SERVER-16677 added platform-dependent class to management creation/locking of mongod.lock in data directory.

5 files changed, 668 insertions, 0 deletions

diff --git a/src/mongo/db/storage/SConscript b/src/mongo/db/storage/SConscript
index 7210c44f420..aec1069cf09 100644
--- a/src/mongo/db/storage/SConscript
+++ b/src/mongo/db/storage/SConscript
@@ -81,6 +81,24 @@ env.Library(
     )
 
 env.Library(
+    target='storage_engine_lock_file',
+    source=[
+        'storage_engine_lock_file_${OS_FAMILY}.cpp',
+        ],
+    LIBDEPS=[
+        ]
+    )
+
+env.CppUnitTest(
+    target= 'storage_engine_lock_file_test',
+    source = 'storage_engine_lock_file_test.cpp',
+    LIBDEPS=[
+        'storage_engine_lock_file',
+        '$BUILD_DIR/mongo/mongocommon',
+    ],
+)
+
+env.Library(
     target='storage_engine_metadata',
     source=[
         'storage_engine_metadata.cpp',
diff --git a/src/mongo/db/storage/storage_engine_lock_file.h b/src/mongo/db/storage/storage_engine_lock_file.h
new file mode 100644
index 00000000000..b28ccc29823
--- /dev/null
+++ b/src/mongo/db/storage/storage_engine_lock_file.h
@@ -0,0 +1,95 @@
+/**
+ *    Copyright (C) 2014 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    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
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    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 GNU Affero General 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.
+ */
+
+#pragma once
+
+#include <boost/scoped_ptr.hpp>
+#include <string>
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/base/status.h"
+
+namespace mongo {
+
+    class StorageEngineLockFile {
+        MONGO_DISALLOW_COPYING(StorageEngineLockFile);
+    public:
+
+        /**
+         * Checks existing lock file, if present, to see if it contains data from a previous
+         * unclean shutdown. A clean shutdown should have produced a zero length lock file.
+         * Uses open() to read existing lock file or create new file.
+         * Uses boost::filesystem to check lock file so may throw boost::exception.
+         */
+        StorageEngineLockFile(const std::string& dbpath);
+
+        virtual ~StorageEngineLockFile();
+
+        /**
+         * Returns the path to the lock file.
+         */
+        std::string getFilespec() const;
+
+        /**
+         * Returns true if lock file was not zeroed out due to previous unclean shutdown.
+         * This state is evaluated at object initialization to allow storage engine
+         * to make decisions on recovery based on this information after open() has been called.
+         */
+        bool createdByUncleanShutdown() const;
+
+        /**
+         * Opens and locks 'mongod.lock' in 'dbpath' directory.
+         */
+        Status open();
+
+        /**
+         * Closes lock file handles.
+         */
+        void close();
+
+        /**
+         * Writes current process ID to file.
+         * Fails if lock file has not been opened.
+         */
+        Status writePid();
+
+        /**
+         * Truncates file contents and releases file locks.
