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Datadog Agent RtLoader

CPython embedding/extending backend with support for multiple Python versions.

Concepts

RtLoader is a C++ wrapper around the CPython API with a C89-compatible public API that can be used by foreign languages like Go. In order to provide support for multiple Python versions, RtLoader fully abstracts Python in order to decouple client applications and CPython. Which Python version to use can be decided at runtime, RtLoader will dlopen the proper backend libraries accordingly.

Architecture

libdatadog-agent-rtloader

RtLoader exposes its C89-compatible API through include/datadog_agent_rtloader.h. By using the make2 and make3 functions, the corresponding Python backend will be loaded at runtime. Under the hood the library provides RtLoader, a C++ interface that must be implemented by any supported backend, see include/rtloader.h for details.

Two and Three

libdatadog-agent-three and libdatadog-agent-two libraries provide Python support for extending and embedding by linking different versions of the CPython library.

Common

The common folder contains C/C++ modules that are compiled into both libdatadog-agent-three and libdatadog-agent-two to avoid code duplication. Most of the code used to extend the embedded interpreter is there.

Requirements

  • C/C++ compiler
  • Python 2.7.x development packages
  • Python 3.8.x development packages
  • Cmake version 3.12 or above
  • Go compiler with cgo capabilities to run the tests

Build

RtLoader can be built using CMake. Run the configurator/generator first:

cmake .

Then just run make to build the project.

Examples

Demo

Examples about how to use RtLoader are provided in form of a C application under demo. The application expects to find a few things installed in the Python env. To easy development, a virtualenv can be used: the base check and the Directory check have to be installed before running the demo, if you have a local clone of integrations-core that should be a matter of pip install /path_to_integrations_core/datadog_checks_base and pip install /path_to_integrations_core/directory. Then depending on which Python version your virtualenv provides, run:

OSX:

DYLD_LIBRARY_PATH=./three:./two ./demo/demo 2 $VIRTUAL_ENV

Unix

LD_LIBRARY_PATH=./three:./two ./demo/demo 2 $VIRTUAL_ENV

or

OSX

DYLD_LIBRARY_PATH=./three:./two ./demo/demo 3 $VIRTUAL_ENV

Unix

LD_LIBRARY_PATH=./three:./two ./demo/demo 3 $VIRTUAL_ENV

Test

Tests are written in Golang using cgo, run the testsuite from the root folder:

make -C test