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rocksdb/utilities/transactions/write_unprepared_txn.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/write_unprepared_txn.h"
#include "db/db_impl/db_impl.h"
#include "util/cast_util.h"
#include "utilities/transactions/write_unprepared_txn_db.h"
namespace rocksdb {
bool WriteUnpreparedTxnReadCallback::IsVisibleFullCheck(SequenceNumber seq) {
auto unprep_seqs = txn_->GetUnpreparedSequenceNumbers();
// Since unprep_seqs maps prep_seq => prepare_batch_cnt, to check if seq is
// in unprep_seqs, we have to check if seq is equal to prep_seq or any of
// the prepare_batch_cnt seq nums after it.
//
// TODO(lth): Can be optimized with std::lower_bound if unprep_seqs is
// large.
for (const auto& it : unprep_seqs) {
if (it.first <= seq && seq < it.first + it.second) {
return true;
}
}
return db_->IsInSnapshot(seq, wup_snapshot_, min_uncommitted_);
}
SequenceNumber WriteUnpreparedTxnReadCallback::CalcMaxUnpreparedSequenceNumber(
WriteUnpreparedTxn* txn) {
const auto& unprep_seqs = txn->GetUnpreparedSequenceNumbers();
if (unprep_seqs.size()) {
return unprep_seqs.rbegin()->first + unprep_seqs.rbegin()->second - 1;
}
return 0;
}
WriteUnpreparedTxn::WriteUnpreparedTxn(WriteUnpreparedTxnDB* txn_db,
const WriteOptions& write_options,
const TransactionOptions& txn_options)
: WritePreparedTxn(txn_db, write_options, txn_options),
wupt_db_(txn_db),
recovered_txn_(false),
largest_validated_seq_(0) {
max_write_batch_size_ = txn_options.max_write_batch_size;
// We set max bytes to zero so that we don't get a memory limit error.
// Instead of trying to keep write batch strictly under the size limit, we
// just flush to DB when the limit is exceeded in write unprepared, to avoid
// having retry logic. This also allows very big key-value pairs that exceed
// max bytes to succeed.
write_batch_.SetMaxBytes(0);
}
WriteUnpreparedTxn::~WriteUnpreparedTxn() {
if (!unprep_seqs_.empty()) {
assert(log_number_ > 0);
assert(GetId() > 0);
assert(!name_.empty());
// We should rollback regardless of GetState, but some unit tests that
// test crash recovery run the destructor assuming that rollback does not
// happen, so that rollback during recovery can be exercised.
if (GetState() == STARTED) {
auto s __attribute__((__unused__)) = RollbackInternal();
// TODO(lth): Better error handling.
assert(s.ok());
dbimpl_->logs_with_prep_tracker()->MarkLogAsHavingPrepSectionFlushed(
log_number_);
}
}
// Call tracked_keys_.clear() so that ~PessimisticTransaction does not
// try to unlock keys for recovered transactions.
if (recovered_txn_) {
tracked_keys_.clear();
}
}
void WriteUnpreparedTxn::Initialize(const TransactionOptions& txn_options) {
PessimisticTransaction::Initialize(txn_options);
max_write_batch_size_ = txn_options.max_write_batch_size;
write_batch_.SetMaxBytes(0);
unprep_seqs_.clear();
recovered_txn_ = false;
largest_validated_seq_ = 0;
}
Status WriteUnpreparedTxn::HandleWrite(std::function<Status()> do_write) {
Status s = MaybeFlushWriteBatchToDB();
if (!s.ok()) {
return s;
}
s = do_write();
if (s.ok()) {
if (snapshot_) {
largest_validated_seq_ =
std::max(largest_validated_seq_, snapshot_->GetSequenceNumber());
} else {
largest_validated_seq_ = kMaxSequenceNumber;
}
}
return s;
}
Status WriteUnpreparedTxn::Put(ColumnFamilyHandle* column_family,
const Slice& key, const Slice& value,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Put(column_family, key, value, assume_tracked);
});
}
Status WriteUnpreparedTxn::Put(ColumnFamilyHandle* column_family,
const SliceParts& key, const SliceParts& value,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Put(column_family, key, value, assume_tracked);
});
}
Status WriteUnpreparedTxn::Merge(ColumnFamilyHandle* column_family,
const Slice& key, const Slice& value,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Merge(column_family, key, value,
assume_tracked);
});
}
Status WriteUnpreparedTxn::Delete(ColumnFamilyHandle* column_family,
const Slice& key, const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Delete(column_family, key, assume_tracked);
});
}
Status WriteUnpreparedTxn::Delete(ColumnFamilyHandle* column_family,
const SliceParts& key,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Delete(column_family, key, assume_tracked);
});
}
Status WriteUnpreparedTxn::SingleDelete(ColumnFamilyHandle* column_family,
const Slice& key,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::SingleDelete(column_family, key,
assume_tracked);
});
}
Status WriteUnpreparedTxn::SingleDelete(ColumnFamilyHandle* column_family,
const SliceParts& key,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::SingleDelete(column_family, key,
assume_tracked);
});
}
// WriteUnpreparedTxn::RebuildFromWriteBatch is only called on recovery. For
// WriteUnprepared, the write batches have already been written into the
// database during WAL replay, so all we have to do is just to "retrack" the key
// so that rollbacks are possible.
