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Code: Select all

public Database()
{
	_conn = new MySqlConnection()
	{
		LocalFailover = true,
		ConnectionString = GetConnectionString("ConnString"),
	};
	_conn.ConnectionLost += _conn_ConnectionLost;
}

private int errc = 0;

private void _conn_ConnectionLost(object sender, ConnectionLostEventArgs e)
{
	if (errc++ > _maxretry)
	{
		e.RetryMode = RetryMode.Raise;
		return;
	}
	if (e.Cause == ConnectionLostCause.Execute)
	{
		if (e.Context == ConnectionLostContext.None)
			e.RetryMode = RetryMode.Reexecute;
		else
			e.RetryMode = RetryMode.Raise;
	} else {
		e.RetryMode = RetryMode.Raise;
	}
}

Code: Select all

private void _conn_StateChange(object sender, StateChangeEventArgs e)
{
	if (e.CurrentState.HasFlag(ConnectionState.Open)) errc = 0;
}

Code: Select all

private string[] _servers;
const int _maxretry = 4; //Retry per server - dotconnect tries 2 times itself
private BackgroundWorker _bgw = new BackgroundWorker() { WorkerSupportsCancellation = true };

public Database()
{
	_conn = new MySqlConnection()
	{
		LocalFailover = true,
		ConnectionString = GetConnectionString("ConnString"),
		ConnectionTimeout = 3
	};
	_servers = _conn.Host.Replace("(", "").Replace(")", "").Split(',');
	if (_servers.Length == 0) throw new Exception("Invalid connection string");
	_conn.Host = _servers[0];
	_conn.ConnectionLost += _conn_ConnectionLost;
	_bgw.DoWork += _bgw_DoWork;
	_bgw.RunWorkerAsync();
}

private void _bgw_DoWork(object sender, DoWorkEventArgs e)
{
	while (!_bgw.CancellationPending)
	{
		if (DateTime.UtcNow.Subtract(_lastError).TotalSeconds > 10 && errc > 0) errc = 0;
		System.Threading.Thread.Sleep(500);
	}
}

private int errc = 0;
private DateTime _lastError = DateTime.UtcNow;

private void _conn_ConnectionLost(object sender, ConnectionLostEventArgs e)
{
	_lastError = DateTime.UtcNow;
	if (
		errc > (_servers.Length * _maxretry) ||
		e.Context == ConnectionLostContext.HasPrepared ||
		e.Context == ConnectionLostContext.InTransaction
	)
	{
		errc = 0;
		e.RetryMode = RetryMode.Raise;
	}
	else
	{
		_conn.Close();
		_conn.Host = _servers[errc % _servers.Length]; //Use next server
		e.RetryMode = RetryMode.Reexecute;
	}
	errc++; //MUST be done last, otherwise backgroundworker might reset it
}

Code: Select all

private T _read<T>(Func<T> execute)
        {
            Exception lastex = null;
            for (int i = 0; i < 4; i++)
            {
                try
                {
                    return execute();
                }
                catch (Devart.Data.Linq.LinqCommandExecutionException ex0) when (ex0.InnerException is MySqlException)
                {
                    lastex = ex0;
                    System.Threading.Thread.Sleep(50);
                    continue;
                }
                catch (Exception ex)
                {
                    throw ex;
                }
            }
            throw lastex;
        }
        
        public void ExampleCall()
        {
        	var data = _read(() => MyContext.Table.Where(x => x.Id = 1));
        }