rocksdb/utilities/blob_db/blob_db_impl.h

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// Copyright (c) 2011-present, Facebook, Inc. 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 <atomic>
#include <condition_variable>
#include <ctime>
#include <limits>
#include <list>
#include <memory>
#include <set>
#include <string>
#include <thread>
#include <utility>
#include <vector>
#include "rocksdb/compaction_filter.h"
#include "rocksdb/db.h"
#include "rocksdb/listener.h"
#include "rocksdb/options.h"
#include "rocksdb/wal_filter.h"
#include "util/file_reader_writer.h"
#include "util/mpsc.h"
#include "util/mutexlock.h"
#include "util/timer_queue.h"
#include "utilities/blob_db/blob_db.h"
#include "utilities/blob_db/blob_log_format.h"
#include "utilities/blob_db/blob_log_reader.h"
#include "utilities/blob_db/blob_log_writer.h"
namespace rocksdb {
class DBImpl;
class ColumnFamilyHandle;
class ColumnFamilyData;
class OptimisticTransactionDBImpl;
struct FlushJobInfo;
namespace blob_db {
class BlobFile;
class BlobDBImpl;
class BlobDBFlushBeginListener : public EventListener {
public:
explicit BlobDBFlushBeginListener() : impl_(nullptr) {}
void OnFlushBegin(DB* db, const FlushJobInfo& info) override;
void SetImplPtr(BlobDBImpl* p) { impl_ = p; }
protected:
BlobDBImpl* impl_;
};
// this implements the callback from the WAL which ensures that the
// blob record is present in the blob log. If fsync/fdatasync in not
// happening on every write, there is the probability that keys in the
// blob log can lag the keys in blobs
class BlobReconcileWalFilter : public WalFilter {
public:
virtual WalFilter::WalProcessingOption LogRecordFound(
unsigned long long log_number, const std::string& log_file_name,
const WriteBatch& batch, WriteBatch* new_batch,
bool* batch_changed) override;
virtual const char* Name() const override { return "BlobDBWalReconciler"; }
void SetImplPtr(BlobDBImpl* p) { impl_ = p; }
protected:
BlobDBImpl* impl_;
};
class EvictAllVersionsCompactionListener : public EventListener {
public:
class InternalListener : public CompactionEventListener {
friend class BlobDBImpl;
public:
virtual void OnCompaction(int level, const Slice& key,
CompactionListenerValueType value_type,
const Slice& existing_value,
const SequenceNumber& sn, bool is_new) override;
void SetImplPtr(BlobDBImpl* p) { impl_ = p; }
private:
BlobDBImpl* impl_;
};
explicit EvictAllVersionsCompactionListener()
: internal_listener_(new InternalListener()) {}
virtual CompactionEventListener* GetCompactionEventListener() override {
return internal_listener_.get();
}
void SetImplPtr(BlobDBImpl* p) { internal_listener_->SetImplPtr(p); }
private:
std::unique_ptr<InternalListener> internal_listener_;
};
#if 0
class EvictAllVersionsFilterFactory : public CompactionFilterFactory {
private:
BlobDBImpl* impl_;
public:
EvictAllVersionsFilterFactory() : impl_(nullptr) {}
void SetImplPtr(BlobDBImpl* p) { impl_ = p; }
virtual std::unique_ptr<CompactionFilter> CreateCompactionFilter(
const CompactionFilter::Context& context) override;
virtual const char* Name() const override {
return "EvictAllVersionsFilterFactory";
}
};
#endif
// Comparator to sort "TTL" aware Blob files based on the lower value of
// TTL range.
struct blobf_compare_ttl {
bool operator()(const std::shared_ptr<BlobFile>& lhs,
const std::shared_ptr<BlobFile>& rhs) const;
};
struct GCStats {
uint64_t blob_count = 0;
uint64_t num_deletes = 0;
uint64_t deleted_size = 0;
uint64_t retry_delete = 0;
uint64_t delete_succeeded = 0;
uint64_t overwritten_while_delete = 0;
uint64_t num_relocate = 0;
uint64_t retry_relocate = 0;
uint64_t relocate_succeeded = 0;
uint64_t overwritten_while_relocate = 0;
std::shared_ptr<BlobFile> newfile = nullptr;
};
/**
* The implementation class for BlobDB. This manages the value
* part in TTL aware sequentially written files. These files are
* Garbage Collected.
