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rocksdb/env/fs_readonly.h

105 lines
3.8 KiB

Make backups openable as read-only DBs (#8142) 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
4 years ago
// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#ifndef ROCKSDB_LITE
#include "rocksdb/file_system.h"
namespace ROCKSDB_NAMESPACE {
// A FileSystem wrapper that only allows read-only operation.
//
// This class has not been fully analyzed for providing strong security
// guarantees.
class ReadOnlyFileSystem : public FileSystemWrapper {
static inline IOStatus FailReadOnly() {
IOStatus s = IOStatus::IOError("Attempted write to ReadOnlyFileSystem");
assert(s.GetRetryable() == false);
return s;
}
public:
explicit ReadOnlyFileSystem(const std::shared_ptr<FileSystem>& base)
Make backups openable as read-only DBs (#8142) 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
4 years ago
: FileSystemWrapper(base) {}
IOStatus NewWritableFile(const std::string& /*fname*/,
const FileOptions& /*options*/,
std::unique_ptr<FSWritableFile>* /*result*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus ReuseWritableFile(const std::string& /*fname*/,
const std::string& /*old_fname*/,
const FileOptions& /*options*/,
std::unique_ptr<FSWritableFile>* /*result*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus NewRandomRWFile(const std::string& /*fname*/,
const FileOptions& /*options*/,
std::unique_ptr<FSRandomRWFile>* /*result*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus NewDirectory(const std::string& /*dir*/,
const IOOptions& /*options*/,
std::unique_ptr<FSDirectory>* /*result*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus DeleteFile(const std::string& /*fname*/,
const IOOptions& /*options*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus CreateDir(const std::string& /*dirname*/,
const IOOptions& /*options*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus CreateDirIfMissing(const std::string& dirname,
const IOOptions& options,
IODebugContext* dbg) override {
// Allow if dir already exists
bool is_dir = false;
IOStatus s = IsDirectory(dirname, options, &is_dir, dbg);
if (s.ok() && is_dir) {
return s;
} else {
return FailReadOnly();
}
Make backups openable as read-only DBs (#8142) 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
4 years ago
}
IOStatus DeleteDir(const std::string& /*dirname*/,
const IOOptions& /*options*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus RenameFile(const std::string& /*src*/, const std::string& /*dest*/,
const IOOptions& /*options*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus LinkFile(const std::string& /*src*/, const std::string& /*dest*/,
const IOOptions& /*options*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus LockFile(const std::string& /*fname*/, const IOOptions& /*options*/,
FileLock** /*lock*/, IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
IOStatus NewLogger(const std::string& /*fname*/, const IOOptions& /*options*/,
std::shared_ptr<Logger>* /*result*/,
IODebugContext* /*dbg*/) override {
return FailReadOnly();
}
};
} // namespace ROCKSDB_NAMESPACE
#endif // ROCKSDB_LITE