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HAProxy topology

HAProxy runs on both nodes of the databases cluster and fronts various backends (databases and potentially other internal services):
  • cluster-n03 – older HAProxy 1.6.3
  • cluster-n04 – newer HAProxy 2.0.13
Both services are enabled and actively running, giving flexibility for routing traffic through either node.

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HAProxy on cluster-n03

  • Version: HA-Proxy version 1.6.3 2015/12/25
  • Service: haproxy.service (enabled, active)
  • Config file: /etc/haproxy/haproxy.cfg
Useful commands: 
ssh cluster-n03
systemctl status haproxy
haproxy -c -f /etc/haproxy/haproxy.cfg

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HAProxy on cluster-n04

  • Version: HA-Proxy version 2.0.13-2ubuntu0.3 2021/08/27
  • Service: haproxy.service (enabled, active)
  • Config file: /etc/haproxy/haproxy.cfg
Useful commands: 
ssh cluster-n04
systemctl status haproxy
haproxy -c -f /etc/haproxy/haproxy.cfg

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Notes

  • Exact frontend/backend definitions (which ports and backends are configured) live in /etc/haproxy/haproxy.cfg on each host.
  • Applications typically hit HAProxy frontends instead of talking directly to database ports, but Redis currently bypasses HAProxy (see the Redis page).