rocksdb/db/db_impl.h
Haobo Xu 645ff8f231 Let's get rid of delete as much as possible, here are some examples.
Summary:
If a class owns an object:
 - If the object can be null => use a unique_ptr. no delete
 - If the object can not be null => don't even need new, let alone delete
 - for runtime sized array => use vector, no delete.

Test Plan: make check

Reviewers: dhruba, heyongqiang

Reviewed By: heyongqiang

CC: leveldb, zshao, sheki, emayanke, MarkCallaghan

Differential Revision: https://reviews.facebook.net/D9783
2013-03-28 17:31:44 -07:00

357 lines
12 KiB
C++

// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#ifndef STORAGE_LEVELDB_DB_DB_IMPL_H_
#define STORAGE_LEVELDB_DB_DB_IMPL_H_
#include <deque>
#include <set>
#include "db/dbformat.h"
#include "db/log_file.h"
#include "db/log_writer.h"
#include "db/snapshot.h"
#include "leveldb/db.h"
#include "leveldb/env.h"
#include "port/port.h"
#include "util/stats_logger.h"
#include "memtablelist.h"
#ifdef USE_SCRIBE
#include "scribe/scribe_logger.h"
#endif
namespace leveldb {
class MemTable;
class TableCache;
class Version;
class VersionEdit;
class VersionSet;
class DBImpl : public DB {
public:
DBImpl(const Options& options, const std::string& dbname);
virtual ~DBImpl();
// Implementations of the DB interface
virtual Status Put(const WriteOptions&, const Slice& key, const Slice& value);
virtual Status Delete(const WriteOptions&, const Slice& key);
virtual Status Write(const WriteOptions& options, WriteBatch* updates);
virtual Status Get(const ReadOptions& options,
const Slice& key,
std::string* value);
virtual Iterator* NewIterator(const ReadOptions&);
virtual const Snapshot* GetSnapshot();
virtual void ReleaseSnapshot(const Snapshot* snapshot);
virtual bool GetProperty(const Slice& property, std::string* value);
virtual void GetApproximateSizes(const Range* range, int n, uint64_t* sizes);
virtual void CompactRange(const Slice* begin, const Slice* end);
virtual int NumberLevels();
virtual int MaxMemCompactionLevel();
virtual int Level0StopWriteTrigger();
virtual Status Flush(const FlushOptions& options);
virtual Status DisableFileDeletions();
virtual Status EnableFileDeletions();
virtual Status GetLiveFiles(std::vector<std::string>&,
uint64_t* manifest_file_size);
virtual SequenceNumber GetLatestSequenceNumber();
virtual Status GetUpdatesSince(SequenceNumber seq_number,
unique_ptr<TransactionLogIterator>* iter);
// Extra methods (for testing) that are not in the public DB interface
// Compact any files in the named level that overlap [*begin,*end]
void TEST_CompactRange(int level, const Slice* begin, const Slice* end);
// Force current memtable contents to be compacted.
Status TEST_CompactMemTable();
// Wait for memtable compaction
Status TEST_WaitForCompactMemTable();
// Wait for any compaction
Status TEST_WaitForCompact();
// Return an internal iterator over the current state of the database.
// The keys of this iterator are internal keys (see format.h).
// The returned iterator should be deleted when no longer needed.
Iterator* TEST_NewInternalIterator();
// Return the maximum overlapping data (in bytes) at next level for any
// file at a level >= 1.
int64_t TEST_MaxNextLevelOverlappingBytes();
// Simulate a db crash, no elegant closing of database.
void TEST_Destroy_DBImpl();
// Return the current manifest file no.
uint64_t TEST_Current_Manifest_FileNo();
protected:
Env* const env_;
const std::string dbname_;
unique_ptr<VersionSet> versions_;
const InternalKeyComparator internal_comparator_;
const Options options_; // options_.comparator == &internal_comparator_
const Comparator* user_comparator() const {
return internal_comparator_.user_comparator();
}
MemTable* GetMemTable() {
return mem_;
}
Iterator* NewInternalIterator(const ReadOptions&,
SequenceNumber* latest_snapshot);
private:
friend class DB;
struct CompactionState;
struct Writer;
