Refactor: add LineFileReader and Status::MustCheck (#8026)
Summary: Removed confusing, awkward, and undocumented internal API ReadOneLine and replaced with very simple LineFileReader. In refactoring backupable_db.cc, this has the side benefit of removing the arbitrary cap on the size of backup metadata files. Also added Status::MustCheck to make it easy to mark a Status as "must check." Using this, I can ensure that after LineFileReader::ReadLine returns false the caller checks GetStatus(). Also removed some excessive conditional compilation in status.h Pull Request resolved: https://github.com/facebook/rocksdb/pull/8026 Test Plan: added unit test, and running tests with ASSERT_STATUS_CHECKED Reviewed By: mrambacher Differential Revision: D26831687 Pulled By: pdillinger fbshipit-source-id: ef749c265a7a26bb13cd44f6f0f97db2955f6f0fmain
Peter Dillinger
4 years ago
committed by
Facebook GitHub Bot
parent
847ca9f964
commit
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// 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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#include "file/line_file_reader.h" |
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#include <cstring> |
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namespace ROCKSDB_NAMESPACE { |
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Status LineFileReader::Create(const std::shared_ptr<FileSystem>& fs, |
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const std::string& fname, |
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const FileOptions& file_opts, |
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std::unique_ptr<LineFileReader>* reader, |
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IODebugContext* dbg) { |
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std::unique_ptr<FSSequentialFile> file; |
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Status s = fs->NewSequentialFile(fname, file_opts, &file, dbg); |
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if (s.ok()) { |
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reader->reset(new LineFileReader(std::move(file), fname)); |
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} |
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return s; |
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} |
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bool LineFileReader::ReadLine(std::string* out) { |
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assert(out); |
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if (!status_.ok()) { |
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// Status should be checked (or permit unchecked) any time we return false.
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status_.MustCheck(); |
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return false; |
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} |
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out->clear(); |
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for (;;) { |
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// Look for line delimiter
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const char* found = static_cast<const char*>( |
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std::memchr(buf_begin_, '\n', buf_end_ - buf_begin_)); |
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if (found) { |
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size_t len = found - buf_begin_; |
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out->append(buf_begin_, len); |
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buf_begin_ += len + /*delim*/ 1; |
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++line_number_; |
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return true; |
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} |
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if (at_eof_) { |
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status_.MustCheck(); |
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return false; |
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} |
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// else flush and reload buffer
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out->append(buf_begin_, buf_end_ - buf_begin_); |
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Slice result; |
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status_ = sfr_.Read(buf_.size(), &result, buf_.data()); |
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if (!status_.ok()) { |
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status_.MustCheck(); |
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return false; |
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} |
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if (result.size() != buf_.size()) { |
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// The obscure way of indicating EOF
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at_eof_ = true; |
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} |
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buf_begin_ = result.data(); |
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buf_end_ = result.data() + result.size(); |
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} |
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} |
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} // namespace ROCKSDB_NAMESPACE
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// 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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#include <array> |
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#include "file/sequence_file_reader.h" |
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namespace ROCKSDB_NAMESPACE { |
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// A wrapper on top of Env::SequentialFile for reading text lines from a file.
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// Lines are delimited by '\n'. The last line may or may not include a
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// trailing newline. Uses SequentialFileReader internally.
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class LineFileReader { |
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private: |
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std::array<char, 8192> buf_; |
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SequentialFileReader sfr_; |
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Status status_; |
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const char* buf_begin_ = buf_.data(); |
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const char* buf_end_ = buf_.data(); |
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size_t line_number_ = 0; |
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bool at_eof_ = false; |
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public: |
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// See SequentialFileReader constructors
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template <typename... Args> |
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explicit LineFileReader(Args&&... args) |
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: sfr_(std::forward<Args&&>(args)...) {} |
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static Status Create(const std::shared_ptr<FileSystem>& fs, |
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const std::string& fname, const FileOptions& file_opts, |
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std::unique_ptr<LineFileReader>* reader, |
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IODebugContext* dbg); |
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LineFileReader(const LineFileReader&) = delete; |
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LineFileReader& operator=(const LineFileReader&) = delete; |
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// Reads another line from the file, returning true on success and saving
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// the line to `out`, without delimiter, or returning false on failure. You
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// must check GetStatus() to determine whether the failure was just
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// end-of-file (OK status) or an I/O error (another status).
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bool ReadLine(std::string* out); |
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// Returns the number of the line most recently returned from ReadLine.
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// Return value is unspecified if ReadLine has returned false due to
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// I/O error. After ReadLine returns false due to end-of-file, return
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// value is the last returned line number, or equivalently the total
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// number of lines returned.
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size_t GetLineNumber() const { return line_number_; } |
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// Returns any error encountered during read. The error is considered
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// permanent and no retry or recovery is attempted with the same
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// LineFileReader.
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const Status& GetStatus() const { return status_; } |
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}; |
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} // namespace ROCKSDB_NAMESPACE
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