Logging-on-Rails 5: hide and seek with formatting, readibility and parsing

Photography skill \o/

Currently under Rails 5.2.1 / Ruby 2.5.1 and I quickly had enough of System.out.prin… oops, enough of puts. Anyway. I just want to track what happens in my application: how many milliseconds is taken by this method? Was this called before that? What happened before this error? And such.