Hi @poonam1120,
I believe ros2 launch should handle restarting a node if it crashes, however I can’t find an example of this in source or documentation (<no title>).
A ‘port’ of ROS1 would involve instantiating several lifecycle nodes inside one process. See the ‘composition’ demos: demos/composition at master · ros2/demos · GitHub
A more interesting implementation would have an executor aware of the pipeline structure (ROS2 pcl_perceptions - #17 by tfoote), however I don’t think any implementation or demo of this exists in the wild.
Correct, this certainly would be valuable to fix in the context of a porting effort.