// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// 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.
#pragma once
#include <atomic>
#include <deque>
#include <set>
#include <vector>
#include "db/dbformat.h"
#include "db/log_writer.h"
#include "db/snapshot.h"
#include "db/version_edit.h"
#include "rocksdb/db.h"
#include "rocksdb/env.h"
#include "rocksdb/memtablerep.h"
#include "rocksdb/transaction_log.h"
#include "port/port.h"
#include "util/stats_logger.h"
#include "memtablelist.h"
namespace rocksdb {
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 Merge(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 std::vector<Status> MultiGet(const ReadOptions& options,
const std::vector<Slice>& keys,
std::vector<std::string>* values);
// Returns false if key doesn't exist in the database and true if it may.
// If value_found is not passed in as null, then return the value if found in
// memory. On return, if value was found, then value_found will be set to true
// , otherwise false.
virtual bool KeyMayExist(const ReadOptions& options,
const Slice& key,
std::string* value,
bool* value_found = nullptr);
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,
bool reduce_level = false, int target_level = -1);
virtual int NumberLevels();
virtual int MaxMemCompactionLevel();
virtual int Level0StopWriteTrigger();
virtual const std::string& GetName() const;
virtual Env* GetEnv() const;
virtual const Options& GetOptions() const;
virtual Status Flush(const FlushOptions& options);
virtual Status DisableFileDeletions();
virtual Status EnableFileDeletions();
// All the returned filenames start with "/"
virtual Status GetLiveFiles(std::vector<std::string>&,
uint64_t* manifest_file_size,
bool flush_memtable = true);
virtual Status GetSortedWalFiles(VectorLogPtr& files);
virtual SequenceNumber GetLatestSequenceNumber() const;
virtual Status GetUpdatesSince(SequenceNumber seq_number,
unique_ptr<TransactionLogIterator>* iter);
virtual Status DeleteFile(std::string name);
virtual void GetLiveFilesMetaData(
std::vector<LiveFileMetaData> *metadata);
virtual Status GetDbIdentity(std::string& identity);
// 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 flushed.
Status TEST_FlushMemTable();
// Wait for memtable compaction
Status TEST_WaitForFlushMemTable();
// 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();
// Trigger's a background call for testing.
void TEST_PurgeObsoleteteWAL();
// get total level0 file size. Only for testing.
uint64_t TEST_GetLevel0TotalSize() { return versions_->NumLevelBytes(0);}
void TEST_SetDefaultTimeToCheck(uint64_t default_interval_to_delete_obsolete_WAL)
{
default_interval_to_delete_obsolete_WAL_ = default_interval_to_delete_obsolete_WAL;
}
// holds references to memtable, all immutable memtables and version
struct SuperVersion {
MemTable* mem;
MemTableList imm;
Version* current;
std::atomic<uint32_t> refs;
// We need to_delete because during Cleanup(), imm.UnrefAll() returns
// all memtables that we need to free through this vector. We then
// delete all those memtables outside of mutex, during destruction
std::vector<MemTable*> to_delete;
// should be called outside the mutex
explicit SuperVersion(const int num_memtables = 0);
~SuperVersion();
SuperVersion* Ref();
// Returns true if this was the last reference and caller should
// call Clenaup() and delete the object
bool Unref();
// call these two methods with db mutex held
// Cleanup unrefs mem, imm and current. Also, it stores all memtables
// that needs to be deleted in to_delete vector. Unrefing those
// objects needs to be done in the mutex
void Cleanup();
void Init(MemTable* new_mem, const MemTableList& new_imm,
Version* new_current);
};
// needed for CleanupIteratorState
struct DeletionState {
inline bool HaveSomethingToDelete() const {
return all_files.size() ||
sst_delete_files.size() ||
log_delete_files.size();
}
// a list of all files that we'll consider deleting
// (every once in a while this is filled up with all files
// in the DB directory)
std::vector<std::string> all_files;
// the list of all live sst files that cannot be deleted
std::vector<uint64_t> sst_live;
// a list of sst files that we need to delete
std::vector<FileMetaData*> sst_delete_files;
// a list of log files that we need to delete
std::vector<uint64_t> log_delete_files;
// a list of memtables to be free
std::vector<MemTable *> memtables_to_free;
SuperVersion* superversion_to_free; // if nullptr nothing to free
SuperVersion* new_superversion; // if nullptr no new superversion
// the current manifest_file_number, log_number and prev_log_number
// that corresponds to the set of files in 'live'.
