rocksdb/db/column_family.h
Cheng Chang fbce7a3808 Track WAL obsoletion when updating empty CF's log number (#7781)
Summary:
In the write path, there is an optimization: when a new WAL is created during SwitchMemtable, we update the internal log number of the empty column families to the new WAL. `FindObsoleteFiles` marks a WAL as obsolete if the WAL's log number is less than `VersionSet::MinLogNumberWithUnflushedData`. After updating the empty column families' internal log number, `VersionSet::MinLogNumberWithUnflushedData` might change, so some WALs might become obsolete to be purged from disk.

For example, consider there are 3 column families: 0, 1, 2:
1. initially, all the column families' log number is 1;
2. write some data to cf0, and flush cf0, but the flush is pending;
3. now a new WAL 2 is created;
4. write data to cf1 and WAL 2, now cf0's log number is 1, cf1's log number is 2, cf2's log number is 2 (because cf1 and cf2 are empty, so their log numbers will be set to the highest log number);
5. now cf0's flush hasn't finished, flush cf1, a new WAL 3 is created, and cf1's flush finishes, now cf0's log number is 1, cf1's log number is 3, cf2's log number is 3, since WAL 1 still contains data for the unflushed cf0, no WAL can be deleted from disk;
6. now cf0's flush finishes, cf0's log number is 2 (because when cf0 was switching memtable, WAL 3 does not exist yet), cf1's log number is 3, cf2's log number is 3, so WAL 1 can be purged from disk now, but WAL 2 still cannot because `MinLogNumberToKeep()` is 2;
7. write data to cf2 and WAL 3, because cf0 is empty, its log number is updated to 3, so now cf0's log number is 3, cf1's log number is 3, cf2's log number is 3;
8. now if the background threads want to purge obsolete files from disk, WAL 2 can be purged because `MinLogNumberToKeep()` is 3. But there are only two flush results written to MANIFEST: the first is for flushing cf1, and the `MinLogNumberToKeep` is 1, the second is for flushing cf0, and the `MinLogNumberToKeep` is 2. So without this PR, if the DB crashes at this point and try to recover, `WalSet` will still expect WAL 2 to exist.

When WAL tracking is enabled, we assume WALs will only become obsolete after a flush result is written to MANIFEST in `MemtableList::TryInstallMemtableFlushResults` (or its atomic flush counterpart). The above situation breaks this assumption.

This PR tracks WAL obsoletion if necessary before updating the empty column families' log numbers.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7781

Test Plan:
watch existing tests and stress tests to pass.
`make -j48 blackbox_crash_test` on devserver

Reviewed By: ltamasi

Differential Revision: D25631695

Pulled By: cheng-chang

fbshipit-source-id: ca7fff967bdb42204b84226063d909893bc0a4ec
2020-12-18 21:34:36 -08:00

788 lines
33 KiB
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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).
//
// 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 <unordered_map>
#include <string>
#include <vector>
#include <atomic>
#include "db/memtable_list.h"
#include "db/table_cache.h"
#include "db/table_properties_collector.h"
#include "db/write_batch_internal.h"
#include "db/write_controller.h"
#include "options/cf_options.h"
#include "rocksdb/compaction_job_stats.h"
#include "rocksdb/db.h"
#include "rocksdb/env.h"
#include "rocksdb/options.h"
#include "trace_replay/block_cache_tracer.h"
#include "util/thread_local.h"
namespace ROCKSDB_NAMESPACE {
class Version;
class VersionSet;
class VersionStorageInfo;
class MemTable;
class MemTableListVersion;
class CompactionPicker;
class Compaction;
class InternalKey;
class InternalStats;
class ColumnFamilyData;
class DBImpl;
class LogBuffer;
class InstrumentedMutex;
class InstrumentedMutexLock;
struct SuperVersionContext;
class BlobFileCache;
extern const double kIncSlowdownRatio;
// This file contains a list of data structures for managing column family
// level metadata.
