Question - Scaling/ Adding more nodes

[m3ki]

First thank you for this wonderful code!

While going through my testing here in the lab, I stumbled on a potential issue for me.

I deployed a 3 node TYPE A cluster with HAproxy LB and etcd DCS.

In the scaling section you talk about adding a PG node and a load balancer node and you mention that those roles do not scale ETCD or consul.

How would I go about adding 2 more nodes, post initial 3 node deployment?

My use case:

1. deploy 3 node cluster
2. later on add 2 more nodes as if I were to initially deploy 5 nodes?

Is this possible?

[vitabaks]

Yes, at the moment PostgreSQL node scaling is implemented, but not for DCS.

I recommend deploying one ETCD cluster of 3 or 5 nodes on separate servers and using it with many Postgresql clusters.

[m3ki]

At the moment my application has to be deployed on 3 physical nodes so having postgres and etcd on same nodes is ideal.

What would be the ideal recovery steps should 1 node physically fail?

Also if I were to add node separately would I create a new empty linux node then add etc then run add_pg_node and add_balancer node?

[vitabaks]

That's right, Playbooks add_pg_node.yml and add_balancer.yml (optional) will do everything for you, but we need to take care of the DCS cluster
by supporting N/2+1 servers in an etcd or consul cluster (usually 3 or 5 nodes), while the number of Postgres cluster servers can be any (2 or more servers).

https://etcd.io/docs/v3.5/op-guide/runtime-configuration/#replace-a-failed-machine

I understand that managing an etcd cluster manually is not very convenient, so I plan to automate the scaling process for etcd and consul - #503

[m3ki]

Hey, did you implement scaling?

[vitabaks]

Postgres cluster scaling was implemented several releases ago. DCS cluster scaling is planned #503

[m3ki]

Postgres cluster scaling was implemented several releases ago. DCS cluster scaling is planned #503

Oh! Got it. For some reason I thought you did the DCS scaling after our last conversation :) I'll keep an eye on #503