SERVER-15986 added storage_engine_metadata - reads and writes storage engine metadata file in data directory

1 files changed, 239 insertions, 0 deletions

diff --git a/src/mongo/db/storage/storage_engine_metadata.cpp b/src/mongo/db/storage/storage_engine_metadata.cpp
new file mode 100644
index 00000000000..c2f4354d7b7
--- /dev/null
+++ b/src/mongo/db/storage/storage_engine_metadata.cpp
@@ -0,0 +1,239 @@
+// storage_engine_metadata.cpp
+
+/**
+ *    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_metadata.h"
+
+#include <cstdio>
+#include <boost/filesystem.hpp>
+#include <fstream>
+#include <limits>
+#include <ostream>
+#include <vector>
+
+#include "mongo/db/jsobj.h"
+#include "mongo/util/assert_util.h"
+#include "mongo/util/log.h"
+#include "mongo/util/mongoutils/str.h"
+
+namespace mongo {
+
+namespace {
+
+    const std::string kMetadataBasename = "storage.bson";
+
+}  // namespace
+
+    // static
+    void StorageEngineMetadata::validate(const std::string& dbpath,
+                                         const std::string& storageEngine) {
+        if (boost::filesystem::is_empty(dbpath)) {
+            return;
+        }
+
+        StorageEngineMetadata metadata(dbpath);
+        Status status = metadata.read();
+        std::string previousStorageEngine;
+        if (status.isOK()) {
+            previousStorageEngine = metadata.getStorageEngine();
+        }
+        else if (status.code() == ErrorCodes::NonExistentPath) {
+            previousStorageEngine = "mmapv1";
+        }
+        else {
+            // The storage metadata file is present but there was an issue
+            // reading its contents.
+            severe() << "Unable to verify the storage engine";
+            uassertStatusOK(status);
+        }
+        uassert(28574, str::stream()
+            << "Cannot start server. Detected data files in " << dbpath
+            << " created by storage engine '" << previousStorageEngine
+            << "'. The configured storage engine is '" << storageEngine << "'.",
+            previousStorageEngine == storageEngine);
+    }
+
+    // static
+    Status StorageEngineMetadata::updateIfMissing(const std::string& dbpath,
+                                                  const std::string& storageEngine) {
+        boost::filesystem::path metadataPath =
+            boost::filesystem::path(dbpath) / kMetadataBasename;
+
+        if (boost::filesystem::exists(metadataPath)) {
+            return Status::OK();
+        }
+
+        StorageEngineMetadata metadata(dbpath);
+        metadata.setStorageEngine(storageEngine);
+        Status status = metadata.write();
+        if (!status.isOK()) {
+            warning() << "Unable to update storage engine metadata in " << dbpath
+                      << ": " << status.toString();
+        }
+        return status;
+    }
+
+    StorageEngineMetadata::StorageEngineMetadata(const std::string& dbpath)
+        : _dbpath(dbpath) {
+        reset();
+    }
+
+    StorageEngineMetadata::~StorageEngineMetadata() { }
+
+    void StorageEngineMetadata::reset() {
+        _storageEngine.clear();
+    }
+
+    const std::string& StorageEngineMetadata::getStorageEngine() const {
+        return _storageEngine;
+    }
+
+    void StorageEngineMetadata::setStorageEngine(const std::string& storageEngine) {
+        _storageEngine = storageEngine;
+    }
+
+    Status StorageEngineMetadata::read() {
+        reset();
+
+        boost::filesystem::path metadataPath =
+            boost::filesystem::path(_dbpath) / kMetadataBasename;
+
+        if (!boost::filesystem::exists(metadataPath)) {
+            return Status(ErrorCodes::NonExistentPath, str::stream()
+                << "Metadata file " << metadataPath.string() << " not found.");
+        }
+
+        boost::uintmax_t fileSize = boost::filesystem::file_size(metadataPath);
+        if (fileSize == 0) {
+            return Status(ErrorCodes::InvalidPath, str::stream()
+                << "Metadata file " << metadataPath.string() << " cannot be empty.");
+        }
+        if (fileSize == static_cast<boost::uintmax_t>(-1)) {
