Tracing C++ Applications

# Requires the "jq" command, which can be installed via
# the package manager, for example "apt install jq",
# "apk add jq", "yum install jq".
if ! command -v jq >/dev/null 2>&1; then
  >&2 echo "jq command not found. Install using the local package manager."
else
  # Gets the latest release version number from GitHub.
  get_latest_release() {
    curl --silent "https://api.github.com/repos/$1/releases/latest" | jq --raw-output .tag_name
  }
  DD_OPENTRACING_CPP_VERSION="$(get_latest_release DataDog/dd-opentracing-cpp)"
  # Download and install dd-opentracing-cpp library.
  wget https://github.com/DataDog/dd-opentracing-cpp/archive/${DD_OPENTRACING_CPP_VERSION}.tar.gz -O dd-opentracing-cpp.tar.gz
  mkdir -p dd-opentracing-cpp/.build
  tar zxvf dd-opentracing-cpp.tar.gz -C ./dd-opentracing-cpp/ --strip-components=1
  cd dd-opentracing-cpp/.build
  # Download and install the correct version of opentracing-cpp, & other deps.
  ../scripts/install_dependencies.sh
  # Configure the project, build it, and install it.
  cmake ..
  make -j
  make install
fi

// tracer_example.cpp
#include <datadog/opentracing.h>
#include <iostream>
#include <string>

int main(int argc, char* argv[]) {
  datadog::opentracing::TracerOptions tracer_options{"localhost", 8126, "compiled-in example"};
  auto tracer = datadog::opentracing::makeTracer(tracer_options);

  // Create some spans.
  {
    auto span_a = tracer->StartSpan("A");
    span_a->SetTag("tag", 123);
    auto span_b = tracer->StartSpan("B", {opentracing::ChildOf(&span_a->context())});
    span_b->SetTag("tag", "value");
  }

  tracer->Close();
  return 0;
}

g++ -std=c++14 -o tracer_example tracer_example.cpp -ldd_opentracing -lopentracing
./tracer_example

get_latest_release() {
  wget -qO- "https://api.github.com/repos/$1/releases/latest" |
    grep '"tag_name":' |
    sed -E 's/.*"([^"]+)".*/\1/';
}
DD_OPENTRACING_CPP_VERSION="$(get_latest_release DataDog/dd-opentracing-cpp)"
OPENTRACING_VERSION="$(get_latest_release opentracing/opentracing-cpp)"
# Download and install OpenTracing-cpp
wget https://github.com/opentracing/opentracing-cpp/archive/${OPENTRACING_VERSION}.tar.gz -O opentracing-cpp.tar.gz
mkdir -p opentracing-cpp/.build
tar zxvf opentracing-cpp.tar.gz -C ./opentracing-cpp/ --strip-components=1
cd opentracing-cpp/.build
cmake ..
make
make install
# Install dd-opentracing-cpp shared plugin.
wget https://github.com/DataDog/dd-opentracing-cpp/releases/download/${DD_OPENTRACING_CPP_VERSION}/linux-amd64-libdd_opentracing_plugin.so.gz
gunzip linux-amd64-libdd_opentracing_plugin.so.gz -c > /usr/local/lib/libdd_opentracing_plugin.so

// tracer_example.cpp
#include <opentracing/dynamic_load.h>
#include <iostream>
#include <string>

int main(int argc, char* argv[]) {
  // Load the tracer library.
  std::string error_message;
  auto handle_maybe = opentracing::DynamicallyLoadTracingLibrary(
      "/usr/local/lib/libdd_opentracing_plugin.so", error_message);
  if (!handle_maybe) {
    std::cerr << "Failed to load tracer library " << error_message << "\n";
    return 1;
  }

  // Read in the tracer's configuration.
  std::string tracer_config = R"({
      "service": "dynamic-load example",
      "agent_host": "localhost",
      "agent_port": 8126
    })";

  // Construct a tracer.
  auto& tracer_factory = handle_maybe->tracer_factory();
  auto tracer_maybe = tracer_factory.MakeTracer(tracer_config.c_str(), error_message);
  if (!tracer_maybe) {
    std::cerr << "Failed to create tracer " << error_message << "\n";
    return 1;
  }
  auto& tracer = *tracer_maybe;

  // Create some spans.
  {
    auto span_a = tracer->StartSpan("A");
    span_a->SetTag("tag", 123);
    auto span_b = tracer->StartSpan("B", {opentracing::ChildOf(&span_a->context())});
    span_b->SetTag("tag", "value");
  }

  tracer->Close();
  return 0;
}

g++ -std=c++11 -o tracer_example tracer_example.cpp -lopentracing
./tracer_example