Rclcpp: [BUG] Namespacing the parameter blackboard node leads to wrong events topic

[maxlein]

Bug report

Our system has all nodes namespaced, e.g. /robot_1/param_server.
Now we switched from eloquent to foxy, and all parameter events failed to fire.

After a bit of testing and asking a question, I found out that adding a namespace breaks parameter events.

Output from demo parameter blackboard started with namespace test_ns:

ros2 node info /test_ns/parameter_blackboard
/test_ns/parameter_blackboard
  Subscribers:
    /test_ns/parameter_events: rcl_interfaces/msg/ParameterEvent
  Publishers:
    /parameter_events: rcl_interfaces/msg/ParameterEvent
    /rosout: rcl_interfaces/msg/Log
  Service Servers:
    /test_ns/parameter_blackboard/describe_parameters: rcl_interfaces/srv/DescribeParameters
    /test_ns/parameter_blackboard/get_parameter_types: rcl_interfaces/srv/GetParameterTypes
    /test_ns/parameter_blackboard/get_parameters: rcl_interfaces/srv/GetParameters
    /test_ns/parameter_blackboard/list_parameters: rcl_interfaces/srv/ListParameters
    /test_ns/parameter_blackboard/set_parameters: rcl_interfaces/srv/SetParameters
    /test_ns/parameter_blackboard/set_parameters_atomically: rcl_interfaces/srv/SetParametersAtomically

parameter_events node:

ros2 node info /test_ns/parameter_events
/test_ns/parameter_events
  Subscribers:
    /test_ns/parameter_events: rcl_interfaces/msg/ParameterEvent
  Publishers:
    /parameter_events: rcl_interfaces/msg/ParameterEvent
    /rosout: rcl_interfaces/msg/Log

As you see the parameter_events topic subscriber has a namespace, whereas the publisher has not.
This doesn't look right to me..

I can get it to work by remapping the node local event topic to a global one: --ros-args -r parameter_events:=/parameter_events

Required Info:

• Operating System:
  
  
  
  • Ubuntu 20.04
  
  
• Installation type:
  
  
  
  • binaries, foxy
  
  
• DDS implementation:
  
  
  
  • Fast-RTPS
  
  
• Client library (if applicable):
  
  
  
  • rclcpp
  
  

Steps to reproduce issue

Start parameter blackboard node and parameter events node from demo_cpp project with a namespace, e.g. add --ros-args -r __ns:=/test_ns

Expected behavior

Parameter events are handled the same as without a namespace

Actual behavior

No parameter events are called

[fujitatomoya]

@maxlein
CC: @clalancette

I confirmed that problem's fixed, but it would be nice if you could double check. then we can close this.

[ivanpauno]

Fixed in https://github.com/ros2/rclcpp/pull/1257.

@maxlein If it doesn't work for you, let me know and I will reopen (the bug was corrected in master, it hasn't been fixed in Foxy yet).