ROS Parameter Server Sync

[baronep]

I saw on the github page that the parameter server is not synced with the current version of the software. What was the reason for this? Is there a blocking issue on this?

[atiderko]

it was a decision to not implement this feature. Key arguments are:

• a lot of parameter are used by nodes only on start.
• the dynamic reconfigure changes the parameter on the ROS parameter server where the ROS node is registered. You need for these parameter also no synchronization.
• not clear collision resolution of global parameter
• parameter with huge amount of data, e.g. robot_description, can lead to unnecessary network load, so it is better to define this locally again.

If you still need parameter synchronization, there is one in a fork with parameter sync node

[atiderko]

added separate script param_sync.py, see commit b5805b3

[marcus011]

Hi @atiderko , How to use this param_sync file ,can you explain more about it

[atiderko]

Hi @marcus011, an example of the .sync file can be found in the launch folder of the fkie_master_sync. Es ist eine ROS-format compatible YAML-Datei mit den gleichen Parametern wie in der Launch-Datei. It can be loaded in the launch file using either the rosparam or the~interface_url parameter.

The ~interface_url parameter was introduced for use with Node Manager. On launch the master_sync using the button in host description panel you can choose a .sync file.

[marcus011]

Hi @atiderko , Thanks for the information, basically I want to load /robot_description parameter from another roscore using a launch file to my gazebo roscore, so can you guide how I can sync those parameter to my gazebo ,so that robot can be loaded up

[atiderko]

On the machine where you need remote parameter run: rosrun fkie_master_sync param_sync.py

It is a simple script which listen to changes published by master_discovery and get parameter from remote roscore.

[marcus011]

I have tested that command & robot_description is not loading up on gazebo side

[atiderko]

Sorry, I see now, a namespace is added by default. Try this: rosrun fkie_master_sync param_sync.py _add_ns:=False

[marcus011]

I am getting this error when using command rosrun fkie_master_sync param_sync.py _add_ns:=False

[ERROR] [1627628967.414029]: bad callback: <function master_changed at 0x7f0eb5c1e2d0>
Traceback (most recent call last):
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/topics.py", line 748, in _invoke_callback
    cb(msg, cb_args)
  File "/home/marcus/catkin_ws/src/multimaster/fkie_master_sync/nodes/param_sync.py", line 32, in master_changed
    master_to['/'+_ns] = params_from
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/msproxy.py", line 138, in __setitem__
    rospy.impl.paramserver.get_param_server_cache().update(resolved_key, val)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/impl/paramserver.py", line 102, in update
    value_key = namespaces[-1]
IndexError: list index out of range

[atiderko]

hmm... currently I have no time to debug. Perhaps something is wrong with provided namespaces to MasterProxy. The script is very easy if you want to try to fix ;-)