fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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752 lines
30 KiB
752 lines
30 KiB
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#ifndef ROCKSDB_LITE
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#ifndef __STDC_FORMAT_MACROS
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#define __STDC_FORMAT_MACROS
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#endif
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#include "utilities/transactions/write_prepared_txn_db.h"
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#include <inttypes.h>
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#include <algorithm>
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#include <string>
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#include <unordered_set>
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#include <vector>
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#include "db/db_impl.h"
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#include "rocksdb/db.h"
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#include "rocksdb/options.h"
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#include "rocksdb/utilities/transaction_db.h"
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#include "util/cast_util.h"
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#include "util/mutexlock.h"
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#include "util/string_util.h"
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#include "util/sync_point.h"
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#include "utilities/transactions/pessimistic_transaction.h"
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#include "utilities/transactions/transaction_db_mutex_impl.h"
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namespace rocksdb {
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Status WritePreparedTxnDB::Initialize(
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const std::vector<size_t>& compaction_enabled_cf_indices,
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const std::vector<ColumnFamilyHandle*>& handles) {
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auto dbimpl = reinterpret_cast<DBImpl*>(GetRootDB());
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assert(dbimpl != nullptr);
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auto rtxns = dbimpl->recovered_transactions();
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for (auto rtxn : rtxns) {
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auto cnt = rtxn.second->batch_cnt_ ? rtxn.second->batch_cnt_ : 1;
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for (size_t i = 0; i < cnt; i++) {
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AddPrepared(rtxn.second->seq_ + i);
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}
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}
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SequenceNumber prev_max = max_evicted_seq_;
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SequenceNumber last_seq = db_impl_->GetLatestSequenceNumber();
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AdvanceMaxEvictedSeq(prev_max, last_seq);
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db_impl_->SetSnapshotChecker(new WritePreparedSnapshotChecker(this));
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// A callback to commit a single sub-batch
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class CommitSubBatchPreReleaseCallback : public PreReleaseCallback {
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public:
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explicit CommitSubBatchPreReleaseCallback(WritePreparedTxnDB* db)
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: db_(db) {}
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virtual Status Callback(SequenceNumber commit_seq,
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bool is_mem_disabled) override {
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#ifdef NDEBUG
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(void)is_mem_disabled;
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#endif
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assert(!is_mem_disabled);
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db_->AddCommitted(commit_seq, commit_seq);
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return Status::OK();
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}
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private:
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WritePreparedTxnDB* db_;
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};
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db_impl_->SetRecoverableStatePreReleaseCallback(
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new CommitSubBatchPreReleaseCallback(this));
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auto s = PessimisticTransactionDB::Initialize(compaction_enabled_cf_indices,
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handles);
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return s;
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}
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Status WritePreparedTxnDB::VerifyCFOptions(
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const ColumnFamilyOptions& cf_options) {
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Status s = PessimisticTransactionDB::VerifyCFOptions(cf_options);
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if (!s.ok()) {
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return s;
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}
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if (!cf_options.memtable_factory->CanHandleDuplicatedKey()) {
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return Status::InvalidArgument(
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"memtable_factory->CanHandleDuplicatedKey() cannot be false with "
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"WritePrpeared transactions");
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}
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return Status::OK();
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}
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Transaction* WritePreparedTxnDB::BeginTransaction(
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const WriteOptions& write_options, const TransactionOptions& txn_options,
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Transaction* old_txn) {
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if (old_txn != nullptr) {
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ReinitializeTransaction(old_txn, write_options, txn_options);
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return old_txn;
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} else {
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return new WritePreparedTxn(this, write_options, txn_options);
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}
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}
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Status WritePreparedTxnDB::Write(
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const WriteOptions& opts,
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const TransactionDBWriteOptimizations& optimizations, WriteBatch* updates) {
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if (optimizations.skip_concurrency_control) {
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// Skip locking the rows
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const size_t UNKNOWN_BATCH_CNT = 0;
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const size_t ONE_BATCH_CNT = 1;
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const size_t batch_cnt = optimizations.skip_duplicate_key_check
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? ONE_BATCH_CNT
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: UNKNOWN_BATCH_CNT;
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WritePreparedTxn* NO_TXN = nullptr;
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return WriteInternal(opts, updates, batch_cnt, NO_TXN);
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} else {
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// TODO(myabandeh): Make use of skip_duplicate_key_check hint
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// Fall back to unoptimized version
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return PessimisticTransactionDB::Write(opts, updates);
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}
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}
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Status WritePreparedTxnDB::WriteInternal(const WriteOptions& write_options_orig,
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WriteBatch* batch, size_t batch_cnt,
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WritePreparedTxn* txn) {
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ROCKS_LOG_DETAILS(db_impl_->immutable_db_options().info_log,
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"CommitBatchInternal");
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if (batch->Count() == 0) {
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// Otherwise our 1 seq per batch logic will break since there is no seq
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// increased for this batch.