uint64_t manifest_file_number, log_number, prev_log_number;
explicit DeletionState(const int num_memtables = 0,
bool create_superversion = false) {
manifest_file_number = 0;
log_number = 0;
prev_log_number = 0;
memtables_to_free.reserve(num_memtables);
superversion_to_free = nullptr;
new_superversion =
create_superversion ? new SuperVersion(num_memtables) : nullptr;
}
~DeletionState() {
// free pending memtables
for (auto m : memtables_to_free) {
delete m;
}
// free superversion. if nullptr, this will be noop
delete superversion_to_free;
// if new_superversion was not used, it will be non-nullptr and needs
// to be freed here
delete new_superversion;
}
};
// Returns the list of live files in 'live' and the list
// of all files in the filesystem in 'all_files'.
// If force == false and the last call was less than
// options_.delete_obsolete_files_period_micros microseconds ago,
// it will not fill up the deletion_state
void FindObsoleteFiles(DeletionState& deletion_state,
bool force,
bool no_full_scan = false);
// Diffs the files listed in filenames and those that do not
// belong to live files are posibly removed. Also, removes all the
// files in sst_delete_files and log_delete_files.
// It is not necessary to hold the mutex when invoking this method.
void PurgeObsoleteFiles(DeletionState& deletion_state);
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;
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();
// Flush the in-memory write buffer to storage. Switches to a new
// log-file/memtable and writes a new descriptor iff successful.
Status FlushMemTableToOutputFile(bool* madeProgress,
DeletionState& deletion_state);
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(std::vector<MemTable*> &mems, VersionEdit* edit,
uint64_t* filenumber);
uint64_t SlowdownAmount(int n, int top, int bottom);
// MakeRoomForWrite will return superversion_to_free through an arugment,
// which the caller needs to delete. We do it because caller can delete
// the superversion outside of mutex
Status MakeRoomForWrite(bool force /* compact even if there is room? */,
SuperVersion** superversion_to_free);
WriteBatch* BuildBatchGroup(Writer** last_writer);
// Force current memtable contents to be flushed.
Status FlushMemTable(const FlushOptions& options);
// Wait for memtable flushed
Status WaitForFlushMemTable();
void MaybeScheduleLogDBDeployStats();
static void BGLogDBDeployStats(void* db);
void LogDBDeployStats();
void MaybeScheduleFlushOrCompaction();
static void BGWorkCompaction(void* db);
static void BGWorkFlush(void* db);
void BackgroundCallCompaction();
void BackgroundCallFlush();
Status BackgroundCompaction(bool* madeProgress,DeletionState& deletion_state);
Status BackgroundFlush(bool* madeProgress, DeletionState& deletion_state);
void CleanupCompaction(CompactionState* compact, Status status);
Status DoCompactionWork(CompactionState* compact,
DeletionState& deletion_state);
Status OpenCompactionOutputFile(CompactionState* compact);
Status FinishCompactionOutputFile(CompactionState* compact, Iterator* input);
Status InstallCompactionResults(CompactionState* compact);
void AllocateCompactionOutputFileNumbers(CompactionState* compact);
void ReleaseCompactionUnusedFileNumbers(CompactionState* compact);
void PurgeObsoleteWALFiles();
Status AppendSortedWalsOfType(const std::string& path,
VectorLogPtr& log_files,
WalFileType type);
// Requires: all_logs should be sorted with earliest log file first
// Retains all log files in all_logs which contain updates with seq no.
// Greater Than or Equal to the requested SequenceNumber.
Status RetainProbableWalFiles(VectorLogPtr& all_logs,
const SequenceNumber target);
// return true if
bool CheckWalFileExistsAndEmpty(const WalFileType type,
const uint64_t number);
Status ReadFirstRecord(const WalFileType type, const uint64_t number,
WriteBatch* const result);
Status ReadFirstLine(const std::string& fname, WriteBatch* const batch);
void PrintStatistics();
// dump rocksdb.stats to LOG
void MaybeDumpStats();
// Return the minimum empty level that could hold the total data in the
// input level. Return the input level, if such level could not be found.
int FindMinimumEmptyLevelFitting(int level);
// Move the files in the input level to the target level.
