I am experiencing a similar issue with filebeat-1.2.3 on centos7.
The log file that is being tracked reaches a maximum size of about 9.6MB and rotates out every couple days.
At startup, filebeat will start using 200-300MB of memory and over the course of 10-15 minutes will ramp up to as much as 900MB.
Attached you'll find my filebeat.yml as well as a memprofile from about a 10 minute period of the filebeat process running.