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return Status::OK();
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}
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if (batch_cnt == 0) { // not provided, then compute it
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// TODO(myabandeh): add an option to allow user skipping this cost
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SubBatchCounter counter(*GetCFComparatorMap());
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auto s = batch->Iterate(&counter);
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assert(s.ok());
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batch_cnt = counter.BatchCount();
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WPRecordTick(TXN_DUPLICATE_KEY_OVERHEAD);
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ROCKS_LOG_DETAILS(info_log_, "Duplicate key overhead: %" PRIu64 " batches",
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static_cast<uint64_t>(batch_cnt));
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}
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assert(batch_cnt);
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bool do_one_write = !db_impl_->immutable_db_options().two_write_queues;
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WriteOptions write_options(write_options_orig);
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bool sync = write_options.sync;
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if (!do_one_write) {
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// No need to sync on the first write
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write_options.sync = false;
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}
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// In the absence of Prepare markers, use Noop as a batch separator
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WriteBatchInternal::InsertNoop(batch);
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const bool DISABLE_MEMTABLE = true;
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const uint64_t no_log_ref = 0;
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uint64_t seq_used = kMaxSequenceNumber;
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const size_t ZERO_PREPARES = 0;
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// Since this is not 2pc, there is no need for AddPrepared but having it in
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// the PreReleaseCallback enables an optimization. Refer to
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// SmallestUnCommittedSeq for more details.
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AddPreparedCallback add_prepared_callback(
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this, batch_cnt, db_impl_->immutable_db_options().two_write_queues);
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WritePreparedCommitEntryPreReleaseCallback update_commit_map(
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this, db_impl_, kMaxSequenceNumber, ZERO_PREPARES, batch_cnt);
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PreReleaseCallback* pre_release_callback;
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if (do_one_write) {
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pre_release_callback = &update_commit_map;
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} else {
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pre_release_callback = &add_prepared_callback;
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}
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auto s = db_impl_->WriteImpl(write_options, batch, nullptr, nullptr,
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no_log_ref, !DISABLE_MEMTABLE, &seq_used,
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batch_cnt, pre_release_callback);
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assert(!s.ok() || seq_used != kMaxSequenceNumber);
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uint64_t prepare_seq = seq_used;
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if (txn != nullptr) {
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txn->SetId(prepare_seq);
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}
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if (!s.ok()) {
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return s;
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}
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if (do_one_write) {
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return s;
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} // else do the 2nd write for commit
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// Set the original value of sync
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write_options.sync = sync;
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ROCKS_LOG_DETAILS(db_impl_->immutable_db_options().info_log,
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"CommitBatchInternal 2nd write prepare_seq: %" PRIu64,
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prepare_seq);
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// Commit the batch by writing an empty batch to the 2nd queue that will
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// release the commit sequence number to readers.
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const size_t ZERO_COMMITS = 0;
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WritePreparedCommitEntryPreReleaseCallback update_commit_map_with_prepare(
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this, db_impl_, prepare_seq, batch_cnt, ZERO_COMMITS);
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WriteBatch empty_batch;
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empty_batch.PutLogData(Slice());
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const size_t ONE_BATCH = 1;
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// In the absence of Prepare markers, use Noop as a batch separator
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WriteBatchInternal::InsertNoop(&empty_batch);
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s = db_impl_->WriteImpl(write_options, &empty_batch, nullptr, nullptr,
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no_log_ref, DISABLE_MEMTABLE, &seq_used, ONE_BATCH,
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&update_commit_map_with_prepare);
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assert(!s.ok() || seq_used != kMaxSequenceNumber);
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// Note RemovePrepared should be called after WriteImpl that publishsed the
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// seq. Otherwise SmallestUnCommittedSeq optimization breaks.
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RemovePrepared(prepare_seq, batch_cnt);
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return s;
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}
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Status WritePreparedTxnDB::Get(const ReadOptions& options,
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ColumnFamilyHandle* column_family,
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const Slice& key, PinnableSlice* value) {
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// We are fine with the latest committed value. This could be done by
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// specifying the snapshot as kMaxSequenceNumber.
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SequenceNumber seq = kMaxSequenceNumber;
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SequenceNumber min_uncommitted = 0;
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if (options.snapshot != nullptr) {
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seq = options.snapshot->GetSequenceNumber();
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min_uncommitted = static_cast_with_check<const SnapshotImpl, const Snapshot>(
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options.snapshot)
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->min_uncommitted_;
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} else {
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min_uncommitted = SmallestUnCommittedSeq();
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}
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WritePreparedTxnReadCallback callback(this, seq, min_uncommitted);
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bool* dont_care = nullptr;
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// Note: no need to specify a snapshot for read options as no specific
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// snapshot is requested by the user.