+            return Status(ErrorCodes::InvalidPath, str::stream()
+                << "Unable to determine size of metadata file " << metadataPath.string());
+        }
+
+        std::vector<char> buffer(fileSize);
+        std::string filename = metadataPath.string();
+        try {
+            std::ifstream ifs(filename.c_str(), std::ios_base::in | std::ios_base::binary);
+            if (!ifs) {
+                return Status(ErrorCodes::FileNotOpen, str::stream()
+                    << "Failed to read metadata from " << filename);
+        }
+
+        // Read BSON from file
+        ifs.read(&buffer[0], buffer.size());
+        if (!ifs) {
+            return Status(ErrorCodes::FileStreamFailed, str::stream()
+                << "Unable to read BSON data from " << filename);
+        }
+        }
+        catch (const std::exception& ex) {
+            return Status(ErrorCodes::FileStreamFailed, str::stream()
+                << "Unexpected error reading BSON data from " << filename
+                << ": " << ex.what());
+        }
+
+        BSONObj obj;
+        try {
+            obj = BSONObj(&buffer[0]);
+        }
+        catch (DBException& ex) {
+            return Status(ErrorCodes::FailedToParse, str::stream()
+                          << "Failed to convert data in " << filename
+                          << " to BSON: " << ex.what());
+        }
+
+        // Validate 'storage.engine' field.
+        BSONElement storageEngineElement = obj.getFieldDotted("storage.engine");
+        if (storageEngineElement.type() != mongo::String) {
+            return Status(ErrorCodes::FailedToParse, str::stream()
+                          << "The 'storage.engine' field in metadata must be a string: "
+                          << storageEngineElement.toString());
+        }
+
+        // Extract storage engine name from 'storage.engine' node.
+        std::string storageEngine = storageEngineElement.String();
+        if (storageEngine.empty()) {
+            return Status(ErrorCodes::FailedToParse,
+                          "The 'storage.engine' field in metadata cannot be empty string.");
+        }
+        _storageEngine = storageEngine;
+        return Status::OK();
+    }
+
+    Status StorageEngineMetadata::write() const {
+        if (_storageEngine.empty()) {
+            return Status(ErrorCodes::BadValue,
+                          "Cannot write empty storage engine name to metadata file.");
+        }
+
+        boost::filesystem::path metadataPath =
+            boost::filesystem::path(_dbpath) / kMetadataBasename;
+        std::string filenameTemp = metadataPath.string() + ".tmp";
+        try {
+            std::ofstream ofs(filenameTemp.c_str(), std::ios_base::out | std::ios_base::binary);
+            if (!ofs) {
+                return Status(ErrorCodes::FileNotOpen, str::stream()
+                    << "Failed to write metadata to " << filenameTemp);
+            }
+
+            BSONObj obj = BSON("storage" << BSON("engine" << _storageEngine));
+            ofs.write(obj.objdata(), obj.objsize());
+            if (!ofs) {
+                return Status(ErrorCodes::InternalError, str::stream()
+                    << "Failed to write BSON data to " << filenameTemp);
+            }
+            ofs.flush();
+        }
+        catch (const std::exception& ex) {
+            return Status(ErrorCodes::InternalError, str::stream()
+                << "Unexpected error while writing metadata to " << filenameTemp
+                << ": " << ex.what());
+        }
+
+        // Rename temp file to actual metadata file.
+        // Removing original metafile first
+        std::string filename = metadataPath.string();
+        ::remove(filename.c_str());
+        if (::rename(filenameTemp.c_str(), filename.c_str())) {
+            return Status(ErrorCodes::FileRenameFailed, str::stream()
+                << "Failed to rename " << filename << " to " << filenameTemp
+                << ": " << errnoWithDescription());
+        }
+
+        return Status::OK();
+    }
+
+}  // namespace mongo