Intrometry

CI status

Introduction

ROS2 telemetry collection utility that addresses the same problem as https://github.com/pal-robotics/pal_statistics, but in a different way. The main API difference is that intrometry relies on ariles serialization library https://github.com/asherikov/ariles instead of macro.

Doxygen documentation: https://asherikov.github.io/intrometry/doxygen/group__API.html

Comparison

pal_statistics

double my_variable = 3.0;
REGISTER_VARIABLE(node, "/statistics_topic", "my_variable_name", &my_variable);
...
for(...)
{
    PUBLISH_STATISTICS(node, "/statistics_topic");
}
...
UNREGISTER_VARIABLE(node, "/statistics_topic", "my_variable_name");

intrometry

class ArilesDebug : public ariles2::DefaultBase
{
#define ARILES2_DEFAULT_ID "ArilesDebug"
#define ARILES2_ENTRIES(v)                              \
    ARILES2_TYPED_ENTRY_(v, duration, double)           \
    ARILES2_TYPED_ENTRY_(v, size, std::size_t)          \
    ARILES2_TYPED_ENTRY_(v, vec, std::vector<float>)
#include ARILES2_INITIALIZE
}
...
intrometry::Publisher publisher;
ArilesDebug debug;
...
publisher.initialize("my_publisher");
publisher.assign(debug);
...
for(...)
{
    publisher.write(debug);
}
publisher.retract(debug);

Example of a published message (plotjuggler_msgs/msg/statistics_names)

header:
  stamp:
    sec: 0
    nanosec: 0
  frame_id: ""
names:
- "ArilesDebug.duration"
- "ArilesDebug.size"
- "ArilesDebug.vec_0"
- "ArilesDebug.vec_1"
- "ArilesDebug.vec_2"

Key features:

• intrometry is less verbose when working with a large number of metrics due to their grouping in classes, e.g., there is no need to explicitly specify topic and node;
• intrometry avoids potential memory violations due to API misuse by not using pointers to variables;
• intrometry hides implementation details from the user, so there is no need to manually control publishing threads as in http://wiki.ros.org/pal_statistics/Tutorials/Registering%20and%20publishing%20variables#Real_Time_usage_example;
• automatic generation of variable names and support for various types suchs as Eigen matrices, stl vectors, maps, etc is provided by ariles.

Dependencies

• C++17 compatible compiler
• cmake
• ariles (ariles2_namevalue2_ws) https://github.com/asherikov/ariles/tree/pkg_ws_2
• thread_supervisor https://github.com/asherikov/thread_supervisor
• rclcpp / plotjuggler_msgs

Design

• Publisher creates a dedicated ROS2 node and spawns a publishing thread that takes care of sending data using plotjuggler_msgs at a given frequency. Recorded ROS bags can be viewed with PlotJuggler https://plotjuggler.io/. Keep in mind that PlotJuggler has a flaw that may result in a collision of metric names facontidavide/PlotJuggler#339 -- intrometry makes an effort to avoid this, but it is still possible.

• intrometry tries to interfere as little as possible with the execution of other code, in particular this means that:

  • intrometry would rather lose data than block calling thread for more time than is needed for copying it;
  • intrometry ignores failures, e.g., due to failed initialization, which allows to disable it by simply providing an empty id.

• API:

  • Public API is ROS2 / plotjuggler_msgs agnostic, other backends may be implemented in the future.
  • initialize(), assign(), and retract() methods are "heavy" and are meant to be used sparingly.
  • write() is a "light" method that should be suitable for soft real time applications.

TODO

• Do data preprocessing in the publisher thread, e.g., with ariles finalize visitor. That would require locking of the data, one option is to keep two copies of the class and swapping them.