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Cart Service

This service maintains items placed in the shopping cart by users. It interacts with a Redis caching service for fast access to shopping cart data.

Cart service source

Note OpenTelemetry for .NET uses the System.Diagnostic library as its API in lieu of the standard OpenTelemetry API.

Traces

Initializing Tracing

OpenTelemetry is configured in the .NET DI container. The AddOpenTelemetryTracing() builder method is used to configure desired instrumentation libraries, add exporters, and set other options. Configuration of the exporter and resource attributes is performed through environment variables.

services.AddOpenTelemetryTracing((builder) => builder
    .ConfigureResource(r => r.AddTelemetrySdk())
    .AddRedisInstrumentation(
        cartStore.GetConnection(),
        options => options.SetVerboseDatabaseStatements = true)
    .AddAspNetCoreInstrumentation()
    .AddGrpcClientInstrumentation()
    .AddHttpClientInstrumentation()
    .AddOtlpExporter());

Add attributes to auto-instrumented spans

Within the execution of auto-instrumented code you can get current span (activity) from context.

    var activity = Activity.Current;

Adding attributes (tags in .NET) to a span (activity) is accomplished using SetTag on the activity object. In the AddItem function from services/CartService.cs several attributes are added to the auto-instrumented span.

    activity?.SetTag("app.user.id", request.UserId);
    activity?.SetTag("app.product.quantity", request.Item.Quantity);
    activity?.SetTag("app.product.id", request.Item.ProductId);

Add span events

Adding span (activity) events is accomplished using AddEvent on the activity object. In the GetCart function from services/CartService.cs a span event is added.

    activity?.AddEvent(new("Fetch cart"));

Metrics

Initializing Metrics

Similar to configuring OpenTelemetry Traces, the .NET DI container requires a call to AddOpenTelemetryMetrics(). This builder configures desired instrumentation libraries, exporters, etc.

services.AddOpenTelemetryMetrics(builder => builder
    .ConfigureResource(r => r.AddTelemetrySdk())
    .AddRuntimeInstrumentation()
    .AddAspNetCoreInstrumentation()
    .AddOtlpExporter());

Logs

TBD