struct DeletionState;
Status NewDB();
// Recover the descriptor from persistent storage. May do a significant
// amount of work to recover recently logged updates. Any changes to
// be made to the descriptor are added to *edit.
Status Recover(VersionEdit* edit, MemTable* external_table = nullptr,
bool error_if_log_file_exist = false);
void MaybeIgnoreError(Status* s) const;
const Status CreateArchivalDirectory();
// Delete any unneeded files and stale in-memory entries.
void DeleteObsoleteFiles();
// Compact the in-memory write buffer to disk. Switches to a new
// log-file/memtable and writes a new descriptor iff successful.
Status CompactMemTable(bool* madeProgress = nullptr);
Status RecoverLogFile(uint64_t log_number,
VersionEdit* edit,
SequenceNumber* max_sequence,
MemTable* external_table);
// The following two methods are used to flush a memtable to
// storage. The first one is used atdatabase RecoveryTime (when the
// database is opened) and is heavyweight because it holds the mutex
// for the entire period. The second method WriteLevel0Table supports
// concurrent flush memtables to storage.
Status WriteLevel0TableForRecovery(MemTable* mem, VersionEdit* edit);
Status WriteLevel0Table(MemTable* mem, VersionEdit* edit,
uint64_t* filenumber);
Status MakeRoomForWrite(bool force /* compact even if there is room? */);
WriteBatch* BuildBatchGroup(Writer** last_writer);
// Force current memtable contents to be flushed.
Status FlushMemTable(const FlushOptions& options);
// Wait for memtable compaction
Status WaitForCompactMemTable();
void MaybeScheduleLogDBDeployStats();
static void BGLogDBDeployStats(void* db);
void LogDBDeployStats();
void MaybeScheduleCompaction();
static void BGWork(void* db);
void BackgroundCall();
Status BackgroundCompaction(bool* madeProgress, DeletionState& deletion_state);
void CleanupCompaction(CompactionState* compact);
Status DoCompactionWork(CompactionState* compact);
Status OpenCompactionOutputFile(CompactionState* compact);
Status FinishCompactionOutputFile(CompactionState* compact, Iterator* input);
Status InstallCompactionResults(CompactionState* compact);
void AllocateCompactionOutputFileNumbers(CompactionState* compact);
void ReleaseCompactionUnusedFileNumbers(CompactionState* compact);
// Returns the list of live files in 'live' and the list
// of all files in the filesystem in 'allfiles'.
void FindObsoleteFiles(DeletionState& deletion_state);
// Diffs the files listed in filenames and those that do not
// belong to live files are posibly removed. If the removed file
// is a sst file, then it returns the file number in files_to_evict.
void PurgeObsoleteFiles(DeletionState& deletion_state);
// Removes the file listed in files_to_evict from the table_cache
void EvictObsoleteFiles(DeletionState& deletion_state);
void PurgeObsoleteWALFiles();
Status ListAllWALFiles(const std::string& path,
std::vector<LogFile>* logFiles,
WalFileType type);
// Find's all the log files which contain updates with seq no.
// Greater Than or Equal to the requested SequenceNumber
Status FindProbableWALFiles(std::vector<LogFile>* const allLogs,
std::vector<LogFile>* const result,
const SequenceNumber target);
// return true if
bool CheckFileExistsAndEmpty(const LogFile& file);
Status ReadFirstRecord(const LogFile& file, WriteBatch* const result);
Status ReadFirstLine(const std::string& fname, WriteBatch* const batch);
// Constant after construction
const InternalFilterPolicy internal_filter_policy_;
bool owns_info_log_;
// table_cache_ provides its own synchronization
unique_ptr<TableCache> table_cache_;
// Lock over the persistent DB state. Non-nullptr iff successfully acquired.
FileLock* db_lock_;
// State below is protected by mutex_
port::Mutex mutex_;
port::AtomicPointer shutting_down_;
port::CondVar bg_cv_; // Signalled when background work finishes
MemTable* mem_;
