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LaunchDarkly C++ Server SDK - OpenTelemetry Integration Example

This example demonstrates how to integrate the LaunchDarkly C++ Server SDK with OpenTelemetry tracing to automatically enrich your distributed traces with feature flag evaluation data.

What This Example Shows

  • Setting up OpenTelemetry with OTLP HTTP exporter
  • Configuring the LaunchDarkly OpenTelemetry tracing hook
  • Creating HTTP spans with Boost.Beast
  • Automatic feature flag span events in traces
  • Passing explicit parent span context to evaluations

Prerequisites

  • C++17 or later
  • CMake 3.19 or later
  • Boost 1.81 or later
  • LaunchDarkly SDK key

Building

From the repository root:

mkdir build && cd build
cmake .. -DLD_BUILD_EXAMPLES=ON -DLD_BUILD_OTEL_SUPPORT=ON
cmake --build . --target hello-cpp-server-otel

Running

1. Set Your LaunchDarkly SDK Key

Either edit main.cpp and set the SDK_KEY constant, or use an environment variable:

export LD_SDK_KEY=your-sdk-key-here

2. Create a Feature Flag

In your LaunchDarkly dashboard, create a boolean flag named show-detailed-weather.

3. Run the Example

./build/examples/hello-cpp-server-otel/hello-cpp-server-otel

You should see:

*** SDK successfully initialized!

*** Weather server running on http://0.0.0.0:8080
*** Try: curl http://localhost:8080/weather
*** OpenTelemetry tracing enabled, sending traces to LaunchDarkly
*** LaunchDarkly integration enabled with OpenTelemetry tracing hook

4. Make Requests

curl http://localhost:8080/weather

5. View Traces in LaunchDarkly

Navigate to your LaunchDarkly project's Observability section to view traces. Each HTTP request will have:

  1. Root Span: "HTTP GET /weather" with HTTP attributes
  2. Feature Flag Event: Attached to the span with evaluation details:
    • feature_flag.key: "show-detailed-weather"
    • feature_flag.provider.name: "LaunchDarkly"
    • feature_flag.context.id: "user:weather-api-user"
    • feature_flag.result.value: The evaluated flag value

Custom OTLP Endpoint

To send traces to a different OpenTelemetry collector, set the LD_OTEL_ENDPOINT environment variable:

export LD_OTEL_ENDPOINT=http://localhost:4318/v1/traces
./build/examples/hello-cpp-server-otel/hello-cpp-server-otel