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Note: C++ does not provide integrations for OOTB instrumentation, but it’s used by Proxy tracing such as Envoy and Nginx. For compatibility requirements for the C++ Tracer, visit the Compatibility Requirements page.
Instrument your application
After the Agent is installed, follow these steps to add the Datadog tracing library to your C++ applications in one of two ways:
- Compile against dd-opentracing-cpp, where the Datadog lib is compiled in and configured in code
- Dynamic loading, where the Datadog OpenTracing library is loaded at runtime and configured via JSON
Compile against dd-opentracing-cpp
# 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
Include <datadog/opentracing.h>
and create the tracer:
// 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;
}
Link against libdd_opentracing
and libopentracing
, making sure that they are both in your LD_LIBRARY_PATH
:
g++ -std=c++14 -o tracer_example tracer_example.cpp -ldd_opentracing -lopentracing
./tracer_example
Dynamic loading
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
Include <opentracing/dynamic_load.h>
and load the tracer from 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;
}
Just link against libopentracing
, making sure that libopentracing.so
is in your LD_LIBRARY_PATH
:
g++ -std=c++11 -o tracer_example tracer_example.cpp -lopentracing
./tracer_example
Note: OpenTracing requires C++ 11 or higher.
Configuration
If needed, configure the tracing library to send application performance telemetry data as you require, including setting up Unified Service Tagging. Read Library Configuration for details.
Further Reading
Documentation, liens et articles supplémentaires utiles: