Queues and fairness

Define a marker type and assign jobs to it:

[QueueDefinition(Name = "transactional-email", Priority = 100, Concurrency = 2)]
public sealed class TransactionalEmailQueue;

[Handler, Job, UsesQueue<TransactionalEmailQueue>]
public sealed partial class SendWelcomeEmail(IEmailSender sender)
{
	// HandleAsync omitted
}

Without [UsesQueue<T>], a job uses the built-in default queue (Priority = 0, Concurrency = 0). A custom persisted name defaults to the class name with a Queue suffix converted to kebab case (TransactionalEmailQueue becomes transactional-email-queue). Set Name explicitly for production. Names must be unique, must not be default, and queue concurrency cannot be negative.

Higher Priority queues are considered first. Concurrency limits in-flight work for that queue on one scheduler node; zero is unbounded. Node-wide MaxParallelJobs and job-level MaxConcurrency still apply, so priority never bypasses capacity.

Fair groups

Enable fairness globally and put a tenant/customer key on each scheduled invocation:

builder.Services.AddMyAppJobs()
	.UseFairQueues(options => options.Configure(fair =>
	{
		fair.ConcurrencyShareThreshold = 0.10;
		fair.MinInflightForNoisy = 30;
		fair.GroupRoundRobin = true;
	}))
	.ConfigureStorage(storage => storage.UseInMemory());

await welcomeEmail.EnqueueAsync(
	new(userId, "v2"),
	groupId: tenantId,
	cancellationToken: cancellationToken
);

The OptionsBuilder<FairQueueOptions> callback can also bind an IConfiguration section:

builder.Services.AddMyAppJobs()
	.UseFairQueues(options => options.Bind(
		builder.Configuration.GetSection("ImmediateJobs:FairQueues")))
	.ConfigureStorage(storage => storage.UseInMemory());

Round-robin alternates between groups that have work ready. A group becomes noisy after it reaches MinInflightForNoisy active jobs and uses more than ConcurrencyShareThreshold of the queue’s capacity. Jobs then favors quieter groups. Jobs without a group remain eligible. Fairness changes which ready job runs next; it does not change priority or retry rules.

Storage and mode	Fair groups
In-memory	Supported
EF Core / LinqToDB	Supported
Redis	Not supported; enabling fair queues causes an error
Single-server	Supported when its durable provider meets the mode requirements

Queue and group names are persisted. Renaming either does not rename already-persisted work.