+         */
+        void clearPidAndUnlock();
+
+    private:
+        std::string _dbpath;
+        std::string _filespec;
+        bool _uncleanShutdown;
+
+        class LockFileHandle;
+        boost::scoped_ptr<LockFileHandle> _lockFileHandle;
+    };
+
+}  // namespace mongo
diff --git a/src/mongo/db/storage/storage_engine_lock_file_posix.cpp b/src/mongo/db/storage/storage_engine_lock_file_posix.cpp
new file mode 100644
index 00000000000..126c53ec4c8
--- /dev/null
+++ b/src/mongo/db/storage/storage_engine_lock_file_posix.cpp
@@ -0,0 +1,192 @@
+/**
+ *    Copyright (C) 2014 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    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
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    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 GNU Affero General 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 "mongo/db/storage/storage_engine_lock_file.h"
+
+#include <boost/filesystem.hpp>
+#include <fcntl.h>
+#include <ostream>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <sstream>
+
+#include "mongo/platform/process_id.h"
+#include "mongo/util/log.h"
+#include "mongo/util/paths.h"
+#include "mongo/util/mongoutils/str.h"
+
+namespace mongo {
+
+namespace {
+
+    const std::string kLockFileBasename = "mongod.lock";
+
+}  // namespace
+
+    class StorageEngineLockFile::LockFileHandle {
+    public:
+        static const int kInvalidFd = -1;
+        LockFileHandle() : _fd(kInvalidFd) { }
+        bool isValid() const { return _fd != kInvalidFd; }
+        void clear() { _fd = kInvalidFd; }
+        int _fd;
+    };
+
+    StorageEngineLockFile::StorageEngineLockFile(const std::string& dbpath)
+        : _dbpath(dbpath),
+          _filespec((boost::filesystem::path(_dbpath) / kLockFileBasename).string()),
+          _uncleanShutdown(boost::filesystem::exists(_filespec) &&
+                           boost::filesystem::file_size(_filespec) > 0),
+          _lockFileHandle(new LockFileHandle()) {
+    }
+
+    StorageEngineLockFile::~StorageEngineLockFile() { }
+
+    std::string StorageEngineLockFile::getFilespec() const {
+        return _filespec;
+    }
+
+    bool StorageEngineLockFile::createdByUncleanShutdown() const {
+        return _uncleanShutdown;
+    }
+
+    Status StorageEngineLockFile::open() {
+        try {
+            if (!boost::filesystem::exists(_dbpath)) {
+                return Status(ErrorCodes::NonExistentPath, str::stream()
+                    << "Data directory " << _dbpath << " not found.");
+            }
+        }
+        catch (const std::exception& ex) {
+            return Status(ErrorCodes::UnknownError, str::stream()
+                << "Unable to check existence of data directory "
+                << _dbpath << ": " << ex.what());
+        }
+
+        int lockFile = ::open(_filespec.c_str(), O_RDWR | O_CREAT, S_IRWXU | S_IRWXG | S_IRWXO);
+        if (lockFile <= 0) {
+            int errorcode = errno;
+            return Status(ErrorCodes::DBPathInUse, str::stream()
+                << "Unable to create/open lock file: "
+                << _filespec << ' ' << errnoWithDescription(errorcode)
+                << " Is a mongod instance already running?");
+        }
+#if !defined(__sunos__)
+        int ret = ::flock(lockFile, LOCK_EX | LOCK_NB);
+#else
+        struct flock fileLockInfo = {0};
+        fileLockInfo.l_type = F_WRLCK;
+        fileLockInfo.l_whence = SEEK_SET;
+        int ret = ::fcntl(lockFile, F_SETLK, &fileLockInfo);
+#endif  // !defined(__sunos__)
+        if (ret != 0) {
+            int errorcode = errno;
+            ::close(lockFile);
+            return Status(ErrorCodes::DBPathInUse, str::stream()
+                << "Unable to lock file: "
+                << _filespec << ' ' << errnoWithDescription(errorcode)
+                << ". Is a mongod instance already running?");
+        }
+        _lockFileHandle->_fd = lockFile;
+        return Status::OK();
+    }
+
+    void StorageEngineLockFile::close() {
+        if (!_lockFileHandle->isValid()) {
+            return;
+        }
+        ::close(_lockFileHandle->_fd);
+        _lockFileHandle->clear();
+    }
+
+    Status StorageEngineLockFile::writePid() {
+        if (!_lockFileHandle->isValid()) {
+            return Status(ErrorCodes::FileNotOpen, str::stream()
+                << "Unable to write process ID to " << _filespec
+                << " because file has not been opened.");
+        }
+
+        if (::ftruncate(_lockFileHandle->_fd, 0)) {
+            int errorcode = errno;
+            return Status(ErrorCodes::FileStreamFailed, str::stream()
