topic_relay_controller

Purpose

The node subscribes to a specified topic, remaps it, and republishes it. Additionally, it has the capability to continue publishing the last received value if the subscription stops.

Inputs / Outputs

Input

Name	Type	Description
/<topic>	<specified message type>	Topic to be subscribed, as defined by the topic parameter.
/tf	tf2_msgs::msg::TFMessage	(Optional) If the topic is /tf, used for transform message relay.
/tf_static	tf2_msgs::msg::TFMessage	(Optional) If the topic is /tf_static, used for static transforms.

Output

Name	Type	Description
/<remap_topic>	<specified message type>	Republished topic after remapping, as defined by the remap_topic parameter.

Parameters

Variable	Type	Description
topic	string	The name of the input topic to subscribe to
remap_topic	string	The name of the output topic to publish to
topic_type	string	The type of messages being relayed
qos	integer	QoS profile to use for subscriptions and publications (default: 1)
transient_local	boolean	Enables transient local QoS for subscribers (default: false)
best_effort	boolean	Enables best-effort QoS for subscribers (default: false)
enable_relay_control	boolean	Allows dynamic relay control via a service (default: true)
srv_name	string	The service name for relay control when enable_relay_control is true
enable_keep_publishing	boolean	Keeps publishing the last received topic value when not subscribed (default: false)
update_rate	integer	The rate (Hz) for publishing the last topic value when enable_keep_publishing is true (optional)
frame_id	string	Frame ID for transform messages when subscribing to /tf or /tf_static (optional)
child_frame_id	string	Child frame ID for transform messages when subscribing to /tf or /tf_static (optional)

Assumptions / Known limits

• The node assumes that the specified topic and remap_topic are valid and accessible within the ROS 2 environment.
• If enable_keep_publishing is true, the node continuously republishes the last received value even if no new messages are being received.
• For /tf and /tf_static, additional parameters like frame_id and child_frame_id are required for selective transformation relays.
• QoS settings must be carefully chosen to match the requirements of the subscribed and published topics.