walletdb: Move BDB specific things into bdb.{cpp/h}

Leave wallet/db.{cpp/h} for generic WalletDatabase stuff. The BDB
specific stuff goes into bdb.{cpp/h}

1 files changed, 805 insertions, 0 deletions

diff --git a/src/wallet/bdb.cpp b/src/wallet/bdb.cpp
new file mode 100644
index 0000000000..7ed9c88122
--- /dev/null
+++ b/src/wallet/bdb.cpp
@@ -0,0 +1,805 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <wallet/bdb.h>
+#include <wallet/db.h>
+
+#include <util/strencodings.h>
+#include <util/translation.h>
+
+#include <stdint.h>
+
+#ifndef WIN32
+#include <sys/stat.h>
+#endif
+
+namespace {
+
+//! Make sure database has a unique fileid within the environment. If it
+//! doesn't, throw an error. BDB caches do not work properly when more than one
+//! open database has the same fileid (values written to one database may show
+//! up in reads to other databases).
+//!
+//! BerkeleyDB generates unique fileids by default
+//! (https://docs.oracle.com/cd/E17275_01/html/programmer_reference/program_copy.html),
+//! so bitcoin should never create different databases with the same fileid, but
+//! this error can be triggered if users manually copy database files.
+void CheckUniqueFileid(const BerkeleyEnvironment& env, const std::string& filename, Db& db, WalletDatabaseFileId& fileid)
+{
+    if (env.IsMock()) return;
+
+    int ret = db.get_mpf()->get_fileid(fileid.value);
+    if (ret != 0) {
+        throw std::runtime_error(strprintf("BerkeleyBatch: Can't open database %s (get_fileid failed with %d)", filename, ret));
+    }
+
+    for (const auto& item : env.m_fileids) {
+        if (fileid == item.second && &fileid != &item.second) {
+            throw std::runtime_error(strprintf("BerkeleyBatch: Can't open database %s (duplicates fileid %s from %s)", filename,
+                HexStr(std::begin(item.second.value), std::end(item.second.value)), item.first));
+        }
+    }
+}
+
+RecursiveMutex cs_db;
+std::map<std::string, std::weak_ptr<BerkeleyEnvironment>> g_dbenvs GUARDED_BY(cs_db); //!< Map from directory name to db environment.
+} // namespace
+
+bool WalletDatabaseFileId::operator==(const WalletDatabaseFileId& rhs) const
+{
+    return memcmp(value, &rhs.value, sizeof(value)) == 0;
+}
+
+bool IsBDBWalletLoaded(const fs::path& wallet_path)
+{
+    fs::path env_directory;
+    std::string database_filename;
+    SplitWalletPath(wallet_path, env_directory, database_filename);
+    LOCK(cs_db);
+    auto env = g_dbenvs.find(env_directory.string());
+    if (env == g_dbenvs.end()) return false;
+    auto database = env->second.lock();
+    return database && database->IsDatabaseLoaded(database_filename);
+}
+
+/**
+ * @param[in] wallet_path Path to wallet directory. Or (for backwards compatibility only) a path to a berkeley btree data file inside a wallet directory.
+ * @param[out] database_filename Filename of berkeley btree data file inside the wallet directory.
+ * @return A shared pointer to the BerkeleyEnvironment object for the wallet directory, never empty because ~BerkeleyEnvironment
+ * erases the weak pointer from the g_dbenvs map.
+ * @post A new BerkeleyEnvironment weak pointer is inserted into g_dbenvs if the directory path key was not already in the map.