MemTableList imm_; // Memtable that are not changing
uint64_t logfile_number_;
unique_ptr<log::Writer> log_;
std::string host_name_;
// Queue of writers.
std::deque<Writer*> writers_;
WriteBatch tmp_batch_;
SnapshotList snapshots_;
// Set of table files to protect from deletion because they are
// part of ongoing compactions.
std::set<uint64_t> pending_outputs_;
// count how many background compaction been scheduled or is running?
int bg_compaction_scheduled_;
// Has a background stats log thread scheduled?
bool bg_logstats_scheduled_;
// Information for a manual compaction
struct ManualCompaction {
int level;
bool done;
bool in_progress; // compaction request being processed?
const InternalKey* begin; // nullptr means beginning of key range
const InternalKey* end; // nullptr means end of key range
InternalKey tmp_storage; // Used to keep track of compaction progress
};
ManualCompaction* manual_compaction_;
// Have we encountered a background error in paranoid mode?
Status bg_error_;
std::unique_ptr<StatsLogger> logger_;
int64_t volatile last_log_ts;
// shall we disable deletion of obsolete files
bool disable_delete_obsolete_files_;
// last time when DeleteObsoleteFiles was invoked
uint64_t delete_obsolete_files_last_run_;
// These count the number of microseconds for which MakeRoomForWrite stalls.
uint64_t stall_level0_slowdown_;
uint64_t stall_memtable_compaction_;
uint64_t stall_level0_num_files_;
std::vector<uint64_t> stall_leveln_slowdown_;
// Time at which this instance was started.
const uint64_t started_at_;
bool flush_on_destroy_; // Used when disableWAL is true.
// Per level compaction stats. stats_[level] stores the stats for
// compactions that produced data for the specified "level".
struct CompactionStats {
uint64_t micros;
// Bytes read from level N during compaction between levels N and N+1
int64_t bytes_readn;
// Bytes read from level N+1 during compaction between levels N and N+1
int64_t bytes_readnp1;
// Total bytes written during compaction between levels N and N+1
int64_t bytes_written;
// Files read from level N during compaction between levels N and N+1
int files_in_leveln;
// Files read from level N+1 during compaction between levels N and N+1
int files_in_levelnp1;
// Files written during compaction between levels N and N+1
int files_out_levelnp1;
// Number of compactions done
int count;
CompactionStats() : micros(0), bytes_readn(0), bytes_readnp1(0),
bytes_written(0), files_in_leveln(0),
files_in_levelnp1(0), files_out_levelnp1(0),
count(0) { }
void Add(const CompactionStats& c) {
this->micros += c.micros;
this->bytes_readn += c.bytes_readn;
this->bytes_readnp1 += c.bytes_readnp1;
this->bytes_written += c.bytes_written;
this->files_in_leveln += c.files_in_leveln;
this->files_in_levelnp1 += c.files_in_levelnp1;
this->files_out_levelnp1 += c.files_out_levelnp1;
this->count += 1;
}
};
std::vector<CompactionStats> stats_;
static const int KEEP_LOG_FILE_NUM = 1000;
std::string db_absolute_path_;
// count of the number of contiguous delaying writes
int delayed_writes_;
// store the last flushed sequence.
// Used by transaction log iterator.
SequenceNumber last_flushed_sequence_;
// The options to access storage files
const StorageOptions storage_options_;
// No copying allowed
DBImpl(const DBImpl&);
void operator=(const DBImpl&);
// dump the delayed_writes_ to the log file and reset counter.
void DelayLoggingAndReset();
// find the earliest snapshot where seqno is visible
inline SequenceNumber findEarliestVisibleSnapshot(SequenceNumber in,
std::vector<SequenceNumber>& snapshots);
};
// Sanitize db options. The caller should delete result.info_log if
// it is not equal to src.info_log.
extern Options SanitizeOptions(const std::string& db,
const InternalKeyComparator* icmp,
const InternalFilterPolicy* ipolicy,
const Options& src);
} // namespace leveldb
#endif // STORAGE_LEVELDB_DB_DB_IMPL_H_