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Dynamic reconfigure default parameters

asked 2012-02-23 09:01:43 -0500

updated 2013-04-05 01:42:17 -0500

Philip gravatar image

I am writing a node which accepts certain parameters. I would like to be able to pass them through a launch file, as well as make them dynamically reconfigurable.

What are the best practices regarding this? In particular:

  • What happens if the value in the launch file is not the same as the default value in the .cfg file?
  • Does it matter whether I register the dynamic reconfigure services before or after getting the parameters from the nodehandle using getParam()?
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Doesn't dynamic_reconfigure initialize the values from the param server automatically?

dornhege gravatar image dornhege  ( 2012-02-23 09:18:36 -0500 )edit

It would, but in configurations with "use_sim_time" and "rosbag play foo.bag --clock --pause" and then stepping through the bag file for debugging you potentially run into problems because no spinning seems to take place on sim_time, so no ros::spin()-based callbacks are called.

Crusty gravatar image Crusty  ( 2014-04-14 02:40:50 -0500 )edit

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answered 2012-02-23 09:37:10 -0500

Patrick Mihelich gravatar image

You should already get the desired behavior for free. When you create the dynamic_reconfigure server in your node, it initializes the configuration in these steps:

  • Load default values as defined in the .cfg.
  • Query parameter server for each parameter, overwriting the default value if it's set.
  • Clamp all parameters to the ranges defined in the .cfg.
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You're right! Unfortunately the ROSNodeTutorialC++ ( is misleading: It reads the parameters "a", "b" and "message" explicitly from the parameter server even though they are included in the dynamic reconfigure callback...

PiotrOrzechowski gravatar image PiotrOrzechowski  ( 2014-01-21 05:33:34 -0500 )edit

That tutorial may very well be in error. Please open a separate question explaining the problem, so we can get it resolved, as explained in the note at the top of each tutorial page.

joq gravatar image joq  ( 2014-01-21 06:13:43 -0500 )edit

answered 2012-02-23 09:33:03 -0500

joq gravatar image

updated 2012-02-23 09:33:57 -0500

Dynamic reconfiguration works fine for your use case.

When you register your callback, it gets invoked immediately with the values currently defined in the parameter server and a level of 0xffffffff. Those initial values will include anything set in your launch file. You don't need to read the parameters yourself using getParam().

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Asked: 2012-02-23 09:01:43 -0500

Seen: 8,489 times

Last updated: Feb 23 '12