*/
class BlobDBImpl : public BlobDB {
friend class BlobDBFlushBeginListener;
friend class EvictAllVersionsCompactionListener;
friend class BlobDB;
friend class BlobFile;
friend class BlobDBIterator;
public:
// deletions check period
static constexpr uint32_t kDeleteCheckPeriodMillisecs = 2 * 1000;
// gc percentage each check period
static constexpr uint32_t kGCFilePercentage = 100;
// gc period
static constexpr uint32_t kGCCheckPeriodMillisecs = 60 * 1000;
// sanity check task
static constexpr uint32_t kSanityCheckPeriodMillisecs = 20 * 60 * 1000;
// how many random access open files can we tolerate
static constexpr uint32_t kOpenFilesTrigger = 100;
// how many periods of stats do we keep.
static constexpr uint32_t kWriteAmplificationStatsPeriods = 24;
// what is the length of any period
static constexpr uint32_t kWriteAmplificationStatsPeriodMillisecs =
3600 * 1000;
// we will garbage collect blob files in
// which entire files have expired. However if the
// ttl_range of files is very large say a day, we
// would have to wait for the entire day, before we
// recover most of the space.
static constexpr uint32_t kPartialExpirationGCRangeSecs = 4 * 3600;
// this should be based on allowed Write Amplification
// if 50% of the space of a blob file has been deleted/expired,
static constexpr uint32_t kPartialExpirationPercentage = 75;
// how often should we schedule a job to fsync open files
static constexpr uint32_t kFSyncFilesPeriodMillisecs = 10 * 1000;
// how often to schedule reclaim open files.
static constexpr uint32_t kReclaimOpenFilesPeriodMillisecs = 1 * 1000;
// how often to schedule delete obs files periods
static constexpr uint32_t kDeleteObsoletedFilesPeriodMillisecs = 10 * 1000;
// how often to schedule check seq files period
static constexpr uint32_t kCheckSeqFilesPeriodMillisecs = 10 * 1000;
using rocksdb::StackableDB::Put;
Status Put(const WriteOptions& options, ColumnFamilyHandle* column_family,
const Slice& key, const Slice& value) override;
using rocksdb::StackableDB::Delete;
Status Delete(const WriteOptions& options, ColumnFamilyHandle* column_family,
const Slice& key) override;
using rocksdb::StackableDB::SingleDelete;
virtual Status SingleDelete(const WriteOptions& wopts,
ColumnFamilyHandle* column_family,
const Slice& key) override;
using rocksdb::StackableDB::Get;
Status Get(const ReadOptions& options, ColumnFamilyHandle* column_family,
const Slice& key, PinnableSlice* value) override;
using rocksdb::StackableDB::NewIterator;
virtual Iterator* NewIterator(const ReadOptions& opts,
ColumnFamilyHandle* column_family) override;
using rocksdb::StackableDB::MultiGet;
virtual std::vector<Status> MultiGet(
const ReadOptions& options,
const std::vector<ColumnFamilyHandle*>& column_family,
const std::vector<Slice>& keys,
std::vector<std::string>* values) override;
virtual Status Write(const WriteOptions& opts, WriteBatch* updates) override;
using BlobDB::PutWithTTL;
Status PutWithTTL(const WriteOptions& options,
ColumnFamilyHandle* column_family, const Slice& key,
const Slice& value, uint64_t ttl) override;
using BlobDB::PutUntil;
Status PutUntil(const WriteOptions& options,
ColumnFamilyHandle* column_family, const Slice& key,
const Slice& value_unc, uint64_t expiration) override;
Status LinkToBaseDB(DB* db) override;
BlobDBOptions GetBlobDBOptions() const override;
BlobDBImpl(DB* db, const BlobDBOptions& bdb_options);
BlobDBImpl(const std::string& dbname, const BlobDBOptions& bdb_options,
const DBOptions& db_options);
~BlobDBImpl();
#ifndef NDEBUG
Status TEST_GetSequenceNumber(const Slice& key, SequenceNumber* sequence);
std::vector<std::shared_ptr<BlobFile>> TEST_GetBlobFiles() const;
void TEST_CloseBlobFile(std::shared_ptr<BlobFile>& bfile);
Status TEST_GCFileAndUpdateLSM(std::shared_ptr<BlobFile>& bfile,
