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Only one model plugin receiving subscription data

asked 2018-05-20 02:50:36 -0500

varunvp gravatar image

updated 2018-05-21 01:10:27 -0500

Hey guys, I am publishing a Vector3 through a world plugin.

This is the code that publishes

namespace gazebo
    class global_wind : public WorldPlugin
        ignition::math::Vector3d wind;
        transport::PublisherPtr pub;
        private: event::ConnectionPtr updateConnection;

        public: void Load(physics::WorldPtr _parent, sdf::ElementPtr /*_sdf*/)
            gazebo::transport::NodePtr node(new gazebo::transport::Node);


            pub = node->Advertise<gazebo::msgs::Vector3d>("~/global_wind");

            this->updateConnection = event::Events::ConnectWorldUpdateBegin(std::bind(&global_wind::OnUpdate, this));

        //  gazebo::transport::fini();

        public: void OnUpdate()
            // pub->WaitForConnection();


            gazebo::msgs::Vector3d msg;
            gazebo::msgs::Set(&msg, wind);


The lines that are commented are causing some problems. The first commented line causes the following error

[Err] [ConnectionManager.cc:611] ConnectionManager is not initialized
[Err] [TransportIface.cc:416] ConnectionManager has not been initialized!
[Err] [Node.cc:125] No namespaces found

The 2nd commented line just makes gazebo hang when launching. Nonetheless, the plugin 'works' when these 2 are commented.

This is the code that sunscribes.

class wind_push : public ModelPlugin
    // Pointer to the model
    private: physics::ModelPtr model;

    // Pointer to the update event connection
    private: event::ConnectionPtr updateConnection;

    math::Vector3 force;

    public: void Load(physics::ModelPtr _parent, sdf::ElementPtr _sdf)
      // Store the pointer to the model
      this->model = _parent;

      // Create our node for communication
      gazebo::transport::NodePtr node(new gazebo::transport::Node());

      sub = node->Subscribe("/gazebo/default/global_wind", &wind_push::publ, this);

      gazebo::physics::LinkPtr link= model->GetChildLink("link_1");
      link->AddForce(gazebo::math::Vector3(20, 20, 0));

      // Listen to the update event. This event is broadcast every
      // simulation iteration.
      this->updateConnection = event::Events::ConnectWorldUpdateBegin(std::bind(&wind_push::OnUpdate, this));

    // Called by the world update start event
    public: void OnUpdate()
      gazebo::physics::LinkPtr link= model->GetChildLink("link_1");

    public: void publ(ConstVector3dPtr &_msg)
      std::cout << this->model->GetName();
  // Register this plugin with the simulator

So what's happening here is that I have many models with the above model plugin. The global_wind plugin publishes a global topic, from which wind_push is supposed to get the wind force vector and apply a suitable force. The problem is that only one model is responding to this force. After further debugging, I found out that only the model plugin on THAT model is calling the callback in the subscriber function, while I actually want all of them to be called. Debugging also revealed that all the model plugins are running, executing other parts of the code. I don't understand why this is happening. Thanks!

Edit:I printed the &wind_push::publ variable in the load function, and all model plugins referred to the same address! Shouldn't gazebo be running a seperate instance of the plugin for each model? Another thing I noticed is that the model which responds to the wind is the last model described with the subscriber plugin in the world file. I think that only the last model plugin's callback is being called. Or there ... (more)

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1 Answer

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answered 2018-05-21 10:39:58 -0500

Some ideas:

  1. Use the fully qualified topic name on both the publisher and the subscriber (i.e. /gazebo/default/global_wind)
  2. Did you try printing this instead of &wind_push::publ to see if that's also the same?
  3. Why do you want to call gazebo::transport::fini() on your load function? That will finish the whole transport system, so no more pub/sub for anyone.
  4. While running the simulation, run gz topic -i /gazebo/default/global_wind to see how many subscribers and publishers are there
  5. Store your subscriber in a member variable, otherwise it will only live in the scope of the load function.
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Apologies for the delay. The 1st solution worked for me! Thank you! Edit:Nope, it was actaully the last solution that worked for me. I reverted to the earlier topic name. Also, I did store the subscriber in a member variable, but it was initialised outside the class. Don't know why I did that. It worked when I added it inside.

varunvp gravatar imagevarunvp ( 2018-05-24 07:32:34 -0500 )edit

Glad to hear it worked out

chapulina gravatar imagechapulina ( 2018-05-24 12:37:01 -0500 )edit
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Asked: 2018-05-20 02:50:36 -0500

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Last updated: May 21 '18