+                << errnoWithDescription(errorcode));
+        }
+
+        ProcessId pid = ProcessId::getCurrent();
+        std::stringstream ss;
+        ss << pid << std::endl;
+        std::string pidStr = ss.str();
+        int bytesWritten = ::write(_lockFileHandle->_fd, pidStr.c_str(), pidStr.size());
+        if (bytesWritten < 0) {
+            int errorcode = errno;
+            return Status(ErrorCodes::FileStreamFailed, str::stream()
+                << "Unable to write process id " << pid.toString() << " to file: "
+                << _filespec << ' ' << errnoWithDescription(errorcode));
+
+        }
+        else if (bytesWritten == 0) {
+            return Status(ErrorCodes::FileStreamFailed, str::stream()
+                << "Unable to write process id " << pid.toString() << " to file: "
+                << _filespec << " no data written.");
+        }
+
+        ::fsync(_lockFileHandle->_fd);
+        flushMyDirectory(_filespec);
+
+        return Status::OK();
+    }
+
+    void StorageEngineLockFile::clearPidAndUnlock() {
+        if (!_lockFileHandle->isValid()) {
+            return;
+        }
+        log() << "shutdown: removing fs lock...";
+        // This ought to be an unlink(), but Eliot says the last
+        // time that was attempted, there was a race condition
+        // with acquirePathLock().
+        if(::ftruncate(_lockFileHandle->_fd, 0)) {
+            int errorcode = errno;
+            log() << "couldn't remove fs lock " << errnoWithDescription(errorcode);
+        }
+#if !defined(__sunos__)
+        ::flock(_lockFileHandle->_fd, LOCK_UN);
+#else
+        struct flock fileLockInfo = {0};
+        fileLockInfo.l_type = F_UNLCK;
+        fileLockInfo.l_whence = SEEK_SET;
+        ::fcntl(_lockFileHandle->_fd, F_SETLK, &fileLockInfo);
+#endif  // !defined(__sunos__)
+    }
+
+}  // namespace mongo
diff --git a/src/mongo/db/storage/storage_engine_lock_file_test.cpp b/src/mongo/db/storage/storage_engine_lock_file_test.cpp
new file mode 100644
index 00000000000..2ca432d0d71
--- /dev/null
+++ b/src/mongo/db/storage/storage_engine_lock_file_test.cpp
@@ -0,0 +1,173 @@
+/**
+ *    Copyright 2014 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    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
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    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 GNU Affero General 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.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include <boost/filesystem.hpp>
+#include <boost/scoped_ptr.hpp>
+#include <fstream>
+#include <ostream>
+
+#include "mongo/db/storage/storage_engine_lock_file.h"
+#include "mongo/platform/process_id.h"
+#include "mongo/unittest/temp_dir.h"
+#include "mongo/unittest/unittest.h"
+
+namespace {
+
+    using std::string;
+    using mongo::unittest::TempDir;
+
+    using namespace mongo;
+
+    TEST(StorageEngineLockFileTest, UncleanShutdownNoExistingFile) {
+        TempDir tempDir("StorageEngineLockFileTest_UncleanShutdownNoExistingFile");
+        StorageEngineLockFile lockFile(tempDir.path());
+        ASSERT_FALSE(lockFile.createdByUncleanShutdown());
+    }
+
+    TEST(StorageEngineLockFileTest, UncleanShutdownEmptyExistingFile) {
+        TempDir tempDir("StorageEngineLockFileTest_UncleanShutdownEmptyExistingFile");
+        {
+            std::string filename(tempDir.path() + "/mongod.lock");
+            std::ofstream(filename.c_str());
+        }
+        StorageEngineLockFile lockFile(tempDir.path());
+        ASSERT_FALSE(lockFile.createdByUncleanShutdown());
+    }
+
+    TEST(StorageEngineLockFileTest, UncleanShutdownNonEmptyExistingFile) {
+        TempDir tempDir("StorageEngineLockFileTest_UncleanShutdownNonEmptyExistingFile");
+        {
+            std::string filename(tempDir.path() + "/mongod.lock");
+            std::ofstream ofs(filename.c_str());
+            ofs << 12345 << std::endl;
+        }
+        StorageEngineLockFile lockFile(tempDir.path());
+        ASSERT_TRUE(lockFile.createdByUncleanShutdown());
+    }
+
+    TEST(StorageEngineLockFileTest, OpenInvalidDirectory) {
+        StorageEngineLockFile lockFile("no_such_directory");
+        ASSERT_EQUALS((boost::filesystem::path("no_such_directory") / "mongod.lock").string(),
+                      lockFile.getFilespec());
+        Status status = lockFile.open();
+        ASSERT_NOT_OK(status);
+        ASSERT_EQUALS(ErrorCodes::NonExistentPath, status.code());
+    }
+
+    // Cause ::open() to fail by providing a regular file instead of a directory for 'dbpath'.