GCStats* gc_stats);
#endif // !NDEBUG
private:
Status OpenPhase1();
Status CommonGet(const ColumnFamilyData* cfd, const Slice& key,
const std::string& index_entry, std::string* value,
SequenceNumber* sequence = nullptr);
Slice GetCompressedSlice(const Slice& raw,
std::string* compression_output) const;
// Just before flush starts acting on memtable files,
// this handler is called.
void OnFlushBeginHandler(DB* db, const FlushJobInfo& info);
// timer queue callback to close a file by appending a footer
// removes file from open files list
std::pair<bool, int64_t> CloseSeqWrite(std::shared_ptr<BlobFile> bfile,
bool aborted);
// is this file ready for Garbage collection. if the TTL of the file
// has expired or if threshold of the file has been evicted
// tt - current time
// last_id - the id of the non-TTL file to evict
bool ShouldGCFile(std::shared_ptr<BlobFile> bfile, uint64_t now,
uint64_t last_id, std::string* reason);
// collect all the blob log files from the blob directory
Status GetAllLogFiles(std::set<std::pair<uint64_t, std::string>>* file_nums);
// appends a task into timer queue to close the file
void CloseIf(const std::shared_ptr<BlobFile>& bfile);
uint64_t ExtractExpiration(const Slice& key, const Slice& value,
Slice* value_slice, std::string* new_value);
Status AppendBlob(const std::shared_ptr<BlobFile>& bfile,
const std::string& headerbuf, const Slice& key,
const Slice& value, std::string* index_entry);
Status AppendSN(const std::shared_ptr<BlobFile>& bfile,
const SequenceNumber& sn);
// find an existing blob log file based on the expiration unix epoch
// if such a file does not exist, return nullptr
std::shared_ptr<BlobFile> SelectBlobFileTTL(uint64_t expiration);
// find an existing blob log file to append the value to
std::shared_ptr<BlobFile> SelectBlobFile();
std::shared_ptr<BlobFile> FindBlobFileLocked(uint64_t expiration) const;
void UpdateWriteOptions(const WriteOptions& options);
void Shutdown();
// periodic sanity check. Bunch of checks
std::pair<bool, int64_t> SanityCheck(bool aborted);
// delete files which have been garbage collected and marked
// obsolete. Check whether any snapshots exist which refer to
// the same
std::pair<bool, int64_t> DeleteObsFiles(bool aborted);
// Major task to garbage collect expired and deleted blobs
std::pair<bool, int64_t> RunGC(bool aborted);
// asynchronous task to fsync/fdatasync the open blob files
std::pair<bool, int64_t> FsyncFiles(bool aborted);
// periodically check if open blob files and their TTL's has expired
// if expired, close the sequential writer and make the file immutable
std::pair<bool, int64_t> CheckSeqFiles(bool aborted);
// if the number of open files, approaches ULIMIT's this
// task will close random readers, which are kept around for
// efficiency
std::pair<bool, int64_t> ReclaimOpenFiles(bool aborted);
// periodically print write amplification statistics
std::pair<bool, int64_t> WaStats(bool aborted);
// background task to do book-keeping of deleted keys
std::pair<bool, int64_t> EvictDeletions(bool aborted);
std::pair<bool, int64_t> EvictCompacted(bool aborted);
bool CallbackEvictsImpl(std::shared_ptr<BlobFile> bfile);
std::pair<bool, int64_t> RemoveTimerQ(TimerQueue* tq, bool aborted);
std::pair<bool, int64_t> CallbackEvicts(TimerQueue* tq,
std::shared_ptr<BlobFile> bfile,
bool aborted);
// Adds the background tasks to the timer queue
void StartBackgroundTasks();
// add a new Blob File
std::shared_ptr<BlobFile> NewBlobFile(const std::string& reason);
Status OpenAllFiles();
// hold write mutex on file and call
// creates a Random Access reader for GET call
std::shared_ptr<RandomAccessFileReader> GetOrOpenRandomAccessReader(
const std::shared_ptr<BlobFile>& bfile, Env* env,
const EnvOptions& env_options);
// hold write mutex on file and call.
