How to specify advertised listeners for Kafka multi broker setup on kubernetes and expose the cluster expernally?

Kubernetes has the concept of Statefulsets to solve these issues. Each instance of a statefulset has it's own DNS name so you can reference to each instance by a dns name.

This concept is described here in more detail. You can also take a look at this complete example:

apiVersion: v1kind: Servicemetadata:  name: zk-headless  labels:    app: zk-headlessspec:  ports:  - port: 2888    name: server  - port: 3888    name: leader-election  clusterIP: None  selector:    app: zk---apiVersion: v1kind: ConfigMapmetadata:  name: zk-configdata:  ensemble: "zk-0;zk-1;zk-2"  jvm.heap: "2G"  tick: "2000"  init: "10"  sync: "5"  client.cnxns: "60"  snap.retain: "3"  purge.interval: "1"---apiVersion: policy/v1beta1kind: PodDisruptionBudgetmetadata:  name: zk-budgetspec:  selector:    matchLabels:      app: zk  minAvailable: 2---apiVersion: apps/v1beta1kind: StatefulSetmetadata:  name: zkspec:  serviceName: zk-headless  replicas: 3  template:    metadata:      labels:        app: zk      annotations:        pod.alpha.kubernetes.io/initialized: "true"    spec:      affinity:        podAntiAffinity:          requiredDuringSchedulingIgnoredDuringExecution:            - labelSelector:                matchExpressions:                  - key: "app"                    operator: In                    values:                     - zk-headless              topologyKey: "kubernetes.io/hostname"      containers:      - name: k8szk        imagePullPolicy: Always        image: gcr.io/google_samples/k8szk:v1        resources:          requests:            memory: "4Gi"            cpu: "1"        ports:        - containerPort: 2181          name: client        - containerPort: 2888          name: server        - containerPort: 3888          name: leader-election        env:        - name : ZK_ENSEMBLE          valueFrom:            configMapKeyRef:              name: zk-config              key: ensemble        - name : ZK_HEAP_SIZE          valueFrom:            configMapKeyRef:                name: zk-config                key: jvm.heap        - name : ZK_TICK_TIME          valueFrom:            configMapKeyRef:                name: zk-config                key: tick        - name : ZK_INIT_LIMIT          valueFrom:            configMapKeyRef:                name: zk-config                key: init        - name : ZK_SYNC_LIMIT          valueFrom:            configMapKeyRef:                name: zk-config                key: tick        - name : ZK_MAX_CLIENT_CNXNS          valueFrom:            configMapKeyRef:                name: zk-config                key: client.cnxns        - name: ZK_SNAP_RETAIN_COUNT          valueFrom:            configMapKeyRef:                name: zk-config                key: snap.retain        - name: ZK_PURGE_INTERVAL          valueFrom:            configMapKeyRef:                name: zk-config                key: purge.interval        - name: ZK_CLIENT_PORT          value: "2181"        - name: ZK_SERVER_PORT          value: "2888"        - name: ZK_ELECTION_PORT          value: "3888"        command:        - sh        - -c        - zkGenConfig.sh && zkServer.sh start-foreground        readinessProbe:          exec:            command:            - "zkOk.sh"          initialDelaySeconds: 15          timeoutSeconds: 5        livenessProbe:          exec:            command:            - "zkOk.sh"          initialDelaySeconds: 15          timeoutSeconds: 5        volumeMounts:        - name: datadir          mountPath: /var/lib/zookeeper      securityContext:        runAsUser: 1000        fsGroup: 1000  volumeClaimTemplates:  - metadata:      name: datadir    spec:      accessModes: [ "ReadWriteOnce" ]      resources:        requests:          storage: 20Gi