Setting Up APM with C++

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Overview

This guide expands on the C++ APM docs to provide step-by-step instructions on how to set up a simple C++ app with APM on your VM for troubleshooting.

Setting up your box

Basic environment

First, spin up a fresh ubuntu/jammy64 Vagrant box and ssh into it with:

vagrant init ubuntu/jammy64
vagrant up
vagrant ssh

Next, install the agent with the instructions in the UI.

Prepping for C++

Install g++ and cmake with:

sudo apt-get update
sudo apt-get -y install g++ cmake

Download and install dd-trace-cpp library with:

wget https://github.com/DataDog/dd-trace-cpp/archive/v0.2.0.tar.gz -O dd-trace-cpp.tar.gz

If you get a rate limited message from GitHub, wait a few minutes and run the command again.

After downloading the tar file, unzip it:

tar zxvf dd-trace-cpp.tar.gz -C ./dd-trace-cpp/ --strip-components=1

Finally, build and install the library:

cd dd-trace-cpp
cmake -B build .
cmake --build build -j
cmake --install build

Building a simple app

Create a new file called tracer_example.cpp and populate it with the below code:

#include <datadog/tracer.h>
#include <iostream>
#include <string>

int main(int argc, char* argv[]) {
  datadog::tracing::TracerConfig tracer_config;
  tracer_config.service = "compiled-in example";

  const auto validated_config = dd::finalize_config(tracer_options);
  if (!validated_config) {
    std::cerr << validated_config.error() << '\n';
    return 1;
  }

  dd::Tracer tracer{*validated_config};

  // Create some spans.
  {
    datadog::tracing::SpanConfig options;
    options.name = "A";
    options.tags.emplace("tag", "123");
    auto span_a = tracer.create_span(options);

    auto span_b = span_a.create_child();
    span_b.set_name("B");
    span_b.set_tag("tag", "value");
  }

  return 0;
}

This creates a tracer that generates two spans, a parent span span_a and a child span span_b, and tags them.

Then, compile and link against libdd_trace_cpp with:

g++ -std=c++17 -o tracer_example tracer_example.cpp -ldd_trace_cpp

Finally, run the app with:

LD_LIBRARY_PATH=/usr/local/lib/ ./tracer_example

Sending traces

Now that an app exists, you can start sending traces and see the Trace Agent in action.

First, tail the Trace Agent log with:

tail -f /var/log/datadog/trace-agent.log

Next, open a new tab and run the example a couple times:

LD_LIBRARY_PATH=/usr/local/lib/ ./tracer_example

On the Trace Agent tab, you will see something similar to:

2019-08-09 20:02:26 UTC | TRACE | INFO | (pkg/trace/info/stats.go:108 in LogStats) | [lang:cpp lang_version:201402 tracer_version:0.2.0] -> traces received: 1, traces filtered: 0, traces amount: 363 bytes, events extracted: 0, events sampled: 0

The service then shows up in the Service Catalog in Datadog.

APM Services Page

Click on the service to view your traces.

APM Traces UI

Further Reading

추가 유용한 문서, 링크 및 기사: