Rest access log reformatting

Here’s a log from my restaccess.log:
2018-02-20 10:01:07,047 DEBUG: org.graylog2.rest.accesslog - 127.0.0.1 at [-] "POST api/cluster/metrics/multiple" Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:57.0) Gecko/20100101 Firefox/57.0 200 -1

As you can see, I am getting the ip of the localhost, but what I am actually interested in is getting the remote address as specified in the source code you provided. So, is there a specific configuration that allows me to get the remote address in the logs as well? Many thanks for your help.