I had exited Gazebo and yet when I looked at my topics
was this with rostopic list and/or rostopic info and/or rqt_graph?
I still saw that cmd_vel (and a bunch of others) were still being subscribed to by Gazebo
Q&As #q285530 (and the linked #q9521) probably are relevant here (note: "abnormal termination" is not a necessary condition for what is described in the Q&As to happen).
If there are no Gazebo processes running any more, then seeing some subscriptions still being reported by the Master is not enough to conclude that "traces of Gazebo [are] left".
Edit:
Question is: was it something about how I exited Gazebo? Is this not unusual? Was my solution the right one? I also notice that with my kinetic install I am not getting the latest Gazebo. Which one should I be running? Thanks!
first a general comment: please try to not ask 4 questions in one ROS Answers post. That is not how this site is intended to work. A ratio of one question per post is ideal.
As to your questions:
was it something about how I exited Gazebo?
we can't know, as you don't tell us how you shut it down.
Is this not unusual?
No, not necessarily. But it depends on whether what you saw was caused by what I so far assume caused it.
Was my solution the right one?
Shutting down the Master? I wouldn't call it a solution, but it will result in all registrations vanishing, so for that specifically this could be a course of action to take, yes.
I also notice that with my kinetic install I am not getting the latest Gazebo. Which one should I be running?
Kinetic comes with Gazebo 7 (see REP 3: Platforms by Distribution - Kinetic Kame (May 2016 - May 2021). That is not the latest, no. It is the one with (probably) the best integration with Kinetic Kame and the packages that come with that.
You could install a newer version, using the procedure documented on gazebosim.org/Which combination of ROS/Gazebo versions to use.
Three things to keep in mind though:
- binary versions of ROS Kinetic packages that make use of / depend on Gazebo will have been built against Gazebo 7. Trying to install those using
apt-get very likely will result in apt trying to remove your new Gazebo version and installing the version 7. - any packages that are to be used with Gazebo (with Gazebo plugins fi) that you build from source for Kinetic will also most likely have been written with Gazebo 7 in mind. Changing to a different version could result in problems with those packages.
- besides build issues, the simulation itself may not behave the same between different versions of Gazebo. Dynamics may be different, resulting in different robot behaviour. Any software you write -- or others have written -- will inevitably (implicitly) assume certain behaviour. If you suddenly invalidate that (implicit) assumption, you may run into issues.
