rocksdb/utilities/transactions/transaction_impl.cc

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// Copyright (c) 2011-present, 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.
#ifndef ROCKSDB_LITE
#include "utilities/transactions/transaction_impl.h"
#include <map>
#include <set>
#include <string>
#include <vector>
#include "db/column_family.h"
#include "db/db_impl.h"
#include "rocksdb/comparator.h"
#include "rocksdb/db.h"
#include "rocksdb/snapshot.h"
#include "rocksdb/status.h"
#include "rocksdb/utilities/transaction_db.h"
#include "util/string_util.h"
#include "util/sync_point.h"
#include "utilities/transactions/transaction_db_impl.h"
#include "utilities/transactions/transaction_util.h"
namespace rocksdb {
struct WriteOptions;
std::atomic<TransactionID> TransactionImpl::txn_id_counter_(1);
TransactionID TransactionImpl::GenTxnID() {
return txn_id_counter_.fetch_add(1);
}
TransactionImpl::TransactionImpl(TransactionDB* txn_db,
const WriteOptions& write_options,
const TransactionOptions& txn_options)
: TransactionBaseImpl(txn_db->GetBaseDB(), write_options),
txn_db_impl_(nullptr),
txn_id_(0),
expiration_time_(0),
lock_timeout_(0),
exec_status_(STARTED) {
txn_db_impl_ = dynamic_cast<TransactionDBImpl*>(txn_db);
assert(txn_db_impl_);
Initialize(txn_options);
}
void TransactionImpl::Initialize(const TransactionOptions& txn_options) {
txn_id_ = GenTxnID();
exec_status_ = STARTED;
lock_timeout_ = txn_options.lock_timeout * 1000;
if (lock_timeout_ < 0) {
// Lock timeout not set, use default
lock_timeout_ =
txn_db_impl_->GetTxnDBOptions().transaction_lock_timeout * 1000;
}
if (txn_options.expiration >= 0) {
expiration_time_ = start_time_ + txn_options.expiration * 1000;
} else {
expiration_time_ = 0;
}
if (txn_options.set_snapshot) {
SetSnapshot();
}
if (expiration_time_ > 0) {
txn_db_impl_->InsertExpirableTransaction(txn_id_, this);
}
}
TransactionImpl::~TransactionImpl() {
txn_db_impl_->UnLock(this, &GetTrackedKeys());
if (expiration_time_ > 0) {
txn_db_impl_->RemoveExpirableTransaction(txn_id_);
}
}
void TransactionImpl::Clear() {
txn_db_impl_->UnLock(this, &GetTrackedKeys());
TransactionBaseImpl::Clear();
}
void TransactionImpl::Reinitialize(const WriteOptions& write_options,
const TransactionOptions& txn_options) {
TransactionBaseImpl::Reinitialize(write_options);
Initialize(txn_options);
}
bool TransactionImpl::IsExpired() const {
if (expiration_time_ > 0) {
if (db_->GetEnv()->NowMicros() >= expiration_time_) {
// Transaction is expired.
return true;
}
}
return false;
}
Status TransactionImpl::CommitBatch(WriteBatch* batch) {
TransactionKeyMap keys_to_unlock;
Status s = LockBatch(batch, &keys_to_unlock);
if (s.ok()) {
s = DoCommit(batch);
txn_db_impl_->UnLock(this, &keys_to_unlock);
}
return s;
}
Status TransactionImpl::Commit() {
Status s = DoCommit(GetWriteBatch()->GetWriteBatch());
Clear();
return s;
}
Status TransactionImpl::DoCommit(WriteBatch* batch) {
Status s;
if (expiration_time_ > 0) {
if (IsExpired()) {
return Status::Expired();
}
// Transaction should only be committed if the thread succeeds
// changing its execution status to COMMITTING. This is because
// A different transaction may consider this one expired and attempt
// to steal its locks between the IsExpired() check and the beginning
// of a commit.
ExecutionStatus expected = STARTED;
bool can_commit = std::atomic_compare_exchange_strong(
&exec_status_, &expected, COMMITTING);
TEST_SYNC_POINT("TransactionTest::ExpirableTransactionDataRace:1");
if (can_commit) {
s = db_->Write(write_options_, batch);
} else {
assert(exec_status_ == LOCKS_STOLEN);
return Status::Expired();
}
} else {
s = db_->Write(write_options_, batch);
}
return s;
}
void TransactionImpl::Rollback() { Clear(); }
Status TransactionImpl::RollbackToSavePoint() {
// Unlock any keys locked since last transaction
const std::unique_ptr<TransactionKeyMap>& keys =
GetTrackedKeysSinceSavePoint();
if (keys) {
txn_db_impl_->UnLock(this, keys.get());
}
return TransactionBaseImpl::RollbackToSavePoint();
}
// Lock all keys in this batch.
// On success, caller should unlock keys_to_unlock
Status TransactionImpl::LockBatch(WriteBatch* batch,
TransactionKeyMap* keys_to_unlock) {
class Handler : public WriteBatch::Handler {
public:
// Sorted map of column_family_id to sorted set of keys.
// Since LockBatch() always locks keys in sorted order, it cannot deadlock
// with itself. We're not using a comparator here since it doesn't matter
// what the sorting is as long as it's consistent.
std::map<uint32_t, std::set<std::string>> keys_;
Handler() {}
void RecordKey(uint32_t column_family_id, const Slice& key) {
std::string key_str = key.ToString();
auto iter = (keys_)[column_family_id].find(key_str);
if (iter == (keys_)[column_family_id].end()) {
// key not yet seen, store it.
