eof() && strLine != HEADER_END)
 326         getline(strDump, strLine); // Skip past header
 327
 328     std::string keyHex, valueHex;
 329     while (!strDump.eof() && keyHex != DATA_END) {
 330         getline(strDump, keyHex);
 331         if (keyHex != DATA_END) {
 332             if (strDump.eof())
 333                 break;
 334             getline(strDump, valueHex);
 335             if (valueHex == DATA_END) {
 336                 LogPrintf("CDBEnv::Salvage: WARNING: Number of keys in data does not match number of values.\n");
 337                 break;
 338             }
 339             vResult.push_back(make_pair(ParseHex(keyHex), ParseHex(valueHex)));
 340         }
 341     }
 342
 343     if (keyHex != DATA_END) {
 344         LogPrintf("CDBEnv::Salvage: WARNING: Unexpected end of file while reading salvage output.\n");
 345         return false;
 346     }
 347
 348     return (result == 0);
 349 }
 350
 351
 352 void CDBEnv::CheckpointLSN(const std::string& strFile)
 353 {
 354     dbenv->txn_checkpoint(0, 0, 0);
 355     if (fMockDb)
 356         return;
 357     dbenv->lsn_reset(strFile.c_str(), 0);
 358 }
 359
 360
 361 CDB::CDB(CWalletDBWrapper& dbw, const char* pszMode, bool fFlushOnCloseIn) : pdb(NULL), activeTxn(NULL)
 362 {
 363     fReadOnly = (!strchr(pszMode, '+') && !strchr(pszMode, 'w'));
 364     fFlushOnClose = fFlushOnCloseIn;
 365     env = dbw.env;
 366     if (dbw.IsDummy()) {
 367         return;
 368     }
 369     const std::string &strFilename = dbw.strFile;
 370
 371     bool fCreate = strchr(pszMode, 'c') != NULL;
 372     unsigned int nFlags = DB_THREAD;
 373     if (fCreate)
 374         nFlags |= DB_CREATE;
 375
 376     {
 377         LOCK(env->cs_db);
 378         if (!env->Open(GetDataDir()))
 379             throw std::runtime_error("CDB: Failed to open database environment.");
 380
 381         strFile = strFilename;
 382         ++env->mapFileUseCount[strFile];
 383         pdb = env->mapDb[strFile];
 384         if (pdb == NULL) {
 385             int ret;
 386             pdb = new Db(env->dbenv, 0);
 387
 388             bool fMockDb = env->IsMock();
 389             if (fMockDb) {
 390                 DbMpoolFile* mpf = pdb->get_mpf();
 391                 ret = mpf->set_flags(DB_MPOOL_NOFILE, 1);
 392                 if (ret != 0)
 393                     throw std::runtime_error(strprintf("CDB: Failed to configure for no temp file backing for database %s", strFile));
 394             }
 395
 396             ret = pdb->open(NULL,                               // Txn pointer
 397                             fMockDb ? NULL : strFile.c_str(),   // Filename
 398                             fMockDb ? strFile.c_str() : "main", // Logical db name
 399                             DB_BTREE,                           // Database type
 400                             nFlags,                             // Flags
 401                             0);
 402
 403             if (ret != 0) {
 404                 delete pdb;
 405                 pdb = NULL;
 406                 --env->mapFileUseCount[strFile];
 407                 strFile = "";
 408                 throw std::runtime_error(strprintf("CDB: Error %d, can't open database %s", ret, strFilename));
 409             }
 410
 411             if (fCreate && !Exists(std::string("version"))) {
 412                 bool fTmp = fReadOnly;
 413                 fReadOnly = false;
 414                 WriteVersion(CLIENT_VERSION);
 415                 fReadOnly = fTmp;
 416             }
 417
 418             env->mapDb[strFile] = pdb;
 419         }
 420     }
 421 }
 422
 423 void CDB::Flush()
 424 {
 425     if (activeTxn)
 426         return;
 427
 428     // Flush database activity from memory pool to disk log
 429     unsigned int nMinutes = 0;
 430     if (fReadOnly)
 431         nMinutes = 1;
 432
 433     env->dbenv->txn_checkpoint(nMinutes ? GetArg("-dblogsize", DEFAULT_WALLET_DBLOGSIZE) * 1024 : 0, nMinutes, 0);
 434 }
 435
 436 void CWalletDBWrapper::IncrementUpdateCounter()
 437 {
 438     ++nUpdateCounter;
 439 }
 440
 441 void CDB::Close()
 442 {
 443     if (!pdb)
 444         return;
 445     if (activeTxn)
 446         activeTxn->abort();
 447     activeTxn = NULL;
 448     pdb = NULL;
 449
 450     if (fFlushOnClose)
 451         Flush();
 452
 453     {
 454         LOCK(env->cs_db);
 455         --env->mapFileUseCount[strFile];
 456     }
 457 }
 458
 459 void CDBEnv::CloseDb(const std::string& strFile)
 460 {
 461     {
 462         LOCK(cs_db);
 463         if (mapDb[strFile] != NULL) {
 464             // Close the database handle
 465             Db* pdb = mapDb[strFile];
 466             pdb->close(0);
 467             delete pdb;