+ */
+std::shared_ptr<BerkeleyEnvironment> GetWalletEnv(const fs::path& wallet_path, std::string& database_filename)
+{
+    fs::path env_directory;
+    SplitWalletPath(wallet_path, env_directory, database_filename);
+    LOCK(cs_db);
+    auto inserted = g_dbenvs.emplace(env_directory.string(), std::weak_ptr<BerkeleyEnvironment>());
+    if (inserted.second) {
+        auto env = std::make_shared<BerkeleyEnvironment>(env_directory.string());
+        inserted.first->second = env;
+        return env;
+    }
+    return inserted.first->second.lock();
+}
+
+//
+// BerkeleyBatch
+//
+
+void BerkeleyEnvironment::Close()
+{
+    if (!fDbEnvInit)
+        return;
+
+    fDbEnvInit = false;
+
+    for (auto& db : m_databases) {
+        auto count = mapFileUseCount.find(db.first);
+        assert(count == mapFileUseCount.end() || count->second == 0);
+        BerkeleyDatabase& database = db.second.get();
+        if (database.m_db) {
+            database.m_db->close(0);
+            database.m_db.reset();
+        }
+    }
+
+    FILE* error_file = nullptr;
+    dbenv->get_errfile(&error_file);
+
+    int ret = dbenv->close(0);
+    if (ret != 0)
+        LogPrintf("BerkeleyEnvironment::Close: Error %d closing database environment: %s\n", ret, DbEnv::strerror(ret));
+    if (!fMockDb)
+        DbEnv((u_int32_t)0).remove(strPath.c_str(), 0);
+
+    if (error_file) fclose(error_file);
+
+    UnlockDirectory(strPath, ".walletlock");
+}
+
+void BerkeleyEnvironment::Reset()
+{
+    dbenv.reset(new DbEnv(DB_CXX_NO_EXCEPTIONS));
+    fDbEnvInit = false;
+    fMockDb = false;
+}
+
+BerkeleyEnvironment::BerkeleyEnvironment(const fs::path& dir_path) : strPath(dir_path.string())
+{
+    Reset();
+}
+
+BerkeleyEnvironment::~BerkeleyEnvironment()
+{
+    LOCK(cs_db);
+    g_dbenvs.erase(strPath);
+    Close();
+}
+
+bool BerkeleyEnvironment::Open(bool retry)
+{
+    if (fDbEnvInit) {
+        return true;
+    }
+
+    fs::path pathIn = strPath;
+    TryCreateDirectories(pathIn);
+    if (!LockDirectory(pathIn, ".walletlock")) {
+        LogPrintf("Cannot obtain a lock on wallet directory %s. Another instance of bitcoin may be using it.\n", strPath);
+        return false;
+    }
+
+    fs::path pathLogDir = pathIn / "database";
+    TryCreateDirectories(pathLogDir);
+    fs::path pathErrorFile = pathIn / "db.log";
+    LogPrintf("BerkeleyEnvironment::Open: LogDir=%s ErrorFile=%s\n", pathLogDir.string(), pathErrorFile.string());
+
+    unsigned int nEnvFlags = 0;
+    if (gArgs.GetBoolArg("-privdb", DEFAULT_WALLET_PRIVDB))
+        nEnvFlags |= DB_PRIVATE;
+
+    dbenv->set_lg_dir(pathLogDir.string().c_str());
+    dbenv->set_cachesize(0, 0x100000, 1); // 1 MiB should be enough for just the wallet
+    dbenv->set_lg_bsize(0x10000);
+    dbenv->set_lg_max(1048576);
+    dbenv->set_lk_max_locks(40000);
+    dbenv->set_lk_max_objects(40000);
+    dbenv->set_errfile(fsbridge::fopen(pathErrorFile, "a")); /// debug
+    dbenv->set_flags(DB_AUTO_COMMIT, 1);
+    dbenv->set_flags(DB_TXN_WRITE_NOSYNC, 1);
+    dbenv->log_set_config(DB_LOG_AUTO_REMOVE, 1);
+    int ret = dbenv->open(strPath.c_str(),
+                         DB_CREATE |
+                             DB_INIT_LOCK |
+                             DB_INIT_LOG |
+                             DB_INIT_MPOOL |
