Separate distributed from single node transaction engine

Reviewers: teon.banek, msantl

Reviewed By: teon.banek

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D1637

src/CMakeLists.txt

@@ -153,7 +153,7 @@ set(mg_distributed_sources
     storage/distributed/vertex_accessor.cpp
     storage/locking/record_lock.cpp
     memgraph_init.cpp
-    transactions/single_node/engine_single_node.cpp
+    transactions/distributed/engine_single_node.cpp
 )
 
 # -----------------------------------------------------------------------------

src/transactions/distributed/engine_master.hpp

@@ -5,7 +5,7 @@
 #include "communication/rpc/server.hpp"
 #include "distributed/coordination.hpp"
 #include "transactions/distributed/engine_distributed.hpp"
-#include "transactions/single_node/engine_single_node.hpp"
+#include "transactions/distributed/engine_single_node.hpp"
 
 namespace tx {
 

src/transactions/distributed/engine_single_node.cpp

@@ -0,0 +1,133 @@
+#include "transactions/distributed/engine_single_node.hpp"
+
+#include <limits>
+#include <mutex>
+
+#include "glog/logging.h"
+
+#include "durability/distributed/state_delta.hpp"
+
+namespace tx {
+
+EngineSingleNode::EngineSingleNode(durability::WriteAheadLog *wal)
+    : wal_(wal) {}
+
+Transaction *EngineSingleNode::Begin() {
+  VLOG(11) << "[Tx] Starting transaction " << counter_ + 1;
+  std::lock_guard<utils::SpinLock> guard(lock_);
+
+  TransactionId id{++counter_};
+  auto t = CreateTransaction(id, active_);
+  active_.insert(id);
+  store_.emplace(id, t);
+  if (wal_) {
+    wal_->Emplace(database::StateDelta::TxBegin(id));
+  }
+  return t;
+}
+
+CommandId EngineSingleNode::Advance(TransactionId id) {
+  std::lock_guard<utils::SpinLock> guard(lock_);
+
+  auto it = store_.find(id);
+  DCHECK(it != store_.end())
+      << "Transaction::advance on non-existing transaction";
+
+  Transaction *t = it->second.get();
+  return AdvanceCommand(t);
+}
+
+CommandId EngineSingleNode::UpdateCommand(TransactionId id) {
+  std::lock_guard<utils::SpinLock> guard(lock_);
+  auto it = store_.find(id);
+  DCHECK(it != store_.end())
+      << "Transaction::advance on non-existing transaction";
+  return it->second->cid();
+}
+
+void EngineSingleNode::Commit(const Transaction &t) {
+  VLOG(11) << "[Tx] Commiting transaction " << t.id_;
+  std::lock_guard<utils::SpinLock> guard(lock_);
+  clog_.set_committed(t.id_);
+  active_.remove(t.id_);
+  if (wal_) {
+    wal_->Emplace(database::StateDelta::TxCommit(t.id_));
+  }
+  store_.erase(store_.find(t.id_));
+}
+
+void EngineSingleNode::Abort(const Transaction &t) {
+  VLOG(11) << "[Tx] Aborting transaction " << t.id_;
+  std::lock_guard<utils::SpinLock> guard(lock_);
+  clog_.set_aborted(t.id_);
+  active_.remove(t.id_);
+  if (wal_) {
+    wal_->Emplace(database::StateDelta::TxAbort(t.id_));
+  }
+  store_.erase(store_.find(t.id_));
+}
+
+CommitLog::Info EngineSingleNode::Info(TransactionId tx) const {
+  return clog_.fetch_info(tx);
+}
+
+Snapshot EngineSingleNode::GlobalGcSnapshot() {
+  std::lock_guard<utils::SpinLock> guard(lock_);
+
+  // No active transactions.
+  if (active_.size() == 0) {
+    auto snapshot_copy = active_;
+    snapshot_copy.insert(counter_ + 1);
+    return snapshot_copy;
+  }
+
+  // There are active transactions.
+  auto snapshot_copy = store_.find(active_.front())->second->snapshot();
+  snapshot_copy.insert(active_.front());
+  return snapshot_copy;
+}
+
+Snapshot EngineSingleNode::GlobalActiveTransactions() {
+  std::lock_guard<utils::SpinLock> guard(lock_);
+  Snapshot active_transactions = active_;
+  return active_transactions;
+}
+
+TransactionId EngineSingleNode::LocalLast() const {
+  std::lock_guard<utils::SpinLock> guard(lock_);
+  return counter_;
+}
+
+TransactionId EngineSingleNode::GlobalLast() const { return LocalLast(); }
+
+TransactionId EngineSingleNode::LocalOldestActive() const {
+  std::lock_guard<utils::SpinLock> guard(lock_);
+  return active_.empty() ? counter_ + 1 : active_.front();
+}
+
+void EngineSingleNode::GarbageCollectCommitLog(TransactionId tx_id) {
+  clog_.garbage_collect_older(tx_id);
+}
+
+void EngineSingleNode::LocalForEachActiveTransaction(
+    std::function<void(Transaction &)> f) {
+  std::lock_guard<utils::SpinLock> guard(lock_);
+  for (auto transaction : active_) {
+    f(*store_.find(transaction)->second);
+  }
+}
+
+Transaction *EngineSingleNode::RunningTransaction(TransactionId tx_id) {
+  std::lock_guard<utils::SpinLock> guard(lock_);
+  auto found = store_.find(tx_id);
+  CHECK(found != store_.end())
+      << "Can't return snapshot for an inactive transaction";
+  return found->second.get();
+}
+
+void EngineSingleNode::EnsureNextIdGreater(TransactionId tx_id) {
+  std::lock_guard<utils::SpinLock> guard(lock_);
+  counter_ = std::max(tx_id, counter_);
+}
+
+}  // namespace tx

