ZeroAlloc.Telemetry

Source-generated OpenTelemetry instrumentation for .NET.

Add [Instrument] to any interface and the generator emits a sealed proxy class that records Activity spans and Meter instruments per method — without reflection, params object[] boxing, or runtime attribute inspection.

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Contents

Page	Description
Getting Started	Install and instrument your first interface
Attribute Reference	[Instrument], [Trace], [Count], [Histogram]
Source Generator	What the generator emits — input/output examples
Testing	Assert spans and metrics with BCL listeners, no exporter needed
AOT & Trimming	Native AOT compatibility

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Quick Example

[Instrument("MyApp.Orders")]
public interface IOrderService
{
    [Trace("order.create")]
    [Count("orders.created")]
    ValueTask<OrderId> CreateOrderAsync(CreateOrderCommand cmd, CancellationToken ct);

    [Trace("order.get")]
    [Histogram("order.get_ms")]
    ValueTask<Order> GetOrderAsync(OrderId id, CancellationToken ct);
}

The generator emits OrderServiceInstrumented : IOrderService. Wrap your implementation at the DI layer:

services.AddSingleton<OrderServiceImpl>();
services.AddSingleton<IOrderService>(sp =>
    new OrderServiceInstrumented(sp.GetRequiredService<OrderServiceImpl>()));

That's all. No OpenTelemetry SDK is required — ActivitySource and Meter are BCL types (net8.0+). Add exporters in your application startup independently.

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Instruments at a Glance

Attribute	What it records	When
[Trace("name")]	Activity span	Every call — Error status on exception
[Count("metric")]	Counter<long> +1	Success only
[Histogram("metric")]	Histogram<double> elapsed ms	Every call including on exception