rocksdb/utilities/transactions/pessimistic_transaction_db.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 <mutex>
#include <queue>
#include <set>
#include <string>
#include <unordered_map>
#include <vector>
#include "rocksdb/db.h"
#include "rocksdb/options.h"
#include "rocksdb/utilities/transaction_db.h"
#include "utilities/transactions/pessimistic_transaction.h"
#include "utilities/transactions/transaction_lock_mgr.h"
#include "utilities/transactions/write_prepared_txn.h"
namespace rocksdb {
class PessimisticTransactionDB : public TransactionDB {
public:
explicit PessimisticTransactionDB(DB* db,
const TransactionDBOptions& txn_db_options);
explicit PessimisticTransactionDB(StackableDB* db,
const TransactionDBOptions& txn_db_options);
virtual ~PessimisticTransactionDB();
Status Initialize(const std::vector<size_t>& compaction_enabled_cf_indices,
const std::vector<ColumnFamilyHandle*>& handles);
Transaction* BeginTransaction(const WriteOptions& write_options,
const TransactionOptions& txn_options,
Transaction* old_txn) override = 0;
using StackableDB::Put;
virtual Status Put(const WriteOptions& options,
ColumnFamilyHandle* column_family, const Slice& key,
const Slice& val) override;
using StackableDB::Delete;
virtual Status Delete(const WriteOptions& wopts,
ColumnFamilyHandle* column_family,
const Slice& key) override;
using StackableDB::Merge;
virtual Status Merge(const WriteOptions& options,
ColumnFamilyHandle* column_family, const Slice& key,
const Slice& value) override;
using StackableDB::Write;
virtual Status Write(const WriteOptions& opts, WriteBatch* updates) override;
using StackableDB::CreateColumnFamily;
virtual Status CreateColumnFamily(const ColumnFamilyOptions& options,
const std::string& column_family_name,
ColumnFamilyHandle** handle) override;
using StackableDB::DropColumnFamily;
virtual Status DropColumnFamily(ColumnFamilyHandle* column_family) override;
Status TryLock(PessimisticTransaction* txn, uint32_t cfh_id,
const std::string& key, bool exclusive);
void UnLock(PessimisticTransaction* txn, const TransactionKeyMap* keys);
void UnLock(PessimisticTransaction* txn, uint32_t cfh_id,
const std::string& key);
void AddColumnFamily(const ColumnFamilyHandle* handle);
static TransactionDBOptions ValidateTxnDBOptions(
const TransactionDBOptions& txn_db_options);
const TransactionDBOptions& GetTxnDBOptions() const {
return txn_db_options_;
}
void InsertExpirableTransaction(TransactionID tx_id,
PessimisticTransaction* tx);
void RemoveExpirableTransaction(TransactionID tx_id);
// If transaction is no longer available, locks can be stolen
// If transaction is available, try stealing locks directly from transaction
// It is the caller's responsibility to ensure that the referred transaction
// is expirable (GetExpirationTime() > 0) and that it is expired.
bool TryStealingExpiredTransactionLocks(TransactionID tx_id);
Transaction* GetTransactionByName(const TransactionName& name) override;
void RegisterTransaction(Transaction* txn);
void UnregisterTransaction(Transaction* txn);
// not thread safe. current use case is during recovery (single thread)
void GetAllPreparedTransactions(std::vector<Transaction*>* trans) override;
TransactionLockMgr::LockStatusData GetLockStatusData() override;
std::vector<DeadlockPath> GetDeadlockInfoBuffer() override;
void SetDeadlockInfoBufferSize(uint32_t target_size) override;
struct CommitEntry {
uint64_t prep_seq;
uint64_t commit_seq;
};
protected:
void ReinitializeTransaction(
Transaction* txn, const WriteOptions& write_options,
const TransactionOptions& txn_options = TransactionOptions());
DBImpl* db_impl_;
private:
const TransactionDBOptions txn_db_options_;
TransactionLockMgr lock_mgr_;
// Must be held when adding/dropping column families.
InstrumentedMutex column_family_mutex_;
Transaction* BeginInternalTransaction(const WriteOptions& options);
// Used to ensure that no locks are stolen from an expirable transaction
// that has started a commit. Only transactions with an expiration time
// should be in this map.
std::mutex map_mutex_;
std::unordered_map<TransactionID, PessimisticTransaction*>
expirable_transactions_map_;
// map from name to two phase transaction instance
std::mutex name_map_mutex_;
std::unordered_map<TransactionName, Transaction*> transactions_;
};
// A PessimisticTransactionDB that writes the data to the DB after the commit.
// In this way the DB only contains the committed data.
class WriteCommittedTxnDB : public PessimisticTransactionDB {
public:
explicit WriteCommittedTxnDB(DB* db,
const TransactionDBOptions& txn_db_options)
: PessimisticTransactionDB(db, txn_db_options) {}
explicit WriteCommittedTxnDB(StackableDB* db,
const TransactionDBOptions& txn_db_options)
: PessimisticTransactionDB(db, txn_db_options) {}
virtual ~WriteCommittedTxnDB() {}
Transaction* BeginTransaction(const WriteOptions& write_options,
const TransactionOptions& txn_options,
Transaction* old_txn) override;
};
// A PessimisticTransactionDB that writes data to DB after prepare phase of 2PC.
