Thanks @Paul_Bovbel for your response.
All these questions were related to existing code of pcl_ros in ROS.
As per my analysis, nodelet/node monitoring is handled by bond package which is already added to nodelet.
I am working on design doc for pcl_ros migration to ros2. Also I am checking how these things will be handled in ros2. Once the document is in good shape, will share with you.
Thanks,