+                             DB_INIT_TXN |
+                             DB_THREAD |
+                             DB_RECOVER |
+                             nEnvFlags,
+                         S_IRUSR | S_IWUSR);
+    if (ret != 0) {
+        LogPrintf("BerkeleyEnvironment::Open: Error %d opening database environment: %s\n", ret, DbEnv::strerror(ret));
+        int ret2 = dbenv->close(0);
+        if (ret2 != 0) {
+            LogPrintf("BerkeleyEnvironment::Open: Error %d closing failed database environment: %s\n", ret2, DbEnv::strerror(ret2));
+        }
+        Reset();
+        if (retry) {
+            // try moving the database env out of the way
+            fs::path pathDatabaseBak = pathIn / strprintf("database.%d.bak", GetTime());
+            try {
+                fs::rename(pathLogDir, pathDatabaseBak);
+                LogPrintf("Moved old %s to %s. Retrying.\n", pathLogDir.string(), pathDatabaseBak.string());
+            } catch (const fs::filesystem_error&) {
+                // failure is ok (well, not really, but it's not worse than what we started with)
+            }
+            // try opening it again one more time
+            if (!Open(false /* retry */)) {
+                // if it still fails, it probably means we can't even create the database env
+                return false;
+            }
+        } else {
+            return false;
+        }
+    }
+
+    fDbEnvInit = true;
+    fMockDb = false;
+    return true;
+}
+
+//! Construct an in-memory mock Berkeley environment for testing
+BerkeleyEnvironment::BerkeleyEnvironment()
+{
+    Reset();
+
+    LogPrint(BCLog::WALLETDB, "BerkeleyEnvironment::MakeMock\n");
+
+    dbenv->set_cachesize(1, 0, 1);
+    dbenv->set_lg_bsize(10485760 * 4);
+    dbenv->set_lg_max(10485760);
+    dbenv->set_lk_max_locks(10000);
+    dbenv->set_lk_max_objects(10000);
+    dbenv->set_flags(DB_AUTO_COMMIT, 1);
+    dbenv->log_set_config(DB_LOG_IN_MEMORY, 1);
+    int ret = dbenv->open(nullptr,
+                         DB_CREATE |
+                             DB_INIT_LOCK |
+                             DB_INIT_LOG |
+                             DB_INIT_MPOOL |
+                             DB_INIT_TXN |
+                             DB_THREAD |
+                             DB_PRIVATE,
+                         S_IRUSR | S_IWUSR);
+    if (ret > 0) {
+        throw std::runtime_error(strprintf("BerkeleyEnvironment::MakeMock: Error %d opening database environment.", ret));
+    }
+
+    fDbEnvInit = true;
+    fMockDb = true;
+}
+
+bool BerkeleyEnvironment::Verify(const std::string& strFile)
+{
+    LOCK(cs_db);
+    assert(mapFileUseCount.count(strFile) == 0);
+
+    Db db(dbenv.get(), 0);
+    int result = db.verify(strFile.c_str(), nullptr, nullptr, 0);
+    return result == 0;
+}
+
+BerkeleyBatch::SafeDbt::SafeDbt()
+{
+    m_dbt.set_flags(DB_DBT_MALLOC);
+}
+
+BerkeleyBatch::SafeDbt::SafeDbt(void* data, size_t size)
+    : m_dbt(data, size)
+{
+}
+
+BerkeleyBatch::SafeDbt::~SafeDbt()
+{
+    if (m_dbt.get_data() != nullptr) {
+        // Clear memory, e.g. in case it was a private key
+        memory_cleanse(m_dbt.get_data(), m_dbt.get_size());
+        // under DB_DBT_MALLOC, data is malloced by the Dbt, but must be
+        // freed by the caller.
