C++ and OpenTelemetry

This page is intended for application developers who want to collect Cloud Trace data for C++ applications by using OpenTelemetry. OpenTelemetry is a vendor-neutral instrumentation framework that you can use to collect trace and metric data. For information about instrumenting your code, see Instrumentation and observability.

This page guides you through the following steps:

  • Install the OpenTelemetry packages.
  • Configure your application to export spans to Cloud Trace.
  • Configure your platform.

For release information, see the following:

For OpenTelemetry reference content, see the following:

For the latest details about OpenTelemetry for C++, along with additional documentation and examples, see OpenTelemetry.

Before you begin

  1. In the navigation panel of the Google Cloud console, select APIs & Services, click Enable APIs and Services, and then enable the Cloud Trace API:

    Go to Cloud Trace API settings

  2. If API enabled is displayed, then the API is already enabled. If not, click the Enable button.

Install the OpenTelemetry packages

Configure the export of spans to Cloud Trace

To configure the export of trace data, call the google::cloud::otel::ConfigureBasicTracing(...) method in your main() method:

namespace gc = ::google::cloud;
[](std::string project_id) {
  auto project = gc::Project(std::move(project_id));
  auto configuration = gc::otel::ConfigureBasicTracing(project);

  MyApplicationCode();
}

The field project_id is the Google Cloud project where you want to store the traces.

The method ConfigureBasicTracing(...) instantiates a TracerProvider object that implements a Cloud Trace exporter. If the object returned by the call to ConfigureBasicTracing(...) goes out of scope, then the previous TracerProvider object is reinstated, when one exists.

Configure sample rate

Applications might generate a large volume of trace data. The following sample illustrates how to configure the sampling rate:

namespace gc = ::google::cloud;
[](std::string project_id) {
  auto project = gc::Project(std::move(project_id));
  auto options = gc::Options{}.set<gc::otel::BasicTracingRateOption>(.001);
  auto configuration = gc::otel::ConfigureBasicTracing(project, options);

  MyApplicationCode();
}

Export to Cloud Trace with a custom TracerProvider

You might have use cases that require a custom TracerProvider object. For example, if you want to use multiple exporters at the same time, you need to make a custom TracerProvider object. In these cases, you can use the Cloud Trace exporter directly:

namespace gc = ::google::cloud;
using ::opentelemetry::trace::Scope;
[](std::string project_id) {
  // Use the Cloud Trace Exporter directly.
  auto project = gc::Project(std::move(project_id));
  auto exporter = gc::otel::MakeTraceExporter(project);

  // Advanced use cases may need to create their own tracer provider, e.g. to
  // export to Cloud Trace and another backend simultaneously. In this
  // example, we just tweak some OpenTelemetry settings that google-cloud-cpp
  // does not expose.
  opentelemetry::sdk::trace::BatchSpanProcessorOptions options;
  options.schedule_delay_millis = std::chrono::milliseconds(1000);
  auto processor =
      opentelemetry::sdk::trace::BatchSpanProcessorFactory::Create(
          std::move(exporter), options);
  auto provider = opentelemetry::sdk::trace::TracerProviderFactory::Create(
      std::move(processor));

  // Set the global trace provider
  opentelemetry::trace::Provider::SetTracerProvider(std::move(provider));

  MyApplicationCode();

  // Clear the global trace provider
  opentelemetry::trace::Provider::SetTracerProvider(
      opentelemetry::nostd::shared_ptr<
          opentelemetry::trace::TracerProvider>());
}

Instrument your own application

For information about how to configure your application to capture trace spans, see OpenTelemetry Tracing. This page describes how to do all of the following:

  • Create a span
  • Create nested spans
  • Set span attributes
  • Create spans with events
  • Create spans with links
// For more details on the OpenTelemetry code in this sample, see:
//     https://opentelemetry.io/docs/instrumentation/cpp/manual/
namespace gc = ::google::cloud;
using ::opentelemetry::trace::Scope;
[](std::string project_id) {
  auto project = gc::Project(std::move(project_id));
  auto configuration = gc::otel::ConfigureBasicTracing(project);

  // Initialize the `Tracer`. This would typically be done once.
  auto provider = opentelemetry::trace::Provider::GetTracerProvider();
  auto tracer = provider->GetTracer("my-application");

  // If your application makes multiple client calls that are logically
  // connected, you may want to instrument your application.
  auto my_function = [tracer] {
    // Start an active span. The span is ended when the `Scope` object is
    // destroyed.
    auto scope = Scope(tracer->StartSpan("my-function-span"));

    // Any spans created by the client library will be children of
    // "my-function-span". i.e. In the distributed trace, the client calls are
    // sub-units of work of `my_function()`, and will be displayed as such in
    // Cloud Trace.
    Client client;
    client.CreateFoo();
    client.DeleteFoo();
  };

  // As an example, start a span to cover both calls to `my_function()`.
  auto scope = Scope(tracer->StartSpan("my-application-span"));
  my_function();
  my_function();
}

Sample application

For a sample application, see the quickstart.

Configure your platform

You can use Cloud Trace on Google Cloud and other platforms.

Running on Google Cloud

When your application is running on Google Cloud, you don't need to provide authentication credentials in the form of a service account to the client library. However, you do need to ensure that your Google Cloud platform has the Cloud Trace API access scope enabled.

For a list of supported Google Cloud environments, see Environment support.

For the following configurations, the default access-scope settings enable the Cloud Trace API:

  • App Engine flexible environment

  • App Engine standard environment

  • Google Kubernetes Engine (GKE)

  • Compute Engine

  • Cloud Run

If you use custom access scopes, then you must ensure that Cloud Trace API access scope is enabled:

  • For information about how to configure the access scopes for your environment by using the Google Cloud console, see Configuring your Google Cloud project.

  • For gcloud users, specify access scopes using the --scopes flag and include the trace.append Cloud Trace API access scope. For example, to create a GKE cluster with only the Cloud Trace API enabled, do the following:

    gcloud container clusters create example-cluster-name --scopes=https://www.googleapis.com/auth/trace.append

Running locally and elsewhere

If your application is running outside of Google Cloud, then you must provide authentication credentials in the form of a service account to the client library. The service account must contain the Cloud Trace agent role. For instructions, see Creating a service account.

Google Cloud client libraries use Application Default Credentials (ADC) to find your application's credentials.

You can provide these credentials in one of three ways:

  • Run gcloud auth application-default login

  • Place the service account in a default path for your operating system. The following lists the default paths for Windows and Linux:

    • Windows: %APPDATA%/gcloud/application_default_credentials.json

    • Linux: $HOME/.config/gcloud/application_default_credentials.json

  • Set the GOOGLE_APPLICATION_CREDENTIALS environment variable to the path to your service account:

Linux/macOS

    export GOOGLE_APPLICATION_CREDENTIALS=path-to-your-service-accounts-private-key

Windows

    set GOOGLE_APPLICATION_CREDENTIALS=path-to-your-service-accounts-private-key

PowerShell:

    $env:GOOGLE_APPLICATION_CREDENTIALS="path-to-your-service-accounts-private-key"

View traces

In the navigation panel of the Google Cloud console, select Trace, and then select Trace explorer:

Go to Trace explorer

Troubleshooting

For information on troubleshooting issues with Cloud Trace, go to the Troubleshooting page.

To debug the C++ Cloud Trace exporter, see the Troubleshooting section of the reference documentation.

Resources