Add redis user with these permissions:
-@all +info +ping
Plugin checks backup nodes automatically for being readonly and connection to master, ie:
master_link_status:up
slave_read_only:1
Number of expected replicas on a master is configurable, ie:
check_redis.py -u monitoring -P $(/usr/bin/cat /etc/check_redis_auth) --backup_nodes=1
Or omit the --backup_nodes flag for a standalone/single instance.