async Task <T> ISqlCommandExecutor.ExecuteQueryAsync <T>(
IActivityMonitor monitor,
SqlConnection connection,
SqlTransaction transaction,
SqlCommand cmd,
Func <SqlCommand, CancellationToken, Task <T> > innerExecutor,
CancellationToken cancellationToken)
{
Debug.Assert(connection != null && connection.State == System.Data.ConnectionState.Open);
DateTime start = DateTime.UtcNow;
int retryCount = 0;
List <SqlDetailedException> previous = null;
T result;
for (; ;)
{
SqlDetailedException e = null;
try
{
cmd.Connection = connection;
cmd.Transaction = transaction;
OnCommandExecuting(cmd, retryCount);
result = await innerExecutor(cmd, cancellationToken).ConfigureAwait(false);
break;
}
catch (IOException ex)
{
e = SqlDetailedException.Create(cmd, ex, retryCount++);
}
catch (SqlException ex)
{
e = SqlDetailedException.Create(cmd, ex, retryCount++);
}
catch (Exception ex)
{
Monitor.Fatal(ex);
throw;
}
Debug.Assert(e != null);
Monitor.Error(e);
if (previous == null)
{
previous = new List <SqlDetailedException>();
}
TimeSpan retry = OnCommandError(cmd, connection, e, previous, start);
if (retry.Ticks < 0 ||
retry == TimeSpan.MaxValue ||
previous.Count > 1000)
{
throw e;
}
previous.Add(e);
await Task.Delay(retry).ConfigureAwait(false);
}
OnCommandExecuted(cmd, retryCount, result);
return(result);
}
/// <summary>
/// Extension point called after a command failed.
/// At this level, this method does nothing and returns <see cref="TimeSpan.MaxValue"/>: no retry will be done.
/// <para>
/// Note that any negative TimeSpan as well as TimeSpan.MaxValue will result in
/// the <see cref="SqlDetailedException"/> being thrown.
/// </para>
/// </summary>
/// <param name="cmd">The executing command.</param>
/// <param name="c">The connection.</param>
/// <param name="ex">The exception caught and wrapped in a <see cref="SqlDetailedException"/>.</param>
/// <param name="previous">Previous errors when retries have been made. Empty on the first error.</param>
/// <param name="firstExecutionTimeUtc">The Utc time of the first try.</param>
/// <returns>The time span to retry. A negative time span or <see cref="TimeSpan.MaxValue"/> to skip retry.</returns>
protected virtual TimeSpan OnCommandError(
SqlCommand cmd,
SqlConnection c,
SqlDetailedException ex,
IReadOnlyList <SqlDetailedException> previous,
DateTime firstExecutionTimeUtc) => TimeSpan.MaxValue;
