cast01–cast03 lab architecture

Goals

Simulate production patterns on three isolated Alpine VMs with shared config only on NFS (/shared/cluster/). No database files on NFS — each node owns /var/lib/mysql locally.

Topology

                    ┌─────────────────────────────────────┐
                    │  FE 10.7.0.10 (NFS export /shared)  │
                    └──────────────────┬──────────────────┘
                                       │ NFS (configs/scripts only)
         ┌─────────────────────────────┼─────────────────────────────┐
         ▼                             ▼                             ▼
   ┌───────────┐               ┌───────────┐               ┌───────────┐
   │  cast01   │  async GTID   │  cast02   │  async GTID   │  cast03   │
   │ .16.236   │◄──────────────│ .16.237   │◄──────────────│ .16.238   │
   │ PRIMARY   │   replica     │ REPLICA   │   replica     │ REPLICA   │
   │ MariaDB   │               │ MariaDB   │               │ MariaDB   │
   │ nginx/php │               │ nginx/php │               │ nginx/php │
   └───────────┘               └───────────┘               └───────────┘
         ▲                             │                             │
         └──────── writes + default reads ────────────────────────────┘
                    (replicas: read-only, failover drill)

Node	IP	MariaDB	App role (planned)
cast01	10.7.16.236	Primary (read/write)	Crashes console primary target
cast02	10.7.16.237	Replica (read_only)	App worker / read replica
cast03	10.7.16.238	Replica (read_only)	App worker / read replica

MariaDB

Engine: MariaDB 11.8 (Alpine 3.24 packages — no edge required)
Replication: GTID async primary → two replicas (server-id 1/2/3)
Bootstrap: app DB dump over TCP (--skip-ssl); GTID position copied from primary; replicate-do-db filters ongoing binlog to app schemas only (avoids mysql.help_topic dump failures)
Databases: androidcast_crashes, url_shortener (schemas from project SQL in /shared/cluster/sql/)
Credentials: see credentials.txt (same lab password on all nodes)

PHP

Version: 8.3 (php83-fpm) on all nodes — matches modern Alpine; prod BE remains 8.1 until upgraded separately
Socket: 127.0.0.1:9000

DNS

Pending external records. Until then: /etc/hosts block maintained by baseline.sh.

Service split (selected for lab)

Service	Write DB host	Read DB host (lab default)	Future app path (local disk)
Crashes / tickets / RA	cast01	cast01 (cast02/03 for drill)	`/var/www/androidcast/` per node
URL shortener API	cast01	cast01	`/var/www/url-shortener/` on cast03
Graphs ingest	cast01	cast01	shared crashes backend

App deploys stay on local VM disk, not NFS.

Operations

sudo sh /shared/cluster/scripts/baseline.sh          # per-node baseline
sudo sh /shared/cluster/scripts/mariadb-primary.sh   # cast01 only
sudo sh /shared/cluster/scripts/load-schemas.sh      # cast01 only
sudo sh /shared/cluster/scripts/mariadb-replica.sh # cast02 + cast03
sudo sh /shared/cluster/scripts/verify-cluster.sh  # any node

NFS mount may be noexec — always invoke scripts with sh.

Not in scope yet

ProxySQL / MaxScale (add if read splitting becomes necessary)
Galera multi-primary (overkill for 3-node lab; async matches prod BE migration path)
TLS between nodes (intra VLAN)

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