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rocksdb/utilities/transactions/pessimistic_transaction.cc

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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).
#ifndef ROCKSDB_LITE
#include "utilities/transactions/pessimistic_transaction.h"
#include <map>
#include <set>
#include <string>
#include <vector>
#include "db/column_family.h"
#include "db/db_impl/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 "test_util/sync_point.h"
#include "util/cast_util.h"
#include "util/string_util.h"
#include "utilities/transactions/pessimistic_transaction_db.h"
#include "utilities/transactions/transaction_util.h"
namespace rocksdb {
struct WriteOptions;
std::atomic<TransactionID> PessimisticTransaction::txn_id_counter_(1);
TransactionID PessimisticTransaction::GenTxnID() {
return txn_id_counter_.fetch_add(1);
}
PessimisticTransaction::PessimisticTransaction(
TransactionDB* txn_db, const WriteOptions& write_options,
const TransactionOptions& txn_options, const bool init)
: TransactionBaseImpl(txn_db->GetRootDB(), write_options),
txn_db_impl_(nullptr),
expiration_time_(0),
txn_id_(0),
waiting_cf_id_(0),
waiting_key_(nullptr),
lock_timeout_(0),
deadlock_detect_(false),
deadlock_detect_depth_(0),
skip_concurrency_control_(false) {
txn_db_impl_ =
static_cast_with_check<PessimisticTransactionDB, TransactionDB>(txn_db);
db_impl_ = static_cast_with_check<DBImpl, DB>(db_);
if (init) {
Initialize(txn_options);
}
}
void PessimisticTransaction::Initialize(const TransactionOptions& txn_options) {
txn_id_ = GenTxnID();
txn_state_ = STARTED;
deadlock_detect_ = txn_options.deadlock_detect;
deadlock_detect_depth_ = txn_options.deadlock_detect_depth;
write_batch_.SetMaxBytes(txn_options.max_write_batch_size);
skip_concurrency_control_ = txn_options.skip_concurrency_control;
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);
}
use_only_the_last_commit_time_batch_for_recovery_ =
txn_options.use_only_the_last_commit_time_batch_for_recovery;
}
PessimisticTransaction::~PessimisticTransaction() {
txn_db_impl_->UnLock(this, &GetTrackedKeys());
if (expiration_time_ > 0) {
txn_db_impl_->RemoveExpirableTransaction(txn_id_);
}
if (!name_.empty() && txn_state_ != COMMITED) {
txn_db_impl_->UnregisterTransaction(this);
}
}
void PessimisticTransaction::Clear() {
txn_db_impl_->UnLock(this, &GetTrackedKeys());
TransactionBaseImpl::Clear();
}
void PessimisticTransaction::Reinitialize(
TransactionDB* txn_db, const WriteOptions& write_options,
const TransactionOptions& txn_options) {
if (!name_.empty() && txn_state_ != COMMITED) {
txn_db_impl_->UnregisterTransaction(this);
}
TransactionBaseImpl::Reinitialize(txn_db->GetRootDB(), write_options);
Initialize(txn_options);
}
bool PessimisticTransaction::IsExpired() const {
if (expiration_time_ > 0) {
if (db_->GetEnv()->NowMicros() >= expiration_time_) {
// Transaction is expired.