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return db_impl_->GetImpl(options, column_family, key, value, dont_care,
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&callback);
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}
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void WritePreparedTxnDB::UpdateCFComparatorMap(
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const std::vector<ColumnFamilyHandle*>& handles) {
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auto cf_map = new std::map<uint32_t, const Comparator*>();
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auto handle_map = new std::map<uint32_t, ColumnFamilyHandle*>();
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for (auto h : handles) {
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auto id = h->GetID();
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const Comparator* comparator = h->GetComparator();
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(*cf_map)[id] = comparator;
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if (id != 0) {
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(*handle_map)[id] = h;
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} else {
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// The pointer to the default cf handle in the handles will be deleted.
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// Use the pointer maintained by the db instead.
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(*handle_map)[id] = DefaultColumnFamily();
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}
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}
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cf_map_.reset(cf_map);
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handle_map_.reset(handle_map);
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}
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void WritePreparedTxnDB::UpdateCFComparatorMap(ColumnFamilyHandle* h) {
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auto old_cf_map_ptr = cf_map_.get();
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assert(old_cf_map_ptr);
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auto cf_map = new std::map<uint32_t, const Comparator*>(*old_cf_map_ptr);
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auto old_handle_map_ptr = handle_map_.get();
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assert(old_handle_map_ptr);
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auto handle_map =
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new std::map<uint32_t, ColumnFamilyHandle*>(*old_handle_map_ptr);
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auto id = h->GetID();
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const Comparator* comparator = h->GetComparator();
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(*cf_map)[id] = comparator;
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(*handle_map)[id] = h;
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cf_map_.reset(cf_map);
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handle_map_.reset(handle_map);
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}
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std::vector<Status> WritePreparedTxnDB::MultiGet(
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const ReadOptions& options,
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const std::vector<ColumnFamilyHandle*>& column_family,
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const std::vector<Slice>& keys, std::vector<std::string>* values) {
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assert(values);
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size_t num_keys = keys.size();
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values->resize(num_keys);
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std::vector<Status> stat_list(num_keys);
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for (size_t i = 0; i < num_keys; ++i) {
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std::string* value = values ? &(*values)[i] : nullptr;
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stat_list[i] = this->Get(options, column_family[i], keys[i], value);
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}
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return stat_list;
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}
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// Struct to hold ownership of snapshot and read callback for iterator cleanup.
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struct WritePreparedTxnDB::IteratorState {
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IteratorState(WritePreparedTxnDB* txn_db, SequenceNumber sequence,
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std::shared_ptr<ManagedSnapshot> s,
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SequenceNumber min_uncommitted)
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: callback(txn_db, sequence, min_uncommitted), snapshot(s) {}
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WritePreparedTxnReadCallback callback;
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std::shared_ptr<ManagedSnapshot> snapshot;
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};
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namespace {
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static void CleanupWritePreparedTxnDBIterator(void* arg1, void* /*arg2*/) {
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delete reinterpret_cast<WritePreparedTxnDB::IteratorState*>(arg1);
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}
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} // anonymous namespace
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Iterator* WritePreparedTxnDB::NewIterator(const ReadOptions& options,
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ColumnFamilyHandle* column_family) {
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constexpr bool ALLOW_BLOB = true;
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constexpr bool ALLOW_REFRESH = true;
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std::shared_ptr<ManagedSnapshot> own_snapshot = nullptr;
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SequenceNumber snapshot_seq = kMaxSequenceNumber;
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SequenceNumber min_uncommitted = 0;
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if (options.snapshot != nullptr) {
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snapshot_seq = options.snapshot->GetSequenceNumber();
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min_uncommitted =
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static_cast_with_check<const SnapshotImpl, const Snapshot>(
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options.snapshot)
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->min_uncommitted_;
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} else {
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auto* snapshot = GetSnapshot();
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// We take a snapshot to make sure that the related data in the commit map
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// are not deleted.