//
// The basic relationships among classes declared here are illustrated as
// following:
//
// +----------------------+ +----------------------+ +--------+
// +---+ ColumnFamilyHandle 1 | +--+ ColumnFamilyHandle 2 | | DBImpl |
// | +----------------------+ | +----------------------+ +----+---+
// | +--------------------------+ |
// | | +-----------------------------+
// | | |
// | | +-----------------------------v-------------------------------+
// | | | |
// | | | ColumnFamilySet |
// | | | |
// | | +-------------+--------------------------+----------------+---+
// | | | | |
// | +-------------------------------------+ | |
// | | | | v
// | +-------------v-------------+ +-----v----v---------+
// | | | | |
// | | ColumnFamilyData 1 | | ColumnFamilyData 2 | ......
// | | | | |
// +---> | | |
// | +---------+ | |
// | | MemTable| | |
// | | List | | |
// +--------+---+--+-+----+----+ +--------------------++
// | | | |
// | | | |
// | | | +-----------------------+
// | | +-----------+ |
// v +--------+ | |
// +--------+--------+ | | |
// | | | | +----------v----------+
// +---> |SuperVersion 1.a +-----------------> |
// | +------+ | | MemTableListVersion |
// +---+-------------+ | | | | |
// | | | | +----+------------+---+
// | current | | | | |
// | +-------------+ | |mem | |
// | | | | | |
// +-v---v-------+ +---v--v---+ +-----v----+ +----v-----+
// | | | | | | | |
// | Version 1.a | | memtable | | memtable | | memtable |
// | | | 1.a | | 1.b | | 1.c |
// +-------------+ | | | | | |
// +----------+ +----------+ +----------+
//
// DBImpl keeps a ColumnFamilySet, which references to all column families by
// pointing to respective ColumnFamilyData object of each column family.
// This is how DBImpl can list and operate on all the column families.
// ColumnFamilyHandle also points to ColumnFamilyData directly, so that
// when a user executes a query, it can directly find memtables and Version
// as well as SuperVersion to the column family, without going through
// ColumnFamilySet.
//
// ColumnFamilySet points to the latest view of the LSM-tree (list of memtables
// and SST files) indirectly, while ongoing operations may hold references
// to a current or an out-of-date SuperVersion, which in turn points to a
// point-in-time view of the LSM-tree. This guarantees the memtables and SST
// files being operated on will not go away, until the SuperVersion is
// unreferenced to 0 and destoryed.
//
// The following graph illustrates a possible referencing relationships:
//
// Column +--------------+ current +-----------+
// Family +---->+ +------------------->+ |
// Data | SuperVersion +----------+ | Version A |
// | 3 | imm | | |
// Iter2 +----->+ | +-------v------+ +-----------+
// +-----+--------+ | MemtableList +----------------> Empty
// | | Version r | +-----------+
// | +--------------+ | |
// +------------------+ current| Version B |
// +--------------+ | +----->+ |
// | | | | +-----+-----+
// Compaction +>+ SuperVersion +-------------+ ^
// Job | 2 +------+ | |current
// | +----+ | | mem | +------------+
// +--------------+ | | +---------------------> |
// | +------------------------> MemTable a |
// | mem | | |
// +--------------+ | | +------------+
// | +--------------------------+
// Iter1 +-----> SuperVersion | | +------------+
// | 1 +------------------------------>+ |
// | +-+ | mem | MemTable b |
// +--------------+ | | | |
// | | +--------------+ +-----^------+
// | |imm | MemtableList | |
// | +--->+ Version s +------------+
// | +--------------+
// | +--------------+
// | | MemtableList |
// +------>+ Version t +--------> Empty
// imm +--------------+
//
// In this example, even if the current LSM-tree consists of Version A and
// memtable a, which is also referenced by SuperVersion, two older SuperVersion
// SuperVersion2 and Superversion1 still exist, and are referenced by a
// compaction job and an old iterator Iter1, respectively. SuperVersion2
// contains Version B, memtable a and memtable b; SuperVersion1 contains
// Version B and memtable b (mutable). As a result, Version B and memtable b
// are prevented from being destroyed or deleted.