return true;
}
}
return false;
}
WriteCommittedTxn::WriteCommittedTxn(TransactionDB* txn_db,
const WriteOptions& write_options,
const TransactionOptions& txn_options)
: PessimisticTransaction(txn_db, write_options, txn_options){};
Status PessimisticTransaction::CommitBatch(WriteBatch* batch) {
TransactionKeyMap keys_to_unlock;
Status s = LockBatch(batch, &keys_to_unlock);
if (!s.ok()) {
return s;
}
bool can_commit = false;
if (IsExpired()) {
s = Status::Expired();
} else if (expiration_time_ > 0) {
TransactionState expected = STARTED;
can_commit = std::atomic_compare_exchange_strong(&txn_state_, &expected,
AWAITING_COMMIT);
} else if (txn_state_ == STARTED) {
// lock stealing is not a concern
can_commit = true;
}
if (can_commit) {
txn_state_.store(AWAITING_COMMIT);
s = CommitBatchInternal(batch);
if (s.ok()) {
txn_state_.store(COMMITED);
}
} else if (txn_state_ == LOCKS_STOLEN) {
s = Status::Expired();
} else {
s = Status::InvalidArgument("Transaction is not in state for commit.");
}
txn_db_impl_->UnLock(this, &keys_to_unlock);
return s;
}
Status PessimisticTransaction::Prepare() {
Status s;
if (name_.empty()) {
return Status::InvalidArgument(
"Cannot prepare a transaction that has not been named.");
}
if (IsExpired()) {
return Status::Expired();
}
bool can_prepare = false;
if (expiration_time_ > 0) {
// must concern ourselves with expiraton and/or lock stealing
// need to compare/exchange bc locks could be stolen under us here
TransactionState expected = STARTED;
can_prepare = std::atomic_compare_exchange_strong(&txn_state_, &expected,
AWAITING_PREPARE);
} else if (txn_state_ == STARTED) {
// expiration and lock stealing is not possible
can_prepare = true;
}
if (can_prepare) {
txn_state_.store(AWAITING_PREPARE);
// transaction can't expire after preparation
expiration_time_ = 0;
assert(log_number_ == 0 ||
txn_db_impl_->GetTxnDBOptions().write_policy == WRITE_UNPREPARED);
s = PrepareInternal();
if (s.ok()) {
txn_state_.store(PREPARED);
}
} else if (txn_state_ == LOCKS_STOLEN) {
s = Status::Expired();
} else if (txn_state_ == PREPARED) {
s = Status::InvalidArgument("Transaction has already been prepared.");
} else if (txn_state_ == COMMITED) {
s = Status::InvalidArgument("Transaction has already been committed.");
} else if (txn_state_ == ROLLEDBACK) {
s = Status::InvalidArgument("Transaction has already been rolledback.");
} else {
s = Status::InvalidArgument("Transaction is not in state for commit.");
}
return s;
}
Status WriteCommittedTxn::PrepareInternal() {
WriteOptions write_options = write_options_;
write_options.disableWAL = false;
WriteBatchInternal::MarkEndPrepare(GetWriteBatch()->GetWriteBatch(), name_);
class MarkLogCallback : public PreReleaseCallback {
public:
MarkLogCallback(DBImpl* db, bool two_write_queues)
: db_(db), two_write_queues_(two_write_queues) {
(void)two_write_queues_; // to silence unused private field warning
}
virtual Status Callback(SequenceNumber, bool is_mem_disabled,
uint64_t log_number, size_t /*index*/,
size_t /*total*/) override {
#ifdef NDEBUG
(void)is_mem_disabled;
#endif
assert(log_number != 0);
assert(!two_write_queues_ || is_mem_disabled); // implies the 2nd queue
db_->logs_with_prep_tracker()->MarkLogAsContainingPrepSection(log_number);
return Status::OK();
}
private:
DBImpl* db_;
bool two_write_queues_;
} mark_log_callback(db_impl_,
db_impl_->immutable_db_options().two_write_queues);
WriteCallback* const kNoWriteCallback = nullptr;
const uint64_t kRefNoLog = 0;
const bool kDisableMemtable = true;
SequenceNumber* const KIgnoreSeqUsed = nullptr;
const size_t kNoBatchCount = 0;
Status s = db_impl_->WriteImpl(
write_options, GetWriteBatch()->GetWriteBatch(), kNoWriteCallback,
&log_number_, kRefNoLog, kDisableMemtable, KIgnoreSeqUsed, kNoBatchCount,
&mark_log_callback);
return s;
}
Status PessimisticTransaction::Commit() {
Status s;
bool commit_without_prepare = false;
bool commit_prepared = false;
if (IsExpired()) {
return Status::Expired();
}
if (expiration_time_ > 0) {
// we must atomicaly compare and exchange the state here because at
// this state in the transaction it is possible for another thread
// to change our state out from under us in the even that we expire and have
// our locks stolen. In this case the only valid state is STARTED because
// a state of PREPARED would have a cleared expiration_time_.