// Close the above Random Access reader
void CloseRandomAccessLocked(const std::shared_ptr<BlobFile>& bfile);
// hold write mutex on file and call
// creates a sequential (append) writer for this blobfile
Status CreateWriterLocked(const std::shared_ptr<BlobFile>& bfile);
// returns a Writer object for the file. If writer is not
// already present, creates one. Needs Write Mutex to be held
std::shared_ptr<Writer> CheckOrCreateWriterLocked(
const std::shared_ptr<BlobFile>& bfile);
// Iterate through keys and values on Blob and write into
// separate file the remaining blobs and delete/update pointers
// in LSM atomically
Status GCFileAndUpdateLSM(const std::shared_ptr<BlobFile>& bfptr,
GCStats* gcstats);
// checks if there is no snapshot which is referencing the
// blobs
bool FileDeleteOk_SnapshotCheckLocked(const std::shared_ptr<BlobFile>& bfile);
bool MarkBlobDeleted(const Slice& key, const Slice& lsmValue);
bool FindFileAndEvictABlob(uint64_t file_number, uint64_t key_size,
uint64_t blob_offset, uint64_t blob_size);
void CopyBlobFiles(std::vector<std::shared_ptr<BlobFile>>* bfiles_copy,
uint64_t* last_id);
void FilterSubsetOfFiles(
const std::vector<std::shared_ptr<BlobFile>>& blob_files,
std::vector<std::shared_ptr<BlobFile>>* to_process, uint64_t epoch,
uint64_t last_id, size_t files_to_collect);
uint64_t EpochNow() { return env_->NowMicros() / 1000000; }
// the base DB
DBImpl* db_impl_;
Env* env_;
TTLExtractor* ttl_extractor_;
// Optimistic Transaction DB used during Garbage collection
// for atomicity
std::unique_ptr<OptimisticTransactionDBImpl> opt_db_;
// a boolean to capture whether write_options has been set
std::atomic<bool> wo_set_;
WriteOptions write_options_;
// the options that govern the behavior of Blob Storage
BlobDBOptions bdb_options_;
DBOptions db_options_;
EnvOptions env_options_;
// name of the database directory
std::string dbname_;
// by default this is "blob_dir" under dbname_
// but can be configured
std::string blob_dir_;
// pointer to directory
std::unique_ptr<Directory> dir_ent_;
std::atomic<bool> dir_change_;
// Read Write Mutex, which protects all the data structures
// HEAVILY TRAFFICKED
port::RWMutex mutex_;
// Writers has to hold write_mutex_ before writing.
mutable port::Mutex write_mutex_;
// counter for blob file number
std::atomic<uint64_t> next_file_number_;
// entire metadata of all the BLOB files memory
std::unordered_map<uint64_t, std::shared_ptr<BlobFile>> blob_files_;
// epoch or version of the open files.