+        // https://docs.oracle.com/cd/E17275_01/html/api_reference/C/dbt.html
+        if (m_dbt.get_flags() & DB_DBT_MALLOC) {
+            free(m_dbt.get_data());
+        }
+    }
+}
+
+const void* BerkeleyBatch::SafeDbt::get_data() const
+{
+    return m_dbt.get_data();
+}
+
+u_int32_t BerkeleyBatch::SafeDbt::get_size() const
+{
+    return m_dbt.get_size();
+}
+
+BerkeleyBatch::SafeDbt::operator Dbt*()
+{
+    return &m_dbt;
+}
+
+bool BerkeleyBatch::VerifyEnvironment(const fs::path& file_path, bilingual_str& errorStr)
+{
+    std::string walletFile;
+    std::shared_ptr<BerkeleyEnvironment> env = GetWalletEnv(file_path, walletFile);
+    fs::path walletDir = env->Directory();
+
+    LogPrintf("Using BerkeleyDB version %s\n", BerkeleyDatabaseVersion());
+    LogPrintf("Using wallet %s\n", file_path.string());
+
+    if (!env->Open(true /* retry */)) {
+        errorStr = strprintf(_("Error initializing wallet database environment %s!"), walletDir);
+        return false;
+    }
+
+    return true;
+}
+
+bool BerkeleyBatch::VerifyDatabaseFile(const fs::path& file_path, bilingual_str& errorStr)
+{
+    std::string walletFile;
+    std::shared_ptr<BerkeleyEnvironment> env = GetWalletEnv(file_path, walletFile);
+    fs::path walletDir = env->Directory();
+
+    if (fs::exists(walletDir / walletFile))
+    {
+        if (!env->Verify(walletFile)) {
+            errorStr = strprintf(_("%s corrupt. Try using the wallet tool bitcoin-wallet to salvage or restoring a backup."), walletFile);
+            return false;
+        }
+    }
+    // also return true if files does not exists
+    return true;
+}
+
+void BerkeleyEnvironment::CheckpointLSN(const std::string& strFile)
+{
+    dbenv->txn_checkpoint(0, 0, 0);
+    if (fMockDb)
+        return;
+    dbenv->lsn_reset(strFile.c_str(), 0);
+}
+
+
+BerkeleyBatch::BerkeleyBatch(BerkeleyDatabase& database, const char* pszMode, bool fFlushOnCloseIn) : pdb(nullptr), activeTxn(nullptr)
+{
+    fReadOnly = (!strchr(pszMode, '+') && !strchr(pszMode, 'w'));
+    fFlushOnClose = fFlushOnCloseIn;
+    env = database.env.get();
+    if (database.IsDummy()) {
+        return;
+    }
+    const std::string &strFilename = database.strFile;
+
+    bool fCreate = strchr(pszMode, 'c') != nullptr;
+    unsigned int nFlags = DB_THREAD;
+    if (fCreate)
+        nFlags |= DB_CREATE;
+
+    {
+        LOCK(cs_db);
+        if (!env->Open(false /* retry */))
+            throw std::runtime_error("BerkeleyBatch: Failed to open database environment.");
+
+        pdb = database.m_db.get();
+        if (pdb == nullptr) {
+            int ret;
+            std::unique_ptr<Db> pdb_temp = MakeUnique<Db>(env->dbenv.get(), 0);
+
+            bool fMockDb = env->IsMock();
+            if (fMockDb) {
+                DbMpoolFile* mpf = pdb_temp->get_mpf();
+                ret = mpf->set_flags(DB_MPOOL_NOFILE, 1);
+                if (ret != 0) {
+                    throw std::runtime_error(strprintf("BerkeleyBatch: Failed to configure for no temp file backing for database %s", strFilename));
+                }
+            }
+
+            ret = pdb_temp->open(nullptr,                             // Txn pointer
+                            fMockDb ? nullptr : strFilename.c_str(),  // Filename
+                            fMockDb ? strFilename.c_str() : "main",   // Logical db name
+                            DB_BTREE,                                 // Database type
+                            nFlags,                                   // Flags
+                            0);
+
+            if (ret != 0) {
+                throw std::runtime_error(strprintf("BerkeleyBatch: Error %d, can't open database %s", ret, strFilename));
+            }
+
+            // Call CheckUniqueFileid on the containing BDB environment to
+            // avoid BDB data consistency bugs that happen when different data
+            // files in the same environment have the same fileid.