TransactionState expected = STARTED;
commit_without_prepare = std::atomic_compare_exchange_strong(
&txn_state_, &expected, AWAITING_COMMIT);
TEST_SYNC_POINT("TransactionTest::ExpirableTransactionDataRace:1");
} else if (txn_state_ == PREPARED) {
// expiration and lock stealing is not a concern
commit_prepared = true;
} else if (txn_state_ == STARTED) {
// expiration and lock stealing is not a concern
commit_without_prepare = true;
// TODO(myabandeh): what if the user mistakenly forgets prepare? We should
// add an option so that the user explictly express the intention of
// skipping the prepare phase.
}
if (commit_without_prepare) {
assert(!commit_prepared);
if (WriteBatchInternal::Count(GetCommitTimeWriteBatch()) > 0) {
s = Status::InvalidArgument(
"Commit-time batch contains values that will not be committed.");
} else {
txn_state_.store(AWAITING_COMMIT);
if (log_number_ > 0) {
dbimpl_->logs_with_prep_tracker()->MarkLogAsHavingPrepSectionFlushed(
log_number_);
}
s = CommitWithoutPrepareInternal();
if (!name_.empty()) {
txn_db_impl_->UnregisterTransaction(this);
}
Clear();
if (s.ok()) {
txn_state_.store(COMMITED);
}
}
} else if (commit_prepared) {
txn_state_.store(AWAITING_COMMIT);
s = CommitInternal();
if (!s.ok()) {
ROCKS_LOG_WARN(db_impl_->immutable_db_options().info_log,
"Commit write failed");
return s;
}
// FindObsoleteFiles must now look to the memtables
// to determine what prep logs must be kept around,
// not the prep section heap.
assert(log_number_ > 0);
dbimpl_->logs_with_prep_tracker()->MarkLogAsHavingPrepSectionFlushed(
log_number_);
txn_db_impl_->UnregisterTransaction(this);
Clear();
txn_state_.store(COMMITED);
} else if (txn_state_ == LOCKS_STOLEN) {
s = Status::Expired();
} else if (txn_state_ == COMMITED) {
s = Status::InvalidArgument("Transaction has already been committed.");
} else if (txn_state_ == ROLLEDBACK) {
s = Status::InvalidArgument("Transaction has already been rolledback.");
} else {
s = Status::InvalidArgument("Transaction is not in state for commit.");
}
return s;
}
Status WriteCommittedTxn::CommitWithoutPrepareInternal() {
uint64_t seq_used = kMaxSequenceNumber;
auto s =
db_impl_->WriteImpl(write_options_, GetWriteBatch()->GetWriteBatch(),
/*callback*/ nullptr, /*log_used*/ nullptr,
/*log_ref*/ 0, /*disable_memtable*/ false, &seq_used);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
if (s.ok()) {
SetId(seq_used);
}
return s;
}
Status WriteCommittedTxn::CommitBatchInternal(WriteBatch* batch, size_t) {
uint64_t seq_used = kMaxSequenceNumber;
auto s = db_impl_->WriteImpl(write_options_, batch, /*callback*/ nullptr,
/*log_used*/ nullptr, /*log_ref*/ 0,
/*disable_memtable*/ false, &seq_used);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
if (s.ok()) {
SetId(seq_used);
}
return s;
}
Status WriteCommittedTxn::CommitInternal() {
// We take the commit-time batch and append the Commit marker.
// The Memtable will ignore the Commit marker in non-recovery mode
WriteBatch* working_batch = GetCommitTimeWriteBatch();
WriteBatchInternal::MarkCommit(working_batch, name_);
// any operations appended to this working_batch will be ignored from WAL
working_batch->MarkWalTerminationPoint();
// insert prepared batch into Memtable only skipping WAL.
