Add Adjust The Production Log Level as a Rails TIL

rails/adjust-the-production-log-level.md

@@ -0,0 +1,33 @@
+# Adjust The Production Log Level
+
+A Rails app by default takes on the `debug` log level. This is great for
+development because it spits out a lot of information as you build and debug.
+
+That's going to typically be a bit too noisy for a production environment
+though. That is why Rails ships with the `config/environments/production.rb`
+file configured to the `info` log level.
+
+```ruby
+# config/environments/production.rb
+Rails.application.configure do
+
+  # ...
+
+  # "info" includes generic and useful information about system operation, but avoids logging too much
+  # information to avoid inadvertent exposure of personally identifiable information (PII). If you
+  # want to log everything, set the level to "debug".
+  config.log_level = ENV.fetch("RAILS_LOG_LEVEL", "info")
+
+  # ...
+end
+```
+
+Sometimes, like when we're trying to track down some buggy behavior, we may
+want to switch Rails from one log level to another. That's why it is configured
+by the `RAILS_LOG_LEVEL` env var and otherwise falls back to `info`.
+
+To, for example, switch production over to the `debug` log level, we'd first
+change the `RAILS_LOG_LEVEL` env var to `debug`. Then we'd need to make sure
+our Rails app is restarted so that the config change is picked up. Heroku's
+`heroku config:set` will do that automatically. Depending on your setup, you
+may need to manually restart your web server (e.g. Puma).