+            //
+            // Also call CheckUniqueFileid on all the other g_dbenvs to prevent
+            // bitcoin from opening the same data file through another
+            // environment when the file is referenced through equivalent but
+            // not obviously identical symlinked or hard linked or bind mounted
+            // paths. In the future a more relaxed check for equal inode and
+            // device ids could be done instead, which would allow opening
+            // different backup copies of a wallet at the same time. Maybe even
+            // more ideally, an exclusive lock for accessing the database could
+            // be implemented, so no equality checks are needed at all. (Newer
+            // versions of BDB have an set_lk_exclusive method for this
+            // purpose, but the older version we use does not.)
+            for (const auto& env : g_dbenvs) {
+                CheckUniqueFileid(*env.second.lock().get(), strFilename, *pdb_temp, this->env->m_fileids[strFilename]);
+            }
+
+            pdb = pdb_temp.release();
+            database.m_db.reset(pdb);
+
+            if (fCreate && !Exists(std::string("version"))) {
+                bool fTmp = fReadOnly;
+                fReadOnly = false;
+                Write(std::string("version"), CLIENT_VERSION);
+                fReadOnly = fTmp;
+            }
+        }
+        ++env->mapFileUseCount[strFilename];
+        strFile = strFilename;
+    }
+}
+
+void BerkeleyBatch::Flush()
+{
+    if (activeTxn)
+        return;
+
+    // Flush database activity from memory pool to disk log
+    unsigned int nMinutes = 0;
+    if (fReadOnly)
+        nMinutes = 1;
+
+    if (env) { // env is nullptr for dummy databases (i.e. in tests). Don't actually flush if env is nullptr so we don't segfault
+        env->dbenv->txn_checkpoint(nMinutes ? gArgs.GetArg("-dblogsize", DEFAULT_WALLET_DBLOGSIZE) * 1024 : 0, nMinutes, 0);
+    }
+}
+
+void BerkeleyDatabase::IncrementUpdateCounter()
+{
+    ++nUpdateCounter;
+}
+
+void BerkeleyBatch::Close()
+{
+    if (!pdb)
+        return;
+    if (activeTxn)
+        activeTxn->abort();
+    activeTxn = nullptr;
+    pdb = nullptr;
+
+    if (fFlushOnClose)
+        Flush();
+
+    {
+        LOCK(cs_db);
+        --env->mapFileUseCount[strFile];
+    }
+    env->m_db_in_use.notify_all();
+}
+
+void BerkeleyEnvironment::CloseDb(const std::string& strFile)
+{
+    {
+        LOCK(cs_db);
+        auto it = m_databases.find(strFile);
+        assert(it != m_databases.end());
+        BerkeleyDatabase& database = it->second.get();
+        if (database.m_db) {
+            // Close the database handle
+            database.m_db->close(0);
+            database.m_db.reset();
+        }
+    }
+}
+
+void BerkeleyEnvironment::ReloadDbEnv()
+{
+    // Make sure that no Db's are in use
+    AssertLockNotHeld(cs_db);
+    std::unique_lock<RecursiveMutex> lock(cs_db);
+    m_db_in_use.wait(lock, [this](){
+        for (auto& count : mapFileUseCount) {
+            if (count.second > 0) return false;
+        }
+        return true;
+    });
+
+    std::vector<std::string> filenames;
+    for (auto it : m_databases) {
+        filenames.push_back(it.first);
+    }
+    // Close the individual Db's
+    for (const std::string& filename : filenames) {
+        CloseDb(filename);
+    }
+    // Reset the environment
+    Flush(true); // This will flush and close the environment
+    Reset();
+    Open(true);
+}
+
+bool BerkeleyBatch::Rewrite(BerkeleyDatabase& database, const char* pszSkip)
+{
+    if (database.IsDummy()) {
+        return true;
+    }
+    BerkeleyEnvironment *env = database.env.get();
+    const std::string& strFile = database.strFile;
