HAProxy configuration to load-balance Monero nodes
To get an understanding of HAProxy’s possibilities, I grabbed a list of nodes from monero.fail and created a configuration that load-balances connections among them.
The configuration would allow you to connect Monero to HAProxy, which in turn takes care of selecting a remote node that responds fairly quickly.
However, using HAProxy makes more sense in a scenario where you want to load balance multiple public nodes that you operate yourself.
Note that there’s also a project named Monerod-Proxy that offers similar functionality.
# HAProxy configuration file (stand-alone)
# to load-balance among a list of public Monero nodes
# /etc/haproxy/haproxy.cfg
global
chroot /var/lib/haproxy
user haproxy
group haproxy
# Enable to access information via socket file
# See https://www.haproxy.com/blog/haproxy-apis
#stats socket /var/run/haproxy.sock mode 0600 level admin expose-fd listeners thread 1
defaults
mode tcp
# https://www.haproxy.com/blog/the-four-essential-sections-of-an-haproxy-configuration#timeout-connect-timeout-client-timeout-server
timeout client 60s
timeout connect 5s
timeout server 60s
## Enable a status page at the given port
#frontend stats
# mode http
# bind *:8404
# stats enable
# stats uri /stats
# #stats refresh 10s
# stats admin if LOCALHOST
# Have HAProxy listen for clients on the defined port
frontend frontend
bind :18081
default_backend nodes
# Have HAProxy forward connections to this list of nodes
backend nodes
# Approach the list of nodes least connected to in a roundrobin manner
balance leastconn
# https://www.haproxy.com/documentation/haproxy-configuration-tutorials/service-reliability/health-checks/#passive-health-checks
# https://www.haproxy.com/blog/how-to-enable-health-checks-in-haproxy#passive-health-checks
#
# "Passive health checks always coexist with active health checks, with the latter
# doing its normal polling while also being responsible for reviving a server after
# it has been marked as down by a passive health check."
#
# Active part: Nodes will be checked every 10 minutes (inter), considered
# "down" if connection fails once (fall 1) and "up" if available
# upon the 2 further cheks (rise 2).
# Passive part: Nodes will be considered "down" if there are at least two
# errors in ongoing connections (observe - error-limit 2).
# Only an active check (explained above) can return it to "up".
default-server check inter 10m observe layer4 error-limit 2 on-error mark-down fall 1 rise 2
server backend-1 node.moneroworld.com:18089
server backend-2 uwillrunanodesoon.moneroworld.com:18089
server backend-3 nodes.hashvault.pro:18081
server backend-4 node1.xmr-tw.org:18081
server backend-8 xmr-de-1.boldsuck.org:18081
# ...You may append as many nodes as you want, but be aware that each one implies more health checks and slows down HAProxy-startup.
Once HAProxy is running (haproxy -W -f <path-to-config>) you can test the connection with Monero RPC or CLI (monero-wallet-cli --daemon-host <haproxy-ip> --daemon-port 18081 <further-options>).
The configuration surely has room for improvement. If you know any tweaks, please comment in our thread on Monero Town.