docs: A-2 — losing the database takes every node down while up stays 1

Both pods go NotReady, the Service endpoint list empties and the front door returns 503, so adding Keycloak replicas buys nothing against database loss. The node holding the session in cache fails too, because a refresh writes LAST_SESSION_REFRESH. Recovery was automatic in about fifteen seconds with no restart, which is what readiness rather than liveness buys. The observability finding matters as much: up stayed at 1 through a total outage, so alerting on it would have caught nothing. kube-state-metrics is missing and pod readiness is therefore not recorded as a metric. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-04 11:57:55 +09:00
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+=== A-2 기준선 — 클러스터가 정상으로 돌아왔는가 ===
+keycloak-0                  true   10.42.1.67   kc-lab-2
+keycloak-1                  true   10.42.0.35   kc-lab-1
+postgres-7b474b88c8-sn9ff   true   10.42.1.24   kc-lab-2
+
+  cluster_size keycloak-1   = 2
+  cluster_size keycloak-0   = 2
+
+=== 노드별 세션 캐시 (실험 설계에 필요) ===
+  keycloak-1   kc-lab-1   = 0 건
+  keycloak-0   kc-lab-2   = 0 건
+
+=== DB 온라인 세션 ===
+  2