[ros-users] [Discourse.ros.org] [Next Generation ROS] ROS1 shim library development proposal

Ingo Lütkebohle ros.discourse at gmail.com
Tue Aug 28 13:48:47 UTC 2018

The option of modifying roscpp and rospy is likely faster and more backwards compatible. It might also help with the other maintenance efforts on ROS1.

That said, if we could eventually transition to something built on top of rcl, it would allow is to get rid of the legacy codebase.

Steps for roscpp, with several design choices to make that also apply to rospy.

1. For hacking the old codebase, we need a rosgraph replacement as well, to get the info about the system. It might be a good start to have a rosmaster node, maybe based on the ROS2 info server (not sure what that's called right now). In a later step, we could replace the roscpp graph calls with queries of the rmw info directly. Or maybe it would be easier to do that right away, that would be something look at.

2. rostime and rosconsole I would have to look at in l more detail.

3. In roscpp, the transport is already pluggable, so it "should" be straightforward to replace with rmw.

Topics and services are a fairly small layer above that, maybe we can even reuse the existing ones.

4. Parameters live in the node in ROS2, which is not a big issue in itself, but we would also need to provide the parameter node interface. Or we could support the old parameter server in the master, which would again be more backwards compatible but is a break from how ROS2, particularly its launch system does it

5. ROS2 node interfaces are required for full integration with ROS2. We have a port of the ROS2 lifecycle to ROS1 already, which could be used to build the lifecycle interface. Not sure about the rest.

Btw, all that's just of the top of my head right now, because I'm traveling with bad Internet access and can only email irregularly. As well as having family things to do ;-) Expect more interaction starting from 10th of September.

However, bouncing around some of the design questions should be possible. I'll try my best.

Cheers, Ingo

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