Flag to throw if synchronous I/O is attempted, similar to AllowSynchronousIO in ASP.NET Core 2.0+

Open
#20,562 5 comments 2 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
30/100
Issue type
Feature
Clarity
Needs clarification
Activity status
Stale
Tech stack
csharp
Domain
database

Research direction

Start by reviewing the two proposed APIs and the linked ASP.NET Core AllowSynchronousIO design. Trace the synchronous I/O cases mentioned in the issue, including lazy loading, ToImmutableArray without ToListAsync, and IQueryable to IEnumerable casts. Done should be a decided, documented approach that reliably throws when synchronous I/O is attempted.

Written by the indexing model from the issue text.

Description

area-global customer-reported

It can be hard to track down existing code and notice new code that causes blocking I/O. This is important not just to prevent thread pool starvation in web apps but also to keep client apps responsive. So, pretty much anywhere we would use Entity Framework.

Some things that cause blocking I/O are easy to avoid, like lazy loading. Other causes can slip past without getting attention. For example, calling .ToImmutableArray() without calling ToListAsync first, or not noticing that an IQueryable is being implicitly cast to IEnumerable.

ASP.NET Core's API:

Placeholder proposal 1

Easy to find, same name as ASP.NET Core. Usage:

optionsBuilder.AllowSynchronousIO(false)

API:

namespace Microsoft.EntityFrameworkCore
{
    public class DbContextOptionsBuilder<TContext> : DbContextOptionsBuilder
        where TContext : DbContext
    {
+       public virtual DbContextOptionsBuilder AllowSynchronousIO(
+           bool synchronousIOEnabled = true);
    }

    public class DbContextOptionsBuilder : IDbContextOptionsBuilderInfrastructure
    {
+       public new virtual DbContextOptionsBuilder<TContext> AllowSynchronousIO(
+           bool synchronousIOEnabled = true);
    }
}
Placeholder proposal 2

Harder to discover, but maybe makes more sense in context. Usage:

optionsBuilder.ConfigureWarnings(warnings => 
    warnings.Throw(CoreEventId.SynchronousIO))
namespace Microsoft.EntityFrameworkCore.Diagnostics
{
    public static class CoreEventId
    {
+       public static readonly EventId SynchronousIO;
    }
}
Dominant language
C#
Stars
14.8k
Forks
3.4k
Avg merge
2d 5h
Merged PRs (30d)
134

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from dotnet/efcore

All issues in dotnet/efcore

Similar issues

More C# issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.