MySQL.Data/src/Framework/netstandard2_0/MySqlPromotableTransaction.cs

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using System;
using System.Transactions;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Threading;
using System.Threading.Tasks;

namespace MySql.Data.MySqlClient
{
  /// <summary>
  /// Represents a single(not nested) TransactionScope
  /// </summary>
  internal class MySqlTransactionScope
  {
    public MySqlConnection connection;
    public Transaction baseTransaction;
    public MySqlTransaction simpleTransaction;
    public int rollbackThreadId;

    public MySqlTransactionScope(MySqlConnection con, Transaction trans,
        MySqlTransaction simpleTransaction)
    {
      connection = con;
      baseTransaction = trans;
      this.simpleTransaction = simpleTransaction;
    }

    public async Task RollbackAsync(SinglePhaseEnlistment singlePhaseEnlistment, bool execAsync)
    {
      // prevent commands in main thread to run concurrently
      Driver driver = connection.driver;

      SemaphoreSlim semaphoreSlim = new(1);
      semaphoreSlim.Wait();

      rollbackThreadId = Thread.CurrentThread.ManagedThreadId;
      while (connection.Reader != null)
      {
        // wait for reader to finish. Maybe we should not wait 
        // forever and cancel it after some time?
        System.Threading.Thread.Sleep(100);
      }
      simpleTransaction.Rollback();
      singlePhaseEnlistment.Aborted();
      DriverTransactionManager.RemoveDriverInTransaction(baseTransaction);

      driver.currentTransaction = null;

      if (connection.State == ConnectionState.Closed)
        await connection.CloseFullyAsync(execAsync).ConfigureAwait(false);
      rollbackThreadId = 0;

      semaphoreSlim.Release();
    }

    public async Task SinglePhaseCommitAsync(SinglePhaseEnlistment singlePhaseEnlistment, bool execAsync)
    {
      simpleTransaction.Commit();
      singlePhaseEnlistment.Committed();
      DriverTransactionManager.RemoveDriverInTransaction(baseTransaction);
      connection.driver.currentTransaction = null;

      if (connection.State == ConnectionState.Closed)
        await connection.CloseFullyAsync(execAsync).ConfigureAwait(false);
    }

    public void ChangeConnection(MySqlConnection connection)
    {
      this.connection = connection;
      this.simpleTransaction.Connection = connection;
    }
  }

  internal sealed class MySqlPromotableTransaction : IPromotableSinglePhaseNotification, ITransactionPromoter
  {
    // Per-thread stack to manage nested transaction scopes
    [ThreadStatic]
    static Stack<MySqlTransactionScope> globalScopeStack;

    MySqlConnection connection;
    Transaction baseTransaction;
    Stack<MySqlTransactionScope> scopeStack;


    public MySqlPromotableTransaction(MySqlConnection connection, Transaction baseTransaction)
    {
      this.connection = connection;
      this.baseTransaction = baseTransaction;
    }

    public Transaction BaseTransaction
    {
      get
      {
        if (scopeStack.Count > 0)
          return scopeStack.Peek().baseTransaction;
        else
          return null;
      }
    }

    public MySqlConnection Connection
    {
      get
      {
        return connection;
      }
      set
      {
        connection = value;
        if (scopeStack.Count > 0)
          scopeStack.Peek().ChangeConnection(value);
      }
    }

    public bool InRollback
    {
      get
      {
        if (scopeStack.Count > 0)
        {
          MySqlTransactionScope currentScope = scopeStack.Peek();
          if (currentScope.rollbackThreadId == Thread.CurrentThread.ManagedThreadId)
          {
            return true;
          }
        }
        return false;
      }
    }
    void IPromotableSinglePhaseNotification.Initialize()
    {
      string valueName = Enum.GetName(
      typeof(System.Transactions.IsolationLevel), baseTransaction.IsolationLevel);
      System.Data.IsolationLevel dataLevel = (System.Data.IsolationLevel)Enum.Parse(
           typeof(System.Data.IsolationLevel), valueName);
      MySqlTransaction simpleTransaction = connection.BeginTransaction(dataLevel, "SESSION");

      // We need to save the per-thread scope stack locally.
      // We cannot always use thread static variable in rollback: when scope
      // times out, rollback is issued by another thread.
      if (globalScopeStack == null)
      {
        globalScopeStack = new Stack<MySqlTransactionScope>();
      }

      scopeStack = globalScopeStack;
      scopeStack.Push(new MySqlTransactionScope(connection, baseTransaction,
         simpleTransaction));
    }

    void IPromotableSinglePhaseNotification.Rollback(SinglePhaseEnlistment singlePhaseEnlistment)
    {

      MySqlTransactionScope current = scopeStack.Peek();
      current.RollbackAsync(singlePhaseEnlistment, false).GetAwaiter().GetResult();
      scopeStack.Pop();
    }

    void IPromotableSinglePhaseNotification.SinglePhaseCommit(SinglePhaseEnlistment singlePhaseEnlistment)
    {
      scopeStack.Pop().SinglePhaseCommitAsync(singlePhaseEnlistment, false).GetAwaiter().GetResult();
    }

    byte[] ITransactionPromoter.Promote()
    {
      throw new NotSupportedException();
    }
  }

  internal class DriverTransactionManager
  {
    private static Hashtable driversInUse = new Hashtable();

    public static Driver GetDriverInTransaction(Transaction transaction)
    {
      lock (driversInUse.SyncRoot)
      {
        Driver d = (Driver)driversInUse[transaction.GetHashCode()];
        return d;
      }
    }

    public static void SetDriverInTransaction(Driver driver)
    {
      lock (driversInUse.SyncRoot)
      {
        driversInUse[driver.currentTransaction.BaseTransaction.GetHashCode()] = driver;
      }
    }

    public static void RemoveDriverInTransaction(Transaction transaction)
    {
      lock (driversInUse.SyncRoot)
      {
        driversInUse.Remove(transaction.GetHashCode());
      }
    }
  }
}