//
// Calling TryLock instead of TrackKey is also possible, but as an optimization,
// recovered transactions do not hold locks on their keys. This follows the
// implementation in PessimisticTransactionDB::Initialize where we set
// skip_concurrency_control to true.
Status WriteUnpreparedTxn::RebuildFromWriteBatch(WriteBatch* wb) {
struct TrackKeyHandler : public WriteBatch::Handler {
WriteUnpreparedTxn* txn_;
bool rollback_merge_operands_;
TrackKeyHandler(WriteUnpreparedTxn* txn, bool rollback_merge_operands)
: txn_(txn), rollback_merge_operands_(rollback_merge_operands) {}
Status PutCF(uint32_t cf, const Slice& key, const Slice&) override {
txn_->TrackKey(cf, key.ToString(), kMaxSequenceNumber,
false /* read_only */, true /* exclusive */);
return Status::OK();
}
Status DeleteCF(uint32_t cf, const Slice& key) override {
txn_->TrackKey(cf, key.ToString(), kMaxSequenceNumber,
false /* read_only */, true /* exclusive */);
return Status::OK();
}
Status SingleDeleteCF(uint32_t cf, const Slice& key) override {
txn_->TrackKey(cf, key.ToString(), kMaxSequenceNumber,
false /* read_only */, true /* exclusive */);
return Status::OK();
}
Status MergeCF(uint32_t cf, const Slice& key, const Slice&) override {
if (rollback_merge_operands_) {
txn_->TrackKey(cf, key.ToString(), kMaxSequenceNumber,
false /* read_only */, true /* exclusive */);
}
return Status::OK();
}
// Recovered batches do not contain 2PC markers.
Status MarkBeginPrepare(bool) override { return Status::InvalidArgument(); }
Status MarkEndPrepare(const Slice&) override {
return Status::InvalidArgument();
}
Status MarkNoop(bool) override { return Status::InvalidArgument(); }
Status MarkCommit(const Slice&) override {
return Status::InvalidArgument();
}
Status MarkRollback(const Slice&) override {
return Status::InvalidArgument();
}
};
TrackKeyHandler handler(this,
wupt_db_->txn_db_options_.rollback_merge_operands);
return wb->Iterate(&handler);
}
Status WriteUnpreparedTxn::MaybeFlushWriteBatchToDB() {
const bool kPrepared = true;
Status s;
if (max_write_batch_size_ != 0 &&
write_batch_.GetDataSize() > max_write_batch_size_) {
assert(GetState() != PREPARED);
s = FlushWriteBatchToDB(!kPrepared);
}
return s;
}
Status WriteUnpreparedTxn::FlushWriteBatchToDB(bool prepared) {
if (name_.empty()) {
return Status::InvalidArgument("Cannot write to DB without SetName.");
}
// TODO(lth): Reduce duplicate code with WritePrepared prepare logic.
WriteOptions write_options = write_options_;
write_options.disableWAL = false;
const bool WRITE_AFTER_COMMIT = true;
const bool first_prepare_batch = log_number_ == 0;
// MarkEndPrepare will change Noop marker to the appropriate marker.
WriteBatchInternal::MarkEndPrepare(GetWriteBatch()->GetWriteBatch(), name_,
!WRITE_AFTER_COMMIT, !prepared);
// For each duplicate key we account for a new sub-batch
prepare_batch_cnt_ = GetWriteBatch()->SubBatchCnt();
// AddPrepared better to be called in the pre-release callback otherwise there
// is a non-zero chance of max advancing prepare_seq and readers assume the
// data as committed.
