If you are using the default Logger in your Elixir/Phoenix web app with no further configuration then your logs will rotate rather quickly. If you are using Distillery then, by default, your log files will be in var/log and they’ll be named like:

erlang.log.1
erlang.log.2
erlang.log.3
erlang.log.4
erlang.log.5

and they won’t exceed 100,000 bytes. This isn’t very much in a production deployment for a web app so you probably want to increase this so that you can tail a single log file to get a quick indication of what is going on with your app.

The default logger is subject to the Erlang environment variables. The one you’ll want to modify to increase the size of your logging file is: RUN_ERL_LOG_MAXSIZE. From the documentation:

RUN_ERL_LOG_MAXSIZE
  The size, in bytes, of a log file before switching to a new
  log file. Defaults to 100000, minimum is 1000, maximum is
  about 2^30.