 468             mapDb[strFile] = NULL;
 469         }
 470     }
 471 }
 472
 473 bool CDB::Rewrite(CWalletDBWrapper& dbw, const char* pszSkip)
 474 {
 475     if (dbw.IsDummy()) {
 476         return true;
 477     }
 478     CDBEnv *env = dbw.env;
 479     const std::string& strFile = dbw.strFile;
 480     while (true) {
 481         {
 482             LOCK(env->cs_db);
 483             if (!env->mapFileUseCount.count(strFile) || env->mapFileUseCount[strFile] == 0) {
 484                 // Flush log data to the dat file
 485                 env->CloseDb(strFile);
 486                 env->CheckpointLSN(strFile);
 487                 env->mapFileUseCount.erase(strFile);
 488
 489                 bool fSuccess = true;
 490                 LogPrintf("CDB::Rewrite: Rewriting %s...\n", strFile);
 491                 std::string strFileRes = strFile + ".rewrite";
 492                 { // surround usage of db with extra {}
 493                     CDB db(dbw, "r");
 494                     Db* pdbCopy = new Db(env->dbenv, 0);
 495
 496                     int ret = pdbCopy->open(NULL,               // Txn pointer
 497                                             strFileRes.c_str(), // Filename
 498                                             "main",             // Logical db name
 499                                             DB_BTREE,           // Database type
 500                                             DB_CREATE,          // Flags
 501                                             0);
 502                     if (ret > 0) {
 503                         LogPrintf("CDB::Rewrite: Can't create database file %s\n", strFileRes);
 504                         fSuccess = false;
 505                     }
 506
 507                     Dbc* pcursor = db.GetCursor();
 508                     if (pcursor)
 509                         while (fSuccess) {
 510                             CDataStream ssKey(SER_DISK, CLIENT_VERSION);
 511                             CDataStream ssValue(SER_DISK, CLIENT_VERSION);
 512                             int ret1 = db.ReadAtCursor(pcursor, ssKey, ssValue);
 513                             if (ret1 == DB_NOTFOUND) {
 514                                 pcursor->close();
 515                                 break;
 516                             } else if (ret1 != 0) {
 517                                 pcursor->close();
 518                                 fSuccess = false;
 519                                 break;
 520                             }
 521                             if (pszSkip &&
 522                                 strncmp(ssKey.data(), pszSkip, std::min(ssKey.size(), strlen(pszSkip))) == 0)
 523                                 continue;
 524                             if (strncmp(ssKey.data(), "\x07version", 8) == 0) {
 525                                 // Update version:
 526                                 ssValue.clear();
 527                                 ssValue << CLIENT_VERSION;
 528                             }
 529                             Dbt datKey(ssKey.data(), ssKey.size());
 530                             Dbt datValue(ssValue.data(), ssValue.size());
 531                             int ret2 = pdbCopy->put(NULL, &datKey, &datValue, DB_NOOVERWRITE);
 532                             if (ret2 > 0)
 533                                 fSuccess = false;
 534                         }
 535                     if (fSuccess) {
 536                         db.Close();
 537                         env->CloseDb(strFile);
 538                         if (pdbCopy->close(0))
 539                             fSuccess = false;
 540                         delete pdbCopy;
 541                     }
 542                 }
 543                 if (fSuccess) {
 544                     Db dbA(env->dbenv, 0);
 545                     if (dbA.remove(strFile.c_str(), NULL, 0))
 546                         fSuccess = false;
 547                     Db dbB(env->dbenv, 0);
 548                     if (dbB.rename(strFileRes.c_str(), NULL, strFile.c_str(), 0))
 549                         fSuccess = false;
 550                 }
 551                 if (!fSuccess)
 552                     LogPrintf("CDB::Rewrite: Failed to rewrite database file %s\n", strFileRes);
 553                 return fSuccess;
 554             }
 555         }
 556         MilliSleep(100);
 557     }
 558     return false;
 559 }
 560
 561
 562 void CDBEnv::Flush(bool fShutdown)
 563 {
 564     int64_t nStart = GetTimeMillis();
 565     // Flush log data to the actual data file on all files that are not in use
 566     LogPrint(BCLog::DB, "CDBEnv::Flush: Flush(%s)%s\n", fShutdown ? "true" : "false", fDbEnvInit ? "" : " database not started");