std::atomic<uint64_t> epoch_of_;
// typically we keep 4 open blob files (simple i.e. no TTL)
std::vector<std::shared_ptr<BlobFile>> open_simple_files_;
// all the blob files which are currently being appended to based
// on variety of incoming TTL's
std::multiset<std::shared_ptr<BlobFile>, blobf_compare_ttl> open_blob_files_;
// packet of information to put in lockess delete(s) queue
struct delete_packet_t {
ColumnFamilyHandle* cfh_;
std::string key_;
SequenceNumber dsn_;
};
struct override_packet_t {
uint64_t file_number_;
uint64_t key_size_;
uint64_t blob_offset_;
uint64_t blob_size_;
SequenceNumber dsn_;
};
// LOCKLESS multiple producer single consumer queue to quickly append
// deletes without taking lock. Can rapidly grow in size!!
// deletes happen in LSM, but minor book-keeping needs to happen on
// BLOB side (for triggering eviction)
mpsc_queue_t<delete_packet_t> delete_keys_q_;
// LOCKLESS multiple producer single consumer queue for values
// that are being compacted
mpsc_queue_t<override_packet_t> override_vals_q_;
// atomic bool to represent shutdown
std::atomic<bool> shutdown_;
// timer based queue to execute tasks
TimerQueue tqueue_;
// timer queues to call eviction callbacks.
std::vector<std::shared_ptr<TimerQueue>> cb_threads_;
// only accessed in GC thread, hence not atomic. The epoch of the
// GC task. Each execution is one epoch. Helps us in allocating
// files to one execution
uint64_t current_epoch_;
// number of files opened for random access/GET
// counter is used to monitor and close excess RA files.
std::atomic<uint32_t> open_file_count_;
// should hold mutex to modify
// STATISTICS for WA of Blob Files due to GC
// collect by default 24 hourly periods
std::list<uint64_t> all_periods_write_;
std::list<uint64_t> all_periods_ampl_;
std::atomic<uint64_t> last_period_write_;
std::atomic<uint64_t> last_period_ampl_;
uint64_t total_periods_write_;
uint64_t total_periods_ampl_;
// total size of all blob files at a given time
std::atomic<uint64_t> total_blob_space_;
std::list<std::shared_ptr<BlobFile>> obsolete_files_;
bool open_p1_done_;
uint32_t debug_level_;
};
class BlobFile {
friend class BlobDBImpl;
friend struct blobf_compare_ttl;
private:
// access to parent
const BlobDBImpl* parent_;
// path to blob directory
std::string path_to_dir_;
// the id of the file.
// the above 2 are created during file creation and never changed
// after that
uint64_t file_number_;
// number of blobs in the file
std::atomic<uint64_t> blob_count_;
// the file will be selected for GC in this future epoch
std::atomic<int64_t> gc_epoch_;
// size of the file
std::atomic<uint64_t> file_size_;
// number of blobs in this particular file which have been evicted
uint64_t deleted_count_;
// size of deleted blobs (used by heuristic to select file for GC)
uint64_t deleted_size_;
BlobLogHeader header_;
// closed_ = true implies the file is no more mutable
// no more blobs will be appended and the footer has been written out
std::atomic<bool> closed_;
// has a pass of garbage collection successfully finished on this file
// can_be_deleted_ still needs to do iterator/snapshot checks
std::atomic<bool> can_be_deleted_;
// should this file been gc'd once to reconcile lost deletes/compactions
std::atomic<bool> gc_once_after_open_;
// et - lt of the blobs
ttlrange_t ttl_range_;
// et - lt of the timestamp of the KV pairs.
tsrange_t time_range_;
// ESN - LSN of the blobs
snrange_t sn_range_;
// Sequential/Append writer for blobs
std::shared_ptr<Writer> log_writer_;
// random access file reader for GET calls
std::shared_ptr<RandomAccessFileReader> ra_file_reader_;
// This Read-Write mutex is per file specific and protects
// all the datastructures
port::RWMutex mutex_;
// time when the random access reader was last created.
std::atomic<std::time_t> last_access_;
// last time file was fsync'd/fdatasyncd
std::atomic<uint64_t> last_fsync_;
bool header_valid_;
public:
BlobFile();
BlobFile(const BlobDBImpl* parent, const std::string& bdir, uint64_t fnum);
~BlobFile();
ColumnFamilyHandle* GetColumnFamily(DB* db);
// Returns log file's pathname relative to the main db dir
// Eg. For a live-log-file = blob_dir/000003.blob
std::string PathName() const;
// Primary identifier for blob file.
