879357fdb0
Summary: A current limitation of backups is that you don't know the exact database state of when the backup was taken. With this new feature, you can at least inspect the backup's DB state without restoring it by opening it as a read-only DB. Rather than add something like OpenAsReadOnlyDB to the BackupEngine API, which would inhibit opening stackable DB implementations read-only (if/when their APIs support it), we instead provide a DB name and Env that can be used to open as a read-only DB. Possible follow-up work: * Add a version of GetBackupInfo for a single backup. * Let CreateNewBackup return the BackupID of the newly-created backup. Implementation details: Refactored ChrootFileSystem to split off new base class RemapFileSystem, which allows more general remapping of files. We use this base class to implement BackupEngineImpl::RemapSharedFileSystem. To minimize API impact, I decided to just add these fields `name_for_open` and `env_for_open` to those set by GetBackupInfo when include_file_details=true. Creating the RemapSharedFileSystem adds a bit to the memory consumption, perhaps unnecessarily in some cases, but this has been mitigated by (a) only initialize the RemapSharedFileSystem lazily when GetBackupInfo with include_file_details=true is called, and (b) using the existing `shared_ptr<FileInfo>` objects to hold most of the mapping data. To enhance API safety, RemapSharedFileSystem is wrapped by new ReadOnlyFileSystem which rejects any attempts to write. This uncovered a couple of places in which DB::OpenForReadOnly would write to the filesystem, so I fixed these. Added a release note because this affects logging. Additional minor refactoring in backupable_db.cc to support the new functionality. Pull Request resolved: https://github.com/facebook/rocksdb/pull/8142 Test Plan: new test (run with ASAN and UBSAN), added to stress test and ran it for a while with amplified backup_one_in Reviewed By: ajkr Differential Revision: D27535408 Pulled By: pdillinger fbshipit-source-id: 04666d310aa0261ef6b2385c43ca793ce1dfd148
132 lines
5.4 KiB
C++
132 lines
5.4 KiB
C++
// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#ifndef ROCKSDB_LITE
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#include <utility>
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#include "rocksdb/file_system.h"
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namespace ROCKSDB_NAMESPACE {
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// An abstract FileSystem wrapper that creates a view of an existing
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// FileSystem by remapping names in some way.
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//
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// This class has not been fully analyzed for providing strong security
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// guarantees.
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class RemapFileSystem : public FileSystemWrapper {
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public:
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RemapFileSystem(const std::shared_ptr<FileSystem>& base);
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protected:
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// Returns status and mapped-to path in the wrapped filesystem.
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// If it returns non-OK status, the returned path should not be used.
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virtual std::pair<IOStatus, std::string> EncodePath(
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const std::string& path) = 0;
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// Similar to EncodePath() except used in cases in which it is OK for
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// no file or directory on 'path' to already exist, such as if the
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// operation would create one. However, the parent of 'path' is expected
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// to exist for the operation to succeed.
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// Default implementation: call EncodePath
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virtual std::pair<IOStatus, std::string> EncodePathWithNewBasename(
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const std::string& path);
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public:
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// Left abstract:
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// const char* Name() const override { ... }
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Status RegisterDbPaths(const std::vector<std::string>& paths) override;
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Status UnregisterDbPaths(const std::vector<std::string>& paths) override;
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IOStatus NewSequentialFile(const std::string& fname,
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const FileOptions& options,
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std::unique_ptr<FSSequentialFile>* result,
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IODebugContext* dbg) override;
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IOStatus NewRandomAccessFile(const std::string& fname,
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const FileOptions& options,
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std::unique_ptr<FSRandomAccessFile>* result,
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IODebugContext* dbg) override;
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IOStatus NewWritableFile(const std::string& fname, const FileOptions& options,
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std::unique_ptr<FSWritableFile>* result,
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IODebugContext* dbg) override;
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IOStatus ReuseWritableFile(const std::string& fname,
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const std::string& old_fname,
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const FileOptions& options,
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std::unique_ptr<FSWritableFile>* result,
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IODebugContext* dbg) override;
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IOStatus NewRandomRWFile(const std::string& fname, const FileOptions& options,
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std::unique_ptr<FSRandomRWFile>* result,
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IODebugContext* dbg) override;
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IOStatus NewDirectory(const std::string& dir, const IOOptions& options,
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std::unique_ptr<FSDirectory>* result,
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IODebugContext* dbg) override;
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IOStatus FileExists(const std::string& fname, const IOOptions& options,
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IODebugContext* dbg) override;
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IOStatus GetChildren(const std::string& dir, const IOOptions& options,
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std::vector<std::string>* result,
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IODebugContext* dbg) override;
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IOStatus GetChildrenFileAttributes(const std::string& dir,
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const IOOptions& options,
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std::vector<FileAttributes>* result,
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IODebugContext* dbg) override;
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IOStatus DeleteFile(const std::string& fname, const IOOptions& options,
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IODebugContext* dbg) override;
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IOStatus CreateDir(const std::string& dirname, const IOOptions& options,
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IODebugContext* dbg) override;
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IOStatus CreateDirIfMissing(const std::string& dirname,
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const IOOptions& options,
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IODebugContext* dbg) override;
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IOStatus DeleteDir(const std::string& dirname, const IOOptions& options,
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IODebugContext* dbg) override;
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IOStatus GetFileSize(const std::string& fname, const IOOptions& options,
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uint64_t* file_size, IODebugContext* dbg) override;
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IOStatus GetFileModificationTime(const std::string& fname,
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const IOOptions& options,
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uint64_t* file_mtime,
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IODebugContext* dbg) override;
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IOStatus IsDirectory(const std::string& path, const IOOptions& options,
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bool* is_dir, IODebugContext* dbg) override;
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IOStatus RenameFile(const std::string& src, const std::string& dest,
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const IOOptions& options, IODebugContext* dbg) override;
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IOStatus LinkFile(const std::string& src, const std::string& dest,
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const IOOptions& options, IODebugContext* dbg) override;
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IOStatus LockFile(const std::string& fname, const IOOptions& options,
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FileLock** lock, IODebugContext* dbg) override;
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IOStatus NewLogger(const std::string& fname, const IOOptions& options,
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std::shared_ptr<Logger>* result,
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IODebugContext* dbg) override;
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IOStatus GetAbsolutePath(const std::string& db_path, const IOOptions& options,
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std::string* output_path,
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IODebugContext* dbg) override;
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};
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} // namespace ROCKSDB_NAMESPACE
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#endif // ROCKSDB_LITE
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