+    while (true) {
+        {
+            LOCK(cs_db);
+            if (!env->mapFileUseCount.count(strFile) || env->mapFileUseCount[strFile] == 0) {
+                // Flush log data to the dat file
+                env->CloseDb(strFile);
+                env->CheckpointLSN(strFile);
+                env->mapFileUseCount.erase(strFile);
+
+                bool fSuccess = true;
+                LogPrintf("BerkeleyBatch::Rewrite: Rewriting %s...\n", strFile);
+                std::string strFileRes = strFile + ".rewrite";
+                { // surround usage of db with extra {}
+                    BerkeleyBatch db(database, "r");
+                    std::unique_ptr<Db> pdbCopy = MakeUnique<Db>(env->dbenv.get(), 0);
+
+                    int ret = pdbCopy->open(nullptr,               // Txn pointer
+                                            strFileRes.c_str(), // Filename
+                                            "main",             // Logical db name
+                                            DB_BTREE,           // Database type
+                                            DB_CREATE,          // Flags
+                                            0);
+                    if (ret > 0) {
+                        LogPrintf("BerkeleyBatch::Rewrite: Can't create database file %s\n", strFileRes);
+                        fSuccess = false;
+                    }
+
+                    Dbc* pcursor = db.GetCursor();
+                    if (pcursor)
+                        while (fSuccess) {
+                            CDataStream ssKey(SER_DISK, CLIENT_VERSION);
+                            CDataStream ssValue(SER_DISK, CLIENT_VERSION);
+                            int ret1 = db.ReadAtCursor(pcursor, ssKey, ssValue);
+                            if (ret1 == DB_NOTFOUND) {
+                                pcursor->close();
+                                break;
+                            } else if (ret1 != 0) {
+                                pcursor->close();
+                                fSuccess = false;
+                                break;
+                            }
+                            if (pszSkip &&
+                                strncmp(ssKey.data(), pszSkip, std::min(ssKey.size(), strlen(pszSkip))) == 0)
+                                continue;
+                            if (strncmp(ssKey.data(), "\x07version", 8) == 0) {
+                                // Update version:
+                                ssValue.clear();
+                                ssValue << CLIENT_VERSION;
+                            }
+                            Dbt datKey(ssKey.data(), ssKey.size());
+                            Dbt datValue(ssValue.data(), ssValue.size());
+                            int ret2 = pdbCopy->put(nullptr, &datKey, &datValue, DB_NOOVERWRITE);
+                            if (ret2 > 0)
+                                fSuccess = false;
+                        }
+                    if (fSuccess) {
+                        db.Close();
+                        env->CloseDb(strFile);
+                        if (pdbCopy->close(0))
+                            fSuccess = false;
+                    } else {
+                        pdbCopy->close(0);
+                    }
+                }
+                if (fSuccess) {
+                    Db dbA(env->dbenv.get(), 0);
+                    if (dbA.remove(strFile.c_str(), nullptr, 0))
+                        fSuccess = false;
+                    Db dbB(env->dbenv.get(), 0);
+                    if (dbB.rename(strFileRes.c_str(), nullptr, strFile.c_str(), 0))
+                        fSuccess = false;
+                }
+                if (!fSuccess)
