Publish a message with OpenTelemetry tracing enabled

Publish a message with OpenTelemetry Tracing enabled while using a Cloud Trace exporter and sample rate of 100%.

Explore further

For detailed documentation that includes this code sample, see the following:

• Trace a C++ Application

Code sample

C++

Before trying this sample, follow the C++ setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub C++ API reference documentation.

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

// Create a few namespace aliases to make the code easier to read.
namespace gc = ::google::cloud;
namespace otel = gc::otel;
namespace pubsub = gc::pubsub;

// This example uses a simple wrapper to export (upload) OTel tracing data
// to Google Cloud Trace. More complex applications may use different
// authentication, or configure their own OTel exporter.
auto project = gc::Project(project_id);
auto configuration = otel::ConfigureBasicTracing(project);

auto publisher = pubsub::Publisher(pubsub::MakePublisherConnection(
    pubsub::Topic(project_id, topic_id),
    // Configure this publisher to enable OTel tracing. Some applications may
    // chose to disable tracing in some publishers or to dynamically enable
    // this option based on their own configuration.
    gc::Options{}.set<gc::OpenTelemetryTracingOption>(true)));

// After this point, use the Cloud Pub/Sub C++ client library as usual.
// In this example, we will send a few messages and configure a callback
// action for each one.
std::vector<gc::future<void>> ids;
for (int i = 0; i < 5; i++) {
  auto id = publisher.Publish(pubsub::MessageBuilder().SetData("Hi!").Build())
                .then([](gc::future<gc::StatusOr<std::string>> f) {
                  auto id = f.get();
                  if (!id) {
                    std::cout << "Error in publish: " << id.status() << "\n";
                    return;
                  }
                  std::cout << "Sent message with id: (" << *id << ")\n";
                });
  ids.push_back(std::move(id));
}
// Block until the messages are actually sent.
for (auto& id : ids) id.get();

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