Option to use wall-time in pose tree tf ROS topic

Currently, the /tf topic only outputs elapsed time, which causes error like

[ WARN] [1615823058.321955994]: Costmap2DROS transform timeout. Current time: 1615823058.3219, global_pose stamp: 10.3690, tolerance: 0.3000

Is there any option to change this to use the wall-time i.e. the current realtime? Thanks.

Or at least is there a method to publish the timestamp as a /clock topic so other ros nodes can be set to use_sim_time? Currently the tf topic is published at a completely separate time than any other node, which makes the development quite difficult.

@henry_z its not currently possible for /clock to publish wall-time, we will add an option to switch between the two.