// Also having it in the PreReleaseCallback allows in-order addition of
// prepared entries to PreparedHeap and hence enables an optimization. Refer
// to SmallestUnCommittedSeq for more details.
AddPreparedCallback add_prepared_callback(
wpt_db_, db_impl_, prepare_batch_cnt_,
db_impl_->immutable_db_options().two_write_queues, first_prepare_batch);
const bool DISABLE_MEMTABLE = true;
uint64_t seq_used = kMaxSequenceNumber;
// log_number_ should refer to the oldest log containing uncommitted data
// from the current transaction. This means that if log_number_ is set,
// WriteImpl should not overwrite that value, so set log_used to nullptr if
// log_number_ is already set.
uint64_t* log_used = log_number_ ? nullptr : &log_number_;
auto s = db_impl_->WriteImpl(write_options, GetWriteBatch()->GetWriteBatch(),
/*callback*/ nullptr, log_used, /*log ref*/
0, !DISABLE_MEMTABLE, &seq_used,
prepare_batch_cnt_, &add_prepared_callback);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
auto prepare_seq = seq_used;
// Only call SetId if it hasn't been set yet.
if (GetId() == 0) {
SetId(prepare_seq);
}
// unprep_seqs_ will also contain prepared seqnos since they are treated in
// the same way in the prepare/commit callbacks. See the comment on the
// definition of unprep_seqs_.
unprep_seqs_[prepare_seq] = prepare_batch_cnt_;
// Reset transaction state.
if (!prepared) {
prepare_batch_cnt_ = 0;
write_batch_.Clear();
WriteBatchInternal::InsertNoop(write_batch_.GetWriteBatch());
}
return s;
}
Status WriteUnpreparedTxn::PrepareInternal() {
const bool kPrepared = true;
return FlushWriteBatchToDB(kPrepared);
}
Status WriteUnpreparedTxn::CommitWithoutPrepareInternal() {
if (unprep_seqs_.empty()) {
assert(log_number_ == 0);
assert(GetId() == 0);
return WritePreparedTxn::CommitWithoutPrepareInternal();
}
// TODO(lth): We should optimize commit without prepare to not perform
// a prepare under the hood.
auto s = PrepareInternal();
if (!s.ok()) {
return s;
}
return CommitInternal();
}
Status WriteUnpreparedTxn::CommitInternal() {
// TODO(lth): Reduce duplicate code with WritePrepared commit logic.
// 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();
const bool empty = working_batch->Count() == 0;
WriteBatchInternal::MarkCommit(working_batch, name_);
const bool for_recovery = use_only_the_last_commit_time_batch_for_recovery_;
if (!empty && for_recovery) {
// When not writing to memtable, we can still cache the latest write batch.
// The cached batch will be written to memtable in WriteRecoverableState
// during FlushMemTable
WriteBatchInternal::SetAsLastestPersistentState(working_batch);
}
const bool includes_data = !empty && !for_recovery;
size_t commit_batch_cnt = 0;
if (UNLIKELY(includes_data)) {
ROCKS_LOG_WARN(db_impl_->immutable_db_options().info_log,
"Duplicate key overhead");
SubBatchCounter counter(*wpt_db_->GetCFComparatorMap());
auto s = working_batch->Iterate(&counter);
assert(s.ok());
commit_batch_cnt = counter.BatchCount();
}
const bool disable_memtable = !includes_data;
const bool do_one_write =
!db_impl_->immutable_db_options().two_write_queues || disable_memtable;
WriteUnpreparedCommitEntryPreReleaseCallback update_commit_map(
wpt_db_, db_impl_, unprep_seqs_, commit_batch_cnt);
const bool kFirstPrepareBatch = true;
AddPreparedCallback add_prepared_callback(
wpt_db_, db_impl_, commit_batch_cnt,
db_impl_->immutable_db_options().two_write_queues, !kFirstPrepareBatch);
PreReleaseCallback* pre_release_callback;
if (do_one_write) {
pre_release_callback = &update_commit_map;
} else {
pre_release_callback = &add_prepared_callback;
}
uint64_t seq_used = kMaxSequenceNumber;
// Since the prepared batch is directly written to memtable, there is
// already a connection between the memtable and its WAL, so there is no
// need to redundantly reference the log that contains the prepared data.
