GraphQL .NET parallel execution strategy doesn't fully run in parallel

Question

I have a graphQL query where I have 10 parallel queries + 2 properties on the second level. This results in 12 queries (10 queries + 2 batched properties).

{
    entries0(pageSize: 10) {
        id
        project {
            id
        }
        partner {
            id
        }
    }
    entries1(pageSize: 10) {
        id
        project {
            id
        }
        partner {
            id
        }
}

}

This is when I forced a serial execution strategy:

And this is when I use the parallel execution strategy:

As you can see, concurrent DB requests do happen now, but they do not start at the same time. What could be the cause of this?

I use GraphQL.NET 4.7.1 with .NET 6.0 and EF Core 6.0.2.

This is the query (duplicated 10 times: entries0, entries1, etc...):

Field<ListGraphType<Entry>, List<EntryEntity>>()
            .Name("entries0")
            .Argument<NonNullGraphType<IntGraphType>>("pageSize")
            .ResolveScopedAsync(ctx =>
            {
                int pageSize = ctx.GetArgument<int>("pageSize");

                var manager = ctx.RequestServices.GetRequiredService<ITestManager>();
                return manager.GetMultiple(pageSize);
            });

And this is the code from the manager

public Task<List<EntryEntity>> GetMultiple(int take)
    {
        return _dbContext.EntryEntities
            .OrderByDescending(x => x.CreatedOn)
            .Take(take)
            .ToListAsync();
    }

So as I see it the query does execute in parallel, but I don't see why it doesn't fully run in parallel. Each dbContext runs as separate instance in its own scope thanks to ResolveScopedAsync.

Shohreh Mortazavi · Answer 1 · 2022-03-14T17:20:54.570

use FieldAsync instead of Field and await inside ResolveScopedAsync and asynce/await inside GetMultiple(int take). Anywhere you use asynce, you should return await to work Asynchronously. if you forget await, it works synchronously.

  FieldAsync<ListGraphType<Entry>, List<EntryEntity>>()
        .Name("entries0")
        .Argument<NonNullGraphType<IntGraphType>>("pageSize")
        .ResolveScopedAsync(ctx =>
        {
        // your code
            return await manager.GetMultiple(pageSize);
        });


public async Task<List<EntryEntity>> GetMultiple(int take)
  {
    return await _dbContext.EntryEntities
        .OrderByDescending(x => x.CreatedOn)
        .Take(take)
        .ToListAsync();
}

GraphQL .NET parallel execution strategy doesn't fully run in parallel

1 Answers1