// Memtable will ignore BeginPrepare/EndPrepare markers
// in non recovery mode and simply insert the values
WriteBatchInternal::Append(working_batch, GetWriteBatch()->GetWriteBatch());
uint64_t seq_used = kMaxSequenceNumber;
auto s =
db_impl_->WriteImpl(write_options_, working_batch, /*callback*/ nullptr,
/*log_used*/ nullptr, /*log_ref*/ log_number_,
/*disable_memtable*/ false, &seq_used);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
if (s.ok()) {
SetId(seq_used);
}
return s;
}
Status PessimisticTransaction::Rollback() {
Status s;
if (txn_state_ == PREPARED) {
txn_state_.store(AWAITING_ROLLBACK);
s = RollbackInternal();
if (s.ok()) {
// we do not need to keep our prepared section around
assert(log_number_ > 0);
dbimpl_->logs_with_prep_tracker()->MarkLogAsHavingPrepSectionFlushed(
log_number_);
Clear();
txn_state_.store(ROLLEDBACK);
}
} else if (txn_state_ == STARTED) {
if (log_number_ > 0) {
assert(txn_db_impl_->GetTxnDBOptions().write_policy == WRITE_UNPREPARED);
assert(GetId() > 0);
s = RollbackInternal();
if (s.ok()) {
dbimpl_->logs_with_prep_tracker()->MarkLogAsHavingPrepSectionFlushed(
log_number_);
}
}
// prepare couldn't have taken place
Clear();
} else if (txn_state_ == COMMITED) {
s = Status::InvalidArgument("This transaction has already been committed.");
} else {
s = Status::InvalidArgument(
"Two phase transaction is not in state for rollback.");
}
return s;
}
Status WriteCommittedTxn::RollbackInternal() {
WriteBatch rollback_marker;
WriteBatchInternal::MarkRollback(&rollback_marker, name_);
auto s = db_impl_->WriteImpl(write_options_, &rollback_marker);
return s;
}
Status PessimisticTransaction::RollbackToSavePoint() {
if (txn_state_ != STARTED) {
return Status::InvalidArgument("Transaction is beyond state for rollback.");
}
// 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 PessimisticTransaction::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& cfh_keys = keys_[column_family_id];
auto iter = cfh_keys.find(key_str);
if (iter == cfh_keys.end()) {
// key not yet seen, store it.
cfh_keys.insert({std::move(key_str)});
}
}
Status PutCF(uint32_t column_family_id, const Slice& key,
const Slice& /* unused */) override {
RecordKey(column_family_id, key);
return Status::OK();
}
Status MergeCF(uint32_t column_family_id, const Slice& key,
const Slice& /* unused */) override {
RecordKey(column_family_id, key);
return Status::OK();
}
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, true /* exclusive */);
if (!s.ok()) {
break;
}
TrackKey(keys_to_unlock, cfh_id, std::move(key), kMaxSequenceNumber,
false, true /* exclusive */);
}
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 PessimisticTransaction::TryLock(ColumnFamilyHandle* column_family,
const Slice& key, bool read_only,
bool exclusive, const bool do_validate,
const bool assume_tracked) {
assert(!assume_tracked || !do_validate);
Status s;
if (UNLIKELY(skip_concurrency_control_)) {
return s;
}
uint32_t cfh_id = GetColumnFamilyID(column_family);
std::string key_str = key.ToString();
bool previously_locked;
bool lock_upgrade = false;
// lock this key if this transactions hasn't already locked it
SequenceNumber tracked_at_seq = 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 {
if (!iter->second.exclusive && exclusive) {
lock_upgrade = true;
}
previously_locked = true;
tracked_at_seq = iter->second.seq;
}
}
// Lock this key if this transactions hasn't already locked it or we require
// an upgrade.
if (!previously_locked || lock_upgrade) {
s = txn_db_impl_->TryLock(this, cfh_id, key_str, exclusive);
}
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 (!do_validate || snapshot_ == nullptr) {
if (assume_tracked && !previously_locked) {
s = Status::InvalidArgument(
"assume_tracked is set but it is not tracked yet");
}
// 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 (tracked_at_seq == kMaxSequenceNumber) {
// Since we haven't checked a snapshot, we only know this key has not
// been modified since after we locked it.
