Mostlylucid.Ephemeral.Patterns.Backpressure 2.3.2

Mostlylucid.Ephemeral.Patterns.Backpressure

Signal-driven backpressure - defer intake when backpressure signals present.

dotnet add package mostlylucid.ephemeral.patterns.backpressure

Quick Start

using Mostlylucid.Ephemeral.Patterns.Backpressure;

var sink = new SignalSink();

var coordinator = SignalDrivenBackpressure.Create<WorkItem>(
    async (item, ct) => await ProcessAsync(item, ct),
    sink,
    maxConcurrency: 4);

sink.Raise("backpressure.downstream");  // New work defers
await coordinator.EnqueueAsync(item);    // Waits until signal clears
sink.Retract("backpressure.downstream"); // Work resumes

All Options

SignalDrivenBackpressure.Create<T>(
    // Required: async work body
    body: async (item, ct) => await ProcessAsync(item, ct),

    // Required: shared signal sink
    sink: signalSink,

    // Max concurrent operations
    // Default: 4
    maxConcurrency: 4
)

API Reference

// Returns a configured EphemeralWorkCoordinator<T>
var coordinator = SignalDrivenBackpressure.Create<T>(body, sink, maxConcurrency);

// Enqueue work (defers if backpressure.* signal present)
await coordinator.EnqueueAsync(item);

// Drain and dispose
coordinator.Complete();
await coordinator.DrainAsync();
await coordinator.DisposeAsync();

How It Works

Items automatically defer when any signal matching backpressure.* is present:

sink.Raise("backpressure.downstream")
  │
  ▼
EnqueueAsync(item) ──> [Defer] ──> Wait 50ms ──> Check signals ──> [Still present] ──> Wait...
                                                        │
                                                        ▼
                                            [Signal cleared] ──> Process item

Example: Downstream Throttling

var sink = new SignalSink();

await using var coordinator = SignalDrivenBackpressure.Create<Message>(
    async (msg, ct) =>
    {
        await downstream.SendAsync(msg, ct);
    },
    sink,
    maxConcurrency: 8);

// Downstream service reports it's overloaded
sink.Raise("backpressure.downstream");

// New messages defer until downstream recovers
foreach (var msg in messages)
    await coordinator.EnqueueAsync(msg);

// Downstream recovers
sink.Retract("backpressure.downstream");
// All deferred work resumes

Configuration Details

The pattern internally configures:

new EphemeralOptions
{
    MaxConcurrency = maxConcurrency,
    Signals = sink,
    DeferOnSignals = new HashSet<string> { "backpressure.*" },
    DeferCheckInterval = TimeSpan.FromMilliseconds(50),
    MaxDeferAttempts = 200
}

Related Packages

License

Unlicense (public domain)