path: root/src/mongo/db/storage/mobile/mobile_kv_engine.cpp

/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kStorage

#include "mongo/platform/basic.h"

#include <boost/filesystem/operations.hpp>
#include <boost/filesystem/path.hpp>
#include <boost/system/error_code.hpp>
#include <memory>
#include <vector>

#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/index/index_descriptor.h"
#include "mongo/db/storage/mobile/mobile_index.h"
#include "mongo/db/storage/mobile/mobile_kv_engine.h"
#include "mongo/db/storage/mobile/mobile_record_store.h"
#include "mongo/db/storage/mobile/mobile_recovery_unit.h"
#include "mongo/db/storage/mobile/mobile_session.h"
#include "mongo/db/storage/mobile/mobile_sqlite_statement.h"
#include "mongo/db/storage/mobile/mobile_util.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/log.h"
#include "mongo/util/scopeguard.h"

namespace mongo {

class MobileSession;
class SqliteStatement;

MobileKVEngine::MobileKVEngine(const std::string& path) {
    _initDBPath(path);

    // Initialize the database to be in WAL mode.
    sqlite3* initSession;
    int status = sqlite3_open(_path.c_str(), &initSession);
    checkStatus(status, SQLITE_OK, "sqlite3_open");

    // Guarantees that sqlite3_close() will be called when the function returns.
    ON_BLOCK_EXIT([&initSession] { sqlite3_close(initSession); });

    // Ensure SQLite is operating in the WAL mode.
    {
        sqlite3_stmt* stmt;
        status = sqlite3_prepare_v2(initSession, "PRAGMA journal_mode=WAL;", -1, &stmt, NULL);
        checkStatus(status, SQLITE_OK, "sqlite3_prepare_v2");

        status = sqlite3_step(stmt);
        checkStatus(status, SQLITE_ROW, "sqlite3_step");

        // Pragma returns current mode in SQLite, ensure it is "wal" mode.
        const void* colText = sqlite3_column_text(stmt, 0);
        const char* mode = reinterpret_cast<const char*>(colText);
        fassert(37001, !strcmp(mode, "wal"));
        status = sqlite3_finalize(stmt);
        checkStatus(status, SQLITE_OK, "sqlite3_finalize");

        LOG(MOBILE_LOG_LEVEL_LOW) << "MobileSE: Confirmed SQLite database opened in WAL mode";
    }

    // Ensure SQLite is operating with "synchronous" flag set to FULL.
    {
#define PRAGMA_SYNC_FULL 2

        sqlite3_stmt* stmt;
        status = sqlite3_prepare_v2(initSession, "PRAGMA main.synchronous;", -1, &stmt, NULL);
        checkStatus(status, SQLITE_OK, "sqlite3_prepare_v2");

        status = sqlite3_step(stmt);
        checkStatus(status, SQLITE_ROW, "sqlite3_step");

        // Pragma returns current "synchronous" setting, ensure it is FULL.
        int sync_val = sqlite3_column_int(stmt, 0);
        fassert(50869, sync_val == PRAGMA_SYNC_FULL);
        status = sqlite3_finalize(stmt);
        checkStatus(status, SQLITE_OK, "sqlite3_finalize");

        LOG(MOBILE_LOG_LEVEL_LOW) << "MobileSE: Confirmed SQLite database has synchronous "
                                  << "set to FULL";
    }

    // Set and ensure SQLite is operating with F_FULLFSYNC if the platform permits.
    {
        // Set to use F_FULLFSYNC
        char* errMsg = NULL;
        status = sqlite3_exec(initSession, "PRAGMA fullfsync = 1;", NULL, NULL, &errMsg);
        checkStatus(status, SQLITE_OK, "sqlite3_exec", errMsg);
        // When the error message is not NULL, it is allocated through sqlite3_malloc and must be
        // freed before exiting the method. If the error message is NULL, sqlite3_free is a no-op.
        sqlite3_free(errMsg);

