transport::Publisher occasionally fails to send messages

[nlamprian]

When calling the delete_model service of gazebo_ros_api_plugin, sometimes the service fails to delete the model. If the service fails once, it never works again after that point. Looking further into it, it seems there is a problem with the request_pub_ publisher. The publisher never publishes the messages. I confirmed that by subscribing to /gazebo/default/request. Also, request_pub_->HasConnections() always returns true, and request_pub_->GetOutgoingCount() shows that the messages are accumulating.

To reproduce this:

1. roslaunch gazebo_ros empty_world.launch
2. rosrun gazebo_ros spawn_model -sdf -file <path_to_model> -model model0
3. rosservice call /gazebo/delete_model "model_name: model0"

and repeat until the problem shows up.

I'm using gazebo 9.13.0

[nlamprian]

Fixed in gazebo 9.15.0