+                    LogPrintf("BerkeleyBatch::Rewrite: Failed to rewrite database file %s\n", strFileRes);
+                return fSuccess;
+            }
+        }
+        UninterruptibleSleep(std::chrono::milliseconds{100});
+    }
+}
+
+
+void BerkeleyEnvironment::Flush(bool fShutdown)
+{
+    int64_t nStart = GetTimeMillis();
+    // Flush log data to the actual data file on all files that are not in use
+    LogPrint(BCLog::WALLETDB, "BerkeleyEnvironment::Flush: [%s] Flush(%s)%s\n", strPath, fShutdown ? "true" : "false", fDbEnvInit ? "" : " database not started");
+    if (!fDbEnvInit)
+        return;
+    {
+        LOCK(cs_db);
+        std::map<std::string, int>::iterator mi = mapFileUseCount.begin();
+        while (mi != mapFileUseCount.end()) {
+            std::string strFile = (*mi).first;
+            int nRefCount = (*mi).second;
+            LogPrint(BCLog::WALLETDB, "BerkeleyEnvironment::Flush: Flushing %s (refcount = %d)...\n", strFile, nRefCount);
+            if (nRefCount == 0) {
+                // Move log data to the dat file
+                CloseDb(strFile);
+                LogPrint(BCLog::WALLETDB, "BerkeleyEnvironment::Flush: %s checkpoint\n", strFile);
+                dbenv->txn_checkpoint(0, 0, 0);
+                LogPrint(BCLog::WALLETDB, "BerkeleyEnvironment::Flush: %s detach\n", strFile);
+                if (!fMockDb)
+                    dbenv->lsn_reset(strFile.c_str(), 0);
+                LogPrint(BCLog::WALLETDB, "BerkeleyEnvironment::Flush: %s closed\n", strFile);
+                mapFileUseCount.erase(mi++);
+            } else
+                mi++;
+        }
+        LogPrint(BCLog::WALLETDB, "BerkeleyEnvironment::Flush: Flush(%s)%s took %15dms\n", fShutdown ? "true" : "false", fDbEnvInit ? "" : " database not started", GetTimeMillis() - nStart);
+        if (fShutdown) {
+            char** listp;
+            if (mapFileUseCount.empty()) {
+                dbenv->log_archive(&listp, DB_ARCH_REMOVE);
+                Close();
+                if (!fMockDb) {
+                    fs::remove_all(fs::path(strPath) / "database");
+                }
+            }
+        }
+    }
+}
+
+bool BerkeleyBatch::PeriodicFlush(BerkeleyDatabase& database)
+{
+    if (database.IsDummy()) {
+        return true;
+    }
+    bool ret = false;
+    BerkeleyEnvironment *env = database.env.get();
+    const std::string& strFile = database.strFile;
+    TRY_LOCK(cs_db, lockDb);
+    if (lockDb)
+    {
+        // Don't do this if any databases are in use
+        int nRefCount = 0;
+        std::map<std::string, int>::iterator mit = env->mapFileUseCount.begin();
+        while (mit != env->mapFileUseCount.end())
+        {
+            nRefCount += (*mit).second;
+            mit++;
+        }
+
+        if (nRefCount == 0)
+        {
+            std::map<std::string, int>::iterator mi = env->mapFileUseCount.find(strFile);
+            if (mi != env->mapFileUseCount.end())
+            {
+                LogPrint(BCLog::WALLETDB, "Flushing %s\n", strFile);
+                int64_t nStart = GetTimeMillis();
+
+                // Flush wallet file so it's self contained
+                env->CloseDb(strFile);
+                env->CheckpointLSN(strFile);
+
+                env->mapFileUseCount.erase(mi++);
+                LogPrint(BCLog::WALLETDB, "Flushed %s %dms\n", strFile, GetTimeMillis() - nStart);
+                ret = true;
+            }
+        }
+    }
+
+    return ret;
+}
+
+bool BerkeleyDatabase::Rewrite(const char* pszSkip)
+{
+    return BerkeleyBatch::Rewrite(*this, pszSkip);
+}
+
+bool BerkeleyDatabase::Backup(const std::string& strDest) const
+{
+    if (IsDummy()) {
+        return false;
+    }
+    while (true)
+    {
+        {