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snapshot_seq = snapshot->GetSequenceNumber();
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min_uncommitted =
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static_cast_with_check<const SnapshotImpl, const Snapshot>(snapshot)
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->min_uncommitted_;
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own_snapshot = std::make_shared<ManagedSnapshot>(db_impl_, snapshot);
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}
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assert(snapshot_seq != kMaxSequenceNumber);
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auto* cfd = reinterpret_cast<ColumnFamilyHandleImpl*>(column_family)->cfd();
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auto* state =
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new IteratorState(this, snapshot_seq, own_snapshot, min_uncommitted);
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auto* db_iter =
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db_impl_->NewIteratorImpl(options, cfd, snapshot_seq, &state->callback,
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!ALLOW_BLOB, !ALLOW_REFRESH);
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db_iter->RegisterCleanup(CleanupWritePreparedTxnDBIterator, state, nullptr);
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return db_iter;
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}
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Status WritePreparedTxnDB::NewIterators(
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const ReadOptions& options,
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const std::vector<ColumnFamilyHandle*>& column_families,
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std::vector<Iterator*>* iterators) {
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constexpr bool ALLOW_BLOB = true;
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constexpr bool ALLOW_REFRESH = true;
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std::shared_ptr<ManagedSnapshot> own_snapshot = nullptr;
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SequenceNumber snapshot_seq = kMaxSequenceNumber;
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SequenceNumber min_uncommitted = 0;
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if (options.snapshot != nullptr) {
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snapshot_seq = options.snapshot->GetSequenceNumber();
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min_uncommitted = static_cast_with_check<const SnapshotImpl, const Snapshot>(
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options.snapshot)
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->min_uncommitted_;
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} else {
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auto* snapshot = GetSnapshot();
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// We take a snapshot to make sure that the related data in the commit map
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// are not deleted.
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snapshot_seq = snapshot->GetSequenceNumber();
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own_snapshot = std::make_shared<ManagedSnapshot>(db_impl_, snapshot);
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min_uncommitted =
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static_cast_with_check<const SnapshotImpl, const Snapshot>(snapshot)
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->min_uncommitted_;
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}
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iterators->clear();
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iterators->reserve(column_families.size());
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for (auto* column_family : column_families) {
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auto* cfd = reinterpret_cast<ColumnFamilyHandleImpl*>(column_family)->cfd();
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auto* state =
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new IteratorState(this, snapshot_seq, own_snapshot, min_uncommitted);
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auto* db_iter =
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db_impl_->NewIteratorImpl(options, cfd, snapshot_seq, &state->callback,
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!ALLOW_BLOB, !ALLOW_REFRESH);
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db_iter->RegisterCleanup(CleanupWritePreparedTxnDBIterator, state, nullptr);
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iterators->push_back(db_iter);
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}
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return Status::OK();
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}
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void WritePreparedTxnDB::Init(const TransactionDBOptions& /* unused */) {
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// Adcance max_evicted_seq_ no more than 100 times before the cache wraps
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// around.
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INC_STEP_FOR_MAX_EVICTED =
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std::max(COMMIT_CACHE_SIZE / 100, static_cast<size_t>(1));
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snapshot_cache_ = unique_ptr<std::atomic<SequenceNumber>[]>(
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new std::atomic<SequenceNumber>[SNAPSHOT_CACHE_SIZE] {});
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commit_cache_ = unique_ptr<std::atomic<CommitEntry64b>[]>(
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new std::atomic<CommitEntry64b>[COMMIT_CACHE_SIZE] {});
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}
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void WritePreparedTxnDB::AddPrepared(uint64_t seq) {
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ROCKS_LOG_DETAILS(info_log_, "Txn %" PRIu64 " Prepareing", seq);
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assert(seq > max_evicted_seq_);
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if (seq <= max_evicted_seq_) {
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throw std::runtime_error(
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"Added prepare_seq is larger than max_evicted_seq_: " + ToString(seq) +
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" <= " + ToString(max_evicted_seq_.load()));
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}
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WriteLock wl(&prepared_mutex_);
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prepared_txns_.push(seq);
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}
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void WritePreparedTxnDB::AddCommitted(uint64_t prepare_seq, uint64_t commit_seq,
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uint8_t loop_cnt) {
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ROCKS_LOG_DETAILS(info_log_, "Txn %" PRIu64 " Committing with %" PRIu64,
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prepare_seq, commit_seq);
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TEST_SYNC_POINT("WritePreparedTxnDB::AddCommitted:start");
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TEST_SYNC_POINT("WritePreparedTxnDB::AddCommitted:start:pause");
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auto indexed_seq = prepare_seq % COMMIT_CACHE_SIZE;
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CommitEntry64b evicted_64b;
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CommitEntry evicted;
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bool to_be_evicted = GetCommitEntry(indexed_seq, &evicted_64b, &evicted);
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if (LIKELY(to_be_evicted)) {
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assert(evicted.prep_seq != prepare_seq);
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auto prev_max = max_evicted_seq_.load(std::memory_order_acquire);
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ROCKS_LOG_DETAILS(info_log_,
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"Evicting %" PRIu64 ",%" PRIu64 " with max %" PRIu64,
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evicted.prep_seq, evicted.commit_seq, prev_max);
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if (prev_max < evicted.commit_seq) {
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// Inc max in larger steps to avoid frequent updates
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auto max_evicted_seq = evicted.commit_seq + INC_STEP_FOR_MAX_EVICTED;
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AdvanceMaxEvictedSeq(prev_max, max_evicted_seq);
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}
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// After each eviction from commit cache, check if the commit entry should
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// be kept around because it overlaps with a live snapshot.