// ColumnFamilyHandleImpl is the class that clients use to access different
// column families. It has non-trivial destructor, which gets called when client
// is done using the column family
class ColumnFamilyHandleImpl : public ColumnFamilyHandle {
public:
// create while holding the mutex
ColumnFamilyHandleImpl(
ColumnFamilyData* cfd, DBImpl* db, InstrumentedMutex* mutex);
// destroy without mutex
virtual ~ColumnFamilyHandleImpl();
virtual ColumnFamilyData* cfd() const { return cfd_; }
virtual uint32_t GetID() const override;
virtual const std::string& GetName() const override;
virtual Status GetDescriptor(ColumnFamilyDescriptor* desc) override;
virtual const Comparator* GetComparator() const override;
private:
ColumnFamilyData* cfd_;
DBImpl* db_;
InstrumentedMutex* mutex_;
};
// Does not ref-count ColumnFamilyData
// We use this dummy ColumnFamilyHandleImpl because sometimes MemTableInserter
// calls DBImpl methods. When this happens, MemTableInserter need access to
// ColumnFamilyHandle (same as the client would need). In that case, we feed
// MemTableInserter dummy ColumnFamilyHandle and enable it to call DBImpl
// methods
class ColumnFamilyHandleInternal : public ColumnFamilyHandleImpl {
public:
ColumnFamilyHandleInternal()
: ColumnFamilyHandleImpl(nullptr, nullptr, nullptr), internal_cfd_(nullptr) {}
void SetCFD(ColumnFamilyData* _cfd) { internal_cfd_ = _cfd; }
virtual ColumnFamilyData* cfd() const override { return internal_cfd_; }
private:
ColumnFamilyData* internal_cfd_;
};
// holds references to memtable, all immutable memtables and version
struct SuperVersion {
// Accessing members of this class is not thread-safe and requires external
// synchronization (ie db mutex held or on write thread).
ColumnFamilyData* cfd;
MemTable* mem;
MemTableListVersion* imm;
Version* current;
MutableCFOptions mutable_cf_options;
// Version number of the current SuperVersion
uint64_t version_number;
WriteStallCondition write_stall_condition;
InstrumentedMutex* db_mutex;
// should be called outside the mutex
SuperVersion() = default;
~SuperVersion();
SuperVersion* Ref();
// If Unref() returns true, Cleanup() should be called with mutex held
// before deleting this SuperVersion.
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(ColumnFamilyData* new_cfd, MemTable* new_mem,
MemTableListVersion* new_imm, Version* new_current);
// The value of dummy is not actually used. kSVInUse takes its address as a
// mark in the thread local storage to indicate the SuperVersion is in use
// by thread. This way, the value of kSVInUse is guaranteed to have no
// conflict with SuperVersion object address and portable on different
// platform.
static int dummy;
static void* const kSVInUse;
static void* const kSVObsolete;
private:
std::atomic<uint32_t> refs;
// We need to_delete because during Cleanup(), imm->Unref() returns
// all memtables that we need to free through this vector. We then
// delete all those memtables outside of mutex, during destruction
autovector<MemTable*> to_delete;
};
extern Status CheckCompressionSupported(const ColumnFamilyOptions& cf_options);
extern Status CheckConcurrentWritesSupported(
const ColumnFamilyOptions& cf_options);
extern Status CheckCFPathsSupported(const DBOptions& db_options,
const ColumnFamilyOptions& cf_options);
extern ColumnFamilyOptions SanitizeOptions(const ImmutableDBOptions& db_options,
const ColumnFamilyOptions& src);
// Wrap user defined table proproties collector factories `from cf_options`
// into internal ones in int_tbl_prop_collector_factories. Add a system internal
// one too.
extern void GetIntTblPropCollectorFactory(
const ImmutableCFOptions& ioptions,
std::vector<std::unique_ptr<IntTblPropCollectorFactory>>*
int_tbl_prop_collector_factories);
class ColumnFamilySet;
// This class keeps all the data that a column family needs.
