dynamic_reconfigure/Reviews

Package proposal

The dynamic_reconfigure package allows a node (the server) to get its configuration parameters in a way that allows parameters to be changed dynamically. The package provides:

• C++ and Python Server and Client APIs.
• GUI tool to dynamically reconfigure any node that uses the Server API.
• A command-line tool analogous to rosparam to dynamically reconfigure any node that uses the Server API.

The package satisfies the following proposed set of core requirements:

• Parameters are obtained from the parameter server at startup.
• Default values are automatically used when no parameter is specified on the parameter server.
• Parameters are maintained up to date on the parameter server when the node is reconfigured.
• Parameters are automatically clamped to be within their acceptable ranges before they are passed to the server code.
• Parameters are passed to the server code in a suitable data structure. In C++ this data structure must be a class in which the parameters are fields.
• The server code can adjust the parameter values it is given if they are illegal.
• Clients can atomically modify a subset of the parameters.
• Clients can be notified of changes to the parameters.
• It is easy for a client to determine when the parameters it set have been changed.

The package should satisfy the following proposed set of desirables:

• Documentation of the parameters can be autogenerated.

The following are hotly debated:

• How to communicate between the server and the client?
  • Via the parameter server.
  • Via service calls and topics.
  • Using the action interface.
• What types are supported?
  • Types that are supported from the C++ param API?
  • Types that are supported by roslaunch?
  • double, int32, string, bool?
  • double, int32, string, bool + lists of these?
  • Any message? (Need better support from roscpp.)
• How much effort should be put into making the GUI customizable by the nodes?
  • Ability to have some parameters be advanced.
  • Ability to dynamically change the ranges of the sliders.
  • Ability to grey out certain fields.
  • Ability to select different scales for the sliders (log scale, ...)

Give it a spin

Make sure you have run make twice in hokuyo_node/wge100_driver (autogeneration of messages is currently partly broken).

Bring up the robot.

Run

rosrun dynamic_reconfigure reconfigure_gui

Select what you want to reconfigure and reconfigure it.

If you don't want to bring up the robot, you can just run a hokuyo_node, a wge100_node or a wge100_multi_reconfigurator, and run the reconfigure_gui. You just won't be able to observe the result of your changes.

You can also play around with dynparam in the dynamic_reconfigure package.

Notes on current implementation

The description of the node's parameters is in the cfg directory (e.g. wge100_camera/cfg or hokuyo_node/cfg). In dynamic_reconfigure, I use message generation, but I don't like this implementation as in practice the message never seems to be built when you want it, and you can't atomically modify a subset of the parameters. I have started an alternate implementation in dynamic_reconfigure2 that uses a generic message. The code generation and C++ server API should be good, but I have stopped there pending the review meeting.

API Proposal

Still rough around the edges... dynamic_reconfigure works, but the C++ API sucks, and I don't like the message format. dynamic_reconfigure2 has only been partially ported to a new message format. Gives a better idea of what the C++ API should be like.

C++

Server

Have a look at dynamic_reconfigure2/test/testserver.cpp and dynamic_reconfigure

Client

Not implemented yet. Not sure how best to support modifying only selected parameters.

Python

Have a look at DynamicReconfigureServer and DynamicReconfigureClient in dynamic_reconfigure/src/dynamic_reconfigure/dynamic_reconfigure.py

Server

Have a look at wge100_camera/nodes/wge100_multi_configurator. This node is both a dynamic_reconfigure server and client. You configure it (server side), and it passes on its configuration to a list of wge100_camera nodes (client side). (Note that handling of configuration returned by wge100_node currently sucks.)

Client

Have a look at dynamic_reconfigure/dynparam for a simple example and dynamic_reconfigure/bin/reconfigure_gui for a more involved one.

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