Balancing Vertica for resiliency

follow up: it seems it was very easy to configure HAproxy in tcp mode for load balancing.
Now i "only" have to configure checks to let HAproxy detect when a Vertica host is down.

The HAproxy config i've made is

listen vertica-cluster
bind 0.0.0.0:5433
mode tcp
balance roundrobin

server vertica01 10.0.1.8:5433
server vertica02 10.0.1.9:5433
server vertica03 10.0.1.10:5433

this simple haproxy confg seems to fit the basic needs to balance the load and avoid sending conns to the nodes in down

frontend vertica
bind 0.0.0.0:5433
mode tcp
option tcplog
default_backend vertica_cluster

backend vertica_cluster
mode tcp
balance leastconn
server vertica01 1.1.1.8:5433 check fall 1 rise 2
server vertica02 1.1..9:5433 check fall 1 rise 2
server vertica03 1.1.1.10:5433 check fall 1 rise 2

just add something like

timeout client 8h <-adjust to your needs

to avoid disconnections on client inactivity

If this is just checking whether port 5433 is accepting a connection, then also consider the scenario where a node is recovering. In this case the process is running, and listening port 5433, but if you try to connect you get a message about the node being in recovery. This is at least true in 7.2 - I haven't tested it in 8.0. So you still want the node to remain out of the load balancer until it's truly up. One way to do this is a health check of sending a "select 1" query to all nodes to verify that they are responding to queries.

--Sharon

thank you for adding this info!
in my scenario probably we don't need such an health check, so i will probably not spend time in trying it, but this can help someother someday.
Alessandro