smnogar / topic_tools

Tools for directing, throttling, selecting, and otherwise manipulating ROS 2 topics at a meta-level.

topic_tools

This package is the ROS 2 port of http://wiki.ros.org/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.

The tools in this package are provided as composable ROS 2 component nodes, so that they can be spawned into an existing process, launched from launchfiles, or invoked from the command line.

Components

Relay

Relay is ROS 2 node that subscribes to a topic and republishes all incoming data to another topic. It can work with any message type.

Usage

ros2 run topic_tools relay <intopic> [outtopic]

Subscribe to intopic and republish to either

• outtopic if specified
• <intopic>_relay if not

E.g. rename base_scan to my_base_scan:

ros2 run topic_tools relay base_scan my_base_scan

Parameters

• input_topic (string)
  • the same as if provided as a command line argument
• output_topic (string, default=<input_topic>_relay)
  • the same as if provided as a command line argument
• lazy (bool, default=False)
  • If True, only subscribe to input_topic if there is at least one subscriber on the output_topic

Transform

Transform is ROS 2 node that allows to take a topic or one of it fields and output it on another topic

Usage

ros2 run topic_tools transform <input topic> <output topic> <output type> [<expression on m>] [--import <modules>] [--field <topic_field>]

Subscribe to input topic and convert topic content or its field into

• output topic whose type is output type based on expression on m

E.g. transform imu orientation to norm:

ros2 run topic_tools transform /imu --field orientation /norm std_msgs/Float64 'std_msgs.msg.Float64(data=numpy.sqrt(numpy.sum(numpy.array([m.x, m.y, m.z, m.w]))))' --import std_msgs numpy

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.

Usage

throttle message (rate)

ros2 run topic_tools throttle messages <intopic> <msgs_per_sec> [outtopic]

Throttle messages on intopic to a particular rate.

• intopic: Incoming topic to subscribe to
• msgs_per_sec: maximum messages per second to let through.
• outtopic: Outgoing topic to publish on (default: intopic_throttle)

E.g. throttle bandwidth-hogging laser scans (base_scan) to 1Hz:

ros2 run topic_tools throttle messages base_scan 1.0

throttle bytes (bandwidth)

ros2 run topic_tools throttle bytes <intopic> <bytes_per_sec> <window> [outtopic]

Throttle messages on intopic to a particular rate.

• intopic: Incoming topic to subscribe to
• msgs_per_sec: maximum messages per second to let through.
• outtopic: Outgoing topic to publish on (default: intopic_throttle)

E.g. throttle bandwidth-hogging laser scans (base_scan) to 1KBps:

ros2 run topic_tools throttle bytes base_scan 1024 1.0

Parameters

• input_topic (string)
  • the same as if provided as a command line argument
• output_topic (string, default=<input_topic>_throttle)
  • the same as if provided as a command line argument
• lazy (bool, default=False)
  • If True, only subscribe to input_topic if there is at least one subscriber on the output_topic
• ues_wall_clock (bool, default=False)
  • If True, then perform all rate measurements against wall clock time, regardless of whether simulation / log time is in effect.

Drop

Drop is ROS 2 node that can subscribe to a topic and republish incoming data to another topic, dropping X out of every Y incoming messages. It's mainly useful for limiting bandwidth usage, e.g., over a wireless link. It can work with any message type.

Usage

ros2 run topic_tools drop <intopic> <X> <Y> [outtopic]

Subscribe to and drop every out of messages.

• intopic: Incoming topic to subscribe to
• X, Y: drop X out of every Y incoming messages
• outtopic: Outgoing topic to publish on (default: intopic_drop, e.g. when intopic is "base_scan", then it will be base_scan_drop)

E.g. drop every other message published to base_scan:

ros2 run topic_tools drop base_scan 1 2

Parameters

• input_topic (string)
  • the same as if provided as a command line argument
• output_topic (string, default=<input_topic>_drop)
  • the same as if provided as a command line argument
• lazy (bool, default=False)
  • If True, only subscribe to input_topic if there is at least one subscriber on the output_topic
• X, Y (int)
  • drop X out of every Y incoming messages