Overview & concepts

What ServersCTL hosting pools are

ServersCTL (serversctl.com) is the control plane for redundant server infrastructure: enrol Linux VMs with the ServersCTL agent, monitor heartbeats, cut over DNS between peers, run stack backups, and (on the cPanel preset) orchestrate account replication and live WHM transfers.

A server pool is one deployment in your dashboard — a set of members sharing failover DNS and pool-level settings. Members run what you actually install on each host. The dashboard exposes member tabs for OpenLiteSpeed, MariaDB/MySQL, Galera, and cPanel/WHM; each tab fills in when the agent detects that stack on that server.

ServersCTL does not host traffic. It moves DNS, queues remote jobs, and calls APIs where configured.

Pool Presets

Server pools are created using a preset template in the UI. This chapter is for the Generic Linux Server Preset. For HAProxy Server Pools, see the HAProxy chapter.

What runs on a member (stack compatibility)

Do not assume one VM runs every stack. Common deployments:

Deployment	Typical member stacks	Notes
cPanel / WHM hosting	cPanel tab + MariaDB tab (cPanel-managed MySQL)	Apache/httpd via cPanel — not OpenLiteSpeed
OpenLiteSpeed web farm	OpenLiteSpeed tab only	Standalone OLS
MariaDB / Galera nodes	MariaDB tab + Galera readout	DNS swing ≠ Galera quorum
Mixed pool	Different tabs per member	e.g. two cPanel standbys + one OLS edge — each member’s tabs reflect its OS

Core terminology

Term	Meaning
Pool	One ServersCTL Pool.
Member	One enrolled server (hostname, egress IP, enrollment secret)
Active member	Host whose IPv4 receives the pool failover A record.
Stack tab	Member workspace: OpenLiteSpeed, MariaDB, cPanel, etc.
Protected account	cPanel account with a replication job.
Agent	`balctl_heartbeat.py` on each member — heartbeats to `serversctl.com`

Architecture

Clients → DNS (Cloudflare / WHM) → A record → Active member IPv4

↑

ServersCTL Worker (serversctl.com)

↑

Standby members' ← agent heartbeats (+ WHM replication on cPanel preset)

Failover health: missed heartbeat beyond failover delay (10–120 s). No HAProxy systemd check on hosting presets.