+            LOCK(cs_db);
+            if (!env->mapFileUseCount.count(strFile) || env->mapFileUseCount[strFile] == 0)
+            {
+                // Flush log data to the dat file
+                env->CloseDb(strFile);
+                env->CheckpointLSN(strFile);
+                env->mapFileUseCount.erase(strFile);
+
+                // Copy wallet file
+                fs::path pathSrc = env->Directory() / strFile;
+                fs::path pathDest(strDest);
+                if (fs::is_directory(pathDest))
+                    pathDest /= strFile;
+
+                try {
+                    if (fs::equivalent(pathSrc, pathDest)) {
+                        LogPrintf("cannot backup to wallet source file %s\n", pathDest.string());
+                        return false;
+                    }
+
+                    fs::copy_file(pathSrc, pathDest, fs::copy_option::overwrite_if_exists);
+                    LogPrintf("copied %s to %s\n", strFile, pathDest.string());
+                    return true;
+                } catch (const fs::filesystem_error& e) {
+                    LogPrintf("error copying %s to %s - %s\n", strFile, pathDest.string(), fsbridge::get_filesystem_error_message(e));
+                    return false;
+                }
+            }
+        }
+        UninterruptibleSleep(std::chrono::milliseconds{100});
+    }
+}
+
+void BerkeleyDatabase::Flush(bool shutdown)
+{
+    if (!IsDummy()) {
+        env->Flush(shutdown);
+        if (shutdown) {
+            LOCK(cs_db);
+            g_dbenvs.erase(env->Directory().string());
+            env = nullptr;
+        } else {
+            // TODO: To avoid g_dbenvs.erase erasing the environment prematurely after the
+            // first database shutdown when multiple databases are open in the same
+            // environment, should replace raw database `env` pointers with shared or weak
+            // pointers, or else separate the database and environment shutdowns so
+            // environments can be shut down after databases.
+            env->m_fileids.erase(strFile);
+        }
+    }
+}
+
+void BerkeleyDatabase::ReloadDbEnv()
+{
+    if (!IsDummy()) {
+        env->ReloadDbEnv();
+    }
+}
+
+Dbc* BerkeleyBatch::GetCursor()
+{
+    if (!pdb)
+        return nullptr;
+    Dbc* pcursor = nullptr;
+    int ret = pdb->cursor(nullptr, &pcursor, 0);
+    if (ret != 0)
+        return nullptr;
+    return pcursor;
+}
+
+int BerkeleyBatch::ReadAtCursor(Dbc* pcursor, CDataStream& ssKey, CDataStream& ssValue)
+{
+    // Read at cursor
+    SafeDbt datKey;
+    SafeDbt datValue;
+    int ret = pcursor->get(datKey, datValue, DB_NEXT);
+    if (ret != 0)
+        return ret;
+    else if (datKey.get_data() == nullptr || datValue.get_data() == nullptr)
+        return 99999;
+
+    // Convert to streams
+    ssKey.SetType(SER_DISK);
+    ssKey.clear();
+    ssKey.write((char*)datKey.get_data(), datKey.get_size());
+    ssValue.SetType(SER_DISK);
+    ssValue.clear();
+    ssValue.write((char*)datValue.get_data(), datValue.get_size());
+    return 0;
+}
+
+bool BerkeleyBatch::TxnBegin()
+{
+    if (!pdb || activeTxn)
+        return false;
+    DbTxn* ptxn = env->TxnBegin();
+    if (!ptxn)
+        return false;
+    activeTxn = ptxn;
+    return true;
+}
+
+bool BerkeleyBatch::TxnCommit()
+{
+    if (!pdb || !activeTxn)
+        return false;
+    int ret = activeTxn->commit(0);
+    activeTxn = nullptr;
+    return (ret == 0);
+}
+
+bool BerkeleyBatch::TxnAbort()
+{
+    if (!pdb || !activeTxn)
+        return false;
+    int ret = activeTxn->abort();
+    activeTxn = nullptr;
+    return (ret == 0);
+}
+
+std::string BerkeleyDatabaseVersion()
+{
+    return DbEnv::version(nullptr, nullptr, nullptr);
+}