// Most methods require DB mutex held, unless otherwise noted
class ColumnFamilyData {
public:
~ColumnFamilyData();
// thread-safe
uint32_t GetID() const { return id_; }
// thread-safe
const std::string& GetName() const { return name_; }
// Ref() can only be called from a context where the caller can guarantee
// that ColumnFamilyData is alive (while holding a non-zero ref already,
// holding a DB mutex, or as the leader in a write batch group).
void Ref() { refs_.fetch_add(1); }
// UnrefAndTryDelete() decreases the reference count and do free if needed,
// return true if this is freed else false, UnrefAndTryDelete() can only
// be called while holding a DB mutex, or during single-threaded recovery.
// sv_under_cleanup is only provided when called from SuperVersion::Cleanup.
bool UnrefAndTryDelete(SuperVersion* sv_under_cleanup = nullptr);
// SetDropped() can only be called under following conditions:
// 1) Holding a DB mutex,
// 2) from single-threaded write thread, AND
// 3) from single-threaded VersionSet::LogAndApply()
// After dropping column family no other operation on that column family
// will be executed. All the files and memory will be, however, kept around
// until client drops the column family handle. That way, client can still
// access data from dropped column family.
// Column family can be dropped and still alive. In that state:
// *) Compaction and flush is not executed on the dropped column family.
// *) Client can continue reading from column family. Writes will fail unless
// WriteOptions::ignore_missing_column_families is true
// When the dropped column family is unreferenced, then we:
// *) Remove column family from the linked list maintained by ColumnFamilySet
// *) delete all memory associated with that column family
// *) delete all the files associated with that column family
void SetDropped();
bool IsDropped() const { return dropped_.load(std::memory_order_relaxed); }
// thread-safe
int NumberLevels() const { return ioptions_.num_levels; }
void SetLogNumber(uint64_t log_number) { log_number_ = log_number; }
uint64_t GetLogNumber() const { return log_number_; }
void SetFlushReason(FlushReason flush_reason) {
flush_reason_ = flush_reason;
}
FlushReason GetFlushReason() const { return flush_reason_; }
// thread-safe
const FileOptions* soptions() const;
const ImmutableCFOptions* ioptions() const { return &ioptions_; }
// REQUIRES: DB mutex held
// This returns the MutableCFOptions used by current SuperVersion
// You should use this API to reference MutableCFOptions most of the time.
const MutableCFOptions* GetCurrentMutableCFOptions() const {
return &(super_version_->mutable_cf_options);
}
// REQUIRES: DB mutex held
// This returns the latest MutableCFOptions, which may be not in effect yet.
const MutableCFOptions* GetLatestMutableCFOptions() const {
return &mutable_cf_options_;
}
// REQUIRES: DB mutex held
// Build ColumnFamiliesOptions with immutable options and latest mutable
// options.
ColumnFamilyOptions GetLatestCFOptions() const;
bool is_delete_range_supported() { return is_delete_range_supported_; }
// Validate CF options against DB options
static Status ValidateOptions(const DBOptions& db_options,
const ColumnFamilyOptions& cf_options);
#ifndef ROCKSDB_LITE
// REQUIRES: DB mutex held
Status SetOptions(
const DBOptions& db_options,
const std::unordered_map<std::string, std::string>& options_map);
#endif // ROCKSDB_LITE
InternalStats* internal_stats() { return internal_stats_.get(); }
MemTableList* imm() { return &imm_; }
MemTable* mem() { return mem_; }
bool IsEmpty() {
return mem()->GetFirstSequenceNumber() == 0 && imm()->NumNotFlushed() == 0;
}
Version* current() { return current_; }
Version* dummy_versions() { return dummy_versions_; }
void SetCurrent(Version* _current);
uint64_t GetNumLiveVersions() const; // REQUIRE: DB mutex held
uint64_t GetTotalSstFilesSize() const; // REQUIRE: DB mutex held
uint64_t GetLiveSstFilesSize() const; // REQUIRE: DB mutex held
void SetMemtable(MemTable* new_mem) {
uint64_t memtable_id = last_memtable_id_.fetch_add(1) + 1;
new_mem->SetID(memtable_id);
mem_ = new_mem;
}
// calculate the oldest log needed for the durability of this column family
uint64_t OldestLogToKeep();
// See Memtable constructor for explanation of earliest_seq param.