// If target_level < 0, automatically calculate the minimum level that could
// hold the data set.
void ReFitLevel(int level, int target_level = -1);
// 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
MemTableRepFactory* mem_rep_factory_;
MemTable* mem_;
MemTableList imm_; // Memtable that are not changing
uint64_t logfile_number_;
unique_ptr<log::Writer> log_;
SuperVersion* super_version_;
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_;
// number of background memtable flush jobs, submitted to the HIGH pool
int bg_flush_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_;
// last time when PurgeObsoleteWALFiles ran.
uint64_t purge_wal_files_last_run_;
// last time stats were dumped to LOG
std::atomic<uint64_t> last_stats_dump_time_microsec_;
// obsolete files will be deleted every this seconds if ttl deletion is
// enabled and archive size_limit is disabled.
uint64_t default_interval_to_delete_obsolete_WAL_;
// 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_;
uint64_t stall_level0_slowdown_count_;
uint64_t stall_memtable_compaction_count_;
uint64_t stall_level0_num_files_count_;
std::vector<uint64_t> stall_leveln_slowdown_count_;
// 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_;
// Used to compute per-interval statistics
struct StatsSnapshot {
uint64_t compaction_bytes_read_; // Bytes read by compaction
uint64_t compaction_bytes_written_; // Bytes written by compaction
uint64_t ingest_bytes_; // Bytes written by user
uint64_t wal_bytes_; // Bytes written to WAL
uint64_t wal_synced_; // Number of times WAL is synced
uint64_t write_with_wal_; // Number of writes that request WAL
// These count the number of writes processed by the calling thread or
// another thread.
uint64_t write_other_;
uint64_t write_self_;
double seconds_up_;
StatsSnapshot() : compaction_bytes_read_(0), compaction_bytes_written_(0),
ingest_bytes_(0), wal_bytes_(0), wal_synced_(0),
write_with_wal_(0), write_other_(0), write_self_(0),
seconds_up_(0) {}
};
// Counters from the previous time per-interval stats were computed
StatsSnapshot last_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_;
// The options to access storage files
const EnvOptions storage_options_;
// A value of true temporarily disables scheduling of background work
bool bg_work_gate_closed_;
// Guard against multiple concurrent refitting
bool refitting_level_;
// No copying allowed
DBImpl(const DBImpl&);
void operator=(const DBImpl&);
// dump the delayed_writes_ to the log file and reset counter.
void DelayLoggingAndReset();
// Return the earliest snapshot where seqno is visible.
// Store the snapshot right before that, if any, in prev_snapshot
inline SequenceNumber findEarliestVisibleSnapshot(
SequenceNumber in,
std::vector<SequenceNumber>& snapshots,
SequenceNumber* prev_snapshot);
// will return a pointer to SuperVersion* if previous SuperVersion
// if its reference count is zero and needs deletion or nullptr if not
// As argument takes a pointer to allocated SuperVersion
// Foreground threads call this function directly (they don't carry
// deletion state and have to handle their own creation and deletion
// of SuperVersion)
SuperVersion* InstallSuperVersion(SuperVersion* new_superversion);
// Background threads call this function, which is just a wrapper around
// the InstallSuperVersion() function above. Background threads carry
// deletion_state which can have new_superversion already allocated.
void InstallSuperVersion(DeletionState& deletion_state);
// Function that Get and KeyMayExist call with no_io true or false
// Note: 'value_found' from KeyMayExist propagates here
Status GetImpl(const ReadOptions& options,
const Slice& key,
std::string* value,
bool* value_found = nullptr);
};
// 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);
// Determine compression type, based on user options, level of the output
// file and whether compression is disabled.
// If enable_compression is false, then compression is always disabled no
// matter what the values of the other two parameters are.
// Otherwise, the compression type is determined based on options and level.
CompressionType GetCompressionType(const Options& options, int level,
const bool enable_compression);
} // namespace rocksdb