HAProxy configuration sample with resolvers options

haproxy.cfg

global
    log         127.0.0.1 local2

    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4096
    user        haproxy
    group       haproxy
    daemon
    stats socket /var/lib/haproxy/stats
    stats maxconn 1
    stats timeout 120s

resolvers awsvpc
    nameserver vpc 172.31.0.2:53

defaults
    mode        tcp
    log         global
    retries     3
    timeout     connect 10s
    timeout     client 1m
    timeout     server 1m
    timeout     check 10s
    maxconn     512

listen mysql
    bind 127.0.0.1:3306
    mode tcp
    option mysql-check user haproxy

#   balance method : [roundrobin, static-rr, leastconn, source]
    balance roundrobin

#   usage: server hostname IP:Port check inter 2000(msec) fall 2
    server read01 read01.XXXXXXXXXXXX.ap-northeast-1.rds.amazonaws.com:3306 check port 3306 resolvers awsvpc inter 2000 fall 5
    server read02 read02.XXXXXXXXXXXX.ap-northeast-1.rds.amazonaws.com:3306 check port 3306 resolvers awsvpc inter 2000 fall 5
    server master master.XXXXXXXXXXXX.ap-northeast-1.rds.amazonaws.com:3306 check port 3306 resolvers awsvpc backup

is line 15 the ip address of read01.XXXXXXXXXXXX.ap-northeast-1.rds.amazonaws.com ?

is line 15 the ip address of read01.XXXXXXXXXXXX.ap-northeast-1.rds.amazonaws.com ?

No. Thats the DNS server / resolver to be used.

I suggest to use 169.254.169.253 as DNS server address, as this is available everywhere in AWS.