MemTable* ConstructNewMemtable(const MutableCFOptions& mutable_cf_options,
SequenceNumber earliest_seq);
void CreateNewMemtable(const MutableCFOptions& mutable_cf_options,
SequenceNumber earliest_seq);
TableCache* table_cache() const { return table_cache_.get(); }
BlobFileCache* blob_file_cache() const { return blob_file_cache_.get(); }
// See documentation in compaction_picker.h
// REQUIRES: DB mutex held
bool NeedsCompaction() const;
// REQUIRES: DB mutex held
Compaction* PickCompaction(const MutableCFOptions& mutable_options,
const MutableDBOptions& mutable_db_options,
LogBuffer* log_buffer);
// Check if the passed range overlap with any running compactions.
// REQUIRES: DB mutex held
bool RangeOverlapWithCompaction(const Slice& smallest_user_key,
const Slice& largest_user_key,
int level) const;
// Check if the passed ranges overlap with any unflushed memtables
// (immutable or mutable).
//
// @param super_version A referenced SuperVersion that will be held for the
// duration of this function.
//
// Thread-safe
Status RangesOverlapWithMemtables(const autovector<Range>& ranges,
SuperVersion* super_version,
bool allow_data_in_errors, bool* overlap);
// A flag to tell a manual compaction is to compact all levels together
// instead of a specific level.
static const int kCompactAllLevels;
// A flag to tell a manual compaction's output is base level.
static const int kCompactToBaseLevel;
// REQUIRES: DB mutex held
Compaction* CompactRange(const MutableCFOptions& mutable_cf_options,
const MutableDBOptions& mutable_db_options,
int input_level, int output_level,
const CompactRangeOptions& compact_range_options,
const InternalKey* begin, const InternalKey* end,
InternalKey** compaction_end, bool* manual_conflict,
uint64_t max_file_num_to_ignore);
CompactionPicker* compaction_picker() { return compaction_picker_.get(); }
// thread-safe
const Comparator* user_comparator() const {
return internal_comparator_.user_comparator();
}
// thread-safe
const InternalKeyComparator& internal_comparator() const {
return internal_comparator_;
}
const std::vector<std::unique_ptr<IntTblPropCollectorFactory>>*
int_tbl_prop_collector_factories() const {
return &int_tbl_prop_collector_factories_;
}
SuperVersion* GetSuperVersion() { return super_version_; }
// thread-safe
// Return a already referenced SuperVersion to be used safely.
SuperVersion* GetReferencedSuperVersion(DBImpl* db);
// thread-safe
// Get SuperVersion stored in thread local storage. If it does not exist,
// get a reference from a current SuperVersion.
SuperVersion* GetThreadLocalSuperVersion(DBImpl* db);
// Try to return SuperVersion back to thread local storage. Retrun true on
// success and false on failure. It fails when the thread local storage
// contains anything other than SuperVersion::kSVInUse flag.
bool ReturnThreadLocalSuperVersion(SuperVersion* sv);
// thread-safe
uint64_t GetSuperVersionNumber() const {
return super_version_number_.load();
}
// 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 to enable
// the clients to allocate SuperVersion outside of mutex.
