FastDDS Publisher ROS2 Subscriber Topic Type Hash

[bshantam97]

Hi, I am publishing MarkerArray Data from fastdds and ROS2 is subscribing to that. I can see ROS2 discovers the topic but when I perform a ros2 topic info i get a Topic Type Hash: INVALID. Under what circumstances does this take place ? I am not able to match it with the ROS2 RIHS for the MarkerArray.
I am using ROS2 rolling and FastDDS3 RMW. Below is the output of ros2 topic info
Publisher count: 1

Node name: CREATED_BY_BARE_DDS_APP
Node namespace: CREATED_BY_BARE_DDS_APP
Topic type: visualization_msgs/msg/MarkerArray
Topic type hash: INVALID
Endpoint type: PUBLISHER
GID: 01.0f.eb.7d.a4.03.5f.df.00.00.00.00.00.00.13.03
QoS profile:
Reliability: RELIABLE
History (Depth): UNKNOWN
Durability: TRANSIENT_LOCAL
Lifespan: Infinite
Deadline: Infinite
Liveliness: AUTOMATIC
Liveliness lease duration: Infinite

[juanlofer-eprosima]

Hi @bshantam97, would you be able to provide a reproducer? Or at least describe better your setup specifying the exact ROS 2 and Fast-DDS versions used in each component. It is expected that the topic type hash is not sent from a pure Fast-DDS application, however this should not be affecting matching or data reception.

[bshantam97]

Hi @juanlofer-eprosima thank you for your response. So i currently reverted back to fastdds 2.13 with ros2 humble and everything works as expected. Previously I used FastDDS 3.0.1 with the ROS2 rolling branch. It seems the data matching happened but On the ROS2 subscriber side aka rviz it was unable to decode the MarkerArray Topic as the hash is invalid.

[juanlofer-eprosima]

Hi @bshantam97, without a reproducer it will be difficult for us to help. Which IDL is your Fast-DDS publisher app using? If it's the one generated by ROS 2 msg to idl converter, that could be the problem and you might need to change it slightly. We are currently preparing a tutorial to deal with this scenario. I can also suggest to try with the latest Fast-DDS release (v3.1.2) just in case.