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CheckAgainstSnapshots(evicted);
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}
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bool succ =
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ExchangeCommitEntry(indexed_seq, evicted_64b, {prepare_seq, commit_seq});
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if (UNLIKELY(!succ)) {
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ROCKS_LOG_ERROR(info_log_,
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"ExchangeCommitEntry failed on [%" PRIu64 "] %" PRIu64
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",%" PRIu64 " retrying...",
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indexed_seq, prepare_seq, commit_seq);
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// A very rare event, in which the commit entry is updated before we do.
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// Here we apply a very simple solution of retrying.
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if (loop_cnt > 100) {
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throw std::runtime_error("Infinite loop in AddCommitted!");
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}
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AddCommitted(prepare_seq, commit_seq, ++loop_cnt);
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return;
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}
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TEST_SYNC_POINT("WritePreparedTxnDB::AddCommitted:end");
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|
TEST_SYNC_POINT("WritePreparedTxnDB::AddCommitted:end:pause");
|
|
}
|
|
|
|
void WritePreparedTxnDB::RemovePrepared(const uint64_t prepare_seq,
|
|
const size_t batch_cnt) {
|
|
WriteLock wl(&prepared_mutex_);
|
|
for (size_t i = 0; i < batch_cnt; i++) {
|
|
prepared_txns_.erase(prepare_seq + i);
|
|
bool was_empty = delayed_prepared_.empty();
|
|
if (!was_empty) {
|
|
delayed_prepared_.erase(prepare_seq + i);
|
|
bool is_empty = delayed_prepared_.empty();
|
|
if (was_empty != is_empty) {
|
|
delayed_prepared_empty_.store(is_empty, std::memory_order_release);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
bool WritePreparedTxnDB::GetCommitEntry(const uint64_t indexed_seq,
|
|
CommitEntry64b* entry_64b,
|
|
CommitEntry* entry) const {
|
|
*entry_64b = commit_cache_[indexed_seq].load(std::memory_order_acquire);
|
|
bool valid = entry_64b->Parse(indexed_seq, entry, FORMAT);
|
|
return valid;
|
|
}
|
|
|
|
bool WritePreparedTxnDB::AddCommitEntry(const uint64_t indexed_seq,
|
|
const CommitEntry& new_entry,
|
|
CommitEntry* evicted_entry) {
|
|
CommitEntry64b new_entry_64b(new_entry, FORMAT);
|
|
CommitEntry64b evicted_entry_64b = commit_cache_[indexed_seq].exchange(
|
|
new_entry_64b, std::memory_order_acq_rel);
|
|
bool valid = evicted_entry_64b.Parse(indexed_seq, evicted_entry, FORMAT);
|
|
return valid;
|
|
}
|
|
|
|
bool WritePreparedTxnDB::ExchangeCommitEntry(const uint64_t indexed_seq,
|
|
CommitEntry64b& expected_entry_64b,
|
|
const CommitEntry& new_entry) {
|
|
auto& atomic_entry = commit_cache_[indexed_seq];
|
|
CommitEntry64b new_entry_64b(new_entry, FORMAT);
|
|
bool succ = atomic_entry.compare_exchange_strong(
|
|
expected_entry_64b, new_entry_64b, std::memory_order_acq_rel,
|
|
std::memory_order_acquire);
|
|
return succ;
|
|
}
|
|
|
|
void WritePreparedTxnDB::AdvanceMaxEvictedSeq(const SequenceNumber& prev_max,
|
|
const SequenceNumber& new_max) {
|
|
ROCKS_LOG_DETAILS(info_log_,
|
|
"AdvanceMaxEvictedSeq overhead %" PRIu64 " => %" PRIu64,
|
|
prev_max, new_max);
|
|
// When max_evicted_seq_ advances, move older entries from prepared_txns_
|
|
// to delayed_prepared_. This guarantees that if a seq is lower than max,
|
|
// then it is not in prepared_txns_ ans save an expensive, synchronized
|
|
// lookup from a shared set. delayed_prepared_ is expected to be empty in
|
|
// normal cases.