// IMPORTANT: Only call this from DBImpl::InstallSuperVersion()
void InstallSuperVersion(SuperVersionContext* sv_context,
InstrumentedMutex* db_mutex,
const MutableCFOptions& mutable_cf_options);
void InstallSuperVersion(SuperVersionContext* sv_context,
InstrumentedMutex* db_mutex);
void ResetThreadLocalSuperVersions();
// Protected by DB mutex
void set_queued_for_flush(bool value) { queued_for_flush_ = value; }
void set_queued_for_compaction(bool value) { queued_for_compaction_ = value; }
bool queued_for_flush() { return queued_for_flush_; }
bool queued_for_compaction() { return queued_for_compaction_; }
enum class WriteStallCause {
kNone,
kMemtableLimit,
kL0FileCountLimit,
kPendingCompactionBytes,
};
static std::pair<WriteStallCondition, WriteStallCause>
GetWriteStallConditionAndCause(int num_unflushed_memtables, int num_l0_files,
uint64_t num_compaction_needed_bytes,
const MutableCFOptions& mutable_cf_options);
// Recalculate some small conditions, which are changed only during
// compaction, adding new memtable and/or
// recalculation of compaction score. These values are used in
// DBImpl::MakeRoomForWrite function to decide, if it need to make
// a write stall
WriteStallCondition RecalculateWriteStallConditions(
const MutableCFOptions& mutable_cf_options);
void set_initialized() { initialized_.store(true); }
bool initialized() const { return initialized_.load(); }
const ColumnFamilyOptions& initial_cf_options() {
return initial_cf_options_;
}
Env::WriteLifeTimeHint CalculateSSTWriteHint(int level);
// created_dirs remembers directory created, so that we don't need to call
// the same data creation operation again.
Status AddDirectories(
std::map<std::string, std::shared_ptr<FSDirectory>>* created_dirs);
FSDirectory* GetDataDir(size_t path_id) const;
// full_history_ts_low_ can only increase.
void SetFullHistoryTsLow(std::string ts_low) {
assert(!ts_low.empty());
const Comparator* ucmp = user_comparator();
assert(ucmp);
if (full_history_ts_low_.empty() ||
ucmp->CompareTimestamp(ts_low, full_history_ts_low_) > 0) {
full_history_ts_low_ = std::move(ts_low);
}
}
const std::string& GetFullHistoryTsLow() const {
return full_history_ts_low_;
}
ThreadLocalPtr* TEST_GetLocalSV() { return local_sv_.get(); }
private:
friend class ColumnFamilySet;
static const uint32_t kDummyColumnFamilyDataId;
ColumnFamilyData(uint32_t id, const std::string& name,
Version* dummy_versions, Cache* table_cache,
WriteBufferManager* write_buffer_manager,
const ColumnFamilyOptions& options,
const ImmutableDBOptions& db_options,
const FileOptions& file_options,
ColumnFamilySet* column_family_set,
BlockCacheTracer* const block_cache_tracer,
const std::shared_ptr<IOTracer>& io_tracer);
std::vector<std::string> GetDbPaths() const;
uint32_t id_;
const std::string name_;
Version* dummy_versions_; // Head of circular doubly-linked list of versions.
Version* current_; // == dummy_versions->prev_
std::atomic<int> refs_; // outstanding references to ColumnFamilyData
std::atomic<bool> initialized_;
std::atomic<bool> dropped_; // true if client dropped it
const InternalKeyComparator internal_comparator_;
std::vector<std::unique_ptr<IntTblPropCollectorFactory>>
int_tbl_prop_collector_factories_;
const ColumnFamilyOptions initial_cf_options_;
const ImmutableCFOptions ioptions_;
MutableCFOptions mutable_cf_options_;
const bool is_delete_range_supported_;
std::unique_ptr<TableCache> table_cache_;
std::unique_ptr<BlobFileCache> blob_file_cache_;
std::unique_ptr<InternalStats> internal_stats_;
WriteBufferManager* write_buffer_manager_;
MemTable* mem_;
MemTableList imm_;
SuperVersion* super_version_;
// An ordinal representing the current SuperVersion. Updated by
// InstallSuperVersion(), i.e. incremented every time super_version_
// changes.