+    TEST(StorageEngineLockFileTest, OpenInvalidFilename) {
+        TempDir tempDir("StorageEngineLockFileTest_OpenInvalidFilename");
+        std::string filename(tempDir.path() + "/some_file");
+        std::ofstream(filename.c_str());
+        StorageEngineLockFile lockFile(filename);
+        Status status = lockFile.open();
+        ASSERT_NOT_OK(status);
+        ASSERT_EQUALS(ErrorCodes::DBPathInUse, status.code());
+    }
+
+    TEST(StorageEngineLockFileTest, OpenNoExistingLockFile) {
+        TempDir tempDir("StorageEngineLockFileTest_OpenNoExistingLockFile");
+        StorageEngineLockFile lockFile(tempDir.path());
+        ASSERT_OK(lockFile.open());
+        lockFile.close();
+    }
+
+    TEST(StorageEngineLockFileTest, OpenEmptyLockFile) {
+        TempDir tempDir("StorageEngineLockFileTest_OpenEmptyLockFile");
+        StorageEngineLockFile lockFile(tempDir.path());
+        std::string filename(lockFile.getFilespec());
+        std::ofstream(filename.c_str());
+        ASSERT_OK(lockFile.open());
+        lockFile.close();
+    }
+
+    TEST(StorageEngineLockFileTest, WritePidFileNotOpened) {
+        TempDir tempDir("StorageEngineLockFileTest_WritePidFileNotOpened");
+        StorageEngineLockFile lockFile(tempDir.path());
+        Status status = lockFile.writePid();
+        ASSERT_NOT_OK(status);
+        ASSERT_EQUALS(ErrorCodes::FileNotOpen, status.code());
+    }
+
+    TEST(StorageEngineLockFileTest, WritePidFileOpened) {
+        TempDir tempDir("StorageEngineLockFileTest_WritePidFileOpened");
+        StorageEngineLockFile lockFile(tempDir.path());
+        ASSERT_OK(lockFile.open());
+        ASSERT_OK(lockFile.writePid());
+        lockFile.close();
+
+        // Read PID from lock file.
+        std::string filename(lockFile.getFilespec());
+        std::ifstream ifs(filename.c_str());
+        int64_t pidFromLockFile = 0;
+        ASSERT_TRUE(ifs >> pidFromLockFile);
+        ASSERT_EQUALS(ProcessId::getCurrent().asInt64(), pidFromLockFile);
+    }
+
+    // Existing data in lock file must be removed before writing process ID.
+    TEST(StorageEngineLockFileTest, WritePidTruncateExistingFile) {
+        TempDir tempDir("StorageEngineLockFileTest_WritePidTruncateExistingFile");
+        StorageEngineLockFile lockFile(tempDir.path());
+        {
+            std::string filename(tempDir.path() + "/mongod.lock");
+            std::ofstream ofs(filename.c_str());
+            std::string currentPidStr = ProcessId::getCurrent().toString();
+            ASSERT_FALSE(currentPidStr.empty());
+            ofs << std::string(currentPidStr.size() * 100, 'X') << std::endl;
+        }
+        ASSERT_OK(lockFile.open());
+        ASSERT_OK(lockFile.writePid());
+        lockFile.close();
+
+        // Read PID from lock file.
