MKS.KeyedLocking.MediatR 1.0.0

MKS.KeyedLocking.MediatR

MediatR pipeline integration for automatic keyed locking in CQRS handlers.

Features

• KeyedLockFilter<TRequest, TResponse> - Generic base class per command/query (similar to audit filter patterns)
• GetAcquireOptions(request) - Build lock key and timeout from the request payload
• Assembly scanning - AddKeyedLockFilters() discovers and registers all filter subclasses
• Explicit registration - AddKeyedLockFilter<TFilter, TRequest, TResponse>() for manual setup
• Backend agnostic - Works with any registered IKeyedLockService

Installation

dotnet add package MKS.KeyedLocking.MediatR

Also install a lock backend:

dotnet add package MKS.KeyedLocking.Redis
dotnet add package MKS.KeyedLocking.Composite

Dependency Injection

builder.Services.AddMediatR(cfg =>
    cfg.RegisterServicesFromAssembly(typeof(Program).Assembly));

builder.Services.AddSingleton<IConnectionMultiplexer>(_ =>
    ConnectionMultiplexer.Connect("localhost:6379"));

builder.Services.AddRedisKeyedLock()
        .AddCompositeKeyedLock();

builder.Services.AddKeyedLockFilters(typeof(Program).Assembly);

Define a Lock Filter

Create one filter class per command or query that needs locking:

public class CreateClientRecipientCommandLock
    : KeyedLockFilter<CreateClientRecipientCommand, ClientRecipientDto>
{
    public CreateClientRecipientCommandLock(IKeyedLockService lockService)
        : base(lockService)
    {
    }

    protected override KeyedLockAcquireOptions GetAcquireOptions(CreateClientRecipientCommand request)
        => new($"client-recipient:{request.ClientId}", TimeSpan.FromSeconds(30));
}

The handler stays lock-free:

public class CreateClientRecipientHandler
    : IRequestHandler<CreateClientRecipientCommand, ClientRecipientDto>
{
    public async Task<ClientRecipientDto> Handle(
        CreateClientRecipientCommand request,
        CancellationToken cancellationToken)
    {
        // Lock already acquired by CreateClientRecipientCommandLock pipeline filter
        // ... business logic only
    }
}

Skip Locking Conditionally

Return null from GetAcquireOptions to skip locking for specific requests:

protected override KeyedLockAcquireOptions? GetAcquireOptions(UpdateCommand request)
    => request.SkipLock ? null : new($"entity:{request.Id}");

Explicit Registration

When you prefer not to scan assemblies:

services.AddKeyedLockFilter<CreateClientRecipientCommandLock, CreateClientRecipientCommand, ClientRecipientDto>();

Requirements

• .NET 10.0
• MediatR 13.0+
• MKS.KeyedLocking.Abstractions 1.0.0+
• A registered IKeyedLockService implementation