std::atomic<uint64_t> super_version_number_;
// Thread's local copy of SuperVersion pointer
// This needs to be destructed before mutex_
std::unique_ptr<ThreadLocalPtr> local_sv_;
// pointers for a circular linked list. we use it to support iterations over
// all column families that are alive (note: dropped column families can also
// be alive as long as client holds a reference)
ColumnFamilyData* next_;
ColumnFamilyData* prev_;
// This is the earliest log file number that contains data from this
// Column Family. All earlier log files must be ignored and not
// recovered from
uint64_t log_number_;
std::atomic<FlushReason> flush_reason_;
// An object that keeps all the compaction stats
// and picks the next compaction
std::unique_ptr<CompactionPicker> compaction_picker_;
ColumnFamilySet* column_family_set_;
std::unique_ptr<WriteControllerToken> write_controller_token_;
// If true --> this ColumnFamily is currently present in DBImpl::flush_queue_
bool queued_for_flush_;
// If true --> this ColumnFamily is currently present in
// DBImpl::compaction_queue_
bool queued_for_compaction_;
uint64_t prev_compaction_needed_bytes_;
// if the database was opened with 2pc enabled
bool allow_2pc_;
// Memtable id to track flush.
std::atomic<uint64_t> last_memtable_id_;
// Directories corresponding to cf_paths.
std::vector<std::shared_ptr<FSDirectory>> data_dirs_;
bool db_paths_registered_;
std::string full_history_ts_low_;
};
// ColumnFamilySet has interesting thread-safety requirements
// * CreateColumnFamily() or RemoveColumnFamily() -- need to be protected by DB
// mutex AND executed in the write thread.
// CreateColumnFamily() should ONLY be called from VersionSet::LogAndApply() AND
// single-threaded write thread. It is also called during Recovery and in
// DumpManifest().
// RemoveColumnFamily() is only called from SetDropped(). DB mutex needs to be
// held and it needs to be executed from the write thread. SetDropped() also
// guarantees that it will be called only from single-threaded LogAndApply(),
// but this condition is not that important.
// * Iteration -- hold DB mutex, but you can release it in the body of
// iteration. If you release DB mutex in body, reference the column
// family before the mutex and unreference after you unlock, since the column
// family might get dropped when the DB mutex is released
// * GetDefault() -- thread safe
// * GetColumnFamily() -- either inside of DB mutex or from a write thread
// * GetNextColumnFamilyID(), GetMaxColumnFamily(), UpdateMaxColumnFamily(),
// NumberOfColumnFamilies -- inside of DB mutex
class ColumnFamilySet {
public:
// ColumnFamilySet supports iteration
class iterator {
public:
explicit iterator(ColumnFamilyData* cfd)
: current_(cfd) {}
iterator& operator++() {
// dropped column families might still be included in this iteration
// (we're only removing them when client drops the last reference to the
// column family).
// dummy is never dead, so this will never be infinite
do {
current_ = current_->next_;
} while (current_->refs_.load(std::memory_order_relaxed) == 0);
return *this;
}
bool operator!=(const iterator& other) {
return this->current_ != other.current_;
}
ColumnFamilyData* operator*() { return current_; }
private:
ColumnFamilyData* current_;
};
ColumnFamilySet(const std::string& dbname,
const ImmutableDBOptions* db_options,
const FileOptions& file_options, Cache* table_cache,
WriteBufferManager* _write_buffer_manager,
WriteController* _write_controller,
BlockCacheTracer* const block_cache_tracer,
const std::shared_ptr<IOTracer>& io_tracer);
~ColumnFamilySet();
ColumnFamilyData* GetDefault() const;
// GetColumnFamily() calls return nullptr if column family is not found
ColumnFamilyData* GetColumnFamily(uint32_t id) const;
ColumnFamilyData* GetColumnFamily(const std::string& name) const;
// this call will return the next available column family ID. it guarantees
// that there is no column family with id greater than or equal to the
// returned value in the current running instance or anytime in RocksDB
// instance history.
