fix(kafka): retain failed message persistence

deploy/argocd/im-server-test/README.md

@@ -25,6 +25,7 @@ After ArgoCD sync, verify the effective configuration:
 kubectl -n im-server-system get statefulset im-server -o jsonpath='{.spec.template.spec.containers[0].resources}'
 kubectl -n im-server-system get statefulset im-server -o jsonpath='{.spec.template.spec.containers[0].livenessProbe.httpGet.path}'
 kubectl -n im-server-system get statefulset im-server -o jsonpath='{.spec.template.spec.containers[0].env}'
+kubectl -n im-server-system get statefulset im-server -o jsonpath='{.spec.template.spec.dnsConfig.options}'
 kubectl auth can-i list pods.metrics.k8s.io \
   --as=system:serviceaccount:argocd:backend-debug \
   -n im-server-system
@@ -36,5 +37,24 @@ liveness path `/livez`. The MySQL pool environment must be
 `MYSQL_REGISTRY_MAX_OPEN_CONNS=4`, and `MYSQL_REGISTRY_MAX_IDLE_CONNS=2`.
 The WebSocket heartbeat environment must be `WS_PING_PERIOD_SECONDS=15` and
 `WS_PONG_WAIT_SECONDS=90`.
+The Pod DNS options must be `ndots:1`, `timeout:2`, and `attempts:2`. Keeping
+`ClusterFirst` preserves short Kubernetes service-name resolution, while the
+lower `ndots` value prevents fully qualified internal and external dependency
+names from being expanded through every cluster search suffix first.
 The application repository's deploy workflow waits for reconciliation and
 fails if ArgoCD restores different values.
+
+After the rollout, verify the generated resolver configuration on every Pod:
+
+```bash
+for pod in im-server-0 im-server-1 im-server-2; do
+  echo "--- ${pod}"
+  kubectl -n im-server-system exec "${pod}" -- cat /etc/resolv.conf
+done
+```
+
+The output must retain the cluster DNS nameserver and search domains, with
+`options ndots:1 timeout:2 attempts:2`. This mitigation reduces amplified DNS
+traffic from the application Pods. If lookup timeouts remain under load,
+CoreDNS capacity or NodeLocal DNSCache must be changed in the cluster
+infrastructure repository by an administrator with `kube-system` access.

deploy/argocd/im-server-test/statefulset-performance-patch.yaml

@@ -6,6 +6,15 @@ metadata:
 spec:
   template:
     spec:
+      dnsPolicy: ClusterFirst
+      dnsConfig:
+        options:
+          - name: ndots
+            value: "1"
+          - name: timeout
+            value: "2"
+          - name: attempts
+            value: "2"
       containers:
         - name: im-server
           env: