minecraft: add hourly world backup CronJob with 3-day local retention

cluster/applications/minecraft/backup-cronjob.yaml

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+---
+# Minecraft world backup — hourly CronJob, 3-day local retention
+#
+# Strategy (two-tier):
+#   Short-term : this CronJob — hourly tarballs on papermc-backups PVC, 72-hour retention
+#   Long-term  : Pure FlashArray protection group snapshots on utilidor (managed separately)
+#
+# Backup sequence:
+#   1. RCON save-all  — flush all dirty chunks to disk
+#   2. RCON save-off  — pause auto-save to keep the world consistent during tar
+#   3. tar world directories to /backups/world-YYYY-MM-DDTHH-MM.tar.gz
+#   4. RCON save-on   — re-enable auto-save
+#   5. Prune backups older than 3 days
+#
+# RCON password sourced from the papermc-rcon Secret (ESO-managed, same as server).
+# The backup pod mounts both PVCs read-write; world-data is safe because the
+# server has already quiesced saves via RCON before the tar runs.
+#
+# Note: both PVCs are RWO. The backup job runs only while the main server pod is
+# running (RCON is reachable), so there is no volume attach conflict — they are
+# mounted on the same node by the scheduler. If the server pod is down, the backup
+# job will fail at the RCON step, which is correct behavior (nothing to back up).
+apiVersion: batch/v1
+kind: CronJob
+metadata:
+  name: minecraft-backup
+  namespace: minecraft
+  labels:
+    app.kubernetes.io/name: minecraft
+    app.kubernetes.io/component: backup
+spec:
+  schedule: "0 * * * *"     # every hour on the hour
+  concurrencyPolicy: Forbid  # skip if a previous backup is still running
+  successfulJobsHistoryLimit: 3
+  failedJobsHistoryLimit: 3
+  jobTemplate:
+    spec:
+      backoffLimit: 0        # don't retry — a partial backup is worse than no backup
+      template:
+        metadata:
+          labels:
+            app.kubernetes.io/name: minecraft
+            app.kubernetes.io/component: backup
+        spec:
+          restartPolicy: Never
+          securityContext:
+            runAsNonRoot: false
+            fsGroup: 1000
+          containers:
+            - name: backup
+              image: itzg/rcon-cli:latest
+              imagePullPolicy: IfNotPresent
+              env:
+                - name: RCON_HOST
+                  value: "journey-into-imagination.minecraft.svc.cluster.local"
+                - name: RCON_PORT
+                  value: "25575"
+                - name: RCON_PASSWORD
+                  valueFrom:
+                    secretKeyRef:
+                      name: papermc-rcon
+                      key: rcon-password
+              command:
+                - /bin/sh
+                - -c
+                - |
+                  set -e
+
+                  TIMESTAMP=$(date -u +%Y-%m-%dT%H-%M)
+                  BACKUP_FILE="/backups/world-${TIMESTAMP}.tar.gz"
+                  RETAIN_DAYS=3
+
+                  echo "[backup] Starting backup at ${TIMESTAMP}"
+
+                  # Step 1: quiesce the world
+                  echo "[backup] Flushing chunks (save-all)..."
+                  rcon-cli save-all
+
+                  echo "[backup] Pausing auto-save (save-off)..."
+                  rcon-cli save-off
+
+                  # Step 2: archive world directories
+                  echo "[backup] Archiving world to ${BACKUP_FILE}..."
+                  tar -czf "${BACKUP_FILE}" \
+                    -C /data \
+                    world \
+                    world_nether \
+                    world_the_end \
+                    whitelist.json \
+                    ops.json \
+                    banned-players.json \
+                    banned-ips.json
+
+                  echo "[backup] Archive complete: $(du -sh ${BACKUP_FILE} | cut -f1)"
+
+                  # Step 3: resume auto-save
+                  echo "[backup] Resuming auto-save (save-on)..."
+                  rcon-cli save-on
+
+                  # Step 4: prune old backups
+                  echo "[backup] Pruning backups older than ${RETAIN_DAYS} days..."
+                  find /backups -name "world-*.tar.gz" -mtime +${RETAIN_DAYS} -delete
+                  REMAINING=$(find /backups -name "world-*.tar.gz" | wc -l)
+                  echo "[backup] Done. ${REMAINING} backup(s) retained."
+              volumeMounts:
+                - name: world-data
+                  mountPath: /data
+                  readOnly: true
+                - name: backups
+                  mountPath: /backups
+          volumes:
+            - name: world-data
+              persistentVolumeClaim:
+                claimName: papermc-world-data
+            - name: backups
+              persistentVolumeClaim:
+                claimName: papermc-backups

cluster/applications/minecraft/backup-pvc.yaml

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+---
+# Minecraft backup storage — local hourly backups, 3-day retention
+# Sized for ~72 backup tarballs; world data compresses well (~90% reduction typical)
+# Long-term retention handled by Pure FlashArray protection group snapshots (utilidor)
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: papermc-backups
+  namespace: minecraft
+  labels:
+    app.kubernetes.io/name: minecraft
+    app.kubernetes.io/component: backup
+spec:
+  accessModes:
+    - ReadWriteOnce
+  storageClassName: px-fa-direct-access
+  resources:
+    requests:
+      storage: 10Gi