const uint64_t zero_log_number = 0ull;
size_t batch_cnt = UNLIKELY(commit_batch_cnt) ? commit_batch_cnt : 1;
auto s = db_impl_->WriteImpl(write_options_, working_batch, nullptr, nullptr,
zero_log_number, disable_memtable, &seq_used,
batch_cnt, pre_release_callback);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
const SequenceNumber commit_batch_seq = seq_used;
if (LIKELY(do_one_write || !s.ok())) {
if (LIKELY(s.ok())) {
// Note RemovePrepared should be called after WriteImpl that publishsed
// the seq. Otherwise SmallestUnCommittedSeq optimization breaks.
for (const auto& seq : unprep_seqs_) {
wpt_db_->RemovePrepared(seq.first, seq.second);
}
}
if (UNLIKELY(!do_one_write)) {
wpt_db_->RemovePrepared(commit_batch_seq, commit_batch_cnt);
}
unprep_seqs_.clear();
return s;
} // else do the 2nd write to publish seq
// Populate unprep_seqs_ with commit_batch_seq, since we treat data in the
// commit write batch as just another "unprepared" batch. This will also
// update the unprep_seqs_ in the update_commit_map callback.
unprep_seqs_[commit_batch_seq] = commit_batch_cnt;
// Note: the 2nd write comes with a performance penality. So if we have too
// many of commits accompanied with ComitTimeWriteBatch and yet we cannot
// enable use_only_the_last_commit_time_batch_for_recovery_ optimization,
// two_write_queues should be disabled to avoid many additional writes here.
// Update commit map only from the 2nd queue
WriteBatch empty_batch;
empty_batch.PutLogData(Slice());
// In the absence of Prepare markers, use Noop as a batch separator
WriteBatchInternal::InsertNoop(&empty_batch);
const bool DISABLE_MEMTABLE = true;
const size_t ONE_BATCH = 1;
const uint64_t NO_REF_LOG = 0;
s = db_impl_->WriteImpl(write_options_, &empty_batch, nullptr, nullptr,
NO_REF_LOG, DISABLE_MEMTABLE, &seq_used, ONE_BATCH,
&update_commit_map);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
// Note RemovePrepared should be called after WriteImpl that publishsed the
// seq. Otherwise SmallestUnCommittedSeq optimization breaks.
for (const auto& seq : unprep_seqs_) {
wpt_db_->RemovePrepared(seq.first, seq.second);
}
unprep_seqs_.clear();
return s;
}
Status WriteUnpreparedTxn::RollbackInternal() {
// TODO(lth): Reduce duplicate code with WritePrepared rollback logic.
WriteBatchWithIndex rollback_batch(
wpt_db_->DefaultColumnFamily()->GetComparator(), 0, true, 0);
assert(GetId() != kMaxSequenceNumber);
assert(GetId() > 0);
Status s;
const auto& cf_map = *wupt_db_->GetCFHandleMap();
auto read_at_seq = kMaxSequenceNumber;
ReadOptions roptions;
// Note that we do not use WriteUnpreparedTxnReadCallback because we do not
// need to read our own writes when reading prior versions of the key for
// rollback.
const auto& tracked_keys = GetTrackedKeys();
WritePreparedTxnReadCallback callback(wpt_db_, read_at_seq);
for (const auto& cfkey : tracked_keys) {
const auto cfid = cfkey.first;
const auto& keys = cfkey.second;
for (const auto& pair : keys) {
const auto& key = pair.first;
const auto& cf_handle = cf_map.at(cfid);
PinnableSlice pinnable_val;
bool not_used;
s = db_impl_->GetImpl(roptions, cf_handle, key, &pinnable_val, &not_used,
&callback);
if (s.ok()) {
s = rollback_batch.Put(cf_handle, key, pinnable_val);
assert(s.ok());
} else if (s.IsNotFound()) {
s = rollback_batch.Delete(cf_handle, key);
assert(s.ok());
} else {
return s;
}
}
}
// The Rollback marker will be used as a batch separator
WriteBatchInternal::MarkRollback(rollback_batch.GetWriteBatch(), name_);
bool do_one_write = !db_impl_->immutable_db_options().two_write_queues;
const bool DISABLE_MEMTABLE = true;
const uint64_t NO_REF_LOG = 0;
uint64_t seq_used = kMaxSequenceNumber;
// TODO(lth): We write rollback batch all in a single batch here, but this
// should be subdivded into multiple batches as well. In phase 2, when key
// sets are read from WAL, this will happen naturally.
const size_t ONE_BATCH = 1;
// We commit the rolled back prepared batches. ALthough this is
// counter-intuitive, i) it is safe to do so, since the prepared batches are
// already canceled out by the rollback batch, ii) adding the commit entry to
// CommitCache will allow us to benefit from the existing mechanism in
// CommitCache that keeps an entry evicted due to max advance and yet overlaps
// with a live snapshot around so that the live snapshot properly skips the
// entry even if its prepare seq is lower than max_evicted_seq_.
