Lean .NET observability on OpenTelemetry. IWitness<T> gives each call site one place for logs, metrics, and traces while keeping ILogger<T>, Meter, ActivitySource, and OpenTelemetry exporters directly accessible. Supports net8.0 and net10.0.
// Program.cs
builder.Services.AddWitness(builder.Configuration.GetSection("Witness"))
.WithStandardInstrumentations()
.WithOtlpExporter();
// In your service
public sealed class OrderService(IWitness<OrderService> witness)
{
public void PlaceOrder(int orderId)
{
using var action = witness.StartAction("PlaceOrder");
action.SetTag("order.id", orderId);
// business logic
}
}AddWitness() binds WitnessOptions from the "Witness" section.
The main injectable bundling ILogger<T>, Meter, and ActivitySource with no new abstractions. Most classes only need IWitness<T>.
Wraps an Activity. Start with witness.StartAction("Name"), attach tags/events, and dispose when done. Outcomes default to success; call Failed(Exception), Failed(string), or Cancelled() as needed.
using var action = witness.StartAction("RetrieveSummary");
try
{
var summary = await _controller.RetrieveSummaryAsync();
return summary;
}
catch (Exception ex)
{
action.Failed(ex);
throw;
}Write extension methods on IWitness<T> for recurring log messages. The analyzer package suggests the [LoggerMessage] pattern for performance:
public static void LogOrderPlaced(this IWitness<OrderService> witness, int orderId) =>
witness.Logger.LogInformation("Order {OrderId} placed", orderId);dotnet add package WitnessSharp
dotnet add package WitnessSharp.AzureMonitor # optional
dotnet add package WitnessSharp.Analyzers # optional
dotnet add package WitnessSharp.Testing # test projectsConfigure from appsettings.json:
appsettings.json:
{
"Witness": {
"ServiceName": "orders-api",
"ServiceNamespace": "Contoso.Commerce",
"ServiceVersion": "1.3.0",
"ServiceInstanceId": "orders-api-01",
"DeploymentEnvironment": "Production",
"AdditionalResourceAttributes": {
"service.owner": "checkout",
"cloud.region": "westeurope"
}
}
}Or via C# options: builder.Services.AddWitness(options => options.ServiceName = "orders-api");
Fluent builder methods like WithStandardInstrumentations(), WithOtlpExporter(), ClearLoggingProviders(), and individual instrumentations (WithAspNetCoreInstrumentation(), etc.). Use ConfigureTracing(), ConfigureMetrics(), or ConfigureLogging() for direct OTel SDK customization.
Filter health-check endpoints via ConfigureTracing():
.ConfigureTracing(tracing =>
{
tracing.AddAspNetCoreInstrumentation(options =>
{
options.Filter = ctx => !ctx.Request.Path.StartsWithSegments("/health");
});
})For duration-based filtering, implement a custom BaseProcessor<Activity> and register via ConfigureTracing().
Use .WithAzureMonitor() (from WitnessSharp.AzureMonitor package). Connection string is read from APPLICATIONINSIGHTS_CONNECTION_STRING. See Azure Monitor docs.
WitnessSharp.Testing provides TestWitness<T> with assertion helpers (AssertLogged, AssertMetricRecorded, AssertActivityStarted):
using var witness = new TestWitness<OrderService>();
witness.Logger.LogInformation("Placed order 42");
witness.Meter.CreateCounter<int>("orders").Add(1);
witness.StartAction("PlaceOrder").Dispose();
witness.AssertLogged(LogLevel.Information, "Placed order");
witness.AssertMetricRecorded("orders");
witness.AssertActivityStarted("PlaceOrder");WitnessSharp.Analyzers suggests the [LoggerMessage] pattern for templated logging in IWitness<T> extension methods. Configure via .editorconfig: dotnet_diagnostic.WS0001.severity = warning. See LoggerMessage docs.
WitnessSharp is AOT/trim-friendly. Upstream instrumentation and exporter packages may emit warnings when publishing with PublishAot=true.
Contributions welcome. Build with dotnet build WitnessSharp.slnx, test with dotnet test WitnessSharp.slnx, then open a pull request. Follow CONTRIBUTING.md if present.
MIT. See LICENSE.