// Note: when last_seq_same_as_publish_seq_==false this is less than the
// latest allocated seq but it is ok since i) this is just a heuristic
// used only as a hint to avoid actual check for conflicts, ii) this would
// cause a false positive only if the snapthot is taken right after the
// lock, which would be an unusual sequence.
tracked_at_seq = db_->GetLatestSequenceNumber();
}
} 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 we already have validated an earilier snapshot it must has been
// reflected in tracked_at_seq and ValidateSnapshot will return OK.
if (s.ok()) {
s = ValidateSnapshot(column_family, key, &tracked_at_seq);
if (!s.ok()) {
// Failed to validate key
if (!previously_locked) {
// Unlock key we just locked
if (lock_upgrade) {
s = txn_db_impl_->TryLock(this, cfh_id, key_str,
false /* exclusive */);
assert(s.ok());
} else {
txn_db_impl_->UnLock(this, cfh_id, key.ToString());
}
}
}
}
}
if (s.ok()) {
// We must track all the locked keys so that we can unlock them later. If
// the key is already locked, this func will update some stats on the
// tracked key. It could also update the tracked_at_seq if it is lower
// than the existing tracked key seq. These stats are necessary for
// RollbackToSavePoint to determine whether a key can be safely removed
// from tracked_keys_. Removal can only be done if a key was only locked
// during the current savepoint.
//
// Recall that if assume_tracked is true, we assume that TrackKey has been
// called previously since the last savepoint, with the same exclusive
// setting, and at a lower sequence number, so skipping here should be
// safe.
if (!assume_tracked) {
TrackKey(cfh_id, key_str, tracked_at_seq, read_only, exclusive);
} else {
#ifndef NDEBUG
assert(tracked_keys_cf->second.count(key_str) > 0);
const auto& info = tracked_keys_cf->second.find(key_str)->second;
assert(info.seq <= tracked_at_seq);
assert(info.exclusive == exclusive);
#endif
}
}
return s;
}
// Return OK() if this key has not been modified more recently than the
// transaction snapshot_.
// tracked_at_seq is the global seq at which we either locked the key or already
// have done ValidateSnapshot.
Status PessimisticTransaction::ValidateSnapshot(
ColumnFamilyHandle* column_family, const Slice& key,
SequenceNumber* tracked_at_seq) {
assert(snapshot_);
SequenceNumber snap_seq = snapshot_->GetSequenceNumber();
if (*tracked_at_seq <= snap_seq) {
// If the key has been previous validated (or locked) at a sequence number
// earlier than the current snapshot's sequence number, we already know it
// has not been modified aftter snap_seq either.
return Status::OK();
}
// Otherwise we have either
// 1: tracked_at_seq == kMaxSequenceNumber, i.e., first time tracking the key
// 2: snap_seq < tracked_at_seq: last time we lock the key was via
// do_validate=false which means we had skipped ValidateSnapshot. In both
// cases we should do ValidateSnapshot now.
*tracked_at_seq = snap_seq;
ColumnFamilyHandle* cfh =
column_family ? column_family : db_impl_->DefaultColumnFamily();
return TransactionUtil::CheckKeyForConflicts(
db_impl_, cfh, key.ToString(), snap_seq, false /* cache_only */);
}
bool PessimisticTransaction::TryStealingLocks() {
assert(IsExpired());
TransactionState expected = STARTED;
return std::atomic_compare_exchange_strong(&txn_state_, &expected,
LOCKS_STOLEN);
}
void PessimisticTransaction::UnlockGetForUpdate(
ColumnFamilyHandle* column_family, const Slice& key) {
txn_db_impl_->UnLock(this, GetColumnFamilyID(column_family), key.ToString());
}
Status PessimisticTransaction::SetName(const TransactionName& name) {
Status s;
if (txn_state_ == STARTED) {
if (name_.length()) {
s = Status::InvalidArgument("Transaction has already been named.");
} else if (txn_db_impl_->GetTransactionByName(name) != nullptr) {
s = Status::InvalidArgument("Transaction name must be unique.");
} else if (name.length() < 1 || name.length() > 512) {
s = Status::InvalidArgument(
"Transaction name length must be between 1 and 512 chars.");
} else {
name_ = name;
txn_db_impl_->RegisterTransaction(this);
}
} else {
s = Status::InvalidArgument("Transaction is beyond state for naming.");
}
return s;
}
} // namespace rocksdb
#endif // ROCKSDB_LITE
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