|
|
{
|
|
WriteLock wl(&prepared_mutex_);
|
|
while (!prepared_txns_.empty() && prepared_txns_.top() <= new_max) {
|
|
auto to_be_popped = prepared_txns_.top();
|
|
delayed_prepared_.insert(to_be_popped);
|
|
ROCKS_LOG_WARN(info_log_,
|
|
"prepared_mutex_ overhead %" PRIu64 " (prep=%" PRIu64
|
|
" new_max=%" PRIu64 " oldmax=%" PRIu64,
|
|
static_cast<uint64_t>(delayed_prepared_.size()),
|
|
to_be_popped, new_max, prev_max);
|
|
prepared_txns_.pop();
|
|
delayed_prepared_empty_.store(false, std::memory_order_release);
|
|
}
|
|
}
|
|
|
|
// With each change to max_evicted_seq_ fetch the live snapshots behind it.
|
|
// We use max as the version of snapshots to identify how fresh are the
|
|
// snapshot list. This works because the snapshots are between 0 and
|
|
// max, so the larger the max, the more complete they are.
|
|
SequenceNumber new_snapshots_version = new_max;
|
|
std::vector<SequenceNumber> snapshots;
|
|
bool update_snapshots = false;
|
|
if (new_snapshots_version > snapshots_version_) {
|
|
// This is to avoid updating the snapshots_ if it already updated
|
|
// with a more recent vesion by a concrrent thread
|
|
update_snapshots = true;
|
|
// We only care about snapshots lower then max
|
|
snapshots = GetSnapshotListFromDB(new_max);
|
|
}
|
|
if (update_snapshots) {
|
|
UpdateSnapshots(snapshots, new_snapshots_version);
|
|
}
|
|
auto updated_prev_max = prev_max;
|
|
while (updated_prev_max < new_max &&
|
|
!max_evicted_seq_.compare_exchange_weak(updated_prev_max, new_max,
|
|
std::memory_order_acq_rel,
|
|
std::memory_order_relaxed)) {
|
|
};
|
|
}
|
|
|
|
const Snapshot* WritePreparedTxnDB::GetSnapshot() {
|
|
// Note: SmallestUnCommittedSeq must be called before GetSnapshotImpl. Refer
|
|
// to WritePreparedTxn::SetSnapshot for more explanation.
|
|
auto min_uncommitted = WritePreparedTxnDB::SmallestUnCommittedSeq();
|
|
const bool FOR_WW_CONFLICT_CHECK = true;
|
|
SnapshotImpl* snap_impl = db_impl_->GetSnapshotImpl(!FOR_WW_CONFLICT_CHECK);
|
|
assert(snap_impl);
|
|
EnhanceSnapshot(snap_impl, min_uncommitted);
|
|
return snap_impl;
|
|
}
|
|
|
|
const std::vector<SequenceNumber> WritePreparedTxnDB::GetSnapshotListFromDB(
|
|
SequenceNumber max) {
|
|
ROCKS_LOG_DETAILS(info_log_, "GetSnapshotListFromDB with max %" PRIu64, max);
|
|
InstrumentedMutex(db_impl_->mutex());
|
|
return db_impl_->snapshots().GetAll(nullptr, max);
|
|
}
|
|
|
|
void WritePreparedTxnDB::ReleaseSnapshot(const Snapshot* snapshot) {
|
|
auto snap_seq = snapshot->GetSequenceNumber();
|
|
ReleaseSnapshotInternal(snap_seq);
|
|
db_impl_->ReleaseSnapshot(snapshot);
|
|
}
|
|
|
|
void WritePreparedTxnDB::ReleaseSnapshotInternal(
|
|
const SequenceNumber snap_seq) {
|
|
// relax is enough since max increases monotonically, i.e., if snap_seq <
|
|
// old_max => snap_seq < new_max as well.
|
|
if (snap_seq < max_evicted_seq_.load(std::memory_order_relaxed)) {
|
|
// Then this is a rare case that transaction did not finish before max
|
|
// advances. It is expected for a few read-only backup snapshots. For such
|
|
// snapshots we might have kept around a couple of entries in the
|
|
// old_commit_map_. Check and do garbage collection if that is the case.
|
|
bool need_gc = false;
|
|
{
|
|
WPRecordTick(TXN_OLD_COMMIT_MAP_MUTEX_OVERHEAD);
|
|
ROCKS_LOG_WARN(info_log_, "old_commit_map_mutex_ overhead");
|
|
ReadLock rl(&old_commit_map_mutex_);
|
|
auto prep_set_entry = old_commit_map_.find(snap_seq);
|
|
need_gc = prep_set_entry != old_commit_map_.end();
|
|
}
|
|
if (need_gc) {
|
|
WPRecordTick(TXN_OLD_COMMIT_MAP_MUTEX_OVERHEAD);
|
|
ROCKS_LOG_WARN(info_log_, "old_commit_map_mutex_ overhead");
|
|
WriteLock wl(&old_commit_map_mutex_);
|
|
old_commit_map_.erase(snap_seq);
|
|
old_commit_map_empty_.store(old_commit_map_.empty(),
|
|
std::memory_order_release);
|
|
}
|
|
}
|
|
}
|
|
|
|
void WritePreparedTxnDB::UpdateSnapshots(
|
|
const std::vector<SequenceNumber>& snapshots,
|
|
const SequenceNumber& version) {
|
|
ROCKS_LOG_DETAILS(info_log_, "UpdateSnapshots with version %" PRIu64,
|
|
version);
|
|
TEST_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:p:start");
|
|
TEST_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:s:start");
|
|
#ifndef NDEBUG
|
|
size_t sync_i = 0;
|
|
#endif
|
|
ROCKS_LOG_DETAILS(info_log_, "snapshots_mutex_ overhead");
|
|
WriteLock wl(&snapshots_mutex_);
|
|
snapshots_version_ = version;
|
|
// We update the list concurrently with the readers.