src/transactions/distributed/engine_single_node.hpp

@@ -0,0 +1,56 @@
+/// @file
+
+#pragma once
+
+#include <atomic>
+#include <experimental/optional>
+#include <unordered_map>
+
+#include "durability/distributed/wal.hpp"
+#include "transactions/commit_log.hpp"
+#include "transactions/engine.hpp"
+#include "transactions/transaction.hpp"
+#include "utils/thread/sync.hpp"
+
+namespace tx {
+
+/// Single-node deployment transaction engine. Has complete functionality.
+class EngineSingleNode final : public Engine {
+ public:
+  /// @param wal - Optional. If present, the Engine will write tx
+  /// Begin/Commit/Abort atomically (while under lock).
+  explicit EngineSingleNode(durability::WriteAheadLog *wal = nullptr);
+
+  EngineSingleNode(const EngineSingleNode &) = delete;
+  EngineSingleNode(EngineSingleNode &&) = delete;
+  EngineSingleNode &operator=(const EngineSingleNode &) = delete;
+  EngineSingleNode &operator=(EngineSingleNode &&) = delete;
+
+  Transaction *Begin() override;
+  CommandId Advance(TransactionId id) override;
+  CommandId UpdateCommand(TransactionId id) override;
+  void Commit(const Transaction &t) override;
+  void Abort(const Transaction &t) override;
+  CommitLog::Info Info(TransactionId tx) const override;
+  Snapshot GlobalGcSnapshot() override;
+  Snapshot GlobalActiveTransactions() override;
+  TransactionId GlobalLast() const override;
+  TransactionId LocalLast() const override;
+  TransactionId LocalOldestActive() const override;
+  void LocalForEachActiveTransaction(
+      std::function<void(Transaction &)> f) override;
+  Transaction *RunningTransaction(TransactionId tx_id) override;
+  void EnsureNextIdGreater(TransactionId tx_id) override;
+  void GarbageCollectCommitLog(TransactionId tx_id) override;
+
+ private:
+  TransactionId counter_{0};
+  CommitLog clog_;
+  std::unordered_map<TransactionId, std::unique_ptr<Transaction>> store_;
+  Snapshot active_;
+  mutable utils::SpinLock lock_;
+  // Optional. If present, the Engine will write tx Begin/Commit/Abort
+  // atomically (while under lock).
+  durability::WriteAheadLog *wal_{nullptr};
+};
+}  // namespace tx

src/transactions/single_node/engine_single_node.cpp

@@ -5,13 +5,7 @@
 
 #include "glog/logging.h"
 
-// TODO: THIS IS A HACK!
-#ifdef MG_SINGLE_NODE
 #include "durability/single_node/state_delta.hpp"
-#endif
-#ifdef MG_DISTRIBUTED
-#include "durability/distributed/state_delta.hpp"
-#endif
 
 namespace tx {
 

src/transactions/single_node/engine_single_node.hpp

@@ -6,14 +6,7 @@
 #include <experimental/optional>
 #include <unordered_map>
 
-// TODO: THIS IS A HACK!
-#ifdef MG_SINGLE_NODE
 #include "durability/single_node/wal.hpp"
-#endif
-#ifdef MG_DISTRIBUTED
-#include "durability/distributed/wal.hpp"
-#endif
-
 #include "transactions/commit_log.hpp"
 #include "transactions/engine.hpp"
 #include "transactions/transaction.hpp"

tests/unit/distributed_serialization.cpp

@@ -10,8 +10,7 @@
 #include "storage/distributed/edge.hpp"
 #include "storage/distributed/serialization.hpp"
 #include "storage/distributed/vertex.hpp"
-// TODO: THIS SHOULD BE CHANGED!
-#include "transactions/single_node/engine_single_node.hpp"
+#include "transactions/distributed/engine_single_node.hpp"
 
 using namespace storage;