Add concepts section

[carlossvg]

I propose to create a concepts section using the same style as in ROS 2 docs (https://docs.ros.org/en/rolling/Concepts.html). Here we can document different issues to take into account when developing a real-time capable application using ROS 2. This issue can work as place to discuss which topics we want to cover. We can open specific issues for each concept once we decide what to include.

Proposal:

• Memory management
  • Real-time capable containers: https://gitlab.com/ApexAI/apex_containers
  • Static Memory Allocation in DDS and rmw implementations
  • Bounded or fixed-sized data types
  • Memory allocations in ROS 2 and middleware
  • Real-time capable memory allocator
    - https://www.youtube.com/watch?v=l14Zkx5OXr4&ab_channel=CppCon
    - https://docs.ros.org/en/foxy/Tutorials/Allocator-Template-Tutorial.html
    - [rosidl_generator_cpp] use polymorphic allocator by default ros2/rosidl#566
  • Memory locking:
    - https://design.ros2.org/articles/realtime_background.html
    - https://wiki.linuxfoundation.org/realtime/documentation/howto/applications/memory
  • Detection of memory allocation and blocking system calls
    - https://github.com/osrf/osrf_testing_tools_cpp
    - https://gitlab.com/ApexAI/apex_test_tools
    - Provide framework for memory allocation and blocking system call detection and tracing community#8
• Logging
• Blocking calls
• Executor
  • ROS 2 callback groups
  • Executor Design https://docs.google.com/document/d/1O53xOVlk4zwsfNukLaDbSWfT64wnoD9xh2EjWwX43qo/edit
  • RCLC executor: https://micro.ros.org//docs/concepts/client_library/execution_management/
• Exceptions safety in C++
  • https://github.com/safety-critical-cpp/papers/blob/master/telecon/Exceptions_in_safety_critical_code.pdf
  • https://github.com/ApexAI/static_exception
  • https://drive.google.com/file/d/1nOhV2pHv24lRDlP5_UnAjwpwhzVLKIi8/view
• Concurrency and synchronization primitives
  • Priority inversion
  • Mutex, lock free, etc