Background-Jobs

ASP.NET Core middleware is a powerful component of the request pipeline, designed to handle HTTP requests and responses efficiently. But what happens when a request needs to kick off a task that shouldn’t block the response? Think of tasks like sending a confirmation email, generating a detailed audit log, or calling a slow third-party service. Running these directly within the middleware can severely impact your application’s performance and responsiveness.

The solution is to decouple these long-running operations from the request pipeline by offloading them to a background service. In this post, we’ll walk through the robust and recommended way to trigger background jobs from your middleware using IHostedService and an in-memory queue.

The Problem: Blocking the Pipeline

The request pipeline in ASP.NET Core is synchronous at its core, even with async/await. Each middleware component must complete its work before passing control to the next one. If your middleware performs a long-running operation, the client is left waiting until that task finishes.

For example, imagine a piece of middleware that logs detailed request information to a slow, remote data store:

// DO NOT DO THIS
app.Use(async (context, next) =>
{
    // This blocks the pipeline until the log is written
    await LogRequestDetailsToSlowStoreAsync(context.Request); 

    await next(context);
});

This approach creates a bottleneck. As traffic increases, requests will pile up waiting for these …