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Topic Tools

Tools for directing, throttling, selecting, and otherwise manipulating ROS 2 topics at a meta-level. These tools do not generally perform serialization on the streams being manipulated, instead acting on generic binary data using rclcpp's GenericPublisher and GenericSubscription

github

  • Relay: Subscribes to a topic and republishes to another.
  • RelayField: Republishes data in a different message type.
  • Transform: Manipulates a topic or a field and outputs data on another topic.
  • Throttle: Republishes data with bandwidth or rate limit.
  • Drop: Republishes by dropping X out of every Y incoming messages.
  • Mux: Multiplexes incoming topics to an output.
  • Delay: Delays and republishes incoming data.

Throttle

Throttle is ROS 2 node that subscribes to a topic and republishes incoming data to another topic, either at a maximum bandwidth or maximum message rate.

Rate (throttle message)

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ros2 run topic_tools throttle messages <in topic> <msgs_per_sec> [out topic]

Demo

Decrease incoming topic rate

  • Node that publish counter data at 10hz
  • topic tool throttle republish message at 1hz
  • Topic echo to view to throttle output
counter_publisher.py
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#!/bin/python3

import rclpy
from rclpy.node import Node
from std_msgs.msg import Int32

class CounterPublisher(Node):
    def __init__(self):
        super().__init__('counter_publisher')
        self.publisher_ = self.create_publisher(Int32, 'counter', 10)
        self.counter = 0
        self.timer = self.create_timer(0.1, self.timer_callback)

    def timer_callback(self):
        msg = Int32()
        msg.data = self.counter
        self.publisher_.publish(msg)
        self.get_logger().info(f'Publishing: {msg.data}')
        self.counter += 1

def main(args=None):
    rclpy.init(args=args)
    node = CounterPublisher()
    rclpy.spin(node)
    node.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()
topic_throttle.yaml
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session_name: my_session
windows:
  - window_name: my_window
    layout: even-vertical
    shell_command_before:
      - source /opt/ros/humble/setup.bash
      - export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp
    panes:
      - shell_command: #
          - printf '\033]2;%s\033\\' 'pub'
          - python3 /workspace/src/g_stream/scripts/counter_publisher.py
      - shell_command: #
          - printf '\033]2;%s\033\\' 'throttle'
          - ros2 run topic_tools throttle messages counter 1.0 counter_t
      - shell_command: #
          - printf '\033]2;%s\033\\' 'sub'
          - ros2 topic echo /counter_t
output

alt text

Mux

Mux is a ROS2 node that subscribes to a set of incoming topics and republishes incoming data from one of them to another topic

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ros2 run topic_tools mux <outopic> <intopic1> [intopic2...]

Demo

Subscribe to multiple (two) image source and select between them using MuxSelect service Using gscam package to create image source

Note

  • list
  • add
  • delete
  • select
topic_mux.yaml
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session_name: my_session
windows:
  - window_name: my_window
    layout: even-vertical
    shell_command_before:
      - source /opt/ros/humble/setup.bash
      - export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp
    panes:
      - shell_command: #
          - printf '\033]2;%s\033\\' 'source1'
          - export GSCAM_CONFIG="videotestsrc ! video/x-raw,width=640,height=480,framerate=30/1 ! videoconvert"
          - ros2 run gscam gscam_node --ros-args -r /camera/image_raw:=image1
      - shell_command: #
          - printf '\033]2;%s\033\\' 'source2'
          - export GSCAM_CONFIG="videotestsrc pattern=snow ! video/x-raw,width=640,height=480,framerate=30/1 ! videoconvert"
          - ros2 run gscam gscam_node --ros-args -r /camera/image_raw:=image2
      - shell_command: #
          - printf '\033]2;%s\033\\' 'mux'
          - ros2 run topic_tools mux out_image image1 image2  
      - shell_command: #
          - printf '\033]2;%s\033\\' 'mux'
          - ros2 run rqt_image_view rqt_image_view out_image
      - shell_command: 
          - printf '\033]2;%s\033\\' 'control'
          - ros2 service call /mux/list topic_tools_interfaces/srv/MuxList "{}"
          # - ros2 service call /mux/select topic_tools_interfaces/srv/MuxSelect "{topic: 'image2'}"

TODO: check transform and implement it in cpp using exprTk library