ros::init() needed for ROS Gazebo plugin?

asked 2013-02-22 02:51:46 -0600

bit-pirate
129 ●8 ●8 ●16

After reading this thread on the Gazebo-list about plugins residing inside the Gazebo ROS node, I found out that my plugin is running fine without the ros::init() call.

The tutorials (e.g. here for 1.3) however make use of this initialisation. So now I wonder, if it is necessary or not?

Since, the plugin is loaded into the Gazebo node, it would make sense to me, that ros::init is not needed (similar to nodelets in ROS).

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answered 2013-03-07 22:38:27 -0600

nkoenig
7676 ●8 ●44 ●71 http://gazebosim.org/

Gazebo does not call ros:init. It's up to one of your plugins (or a plugin that you load) to call ros::init.

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Right, but the question is, if it is needed. My plugin for example has subs & pubs, but since it is loaded into gazebo, which is also acting as a ROS node, it works fine without calling ros::init(). So, I wonder in which case it is actually needed.

bit-pirate ( 2013-03-08 04:04:13 -0600 )edit

2

Gazebo is acting as a ROS node because someone inside the process called ros::init(). If it wasn't your plugin, some other plugin must have done it, as standalone Gazebo does not do it. So yes, it is needed to make your plugin robust to the case when it's the only ROS-enabled component inside the Gazebo process.

Adolfo Rodríguez T ( 2013-03-08 04:16:18 -0600 )edit

You should have posted this as an answer. :-) Anyway, if I remove all plugins I am using, Gazebo is still showing up as a ROS node and is publishing/subscribing to topics. AFAIK this requires a ros::init(). Am I missing something?

bit-pirate ( 2013-03-08 04:44:03 -0600 )edit

ROS wraps gazebo. So when you say you run gazebo, you're probably running a special gazebo script that loads in a plugin that in turn calls ros::init. Take a look in the simulator_gazebo package.

nkoenig ( 2013-03-15 18:23:11 -0600 )edit

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answered 2013-02-22 04:03:52 -0600

Boris

330 ●11 ●14 ●22

I think in some cases it may fail. Most of the gazebo_ros_* plugins in ROS have the following code:

if (!ros::isInitialized())
{
  int argc = 0;
  char** argv = NULL;
  ros::init(argc, argv, "gazebo", ros::init_options::NoSigintHandler |
                                  ros::init_options::AnonymousName);
}

So, probably in your case ROS is just initialized already. Though, I am not sure what "initialized" means in this case.

Boris