BackgroundJobManager can't insert record because DbContext is already used

GitHub Issues

Informations:

• Abp package version: 5.14.0
• Your base framework: .Net Core.
• Exception message and stack trace if available:

InvalidOperationException: A second operation started on this context before a previous operation completed. This is usually caused by different threads using the same instance of DbContext. For more information on how to avoid threading issues with DbContext, see https://go.microsoft.com/fwlink/?linkid=2097913.
STACK TRACE:    at Microsoft.EntityFrameworkCore.Internal.ConcurrencyDetector.EnterCriticalSection()
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList`1 entriesToSave, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(DbContext _, Boolean acceptAllChangesOnSuccess, 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.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Abp.EntityFrameworkCore.AbpDbContext.SaveChangesAsync(CancellationToken cancellationToken)
   at Abp.Zero.EntityFrameworkCore.AbpZeroCommonDbContext`3.SaveChangesAsync(CancellationToken cancellationToken)
   at Abp.EntityFrameworkCore.Uow.EfCoreUnitOfWork.SaveChangesInDbContextAsync(DbContext dbContext)
   at Abp.EntityFrameworkCore.Uow.EfCoreUnitOfWork.SaveChangesAsync()
   at Abp.BackgroundJobs.BackgroundJobManager.EnqueueAsync[TJob,TArgs](TArgs args, BackgroundJobPriority priority, Nullable`1 delay)
   at Abp.Domain.Uow.UnitOfWorkInterceptor.InternalInterceptAsynchronous[TResult](IInvocation invocation)
   at BilancioSociale.Report.ReportAppService.DownloadBilancioReport(PagedReportRequestDto input) in C:\\GitHub\\Platform\\5.8.1\\aspnet-core\\src\\Application\\Report\\ReportAppService.cs:line 134
   at lambda_method(Closure , Object )
   at Microsoft.Extensions.Internal.ObjectMethodExecutorAwaitable.Awaiter.GetResult()
   at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.AwaitableObjectResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask`1 actionResultValueTask)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextExceptionFilterAsync>g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)

• Steps needed to reproduce the problem.

I’ve implemented a functionality that should generate a Excel File within a certains input data in two ways basically:

1. if DB query and excel generation are executed into a 10 seconds time frame, the result is directly returned by the HttpResponse
2. if the execution lasts more than 10 seconds, i enqueue the job using BackgroundJobManager as the guide explains.

but i’m getting the exception i reported above.

AppService method:

ReportAppService.cs

[HttpGet]
public async Task<ReportResultDto> DownloadBilancioReport(PagedReportRequestDto input)
{
	var tokenSource = new CancellationTokenSource();
	var token = tokenSource.Token;

	Task<byte[]> exportTask = Task.Run(async () =>
	{
		var registration = token.Register(() =>
		{
			try { token.ThrowIfCancellationRequested(); } catch { }
		});

		using (var unitOfWork = _unitOfWorkManager.Begin(new UnitOfWorkOptions() { AsyncFlowOption = TransactionScopeAsyncFlowOption.Enabled, IsolationLevel = IsolationLevel.Serializable, Scope = TransactionScopeOption.RequiresNew, Timeout = TimeSpan.FromMilliseconds(CancellationExportTaskTime) }))
		{
			var fileBytes = await _exportationManager.ExportAsync(input.Anno, input.RegioneId, input.StrutturaId);
			unitOfWork.Complete();
			return fileBytes;
		}

	}, cancellationToken: token);

	if (!exportTask.Wait(CancellationExportTaskTime))
	{
		var jobId = await _backgroundJobManager.EnqueueAsync<QueryAndCreateReportJob, ReportJobArg>(new ReportJobArg(input.Anno, input.RegioneId, input.StrutturaId));

		try
		{
			tokenSource.Cancel();
		}
		catch (OperationCanceledException oce)
		{
			Logger.InfoFormat("ReportAppService.DownloadBilancioReport synchronous task was aborted because it exceeded the maximum execution time limit.");
		}

		return new ReportResultDto
		{
			Message = "L'elaborazione dell'export richesto richiede più tempo del previsto. Riceverai una email con il report in allegato al termine dell'operazione",
			File = null
		};
	}
	else
	{
		var byteArray = await exportTask;

		return new ReportResultDto
		{
			Message = null,
			File = new FileDto
			{
				FileName = $"EsportazioneBilanci{DateTime.Now.Date:yyyyMMdd}",
				FileData = byteArray,
				MimeType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
			}
		};
	}
}

QueryAndCreateReportJob.cs

using Abp.BackgroundJobs;
using Abp.Dependency;
using Abp.Domain.Uow;
using Abp.Net.Mail;
using System.IO;
using System.Threading.Tasks;
using System.Transactions;

namespace BilancioSociale.Report
{
    public class QueryAndCreateReportJob : AsyncBackgroundJob<ReportJobArg>, ITransientDependency
    {
        private readonly ExportationManager _exportationManager;
        private readonly IEmailSender _emailSender;

        public QueryAndCreateReportJob(ExportationManager exportationManager, IEmailSender emailSender)
        {
            _unitOfWorkManager = unitOfWorkManager;
            _emailSender = emailSender;
        }

        protected override async Task ExecuteAsync(ReportJobArg arg)
        {
            Logger.Info("QueryAndCreateReportJob.ExecuteAsync started..");

            byte[] result = await _exportationManager.ExportAsync(arg.Anno, arg.RegioneId, arg.StrutturaId);
            File.WriteAllBytes(@"C:\Temp\Test.xlsx", result);

            Logger.Info("QueryAndCreateReportJob.ExecuteAsync completed!!!");
        }
    }
}

As i can see, EntityFramework DbContext is registered as Transient but seems it’s not. The first execution is cancelled from the CancellationToken, used into the Task.Run.

[ismcagdas]

@egrassinode I will test this but it might take some time.

[ismcagdas]

Hi @egrassinode sorry for my late reply. I have investigated the problem and it seems like current DbContext creation logic doesn’t support this usage, see https://github.com/aspnetboilerplate/aspnetboilerplate/issues/1903#issuecomment-283577173. Sorry that I forgot this and kept you waiting.