8000 A second operation started on this context before a previous operation completed · Issue #219 · elsa-workflows/elsa-core · GitHub
[go: up one dir, main page]
More Web Proxy on the site http://driver.im/
Skip to content

A second operation started on this context before a previous operation completed #219

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Closed
martin-indexeb opened this issue Jan 3, 2020 · 4 comments
Closed

A second operation started on this context before a previous operation completed #219

martin-indexeb opened this issue Jan 3, 2020 · 4 comments
Labels
bug Something isn't working

Comments

@martin-indexeb
Copy link

Hi, not sure if this is something I have set up wrong, but I'm trying to test Elsa with the dashboard and designer and have used SQL Server as the EF provider. After successfully adding a couple of workflows I now get the 'second operation' error when trying to view the workflows list. Here's the stack trace:

System.AggregateException: One or more errors occurred. (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.)
 ---> System.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.
  at Microsoft.EntityFrameworkCore.Internal.ConcurrencyDetector.EnterCriticalSection()
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at Elsa.Persistence.EntityFrameworkCore.Services.EntityFrameworkCoreWorkflowInstanceStore.ListByDefinitionAsync(String definitionId, CancellationToken cancellationToken)
   at Elsa.Extensions.AsyncEnumerableExtensions.ToListAsync[T](Task`1 task)
   at Elsa.Dashboard.Areas.Elsa.Controllers.WorkflowDefinitionController.CreateWorkflowDefinitionListItemModelAsync(WorkflowDefinitionVersion workflowDefinition, CancellationToken cancellationToken)
   at Elsa.Dashboard.Areas.Elsa.Controllers.WorkflowDefinitionController.<>c__DisplayClass7_0.<<Index>b__0>d.MoveNext()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
   at System.Threading.Tasks.Task`1.get_Result()
   at Elsa.Dashboard.Areas.Elsa.Controllers.WorkflowDefinitionController.<>c.<Index>b__7_1(Task`1 x)
   at System.Linq.Enumerable.SelectListIterator`2.MoveNext()
   at System.Linq.Lookup`2.Create(IEnumerable`1 source, Func`2 keySelector, IEqualityComparer`1 comparer)
   at System.Linq.GroupedEnumerable`2.ToList()
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Elsa.Dashboard.Areas.Elsa.Controllers.WorkflowDefinitionController.Index(CancellationToken cancellationToken)
   at lambda_method(Closure , Object )
   at Microsoft.Extensions.Internal.ObjectMethodExecutorAwaitable.Awaiter.GetResult()
   at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfActionResultExecutor.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.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Builder.Extensions.MapMiddleware.Invoke(HttpContext context)
   at Elsa.Activities.Http.Middleware.RequestHandlerMiddleware`1.InvokeAsync(HttpContext httpContext, THandler handler)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

I've stepped through the WorkflowDefinitionController.Index task and this line run's okay:

var workflows = await workflowDefinitionStore.ListAsync(
                VersionOptions.LatestOrPublished,
                cancellationToken
            );

but then it errors out on the subsequent call:

var workflowModelTasks = workflows.Select(
                    async x => await CreateWorkflowDefinitionListItemModelAsync(x, cancellationToken)
                )
                .ToList();

Which, as you can see from the stack trace is getting as far as EntityFrameworkCoreWorkflowInstanceStore.ListByDefinitionAsync for the next call to the dbContext which throws the error.

Has anyone got any thoughts on what's causing this?
@sfmskywalker sfmskywalker added the bug Something isn't working label Jan 4, 2020
@sfmskywalker
Copy link
Member

I just tried this with the latest version from the master branch (0fbb47f), but I'm unable to reproduce the issue. Here's what I did:

  1. Update Elsa.Dashboard.Web to use EF with Sqlite.
  2. Create 5 workflows using the dashboard.

Couple of questions:

  1. Which version are you using?
  2. Are you using Sqlite, SQL Server, or something else?

@martin-indexeb
Copy link
Author
martin-indexeb commented Jan 6, 2020 •
edited
Loading

Hi Sipke, thanks for looking at this. I can confirm that it works fine for me with Sqlite, but I'm trying to use SQL Server. This is with the latest build on master, and also if I create a separate project and add the current Elsa packages (v1.1.4.2). I'm using a local SQL Server Express v14.0.2027

If it helps here's my Startup class:

public class Startup
  {
    public Startup(IConfiguration configuration) {
      Configuration = configuration;
    }
    private IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services) {
      var migrationAssembly = typeof(ElsaContext).Assembly.FullName;
      services
                .AddElsa(elsa => 
                  elsa.AddEntityFrameworkStores(options => 
                    options.UseSqlServer(Configuration.GetConnectionString("SqlServer"), 
                      s => s.MigrationsAssembly(migrationAssembly))))
                .AddHttpActivities(options => options.Bind(Configuration.GetSection("Elsa:Http")))
                .AddEmailActivities(options => options.Bind(Configuration.GetSection("Elsa:Smtp")))
                .AddTimerActivities(options => options.Bind(Configuration.GetSection("Elsa:Timers")))
                .AddElsaDashboard();
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
      if (env.IsDevelopment()) {
        app.UseDeveloperExceptionPage();
      }

      app
          .UseStaticFiles()
          .UseHttpActivities()
          .UseRouting()
          .UseEndpoints(endpoints => endpoints.MapControllers())
          .UseWelcomePage();
    }
  }

@sfmskywalker
Copy link
Member

Hi Martin,

I was able to reproduce the issue with SqlServer. For some reason, the following code appears to run in parallel instead of sequentially:

var workflowModelTasks = workflows.Select(async x => await CreateWorkflowDefinitionListItemModelAsync(x, cancellationToken));

I would have expected that statement would basically iterate over each workflow in the list, async/awaiting each creation of a model object, like so:

var workflowModels = new List<WorkflowDefinitionListItemModel>();

foreach (var workflow in workflows)
{
    var workflowModel = await CreateWorkflowDefinitionListItemModelAsync(workflow, cancellationToken);
    workflowModels.Add(workflowModel);
}

The above works. Clearly I'm not understanding something correctly, but I committed the "explicit" for each loop to develop and will merge it to master.

@martin-indexeb
Copy link
Author

Great, thanks Sipke.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
bug Something isn't working
Projects
None yet
Milestone
No milestone
Development

No branches or pull requests
2 participants
@sfmskywalker @martin-indexeb
0