// once the file is created, this never changes
uint64_t BlobFileNumber() const { return file_number_; }
// the following functions are atomic, and don't need
// read lock
uint64_t BlobCount() const {
return blob_count_.load(std::memory_order_acquire);
}
std::string DumpState() const;
// if the file has gone through GC and blobs have been relocated
bool Obsolete() const { return can_be_deleted_.load(); }
// if the file is not taking any more appends.
bool Immutable() const { return closed_.load(); }
// we will assume this is atomic
bool NeedsFsync(bool hard, uint64_t bytes_per_sync) const;
uint64_t GetFileSize() const {
return file_size_.load(std::memory_order_acquire);
}
// All Get functions which are not atomic, will need ReadLock on the mutex
tsrange_t GetTimeRange() const {
assert(HasTimestamp());
return time_range_;
}
ttlrange_t GetTTLRange() const { return ttl_range_; }
snrange_t GetSNRange() const { return sn_range_; }
bool HasTTL() const {
assert(header_valid_);
return header_.HasTTL();
}
bool HasTimestamp() const {
assert(header_valid_);
return header_.HasTimestamp();
}
std::shared_ptr<Writer> GetWriter() const { return log_writer_; }
void Fsync();
private:
std::shared_ptr<Reader> OpenSequentialReader(
Env* env, const DBOptions& db_options,
const EnvOptions& env_options) const;
Status ReadFooter(BlobLogFooter* footer);
Status WriteFooterAndCloseLocked();
std::shared_ptr<RandomAccessFileReader> GetOrOpenRandomAccessReader(
Env* env, const EnvOptions& env_options, bool* fresh_open);
void CloseRandomAccessLocked();
// this is used, when you are reading only the footer of a
// previously closed file
Status SetFromFooterLocked(const BlobLogFooter& footer);
void set_time_range(const tsrange_t& tr) { time_range_ = tr; }
void set_ttl_range(const ttlrange_t& ttl) { ttl_range_ = ttl; }
void SetSNRange(const snrange_t& snr) { sn_range_ = snr; }
// The following functions are atomic, and don't need locks
void SetFileSize(uint64_t fs) { file_size_ = fs; }
void SetBlobCount(uint64_t bc) { blob_count_ = bc; }
void SetCanBeDeleted() { can_be_deleted_ = true; }
};
class BlobDBIterator : public Iterator {
public:
explicit BlobDBIterator(Iterator* iter, ColumnFamilyHandle* column_family,
BlobDBImpl* impl)
: iter_(iter), cfh_(column_family), db_impl_(impl) {
assert(iter_);
}
~BlobDBIterator() { delete iter_; }
bool Valid() const override { return iter_->Valid(); }
void SeekToFirst() override { iter_->SeekToFirst(); }
void SeekToLast() override { iter_->SeekToLast(); }
void Seek(const Slice& target) override { iter_->Seek(target); }
void SeekForPrev(const Slice& target) override { iter_->SeekForPrev(target); }
void Next() override { iter_->Next(); }
void Prev() override { iter_->Prev(); }
Slice key() const override { return iter_->key(); }
Slice value() const override;
Status status() const override { return iter_->status(); }
private:
Iterator* iter_;
ColumnFamilyHandle* cfh_;
BlobDBImpl* db_impl_;
mutable std::string vpart_;
};
} // namespace blob_db
} // namespace rocksdb
#endif // ROCKSDB_LITE