        // Confirm that the setting holds
        sqlite3_stmt* stmt;
        status = sqlite3_prepare_v2(initSession, "PRAGMA fullfsync;", -1, &stmt, NULL);
        checkStatus(status, SQLITE_OK, "sqlite3_prepare_v2");

        status = sqlite3_step(stmt);
        checkStatus(status, SQLITE_ROW, "sqlite3_step");

        // Pragma returns current fullsync setting, ensure it is enabled.
        int fullfsync_val = sqlite3_column_int(stmt, 0);
        fassert(50868, fullfsync_val == 1);
        status = sqlite3_finalize(stmt);
        checkStatus(status, SQLITE_OK, "sqlite3_finalize");

        LOG(MOBILE_LOG_LEVEL_LOW) << "MobileSE: Confirmed SQLite database is set to fsync "
                                  << "with F_FULLFSYNC if the platform supports"
                                  << ". Val: " << fullfsync_val;
    }

    _sessionPool.reset(new MobileSessionPool(_path));
}

void MobileKVEngine::_initDBPath(const std::string& path) {
    boost::system::error_code err;
    boost::filesystem::path dbPath(path);

    if (!boost::filesystem::exists(dbPath, err)) {
        if (err) {
            uasserted(4085, err.message());
        }
        std::string errMsg("DB path not found: ");
        errMsg += dbPath.generic_string();
        uasserted(4086, errMsg);

    } else if (!boost::filesystem::is_directory(dbPath, err)) {
        if (err) {
            uasserted(4087, err.message());
        }
        std::string errMsg("DB path is not a valid directory: ");
        errMsg += dbPath.generic_string();
        uasserted(4088, errMsg);
    }

    dbPath /= "mobile.sqlite";

    if (boost::filesystem::exists(dbPath, err)) {
        if (err) {
            uasserted(4089, err.message());
        } else if (!boost::filesystem::is_regular_file(dbPath)) {
            std::string errMsg("Failed to open " + dbPath.generic_string() +
                               ": not a regular file");
            uasserted(4090, errMsg);
        }
    }
    _path = dbPath.generic_string();
}

RecoveryUnit* MobileKVEngine::newRecoveryUnit() {
    return new MobileRecoveryUnit(_sessionPool.get());
}

Status MobileKVEngine::createRecordStore(OperationContext* opCtx,
                                         StringData ns,
                                         StringData ident,
                                         const CollectionOptions& options) {
    // TODO: eventually will support file renaming but otherwise do not use collection options.

    // Mobile SE doesn't support creating an oplog
    if (NamespaceString::oplog(ns)) {
        return Status(ErrorCodes::InvalidOptions,
                      "Replication is not supported by the mobile storage engine");
    }

    // Mobile doesn't support capped collections
    if (options.capped) {
        return Status(ErrorCodes::InvalidOptions,
                      "Capped collections are not supported by the mobile storage engine");
    }

    MobileRecordStore::create(opCtx, ident.toString());
    return Status::OK();
}

std::unique_ptr<RecordStore> MobileKVEngine::getRecordStore(OperationContext* opCtx,
                                                            StringData ns,
                                                            StringData ident,
                                                            const CollectionOptions& options) {
    return stdx::make_unique<MobileRecordStore>(opCtx, ns, _path, ident.toString(), options);
}

std::unique_ptr<RecordStore> MobileKVEngine::makeTemporaryRecordStore(OperationContext* opCtx,
                                                                      StringData ident) {
    MobileRecordStore::create(opCtx, ident.toString());
    return std::make_unique<MobileRecordStore>(
        opCtx, "", _path, ident.toString(), CollectionOptions());
}


Status MobileKVEngine::createSortedDataInterface(OperationContext* opCtx,
                                                 StringData ident,
                                                 const IndexDescriptor* desc) {
    return MobileIndex::create(opCtx, ident.toString());
}