+        std::string filename(lockFile.getFilespec());
+        std::ifstream ifs(filename.c_str());
+        int64_t pidFromLockFile = 0;
+        ASSERT_TRUE(ifs >> pidFromLockFile);
+        ASSERT_EQUALS(ProcessId::getCurrent().asInt64(), pidFromLockFile);
+
+        // There should not be any data in the file after the process ID.
+        std::string extraData;
+        ASSERT_FALSE(ifs >> extraData);
+    }
+
+    TEST(StorageEngineLockFileTest, ClearPidAndUnlock) {
+        TempDir tempDir("StorageEngineLockFileTest_ClearPidAndUnlock");
+        StorageEngineLockFile lockFile(tempDir.path());
+        ASSERT_OK(lockFile.open());
+        ASSERT_OK(lockFile.writePid());
+
+        // Clear lock file contents.
+        lockFile.clearPidAndUnlock();
+        ASSERT_TRUE(boost::filesystem::exists(lockFile.getFilespec()));
+        ASSERT_EQUALS(0U, boost::filesystem::file_size(lockFile.getFilespec()));
+    }
+
+}  // namespace
diff --git a/src/mongo/db/storage/storage_engine_lock_file_win.cpp b/src/mongo/db/storage/storage_engine_lock_file_win.cpp
new file mode 100644
index 00000000000..41fc74ea736
--- /dev/null
+++ b/src/mongo/db/storage/storage_engine_lock_file_win.cpp
@@ -0,0 +1,190 @@
+/**
+ *    Copyright (C) 2014 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    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
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    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 GNU Affero General 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 "mongo/db/storage/storage_engine_lock_file.h"
+
+#include <boost/filesystem.hpp>
+#include <io.h>
+#include <ostream>
+#include <sstream>
+
+#include "mongo/platform/process_id.h"
+#include "mongo/util/log.h"
+#include "mongo/util/mongoutils/str.h"
+
+namespace mongo {
+
+namespace {
+
+    const std::string kLockFileBasename = "mongod.lock";
+
+    Status _truncateFile(HANDLE handle) {
+        invariant(handle != INVALID_HANDLE_VALUE);
+
+        LARGE_INTEGER largeint;
+        largeint.QuadPart = 0;
+        if (::SetFilePointerEx(handle, largeint, NULL, FILE_BEGIN) == FALSE) {
+            int errorcode = GetLastError();
+            return Status(ErrorCodes::FileStreamFailed, str::stream()
+                << "Unable to truncate lock file (SetFilePointerEx failed) "
+                << errnoWithDescription(errorcode));
+        }
+
+        if (::SetEndOfFile(handle) == FALSE) {
+            int errorcode = GetLastError();
+            return Status(ErrorCodes::FileStreamFailed, str::stream()
+                << "Unable to truncate lock file (SetEndOfFile failed) "
+                << errnoWithDescription(errorcode));
+        }
+
+        return Status::OK();
+    }
+
+}  // namespace
+
+    class StorageEngineLockFile::LockFileHandle {
+    public:
+        LockFileHandle() : _handle(INVALID_HANDLE_VALUE) { }
+        bool isValid() const { return _handle != INVALID_HANDLE_VALUE; }
+        void clear() { _handle = INVALID_HANDLE_VALUE; }
+        HANDLE _handle;
+    };
+
+    StorageEngineLockFile::StorageEngineLockFile(const std::string& dbpath)
+        : _dbpath(dbpath),
+          _filespec((boost::filesystem::path(_dbpath) / kLockFileBasename).string()),
+          _uncleanShutdown(boost::filesystem::exists(_filespec) &&
+                           boost::filesystem::file_size(_filespec) > 0),
+          _lockFileHandle(new LockFileHandle()) {
+    }
+
+    StorageEngineLockFile::~StorageEngineLockFile() { }
+
+    std::string StorageEngineLockFile::getFilespec() const {
+        return _filespec;
+    }
+
+    bool StorageEngineLockFile::createdByUncleanShutdown() const {
