迭代查询结果时发生异常...取消了任务

Question

当创建租户时执行我的 ABP 生成的 MyAppTenantDatabaseMigrationHandler 中的以下代码行时：

private async Task MigrateAndSeedForTenantAsync(
    Guid tenantId,
    string adminEmail,
    string adminPassword)
{
  try
  {
    using (_currentTenant.Change(tenantId))
    {

      // Create database tables if needed
      using (var uow = _unitOfWorkManager.Begin(requiresNew: true, isTransactional: false, timeout: TimeSpan.FromMinutes(10).TotalMilliseconds.To<Int32>()))
      {
        var tenantConfiguration = await _tenantStore.FindAsync(tenantId); // <-- This line

        //  code continues…
      }
    }
  }
}

我的日志文件中出现以下异常：

2021-10-25 13:45:57.644 -05:00 [INF] Executed DbCommand (93,812ms) [Parameters=[@__ef_filter__p_0='?' (DbType = Boolean), @__id_0='?' (DbType = Guid)], CommandType='"Text"', CommandTimeout='600']
SELECT [t].[Id], [t].[ActivationEndDate], [t].[ActivationState], [t].[ConcurrencyStamp], [t].[CreationTime], [t].[CreatorId], [t].[DeleterId], [t].[DeletionTime], [t].[EditionEndDateUtc], [t].[EditionId], [t].[ExtraProperties], [t].[IsDeleted], [t].[LastModificationTime], [t].[LastModifierId], [t].[Name]
FROM (
    SELECT TOP(1) [s].[Id], [s].[ActivationEndDate], [s].[ActivationState], [s].[ConcurrencyStamp], [s].[CreationTime], [s].[CreatorId], [s].[DeleterId], [s].[DeletionTime], [s].[EditionEndDateUtc], [s].[EditionId], [s].[ExtraProperties], [s].[IsDeleted], [s].[LastModificationTime], [s].[LastModifierId], [s].[Name]
    FROM [SaasTenants] AS [s]
    WHERE ((@__ef_filter__p_0 = CAST(1 AS bit)) OR ([s].[IsDeleted] <> CAST(1 AS bit))) AND ([s].[Id] = @__id_0)
    ORDER BY [s].[Id]
) AS [t]
ORDER BY [t].[Id]
2021-10-25 13:45:57.651 -05:00 [ERR] An exception occurred while iterating over the results of a query for context type 'Volo.Saas.EntityFrameworkCore.SaasDbContext'.
System.Threading.Tasks.TaskCanceledException: A task was canceled.
   at Microsoft.EntityFrameworkCore.Query.Internal.BufferedDataReader.BufferedDataRecord.InitializeAsync(DbDataReader reader, IReadOnlyList`1 columns, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.BufferedDataReader.InitializeAsync(IReadOnlyList`1 columns, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.BufferedDataReader.InitializeAsync(IReadOnlyList`1 columns, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.SplitQueryingEnumerable`1.AsyncEnumerator.InitializeReaderAsync(DbContext _, Boolean result, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.SplitQueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()

这是怎么回事？如您所见，我增加了超时时间，因为在此之前我遇到了超时异常。谢谢。

PS：看了一圈，根据这个post：EF Core: An exception occurred in the database while iterating the results of a query，我认为可能与MARS有关。因此，我已将 ;MultipleActiveResultSets=true 添加到我的连接字符串中。不幸的是，这没有效果。

异常发生前有很长的延迟 - 大约一分钟。

为清楚起见，这里是显示产生异常（断点）的行的屏幕截图

重现的具体步骤：

使用 ABP Suite 创建一个新项目
在[Project]TenantDatabaseMigrationHandler.cs文件的第98行设置断点(var tenantConfiguration = await _tenantStore.FindAsync(tenantId);).
在同一文件的第 126 行设置断点 (_logger.LogException(ex);)
调试应用程序，创建新租户。执行应在第 98 行停止。
按 F10。执行应在第 126 行停止。该消息应指示超时。
修改第 96 行，添加 10 分钟的超时。
调试应用程序，创建新租户。执行应在第 98 行停止。
按 F10。执行应在第 126 行停止。消息应指示上述异常。

Answer 1

1

终于在这个post找到了答案：https://support.abp.io/QA/Questions/2084/An-exception-occurred-while-iterating-over-the-results-of-a-query-for-context-type-%27VoloSaasEntityFrameworkCoreSaasDbContexspendinng

正如您从屏幕截图中看到的那样，解决方案是将 requiresNew 参数设置为 false。这是必要的，因为调用方法上已经有一个由 [UnitOfWork] 属性启动的正在处理的事务。

迭代查询结果时发生异常...取消了任务

An exception occurred while iterating over the results of a query ... A task was canceled

sql-server

entity-framework-core

abp