This is a Redis read replica that is configured to slave off of $REDIS_MASTER_IP_ADDRESS, port 6379. Note that this read replica itself runs on port 7000.
An example command for running this script so that it slaves off of a master running at 10.0.8.101:
docker run -d -p 7000:7000 -e "REDIS_MASTER_IP_ADDRESS=10.0.8.101" mdgraboski/redis-read-replica
This image is a derivative work from the Redis dockerfile found at: https://github.com/dockerfile/redis