|
|
// Both new and old lists are sorted and the new list is subset of the
|
|
// previous list plus some new items. Thus if a snapshot repeats in
|
|
// both new and old lists, it will appear upper in the new list. So if
|
|
// we simply insert the new snapshots in order, if an overwritten item
|
|
// is still valid in the new list is either written to the same place in
|
|
// the array or it is written in a higher palce before it gets
|
|
// overwritten by another item. This guarantess a reader that reads the
|
|
// list bottom-up will eventaully see a snapshot that repeats in the
|
|
// update, either before it gets overwritten by the writer or
|
|
// afterwards.
|
|
size_t i = 0;
|
|
auto it = snapshots.begin();
|
|
for (; it != snapshots.end() && i < SNAPSHOT_CACHE_SIZE; it++, i++) {
|
|
snapshot_cache_[i].store(*it, std::memory_order_release);
|
|
TEST_IDX_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:p:", ++sync_i);
|
|
TEST_IDX_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:s:", sync_i);
|
|
}
|
|
#ifndef NDEBUG
|
|
// Release the remaining sync points since they are useless given that the
|
|
// reader would also use lock to access snapshots
|
|
for (++sync_i; sync_i <= 10; ++sync_i) {
|
|
TEST_IDX_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:p:", sync_i);
|
|
TEST_IDX_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:s:", sync_i);
|
|
}
|
|
#endif
|
|
snapshots_.clear();
|
|
for (; it != snapshots.end(); it++) {
|
|
// Insert them to a vector that is less efficient to access
|
|
// concurrently
|
|
snapshots_.push_back(*it);
|
|
}
|
|
// Update the size at the end. Otherwise a parallel reader might read
|
|
// items that are not set yet.
|
|
snapshots_total_.store(snapshots.size(), std::memory_order_release);
|
|
TEST_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:p:end");
|
|
TEST_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:s:end");
|
|
}
|
|
|
|
void WritePreparedTxnDB::CheckAgainstSnapshots(const CommitEntry& evicted) {
|
|
TEST_SYNC_POINT("WritePreparedTxnDB::CheckAgainstSnapshots:p:start");
|
|
TEST_SYNC_POINT("WritePreparedTxnDB::CheckAgainstSnapshots:s:start");
|
|
#ifndef NDEBUG
|
|
size_t sync_i = 0;
|
|
#endif
|
|
// First check the snapshot cache that is efficient for concurrent access
|
|
auto cnt = snapshots_total_.load(std::memory_order_acquire);
|
|
// The list might get updated concurrently as we are reading from it. The
|
|
// reader should be able to read all the snapshots that are still valid
|
|
// after the update. Since the survived snapshots are written in a higher
|
|
// place before gets overwritten the reader that reads bottom-up will
|
|
// eventully see it.
