memgraph/src/transactions/engine_worker.hpp

#pragma once

#include <atomic>
#include <mutex>

#include "communication/rpc/client_pool.hpp"
#include "data_structures/concurrent/concurrent_map.hpp"
#include "io/network/endpoint.hpp"
#include "transactions/commit_log.hpp"
#include "transactions/engine.hpp"
#include "transactions/transaction.hpp"

namespace tx {

/** Distributed worker transaction engine. Connects to a MasterEngine (single
 * source of truth) to obtain transactional info. Caches most info locally. Can
 * begin/advance/end transactions on the master. */
class WorkerEngine : public Engine {
 public:
  WorkerEngine(const io::network::Endpoint &endpoint);
  ~WorkerEngine();

  Transaction *Begin() override;
  command_id_t Advance(transaction_id_t id) override;
  void Commit(const Transaction &t) override;
  void Abort(const Transaction &t) override;
  CommitLog::Info Info(transaction_id_t tid) const override;
  Snapshot GlobalGcSnapshot() override;
  Snapshot GlobalActiveTransactions() override;
  bool GlobalIsActive(transaction_id_t tid) const override;
  tx::transaction_id_t LocalLast() const override;
  void LocalForEachActiveTransaction(
      std::function<void(Transaction &)> f) override;
  tx::Transaction *RunningTransaction(tx::transaction_id_t tx_id) override;

 private:
  // Local caches.
  ConcurrentMap<transaction_id_t, Transaction *> active_;
  std::atomic<transaction_id_t> local_last_{0};
  // Mutable because just getting info can cause a cache fill.
  mutable CommitLog clog_;

  // Communication to the transactional master.
  mutable communication::rpc::ClientPool rpc_client_pool_;
};

}  // namespace tx