// In this way some data in the DB might not be committed. The DB provides
// mechanisms to tell such data apart from committed data.
class WritePreparedTxnDB : public PessimisticTransactionDB {
public:
explicit WritePreparedTxnDB(DB* db,
const TransactionDBOptions& txn_db_options)
: PessimisticTransactionDB(db, txn_db_options),
COMMIT_CACHE_SIZE(DEF_COMMIT_CACHE_SIZE) {
init(txn_db_options);
}
explicit WritePreparedTxnDB(StackableDB* db,
const TransactionDBOptions& txn_db_options)
: PessimisticTransactionDB(db, txn_db_options),
COMMIT_CACHE_SIZE(DEF_COMMIT_CACHE_SIZE) {
init(txn_db_options);
}
virtual ~WritePreparedTxnDB() {}
Transaction* BeginTransaction(const WriteOptions& write_options,
const TransactionOptions& txn_options,
Transaction* old_txn) override;
// Check whether the transaction that wrote the value with seqeunce number seq
// is visible to the snapshot with sequence number snapshot_seq
bool IsInSnapshot(uint64_t seq, uint64_t snapshot_seq);
// Add the trasnaction with prepare sequence seq to the prepared list
void AddPrepared(uint64_t seq);
// Add the transaction with prepare sequence prepare_seq and commit sequence
// commit_seq to the commit map
void AddCommitted(uint64_t prepare_seq, uint64_t commit_seq);
private:
friend class WritePreparedTransactionTest_IsInSnapshotTest_Test;
void init(const TransactionDBOptions& /* unused */) {
commit_cache_ =
unique_ptr<CommitEntry[]>(new CommitEntry[COMMIT_CACHE_SIZE]{});
}
// A heap with the amortized O(1) complexity for erase. It uses one extra heap
// to keep track of erased entries that are not yet on top of the main heap.
class PreparedHeap {
std::priority_queue<uint64_t> heap_;
std::priority_queue<uint64_t> erased_heap_;
public:
bool empty() { return heap_.empty(); }
uint64_t top() { return heap_.top(); }
void push(uint64_t v) { heap_.push(v); }
void pop() {
heap_.pop();
while (!heap_.empty() && !erased_heap_.empty() &&
heap_.top() == erased_heap_.top()) {
heap_.pop();
erased_heap_.pop();
}
}
void erase(uint64_t seq) {
if (!heap_.empty()) {
if (heap_.top() < seq) {
// Already popped, ignore it.
} else if (heap_.top() == seq) {
heap_.pop();
} else { // (heap_.top() > seq)
// Down the heap, remember to pop it later
erased_heap_.push(seq);
}
}
}
};
// Get the commit entry with index indexed_seq from the commit table. It
// returns true if such entry exists.
bool GetCommitEntry(uint64_t indexed_seq, CommitEntry* entry);
// Rewrite the entry with the index indexed_seq in the commit table with the
// commit entry <prep_seq, commit_seq>. If the rewrite results into eviction,
// sets the evicted_entry and returns true.
bool AddCommitEntry(uint64_t indexed_seq, CommitEntry& new_entry,
CommitEntry* evicted_entry);
// Rewrite the entry with the index indexed_seq in the commit table with the
// commit entry new_entry only if the existing entry matches the
// expected_entry. Returns false otherwise.
bool ExchangeCommitEntry(uint64_t indexed_seq, CommitEntry& expected_entry,
CommitEntry new_entry);
// The list of live snapshots at the last time that max_evicted_seq_ advanced.
// The list sorted in ascending order. Thread-safety is provided with
// snapshots_mutex_.
std::vector<SequenceNumber> snapshots_;
// A heap of prepared transactions. Thread-safety is provided with
// prepared_mutex_.
PreparedHeap prepared_txns_;
static uint64_t DEF_COMMIT_CACHE_SIZE;
const uint64_t COMMIT_CACHE_SIZE;
// commit_cache_ must be initialized to zero to tell apart an empty index from
// a filled one. Thread-safety is provided with commit_cache_mutex_.
unique_ptr<CommitEntry[]> commit_cache_;
// The largest evicted *commit* sequence number from the commit_cache_
std::atomic<uint64_t> max_evicted_seq_ = {};
// A map of the evicted entries from commit_cache_ that has to be kept around
// to service the old snapshots. This is expected to be empty normally.
// Thread-safety is provided with old_commit_map_mutex_.
std::map<uint64_t, uint64_t> old_commit_map_;
// A set of long-running prepared transactions that are not finished by the
// time max_evicted_seq_ advances their sequence number. This is expected to
// be empty normally. Thread-safety is provided with prepared_mutex_.
std::set<uint64_t> delayed_prepared_;
// Update when delayed_prepared_.empty() changes. Expected to be true
// normally.
std::atomic<bool> delayed_prepared_empty_ = {true};
// Update when old_commit_map_.empty() changes. Expected to be true normally.
std::atomic<bool> old_commit_map_empty_ = {true};
port::RWMutex prepared_mutex_;
port::RWMutex old_commit_map_mutex_;
port::RWMutex commit_cache_mutex_;
port::RWMutex snapshots_mutex_;
};
} // namespace rocksdb
#endif // ROCKSDB_LITE