|
|
const bool next_is_larger = true;
|
|
SequenceNumber snapshot_seq = kMaxSequenceNumber;
|
|
size_t ip1 = std::min(cnt, SNAPSHOT_CACHE_SIZE);
|
|
for (; 0 < ip1; ip1--) {
|
|
snapshot_seq = snapshot_cache_[ip1 - 1].load(std::memory_order_acquire);
|
|
TEST_IDX_SYNC_POINT("WritePreparedTxnDB::CheckAgainstSnapshots:p:",
|
|
++sync_i);
|
|
TEST_IDX_SYNC_POINT("WritePreparedTxnDB::CheckAgainstSnapshots:s:", sync_i);
|
|
if (!MaybeUpdateOldCommitMap(evicted.prep_seq, evicted.commit_seq,
|
|
snapshot_seq, !next_is_larger)) {
|
|
break;
|
|
}
|
|
}
|
|
#ifndef NDEBUG
|
|
// Release the remaining sync points before accquiring the lock
|
|
for (++sync_i; sync_i <= 10; ++sync_i) {
|
|
TEST_IDX_SYNC_POINT("WritePreparedTxnDB::CheckAgainstSnapshots:p:", sync_i);
|
|
TEST_IDX_SYNC_POINT("WritePreparedTxnDB::CheckAgainstSnapshots:s:", sync_i);
|
|
}
|
|
#endif
|
|
TEST_SYNC_POINT("WritePreparedTxnDB::CheckAgainstSnapshots:p:end");
|
|
TEST_SYNC_POINT("WritePreparedTxnDB::CheckAgainstSnapshots:s:end");
|
|
if (UNLIKELY(SNAPSHOT_CACHE_SIZE < cnt && ip1 == SNAPSHOT_CACHE_SIZE &&
|
|
snapshot_seq < evicted.prep_seq)) {
|
|
// Then access the less efficient list of snapshots_
|
|
WPRecordTick(TXN_SNAPSHOT_MUTEX_OVERHEAD);
|
|
ROCKS_LOG_WARN(info_log_, "snapshots_mutex_ overhead");
|
|
ReadLock rl(&snapshots_mutex_);
|
|
// Items could have moved from the snapshots_ to snapshot_cache_ before
|
|
// accquiring the lock. To make sure that we do not miss a valid snapshot,
|
|
// read snapshot_cache_ again while holding the lock.
|
|
for (size_t i = 0; i < SNAPSHOT_CACHE_SIZE; i++) {
|
|
snapshot_seq = snapshot_cache_[i].load(std::memory_order_acquire);
|
|
if (!MaybeUpdateOldCommitMap(evicted.prep_seq, evicted.commit_seq,
|
|
snapshot_seq, next_is_larger)) {
|
|
break;
|
|
}
|
|
}
|
|
for (auto snapshot_seq_2 : snapshots_) {
|
|
if (!MaybeUpdateOldCommitMap(evicted.prep_seq, evicted.commit_seq,
|
|
snapshot_seq_2, next_is_larger)) {
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
bool WritePreparedTxnDB::MaybeUpdateOldCommitMap(
|
|
const uint64_t& prep_seq, const uint64_t& commit_seq,
|
|
const uint64_t& snapshot_seq, const bool next_is_larger = true) {
|
|
// If we do not store an entry in old_commit_map_ we assume it is committed in
|
|
// all snapshots. If commit_seq <= snapshot_seq, it is considered already in
|
|
// the snapshot so we need not to keep the entry around for this snapshot.
|
|
if (commit_seq <= snapshot_seq) {
|
|
// continue the search if the next snapshot could be smaller than commit_seq
|
|
return !next_is_larger;
|
|
}
|
|
// then snapshot_seq < commit_seq
|
|
if (prep_seq <= snapshot_seq) { // overlapping range
|
|
WPRecordTick(TXN_OLD_COMMIT_MAP_MUTEX_OVERHEAD);
|
|
ROCKS_LOG_WARN(info_log_, "old_commit_map_mutex_ overhead");
|
|
WriteLock wl(&old_commit_map_mutex_);
|
|
old_commit_map_empty_.store(false, std::memory_order_release);
|
|
auto& vec = old_commit_map_[snapshot_seq];
|
|
vec.insert(std::upper_bound(vec.begin(), vec.end(), prep_seq), prep_seq);
|
|
// We need to store it once for each overlapping snapshot. Returning true to
|
|
// continue the search if there is more overlapping snapshot.
|
|
return true;
|
|
}
|
|
// continue the search if the next snapshot could be larger than prep_seq
|
|
return next_is_larger;
|
|
}
|
|
|
|
WritePreparedTxnDB::~WritePreparedTxnDB() {
|
|
// At this point there could be running compaction/flush holding a
|
|
// SnapshotChecker, which holds a pointer back to WritePreparedTxnDB.
|
|
// Make sure those jobs finished before destructing WritePreparedTxnDB.
|
|
db_impl_->CancelAllBackgroundWork(true /*wait*/);
|
|
}
|
|
|
|
void SubBatchCounter::InitWithComp(const uint32_t cf) {
|
|
auto cmp = comparators_[cf];
|
|
keys_[cf] = CFKeys(SetComparator(cmp));
|
|
}
|
|
|
|
void SubBatchCounter::AddKey(const uint32_t cf, const Slice& key) {
|
|
CFKeys& cf_keys = keys_[cf];
|
|
if (cf_keys.size() == 0) { // just inserted
|
|
InitWithComp(cf);
|
|
}
|
|
auto it = cf_keys.insert(key);
|
|
if (it.second == false) { // second is false if a element already existed.
|
|
batches_++;
|
|
keys_.clear();
|
|
InitWithComp(cf);
|
|
keys_[cf].insert(key);
|
|
}
|
|
}
|
|
|
|
} // namespace rocksdb
|
|
#endif // ROCKSDB_LITE
|
|
|