# C++

Instrument C++ applications with OpenTelemetry

# Integration

Instrument your C++ applications to send traces, logs, and metrics to Kopai.

## Installation

### CMake (Recommended)

```cmake
find_package(opentelemetry-cpp CONFIG REQUIRED)

target_link_libraries(myapp
    opentelemetry-cpp::trace
    opentelemetry-cpp::logs
    opentelemetry-cpp::metrics
    opentelemetry-cpp::otlp_http_exporter
)
```

### vcpkg

```bash
vcpkg install opentelemetry-cpp[otlp-http]
```

## Basic Setup

```cpp
#include <opentelemetry/exporters/otlp/otlp_http_exporter_factory.h>
#include <opentelemetry/exporters/otlp/otlp_http_exporter_options.h>
#include <opentelemetry/sdk/trace/tracer_provider_factory.h>
#include <opentelemetry/sdk/trace/simple_processor_factory.h>
#include <opentelemetry/trace/provider.h>

namespace otlp = opentelemetry::exporter::otlp;
namespace trace_sdk = opentelemetry::sdk::trace;
namespace trace_api = opentelemetry::trace;

void initTracer() {
    // Get endpoint from environment
    const char* endpoint = std::getenv("OTEL_EXPORTER_OTLP_ENDPOINT");
    if (!endpoint) endpoint = "http://localhost:4318";

    otlp::OtlpHttpExporterOptions options;
    options.url = std::string(endpoint) + "/v1/traces";

    auto exporter = otlp::OtlpHttpExporterFactory::Create(options);
    auto processor = trace_sdk::SimpleSpanProcessorFactory::Create(
        std::move(exporter)
    );
    auto provider = trace_sdk::TracerProviderFactory::Create(
        std::move(processor)
    );

    trace_api::Provider::SetTracerProvider(std::move(provider));
}
```

## Creating Spans

```cpp
auto tracer = trace_api::Provider::GetTracerProvider()
    ->GetTracer("my-app", "1.0.0");

auto span = tracer->StartSpan("my-operation");
auto scope = tracer->WithActiveSpan(span);

// Your code here

span->End();
```

## Running Your Application

```bash
export OTEL_EXPORTER_OTLP_ENDPOINT="https://otlp-http.kopai.app"
export OTEL_SERVICE_NAME="my-service"
./myapp
```

| Variable | Description |
|----------|-------------|
| `OTEL_EXPORTER_OTLP_ENDPOINT` | Kopai OTLP endpoint |
| `OTEL_SERVICE_NAME` | Name shown in Kopai UI |

## Build Notes

Building opentelemetry-cpp requires:
- CMake 3.12+
- C++14 or later
- curl, gRPC, protobuf dependencies

For a complete working example:                                                                                                   
[C++ Example](https://github.com/kopai-app/kopai-integration-examples/tree/main/cpp)

## Reference

[OpenTelemetry C++](https://opentelemetry.io/docs/languages/cpp/)