SortedDataInterface* MobileKVEngine::getSortedDataInterface(OperationContext* opCtx,
                                                            StringData ident,
                                                            const IndexDescriptor* desc) {
    if (desc->unique()) {
        return new MobileIndexUnique(opCtx, desc, ident.toString());
    }
    return new MobileIndexStandard(opCtx, desc, ident.toString());
}

Status MobileKVEngine::dropIdent(OperationContext* opCtx, StringData ident) {
    MobileSession* session = MobileRecoveryUnit::get(opCtx)->getSessionNoTxn(opCtx);
    std::string dropQuery = "DROP TABLE IF EXISTS \"" + ident + "\";";

    try {
        SqliteStatement::execQuery(session, dropQuery.c_str());
    } catch (const WriteConflictException&) {
        // It is possible that this drop fails because of transaction running in parallel.
        // We pretend that it succeeded, queue it for now and keep retrying later.
        LOG(MOBILE_LOG_LEVEL_LOW)
            << "MobileSE: Caught WriteConflictException while dropping table, "
               "queuing to retry later";
        MobileRecoveryUnit::get(opCtx)->enqueueFailedDrop(dropQuery);
    }
    return Status::OK();
}

/**
 * Note: this counts the total number of bytes in the key and value columns, not the actual number
 * of bytes on disk used by this ident.
 */
int64_t MobileKVEngine::getIdentSize(OperationContext* opCtx, StringData ident) {
    MobileSession* session = MobileRecoveryUnit::get(opCtx)->getSession(opCtx);

    // Get key-value column names.
    std::string colNameQuery = "PRAGMA table_info(\"" + ident + "\")";
    SqliteStatement colNameStmt(*session, colNameQuery);

    colNameStmt.step(SQLITE_ROW);
    std::string keyColName(static_cast<const char*>(colNameStmt.getColText(1)));
    colNameStmt.step(SQLITE_ROW);
    std::string valueColName(static_cast<const char*>(colNameStmt.getColText(1)));
    colNameStmt.step(SQLITE_DONE);

    // Get total data size of key-value columns.
    str::stream dataSizeQuery;
    dataSizeQuery << "SELECT IFNULL(SUM(LENGTH(" << keyColName << ")), 0) + "
                  << "IFNULL(SUM(LENGTH(" << valueColName << ")), 0) FROM \"" << ident + "\";";
    SqliteStatement dataSizeStmt(*session, dataSizeQuery);

    dataSizeStmt.step(SQLITE_ROW);
    return dataSizeStmt.getColInt(0);
}

bool MobileKVEngine::hasIdent(OperationContext* opCtx, StringData ident) const {
    MobileSession* session = MobileRecoveryUnit::get(opCtx)->getSession(opCtx);

    std::string findTableQuery = "SELECT * FROM sqlite_master WHERE type='table' AND name = ?;";
    SqliteStatement findTableStmt(*session, findTableQuery);
    findTableStmt.bindText(0, ident.rawData(), ident.size());

    int status = findTableStmt.step();
    if (status == SQLITE_DONE) {
        return false;
    }
    checkStatus(status, SQLITE_ROW, "sqlite3_step");

    return true;
}

std::vector<std::string> MobileKVEngine::getAllIdents(OperationContext* opCtx) const {
    std::vector<std::string> idents;
    MobileSession* session = MobileRecoveryUnit::get(opCtx)->getSession(opCtx);
    std::string getTablesQuery = "SELECT name FROM sqlite_master WHERE type='table';";
    SqliteStatement getTablesStmt(*session, getTablesQuery);

    int status;
    while ((status = getTablesStmt.step()) == SQLITE_ROW) {
        std::string tableName(reinterpret_cast<const char*>(getTablesStmt.getColText(0)));
        idents.push_back(tableName);
    }
    checkStatus(status, SQLITE_DONE, "sqlite3_step");
    return idents;
}

}  // namespace mongo