config/environments/production.rb? The default should be:
config.log_level = :info RAILS_DEFAULT_LOGGER = Logger.new('log/production.log')Make sure you haven't used
SyslogLoggeras that will log to the OS syslog, not a separate Rails app log, and Dokku won't find it. If you need to dig around in the container itself to debug and make sure the log is actually being created, you can run:
dokku run app_name '/bin/bash'