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[QUESTION] Sentinel host name support not working as expected. #8507

Description

@satheeshaGowda

Hello @yossigo , thank you for adding #8282 , this is the much awaited PR .

we have spent sometime testing that feature on redis:6.2-rc3 from dockerhub with the configuration suggested here #8282 (comment)

at the outset Sentinel vends out the host name of the shard master when we query SENTINEL get-master-addr-by-name mymaster, but after we trigger a failover , it started vending out IPs again, isnt the expectation is to return host name?

here is the yaml spec we used, if it helps you reproduce .

Redis

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: redis
spec:
  serviceName: redis
  replicas: 5
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      initContainers:
      - name: config
        image: redis:6.2-rc3
        command: [ "bash", "-c" ]
        args:
          - |
            cp /tmp/redis/redis.conf /etc/redis/redis.conf

            MASTER_FQDN=redis-0.redis.REDACTED
            POD_FQDN=$(hostname -f)
            echo "replica-announce-ip  $POD_FQDN" >> /etc/redis/redis.conf
            echo "replica-announce-port 6379" >> /etc/redis/redis.conf
            if [ "$POD_FQDN" =  "$MASTER_FQDN" ]; then
                echo "this is master, not updating config..."
            else
                echo "updating replica redis.conf..."
                echo "replicaof $MASTER_FQDN 6379" >> /etc/redis/redis.conf
            fi
            cat /etc/redis/redis.conf
        volumeMounts:
        - name: redis-config
          mountPath: /etc/redis/
        - name: config
          mountPath: /tmp/redis/
      containers:
      - name: redis
        image: redis:6.2-rc3
        command: ["redis-server"]
        args: ["/etc/redis/redis.conf"]
        ports:
        - containerPort: 6379
          name: redis
        volumeMounts:
        - name: data
          mountPath: /data
        - name: redis-config
          mountPath: /etc/redis/
      volumes:
      - name: redis-config
        emptyDir: {}
      - name: config
        configMap:
          name: redis-config
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      accessModes: [ "ReadWriteOnce" ]
      storageClassName: scaleio
      resources:
        requests:
          storage: 100Mi

---
apiVersion: v1
kind: Service
metadata:
  name: redis
spec:
  clusterIP: None
  ports:
  - port: 6379
    targetPort: 6379
    name: redis
  selector:
    app: redis

Sentinel

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: sentinel
spec:
  serviceName: sentinel
  replicas: 3
  selector:
    matchLabels:
      app: sentinel
  template:
    metadata:
      labels:
        app: sentinel
    spec:
      initContainers:
      - name: config
        image: redis:6.2-rc3
        command: [ "sh", "-c" ]
        args:
          - |
            REDIS_PASSWORD=testpassword
            MASTER_FQDN=redis-0.redis.REDACTED
            POD_FQDN=$(hostname -f)
            echo "port 26379
            protected-mode no
            sentinel resolve-hostnames yes
            sentinel announce-hostnames yes
            sentinel announce-ip $POD_FQDN
            sentinel announce-port 26379
            sentinel monitor mymaster $MASTER_FQDN 6379 2
            sentinel down-after-milliseconds mymaster 5000
            sentinel failover-timeout mymaster 60000
            sentinel parallel-syncs mymaster 1
            sentinel auth-pass mymaster $REDIS_PASSWORD
            " > /etc/redis/sentinel.conf
            cat /etc/redis/sentinel.conf
        volumeMounts:
        - name: redis-config
          mountPath: /etc/redis/
      containers:
      - name: sentinel
        image: redis:6.2-rc3
        command: ["redis-server", "/etc/redis/sentinel.conf", "--sentinel"]
        ports:
        - containerPort: 26379
          name: sentinel
        volumeMounts:
        - name: redis-config
          mountPath: /etc/redis/
        - name: data
          mountPath: /data
      volumes:
      - name: redis-config
        emptyDir: {}
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      accessModes: [ "ReadWriteOnce" ]
      storageClassName: scaleio
      resources:
        requests:
          storage: 100Mi

---
apiVersion: v1
kind: Service
metadata:
  name: sentinel
spec:
  clusterIP: None
  ports:
  - port: 26379
    targetPort: 26379
    name: sentinel
  selector:
    app: sentinel

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