(keys_)[column_family_id].insert({std::move(key_str)});
}
}
virtual Status PutCF(uint32_t column_family_id, const Slice& key,
const Slice& value) override {
RecordKey(column_family_id, key);
return Status::OK();
}
virtual Status MergeCF(uint32_t column_family_id, const Slice& key,
const Slice& value) override {
RecordKey(column_family_id, key);
return Status::OK();
}
virtual Status DeleteCF(uint32_t column_family_id,
const Slice& key) override {
RecordKey(column_family_id, key);
return Status::OK();
}
};
// Iterating on this handler will add all keys in this batch into keys
Handler handler;
batch->Iterate(&handler);
Status s;
// Attempt to lock all keys
for (const auto& cf_iter : handler.keys_) {
uint32_t cfh_id = cf_iter.first;
auto& cfh_keys = cf_iter.second;
for (const auto& key_iter : cfh_keys) {
const std::string& key = key_iter;
s = txn_db_impl_->TryLock(this, cfh_id, key);
if (!s.ok()) {
break;
}
TrackKey(keys_to_unlock, cfh_id, std::move(key), kMaxSequenceNumber,
false);
}
if (!s.ok()) {
break;
}
}
if (!s.ok()) {
txn_db_impl_->UnLock(this, keys_to_unlock);
}
return s;
}
// Attempt to lock this key.
// Returns OK if the key has been successfully locked. Non-ok, otherwise.
// If check_shapshot is true and this transaction has a snapshot set,
// this key will only be locked if there have been no writes to this key since
// the snapshot time.
Status TransactionImpl::TryLock(ColumnFamilyHandle* column_family,
const Slice& key, bool read_only,
bool untracked) {
uint32_t cfh_id = GetColumnFamilyID(column_family);
std::string key_str = key.ToString();
bool previously_locked;
Status s;
// lock this key if this transactions hasn't already locked it
SequenceNumber current_seqno = kMaxSequenceNumber;
SequenceNumber new_seqno = kMaxSequenceNumber;
const auto& tracked_keys = GetTrackedKeys();
const auto tracked_keys_cf = tracked_keys.find(cfh_id);
if (tracked_keys_cf == tracked_keys.end()) {
previously_locked = false;
} else {
auto iter = tracked_keys_cf->second.find(key_str);
if (iter == tracked_keys_cf->second.end()) {
previously_locked = false;
} else {
previously_locked = true;
current_seqno = iter->second.seq;
}
}
// lock this key if this transactions hasn't already locked it
if (!previously_locked) {
s = txn_db_impl_->TryLock(this, cfh_id, key_str);
}
SetSnapshotIfNeeded();
// Even though we do not care about doing conflict checking for this write,
// we still need to take a lock to make sure we do not cause a conflict with
// some other write. However, we do not need to check if there have been
// any writes since this transaction's snapshot.
// TODO(agiardullo): could optimize by supporting shared txn locks in the
// future
if (untracked || snapshot_ == nullptr) {
// Need to remember the earliest sequence number that we know that this
// key has not been modified after. This is useful if this same
// transaction
// later tries to lock this key again.
if (current_seqno == kMaxSequenceNumber) {
// Since we haven't checked a snapshot, we only know this key has not
// been modified since after we locked it.
new_seqno = db_->GetLatestSequenceNumber();
} else {
new_seqno = current_seqno;
}
} else {
// If a snapshot is set, we need to make sure the key hasn't been modified
// since the snapshot. This must be done after we locked the key.
if (s.ok()) {
s = ValidateSnapshot(column_family, key, current_seqno, &new_seqno);
if (!s.ok()) {
// Failed to validate key
if (!previously_locked) {
// Unlock key we just locked
txn_db_impl_->UnLock(this, cfh_id, key.ToString());
}
}
}
}
if (s.ok()) {
// Let base class know we've conflict checked this key.
TrackKey(cfh_id, key_str, new_seqno, read_only);
}
return s;
}
// Return OK() if this key has not been modified more recently than the
// transaction snapshot_.
Status TransactionImpl::ValidateSnapshot(ColumnFamilyHandle* column_family,
const Slice& key,
SequenceNumber prev_seqno,
SequenceNumber* new_seqno) {
assert(snapshot_);
SequenceNumber seq = snapshot_->GetSequenceNumber();
if (prev_seqno <= seq) {
// If the key has been previous validated at a sequence number earlier
// than the curent snapshot's sequence number, we already know it has not
// been modified.
return Status::OK();
}
*new_seqno = seq;
assert(dynamic_cast<DBImpl*>(db_) != nullptr);
auto db_impl = reinterpret_cast<DBImpl*>(db_);
ColumnFamilyHandle* cfh =
column_family ? column_family : db_impl->DefaultColumnFamily();
return TransactionUtil::CheckKeyForConflicts(db_impl, cfh, key.ToString(),
snapshot_->GetSequenceNumber(),
false /* cache_only */);
}
bool TransactionImpl::TryStealingLocks() {
assert(IsExpired());
ExecutionStatus expected = STARTED;
return std::atomic_compare_exchange_strong(&exec_status_, &expected,
LOCKS_STOLEN);
}
void TransactionImpl::UnlockGetForUpdate(ColumnFamilyHandle* column_family,
const Slice& key) {
txn_db_impl_->UnLock(this, GetColumnFamilyID(column_family), key.ToString());
}
} // namespace rocksdb
#endif // ROCKSDB_LITE