dbwrapper.cpp

// Copyright (c) 2012-2014 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "dbwrapper.h"

#include <leveldb/cache.h>
#include <leveldb/env.h>
#include <leveldb/filter_policy.h>
#include <memenv.h>
#include <stdint.h>


static void SetMaxOpenFiles(leveldb::Options *options) {
    // On most platforms the default setting of max_open_files (which is 1000)
    // is optimal. On Windows using a large file count is OK because the handles
    // do not interfere with select() loops. On 64-bit Unix hosts this value is
    // also OK, because up to that amount LevelDB will use an mmap
    // implementation that does not use extra file descriptors (the fds are
    // closed after being mmaped).
    //
    // Increasing the value beyond the default is dangerous because LevelDB will
    // fall back to a non-mmap implementation when the file count is too large.
    // On 32-bit Unix host we should decrease the value because the handles use
    // up real fds, and we want to avoid fd exhaustion issues.
    //
    // See PR #12495 for further discussion.

    int default_open_files = options->max_open_files;
#ifndef WIN32
    if (sizeof(void*) < 8) {
        options->max_open_files = 64;
    }
#endif
    LogPrint(BCLog::LEVELDB, "LevelDB using max_open_files=%d (default=%d)\n",
             options->max_open_files, default_open_files);
}

static leveldb::Options GetOptions(size_t nCacheSize)
{
    leveldb::Options options;
    options.block_cache = leveldb::NewLRUCache(nCacheSize / 2);
    options.write_buffer_size = nCacheSize / 4; // up to two write buffers may be held in memory simultaneously
    options.filter_policy = leveldb::NewBloomFilterPolicy(10);
    options.compression = leveldb::kNoCompression;
    if (leveldb::kMajorVersion > 1 || (leveldb::kMajorVersion == 1 && leveldb::kMinorVersion >= 16)) {
        // LevelDB versions before 1.16 consider short writes to be corruption. Only trigger error
        // on corruption in later versions.
        options.paranoid_checks = true;
    }
    SetMaxOpenFiles(&options);
    return options;
}

CDBWrapper::CDBWrapper(const fs::path& path, size_t nCacheSize, bool fMemory, bool fWipe)
{
    penv = nullptr;
    readoptions.verify_checksums = true;
    iteroptions.verify_checksums = true;
    iteroptions.fill_cache = false;
    syncoptions.sync = true;
    options = GetOptions(nCacheSize);
    options.create_if_missing = true;
    if (fMemory) {
        penv = leveldb::NewMemEnv(leveldb::Env::Default());
        options.env = penv;
    } else {
        if (fWipe) {
            LogPrintf("Wiping LevelDB in %s\n", path.string());
            leveldb::Status result = leveldb::DestroyDB(path.string(), options);
            dbwrapper_private::HandleError(result);
        }
        TryCreateDirectories(path);
        LogPrintf("Opening LevelDB in %s\n", path.string());
    }
    leveldb::Status status = leveldb::DB::Open(options, path.string(), &pdb);
    dbwrapper_private::HandleError(status);
    LogPrintf("Opened LevelDB successfully\n");
}

CDBWrapper::~CDBWrapper()
{
    delete pdb;
    pdb = nullptr;
    delete options.filter_policy;
    options.filter_policy = nullptr;
    delete options.block_cache;
    options.block_cache = nullptr;
    delete penv;
    options.env = nullptr;
}

bool CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync)
{
    leveldb::Status status = pdb->Write(fSync ? syncoptions : writeoptions, &batch.batch);
    dbwrapper_private::HandleError(status);
    return true;
}

bool CDBWrapper::IsEmpty()
{
    std::unique_ptr<CDBIterator> it(NewIterator());
    it->SeekToFirst();
    return !(it->Valid());
}

CDBIterator::~CDBIterator() { delete piter; }
bool CDBIterator::Valid() { return piter->Valid(); }
void CDBIterator::SeekToFirst() { piter->SeekToFirst(); }
void CDBIterator::Next() { piter->Next(); }


namespace dbwrapper_private {

void HandleError(const leveldb::Status& status)
{
    if (status.ok())
        return;
    LogPrintf("%s\n", status.ToString());
    if (status.IsCorruption())
        throw dbwrapper_error("Database corrupted");
    if (status.IsIOError())
        throw dbwrapper_error("Database I/O error");
    if (status.IsNotFound())
        throw dbwrapper_error("Database entry missing");
    throw dbwrapper_error("Unknown database error");
}

};