 567     if (!fDbEnvInit)
 568         return;
 569     {
 570         LOCK(cs_db);
 571         std::map<std::string, int>::iterator mi = mapFileUseCount.begin();
 572         while (mi != mapFileUseCount.end()) {
 573             std::string strFile = (*mi).first;
 574             int nRefCount = (*mi).second;
 575             LogPrint(BCLog::DB, "CDBEnv::Flush: Flushing %s (refcount = %d)...\n", strFile, nRefCount);
 576             if (nRefCount == 0) {
 577                 // Move log data to the dat file
 578                 CloseDb(strFile);
 579                 LogPrint(BCLog::DB, "CDBEnv::Flush: %s checkpoint\n", strFile);
 580                 dbenv->txn_checkpoint(0, 0, 0);
 581                 LogPrint(BCLog::DB, "CDBEnv::Flush: %s detach\n", strFile);
 582                 if (!fMockDb)
 583                     dbenv->lsn_reset(strFile.c_str(), 0);
 584                 LogPrint(BCLog::DB, "CDBEnv::Flush: %s closed\n", strFile);
 585                 mapFileUseCount.erase(mi++);
 586             } else
 587                 mi++;
 588         }
 589         LogPrint(BCLog::DB, "CDBEnv::Flush: Flush(%s)%s took %15dms\n", fShutdown ? "true" : "false", fDbEnvInit ? "" : " database not started", GetTimeMillis() - nStart);
 590         if (fShutdown) {
 591             char** listp;
 592             if (mapFileUseCount.empty()) {
 593                 dbenv->log_archive(&listp, DB_ARCH_REMOVE);
 594                 Close();
 595                 if (!fMockDb)
 596                     fs::remove_all(fs::path(strPath) / "database");
 597             }
 598         }
 599     }
 600 }
 601
 602 bool CDB::PeriodicFlush(CWalletDBWrapper& dbw)
 603 {
 604     if (dbw.IsDummy()) {
 605         return true;
 606     }
 607     bool ret = false;
 608     CDBEnv *env = dbw.env;
 609     const std::string& strFile = dbw.strFile;
 610     TRY_LOCK(bitdb.cs_db,lockDb);
 611     if (lockDb)
 612     {
 613         // Don't do this if any databases are in use
 614         int nRefCount = 0;
 615         std::map<std::string, int>::iterator mit = env->mapFileUseCount.begin();
 616         while (mit != env->mapFileUseCount.end())
 617         {
 618             nRefCount += (*mit).second;
 619             mit++;
 620         }
 621
 622         if (nRefCount == 0)
 623         {
 624             boost::this_thread::interruption_point();
 625             std::map<std::string, int>::iterator mi = env->mapFileUseCount.find(strFile);
 626             if (mi != env->mapFileUseCount.end())
 627             {
 628                 LogPrint(BCLog::DB, "Flushing %s\n", strFile);
 629                 int64_t nStart = GetTimeMillis();
 630
 631                 // Flush wallet file so it's self contained
 632                 env->CloseDb(strFile);
 633                 env->CheckpointLSN(strFile);
 634
 635                 env->mapFileUseCount.erase(mi++);
 636                 LogPrint(BCLog::DB, "Flushed %s %dms\n", strFile, GetTimeMillis() - nStart);
 637                 ret = true;
 638             }
 639         }
 640     }
 641
 642     return ret;
 643 }
 644
 645 bool CWalletDBWrapper::Rewrite(const char* pszSkip)
 646 {
 647     return CDB::Rewrite(*this, pszSkip);
 648 }
 649
 650 bool CWalletDBWrapper::Backup(const std::string& strDest)
 651 {
 652     if (IsDummy()) {
 653         return false;
 654     }
 655     while (true)
 656     {
 657         {
 658             LOCK(env->cs_db);
 659             if (!env->mapFileUseCount.count(strFile) || env->mapFileUseCount[strFile] == 0)
 660             {
 661                 // Flush log data to the dat file
 662                 env->CloseDb(strFile);
 663                 env->CheckpointLSN(strFile);
 664                 env->mapFileUseCount.erase(strFile);
 665
 666                 // Copy wallet file
 667                 fs::path pathSrc = GetDataDir() / strFile;
 668                 fs::path pathDest(strDest);
 669                 if (fs::is_directory(pathDest))
 670                     pathDest /= strFile;
 671
 672                 try {
 673                     fs::copy_file(pathSrc, pathDest, fs::copy_option::overwrite_if_exists);
 674                     LogPrintf("copied %s to %s\n", strFile, pathDest.string());
 675                     return true;
 676                 } catch (const fs::filesystem_error& e) {
 677                     LogPrintf("error copying %s to %s - %s\n", strFile, pathDest.string(), e.what());
 678                     return false;
 679                 }
 680             }
 681         }
 682         MilliSleep(100);
 683     }
 684     return false;
 685 }
 686
 687 void CWalletDBWrapper::Flush(bool shutdown)
 688 {
 689     if (!IsDummy()) {
 690         env->Flush(shutdown);
 691     }
 692 }