when i change the configuration of a slave, the slave should relaunch itself to adopt the new configuration, or a flag/message should be shown that the config is out of date on that node (updated since launch).

For instance, if I change the host or port for the slave, and then run a job, I expect that job to run on the new host.

However, I accept there may be times when I want to defer the launch (for instance to launch all slaves at a cutover time), so a warning that the slave needs to be re-launched may be a suitable compromise.