TaskMuxer

Task Multiplexer.

The purpose of this package is to provide the ability to reduce the amount of parallel repetitive work.

In practical terms, imagine a service that requests data from a slow external API serving multiple requests in parallel.

By using this library, for any number of parallel requests only one will be executed.

Tasks are being identified / segmented by a key and their respective return type.

Nuget

Note

There appears to be a compatibility issue for projects targeting .NET 7 and assembly Assembly Microsoft.Extensions.Hosting, Version=7.0.0.0 and more specifically OptionsBuilderExtensions.ValidateOnStart resulting in error:

The call is ambiguous between the following methods or properties: 'Microsoft.Extensions.DependencyInjection.OptionsBuilderExtensions.ValidateOnStart(Microsoft.Extensions.Options.OptionsBuilder)' and 'Microsoft.Extensions.DependencyInjection.OptionsBuilderExtensions.ValidateOnStart(Microsoft.Extensions.Options.OptionsBuilder)'

Until resolved please consider using a previous version of the package targeting .NET 7.

Usage

Registration

Locate the services registration and append one of:

• .AddInstanceTaskMultiplexerNoLogger - use when no logging is required
• .AddInstanceTaskMultiplexerWithILogger - use when the ILogger provider is available
• .AddInstanceTaskMultiplexerWithILoggerFactory - use when the ILoggerFactory provider is available
• .AddInstanceTaskMultiplexerWithOptionsAndNoLogger - use when no logging is required and options are defined
• .AddInstanceTaskMultiplexerWithOptionsAndILogger - use when the ILogger provider is available and options are defined
• .AddInstanceTaskMultiplexerWithOptionsAndILoggerFactory - use when the ILoggerFactory provider is available and options are defined

ex.

// Startup.cs
public void ConfigureServices(IServiceCollection services)
{
    // ...
    services
        .AddInstanceTaskMultiplexerWithILogger();
    // ...
}

📝 If further customization is required, consider wiring up any of the ITaskMultiplexer implementations as required.

Code

Please check the ITaskMultiplexer interface for the API surface provided.

ex.

public class ItemsCountService
{
    readonly ITaskMultiplexer _taskMultiplexer;

    public ItemsCountService(ITaskMultiplexer taskMultiplexer) => _taskMultiplexer = taskMultiplexer;

    public async Task<long> GetCountOfItems(CancellationToken cancellationToken = default) =>
        await _taskMultiplexer.AddTask(
            "items_count",
            async ct =>
            {
                await Task.Delay(250, ct);
                return Random.Shared.Next();
            },
            cancellationToken
        );
}

Config

Please consult the InstanceTaskMultiplexerConfig for all the possible options available.

public record InstanceTaskMultiplexerConfig : IValidatableObject
{
    //
    public TimeSpan PreserveExecutionResultDuration { get; set; } = TimeSpan.Zero;

    public TimeSpan ExecutionTimeout { get; set; } = TimeSpan.FromSeconds(30);

    [Range(10, 100_000)]
    public int CollectionCapacity { get; set; } = 100;

    public virtual IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        if (PreserveExecutionResultDuration < TimeSpan.Zero)
            yield return new($"{nameof(PreserveExecutionResultDuration)} must be equal or greater than {TimeSpan.Zero}", new[] { nameof(ExecutionTimeout) });

        if (ExecutionTimeout <= TimeSpan.Zero)
            yield return new($"{nameof(ExecutionTimeout)} must be greater than {TimeSpan.Zero}", new[] { nameof(ExecutionTimeout) });
    }
}

Thread Safety

To achieve thread safety in cases like entity framework core accessing and / or writing data at the same time through parallel threads consider using semaphores or some other form of locking.

ex.

public record SampleEntity
{
    public int Id { get; set; }

    public string Text { get; set; } = string.Empty;
}

public class SampleDataContext : DbContext
{
    public SampleDataContext(DbContextOptions<SampleDataContext> options) : base(options) { }

    public DbSet<SampleEntity> Samples { get; set; } = default!;
}

public class SampleService
{
    readonly ITaskMultiplexer _taskMultiplexer;
    readonly SampleDataContext _dbContext;

    private SemaphoreSlim _semaphoreSlim = new(1);

    public SampleService(ITaskMultiplexer taskMultiplexer, SampleDataContext dbContext) =>
        (_taskMultiplexer, _dbContext) = (taskMultiplexer, dbContext);

    public async Task<SampleEntity?> GetById(int id, CancellationToken cancellationToken = default) =>
        await _taskMultiplexer.AddTask(
            "get_by_id_with_semaphore",
            async ct =>
            {
                await _semaphoreSlim.WaitAsync(ct);

                try
                {
                    return await _dbContext.Samples.FirstOrDefaultAsync(x => x.Id == id, ct);
                }
                finally
                {
                    _semaphoreSlim.Release();
                }
            },
            cancellationToken
        );

    public async Task<SampleEntity?> Add(SampleEntity obj, CancellationToken cancellationToken = default) =>
        await _taskMultiplexer.AddTask(
            "add_with_semaphore",
            async ct =>
            {
                await _semaphoreSlim.WaitAsync(ct);

                try
                {
                    _dbContext.Add(obj);
                    await _dbContext.SaveChangesAsync(ct);
                }
                finally
                {
                    _semaphoreSlim.Release();
                }

                return obj;
            },
            cancellationToken
        );
}

var service = new SampleService(
    new InstanceTaskMultiplexer(),
    new SampleDataContext(
        new DbContextOptionsBuilder<SampleDataContext>()
            .UseInMemoryDatabase("sample_database")
            .Options
    )
);

await Task.WhenAll(
    service.GetById(1),
    service.Add(
        new()
        {
            Text = "Random " + Random.Shared.Next()
        }
    ),
    service.GetById(1)
);

Similar Projects

• https://github.com/lundog/TaskMultiplexer