uint32_t GetNextColumnFamilyID();
uint32_t GetMaxColumnFamily();
void UpdateMaxColumnFamily(uint32_t new_max_column_family);
size_t NumberOfColumnFamilies() const;
ColumnFamilyData* CreateColumnFamily(const std::string& name, uint32_t id,
Version* dummy_version,
const ColumnFamilyOptions& options);
iterator begin() { return iterator(dummy_cfd_->next_); }
iterator end() { return iterator(dummy_cfd_); }
// REQUIRES: DB mutex held
// Don't call while iterating over ColumnFamilySet
void FreeDeadColumnFamilies();
Cache* get_table_cache() { return table_cache_; }
WriteBufferManager* write_buffer_manager() { return write_buffer_manager_; }
WriteController* write_controller() { return write_controller_; }
private:
friend class ColumnFamilyData;
// helper function that gets called from cfd destructor
// REQUIRES: DB mutex held
void RemoveColumnFamily(ColumnFamilyData* cfd);
// column_families_ and column_family_data_ need to be protected:
// * when mutating both conditions have to be satisfied:
// 1. DB mutex locked
// 2. thread currently in single-threaded write thread
// * when reading, at least one condition needs to be satisfied:
// 1. DB mutex locked
// 2. accessed from a single-threaded write thread
std::unordered_map<std::string, uint32_t> column_families_;
std::unordered_map<uint32_t, ColumnFamilyData*> column_family_data_;
uint32_t max_column_family_;
ColumnFamilyData* dummy_cfd_;
// We don't hold the refcount here, since default column family always exists
// We are also not responsible for cleaning up default_cfd_cache_. This is
// just a cache that makes common case (accessing default column family)
// faster
ColumnFamilyData* default_cfd_cache_;
const std::string db_name_;
const ImmutableDBOptions* const db_options_;
const FileOptions file_options_;
Cache* table_cache_;
WriteBufferManager* write_buffer_manager_;
WriteController* write_controller_;
BlockCacheTracer* const block_cache_tracer_;
std::shared_ptr<IOTracer> io_tracer_;
};
// We use ColumnFamilyMemTablesImpl to provide WriteBatch a way to access
// memtables of different column families (specified by ID in the write batch)
class ColumnFamilyMemTablesImpl : public ColumnFamilyMemTables {
public:
explicit ColumnFamilyMemTablesImpl(ColumnFamilySet* column_family_set)
: column_family_set_(column_family_set), current_(nullptr) {}
// Constructs a ColumnFamilyMemTablesImpl equivalent to one constructed
// with the arguments used to construct *orig.
explicit ColumnFamilyMemTablesImpl(ColumnFamilyMemTablesImpl* orig)
: column_family_set_(orig->column_family_set_), current_(nullptr) {}
// sets current_ to ColumnFamilyData with column_family_id
// returns false if column family doesn't exist
// REQUIRES: use this function of DBImpl::column_family_memtables_ should be
// under a DB mutex OR from a write thread
bool Seek(uint32_t column_family_id) override;
// Returns log number of the selected column family
// REQUIRES: under a DB mutex OR from a write thread
uint64_t GetLogNumber() const override;
// REQUIRES: Seek() called first
// REQUIRES: use this function of DBImpl::column_family_memtables_ should be
// under a DB mutex OR from a write thread
virtual MemTable* GetMemTable() const override;
// Returns column family handle for the selected column family
// REQUIRES: use this function of DBImpl::column_family_memtables_ should be
// under a DB mutex OR from a write thread
virtual ColumnFamilyHandle* GetColumnFamilyHandle() override;
// Cannot be called while another thread is calling Seek().
// REQUIRES: use this function of DBImpl::column_family_memtables_ should be
// under a DB mutex OR from a write thread
virtual ColumnFamilyData* current() override { return current_; }
private:
ColumnFamilySet* column_family_set_;
ColumnFamilyData* current_;
ColumnFamilyHandleInternal handle_;
};
extern uint32_t GetColumnFamilyID(ColumnFamilyHandle* column_family);
extern const Comparator* GetColumnFamilyUserComparator(
ColumnFamilyHandle* column_family);
} // namespace ROCKSDB_NAMESPACE