Overview

There are a few reasons to manually instrument your applications with the OpenTelemetry API:

• You are not using Datadog supported library instrumentation.
• You want to extend the ddtrace library’s functionality.
• You need finer control over instrumenting your applications.

The ddtrace library provides several techniques to help you achieve these goals. The following sections demonstrate how to use the OpenTelemetry API for custom instrumentation to use with Datadog.

Setup

To configure OpenTelemetry to use the Datadog trace provider:

1. Add your desired manual OpenTelemetry instrumentation to your .NET code following the OpenTelemetry .NET Manual Instrumentation documentation. Note: Where those instructions indicate that your code should call the OpenTelemetry SDK, call the Datadog tracing library instead.

2. Install the Datadog .NET tracing library and enable the tracer for your .NET Framework service or your .NET Core (and .NET 5+) service. Beta: You can optionally do this with Single Step APM Instrumentation.

3. Set DD_TRACE_OTEL_ENABLED environment variable to true.

4. Run your application.

Datadog combines these OpenTelemetry spans with other Datadog APM spans into a single trace of your application. It also supports OpenTelemetry instrumentation libraries.

Creating custom spans

To manually create spans that start a new, independent trace:

using OpenTelemetry.Resources;
using OpenTelemetry.Trace;

// Start a new span
using (Activity? activity = Telemetry.ActivitySource.StartActivity("<RESOURCE NAME>"))
            {
  activity?.SetTag("operation.name", "custom-operation");
               // Do something
            }

Creating spans

To create custom spans within an existing trace context:

using OpenTelemetry.Resources;
using OpenTelemetry.Trace;

using (Activity? parentScope = Telemetry.ActivitySource.StartActivity("<RESOURCE NAME>"))
{
   parentScope?.SetTag("operation.name", "manual.sortorders");
   using (Activity? childScope = Telemetry.ActivitySource.StartActivity("<RESOURCE NAME>"))
   {
       // Nest using statements around the code to trace
       childScope?.SetTag("operation.name", "manual.sortorders.child");
       SortOrders();
   }
}

Adding span tags

Add custom tags to your spans to provide additional context:

using OpenTelemetry.Resources;
using OpenTelemetry.Trace;

public class ShoppingCartController : Controller
{
    private IShoppingCartRepository _shoppingCartRepository;

    [HttpGet]
    public IActionResult Index(int customerId)
    {
      Activity? activity =
      Telemetry.ActivitySource.StartActivity("<RESOURCE NAME>")

        // Add a tag to the span for use in the Datadog web UI
        activity?.SetTag("customer.id", customerId.ToString());

        var cart = _shoppingCartRepository.Get(customerId);

        return View(cart);
    }
}

Setting errors on spans

Set error information on a span when an error occurs during its execution.

try
{
    // do work that can throw an exception
}
catch(Exception e)
{
    activity?.SetTag("error", 1);
    activity?.SetTag("error.message", exception.Message);
    activity?.SetTag("error.stack", exception.ToString());
    activity?.SetTag("error.type", exception.GetType().ToString());
}

Adding span events

Minimum SDK version: 2.53.0.

You can add span events using the AddEvent API. This method requires an ActivityEventconstructed with the name parameter and optionally accepts attributes and timestamp parameters. The method creates a new span event with the specified properties and associates it with the corresponding span.

• Name [required]: A string representing the event’s name.
• Timestamp [optional]: A UNIX timestamp representing the event’s occurrence time, expects a DateTimeOffset object.
• Attributes [optional]: Zero or more key-value pairs with the following properties:
  • The key must be a non-empty string.
  • The value can be either:
    • A primitive type: string, Boolean, or number.
    • A homogeneous array of primitive type values (for example, an array of strings).
  • Nested arrays and arrays containing elements of different data types are not allowed.

The following examples demonstrate different ways to add events to a span:

var eventTags = new ActivityTagsCollection
{
    { "int_val", 1 },
    { "string_val", "two" },
    { "int_array", new int[] { 3, 4 } },
    { "string_array", new string[] { "5", "6" } },
    { "bool_array", new bool[] { true, false } }
};

activity.AddEvent(new ActivityEvent("Event With No Attributes"));
activity.AddEvent(new ActivityEvent("Event With Some Attributes", DateTimeOffset.Now, eventTags));

Read the OpenTelemetry specification for more information.

Propagating context with headers extraction and injection

You can configure the propagation of context for distributed traces by injecting and extracting headers. Read Trace Context Propagation for information.

Further Reading

Additional helpful documentation, links, and articles:

Explore your services, resources, and tracesDOCUMENTATION Interoperability of OpenTelemetry API and Datadog instrumented tracesDOCUMENTATION