HostLoom.Locking.Pipelines 0.4.0

HostLoom.Locking.Pipelines

A distributed-lock filter for HostLoom.Pipelines, built on the HostLoom.Locking kernel. The package references those two and nothing else; HostLoom.Pipelines stays dependency-free.

var pipeline = Pipe.Create<RefreshContext>(pipe =>
{
    pipe.UseDistributedLock(
        distributedLock,
        context => $"refresh:{context.Region}",
        new LockOptions { Lease = TimeSpan.FromSeconds(30), OnLost = LostLeaseBehavior.Cancel });
    pipe.UseExecute(context => RefreshAsync(context));
});

UseDistributedLock runs the rest of the pipe inside IDistributedLock.ExecuteWithLockAsync, so two contexts with the same key never run downstream at once, across every instance sharing the lock's provider. Different keys run concurrently. LockNotAcquiredException and LockProviderUnavailableException propagate unchanged; a retry filter ahead of this one is the place to decide whether to try again.

Before the rest of the pipe runs, a HeldLock payload is put on the context with the key and the cancellation token the lock handed to the run. The context's own token cannot be replaced, so a downstream filter that must stop when the lease is lost watches HeldLock.CancellationToken, which the lock cancels when the options ask for LostLeaseBehavior.Cancel.

The lock is coordination, not correctness, for persisted state: database transactions, row locks, unique constraints, and idempotency records own correctness.

From the container

The filter has a public constructor taking IDistributedLock and DistributedLockFilterOptions<TContext>, so HostLoom.Pipelines.DependencyInjection resolves it per run:

services.AddSingleton(new DistributedLockFilterOptions<RefreshContext>
{
    KeySelector = context => $"refresh:{context.Region}",
    Lock = new LockOptions { Lease = TimeSpan.FromSeconds(30) },
});
services.AddPipeline<RefreshContext>("refresh", pipeline =>
    pipeline.Stage("run", stage =>
        stage.AddFilter<DistributedLockFilter<RefreshContext>>().AddFilter<RefreshFilter>()));

The filter describes itself to PipelineProbe.Inspect as a distributedLock scope with the lease, wait bound, retry policy, and lost-lease behaviour.