+        return _uncleanShutdown;
+    }
+
+    Status StorageEngineLockFile::open() {
+        try {
+            if (!boost::filesystem::exists(_dbpath)) {
+                return Status(ErrorCodes::NonExistentPath, str::stream()
+                    << "Data directory " << _dbpath << " not found.");
+            }
+        }
+        catch (const std::exception& ex) {
+            return Status(ErrorCodes::UnknownError, str::stream()
+                << "Unable to check existence of data directory "
+                << _dbpath << ": " << ex.what());
+        }
+
+        HANDLE lockFileHandle = CreateFileA(_filespec.c_str(), GENERIC_READ | GENERIC_WRITE,
+            0 /* do not allow anyone else access */, NULL,
+            OPEN_ALWAYS /* success if fh can open */, 0, NULL);
+
+        if (lockFileHandle == INVALID_HANDLE_VALUE) {
+            int errorcode = GetLastError();
+            return Status(ErrorCodes::DBPathInUse, str::stream()
+                << "Unable to create/open lock file: " << _filespec << ' '
+                << errnoWithDescription(errorcode)
+                << ". Is a mongod instance already running?");
+        }
+        _lockFileHandle->_handle = lockFileHandle;
+        return Status::OK();
+    }
+
+    void StorageEngineLockFile::close() {
+        if (!_lockFileHandle->isValid()) {
+            return;
+        }
+        CloseHandle(_lockFileHandle->_handle);
+        _lockFileHandle->clear();
+    }
+
+    Status StorageEngineLockFile::writePid() {
+        if (!_lockFileHandle->isValid()) {
+            return Status(ErrorCodes::FileNotOpen, str::stream()
+                << "Unable to write process ID to " << _filespec
+                << " because file has not been opened.");
+        }
+
+        Status status = _truncateFile(_lockFileHandle->_handle);
+        if (!status.isOK()) {
+            return status;
+        }
+
+        ProcessId pid = ProcessId::getCurrent();
+        std::stringstream ss;
+        ss << pid << std::endl;
+        std::string pidStr = ss.str();
+        DWORD bytesWritten = 0;
+        if (::WriteFile(_lockFileHandle->_handle,
+                        static_cast<LPCVOID>(pidStr.c_str()),
+                        static_cast<DWORD>(pidStr.size()),
+                        &bytesWritten,
+                        NULL) == FALSE) {
+            int errorcode = GetLastError();
+            return Status(ErrorCodes::FileStreamFailed, str::stream()
+                << "Unable to write process id " << pid.toString() << " to file: "
+                << _filespec << ' ' << errnoWithDescription(errorcode));
+        }
+        else if (bytesWritten == 0) {
+            return Status(ErrorCodes::FileStreamFailed, str::stream()
+                << "Unable to write process id " << pid.toString() << " to file: "
+                << _filespec << " no data written.");
+        }
+
+        ::FlushFileBuffers(_lockFileHandle->_handle);
+
+        return Status::OK();
+    }
+
+    void StorageEngineLockFile::clearPidAndUnlock() {
+        if (!_lockFileHandle->isValid()) {
+            return;
+        }
+        log() << "shutdown: removing fs lock...";
+        // This ought to be an unlink(), but Eliot says the last
+        // time that was attempted, there was a race condition
+        // with acquirePathLock().
+        Status status = _truncateFile(_lockFileHandle->_handle);
+        if (!status.isOK()) {
+            log() << "couldn't remove fs lock " << status.toString();
+        }
+        CloseHandle(_lockFileHandle->_handle);
+        _lockFileHandle->clear();
+    }
+
+}  // namespace mongo