WriteUnpreparedCommitEntryPreReleaseCallback update_commit_map(
wpt_db_, db_impl_, unprep_seqs_, ONE_BATCH);
// Note: the rollback batch does not need AddPrepared since it is written to
// DB in one shot. min_uncommitted still works since it requires capturing
// data that is written to DB but not yet committed, while the roolback
// batch commits with PreReleaseCallback.
s = db_impl_->WriteImpl(write_options_, rollback_batch.GetWriteBatch(),
nullptr, nullptr, NO_REF_LOG, !DISABLE_MEMTABLE,
&seq_used, rollback_batch.SubBatchCnt(),
do_one_write ? &update_commit_map : nullptr);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
if (!s.ok()) {
return s;
}
if (do_one_write) {
for (const auto& seq : unprep_seqs_) {
wpt_db_->RemovePrepared(seq.first, seq.second);
}
unprep_seqs_.clear();
return s;
} // else do the 2nd write for commit
uint64_t& prepare_seq = seq_used;
ROCKS_LOG_DETAILS(db_impl_->immutable_db_options().info_log,
"RollbackInternal 2nd write prepare_seq: %" PRIu64,
prepare_seq);
// Commit the batch by writing an empty batch to the queue that will release
// the commit sequence number to readers.
WriteUnpreparedRollbackPreReleaseCallback update_commit_map_with_prepare(
wpt_db_, db_impl_, unprep_seqs_, prepare_seq);
WriteBatch empty_batch;
empty_batch.PutLogData(Slice());
// In the absence of Prepare markers, use Noop as a batch separator
WriteBatchInternal::InsertNoop(&empty_batch);
s = db_impl_->WriteImpl(write_options_, &empty_batch, nullptr, nullptr,
NO_REF_LOG, DISABLE_MEMTABLE, &seq_used, ONE_BATCH,
&update_commit_map_with_prepare);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
// Mark the txn as rolled back
if (s.ok()) {
for (const auto& seq : unprep_seqs_) {
wpt_db_->RemovePrepared(seq.first, seq.second);
}
}
unprep_seqs_.clear();
return s;
}
void WriteUnpreparedTxn::Clear() {
if (!recovered_txn_) {
txn_db_impl_->UnLock(this, &GetTrackedKeys());
}
TransactionBaseImpl::Clear();
}
Status WriteUnpreparedTxn::Get(const ReadOptions& options,
ColumnFamilyHandle* column_family,
const Slice& key, PinnableSlice* value) {
SequenceNumber min_uncommitted, snap_seq;
const bool backed_by_snapshot =
wupt_db_->AssignMinMaxSeqs(options.snapshot, &min_uncommitted, &snap_seq);
WriteUnpreparedTxnReadCallback callback(wupt_db_, snap_seq, min_uncommitted,
this);
auto res = write_batch_.GetFromBatchAndDB(db_, options, column_family, key,
value, &callback);
if (LIKELY(wupt_db_->ValidateSnapshot(snap_seq, backed_by_snapshot))) {
return res;
} else {
return Status::TryAgain();
}
}
Iterator* WriteUnpreparedTxn::GetIterator(const ReadOptions& options) {
return GetIterator(options, wupt_db_->DefaultColumnFamily());
}
Iterator* WriteUnpreparedTxn::GetIterator(const ReadOptions& options,
ColumnFamilyHandle* column_family) {
// Make sure to get iterator from WriteUnprepareTxnDB, not the root db.
Iterator* db_iter = wupt_db_->NewIterator(options, column_family, this);
assert(db_iter);
return write_batch_.NewIteratorWithBase(column_family, db_iter);
}
const std::map<SequenceNumber, size_t>&
WriteUnpreparedTxn::GetUnpreparedSequenceNumbers() {
return unprep_seqs_;
}
} // namespace rocksdb
#endif // ROCKSDB_LITE