<p>I am using Kafka Helm charts from <a href="https://github.com/helm/charts/tree/master/incubator/kafka" rel="nofollow noreferrer">here</a>.
I was trying Horizontal Pod Autoscaler for the same.</p>

<p>I added a hpa.yaml file as given below inside the templates folder.</p>

<pre><code>apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
metadata:
  name: kafka-hpa
spec:
  scaleTargetRef:
    apiVersion: extensions/v1beta1
    kind: Deployment
    name: {{ include "kafka.fullname" . }}
minReplicas: {{ .Values.replicas }}
maxReplicas: 5
metrics:
- type: Resource
  resource:
    name: cpu
    targetAverageUtilization: 50
- type: Resource
  resource:
    name: memory
    targetAverageValue: 8000Mi
</code></pre>

<p>I have also tried the above YAML with <strong>kind: StatefulSet</strong> but the same issue persists.</p>

<p>My intention is to have 3 Kafka pods initially and scale it up to 5 based on CPU and memory targetValues as mentioned above.</p>

<p>However, the hpa gets deployed but it is unable to read the metrics as per my understanding as the current usage shows unknown as mentioned below.</p>

<pre><code>NAME        REFERENCE                          TARGETS                          MINPODS   MAXPODS   REPLICAS   AGE
kafka-hpa   Deployment/whopping-walrus-kafka   &lt;unknown&gt;/8000Mi, &lt;unknown&gt;/50%   3         5         0          1h . 
</code></pre>

<p>I am new to helm and Kubernetes, so I am assuming there might be some issue with my understanding.</p>

<p>I have also deployed metrics-server.</p>

<pre><code>$ kubectl get deployments
NAME                             DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
metrics-server                   1         1         1            1           1d
whopping-walrus-kafka-exporter   1         1         1            1           1h
</code></pre>

<p>Pods output</p>

<pre><code>$ kubectl get pods
NAME                                              READY     STATUS    RESTARTS   AGE
metrics-server-55cbf87bbb-vm2v5                   1/1       Running   0          15m
whopping-walrus-kafka-0                           1/1       Running   1          1h
whopping-walrus-kafka-1                           1/1       Running   0          1h
whopping-walrus-kafka-2                           1/1       Running   0          1h
whopping-walrus-kafka-exporter-5c66b5b4f9-mv5kv   1/1       Running   1          1h
whopping-walrus-zookeeper-0                       1/1       Running   0          1h
</code></pre>

<p>I want the <strong>whopping-walrus-kafka</strong> pod to scale up to 5 on load, however, there's no deployment corresponding to it.</p>

<p>StatefulSet Output</p>

<pre><code>$ kubectl get statefulset
NAME                        DESIRED   CURRENT   AGE
original-bobcat-kafka       3         2         2m
original-bobcat-zookeeper   1         1         2m
</code></pre>

<p>Output of describe hpa when kind in hpa.yaml is <strong>StatefulSet</strong>.</p>

<pre><code>$ kubectl describe hpa
Name:                                                  kafka-hpa
Namespace:                                             default
Labels:                                                &lt;none&gt;
Annotations:                                           &lt;none&gt;
CreationTimestamp:                                     Fri, 18 Jan 2019 12:13:59 +0530
Reference:                                             StatefulSet/original-bobcat-kafka
Metrics:                                               ( current / target )
  resource memory on pods:                             &lt;unknown&gt; / 8000Mi
  resource cpu on pods  (as a percentage of request):  &lt;unknown&gt; / 5%
Min replicas:                                          3
Max replicas:                                          5
Conditions:
  Type         Status  Reason          Message
  ----         ------  ------          -------
  AbleToScale  False   FailedGetScale  the HPA controller was unable to get the target's current scale: no matches for kind "StatefulSet" in group "extensions"
Events:
  Type     Reason          Age                From                       Message
  ----     ------          ----               ----                       -------
  Warning  FailedGetScale  15s (x17 over 8m)  horizontal-pod-autoscaler  no matches for kind "StatefulSet" in group "extensions"
</code></pre>

<p>Output of describe hpa when kind in hpa.yaml is <strong>Deployment</strong>.</p>

<pre><code>$ kubectl describe hpa
Name:                                                  kafka-hpa
Namespace:                                             default
Labels:                                                &lt;none&gt;
Annotations:                                           &lt;none&gt;
CreationTimestamp:                                     Fri, 18 Jan 2019 12:30:07 +0530
Reference:                                             Deployment/good-elephant-kafka
Metrics:                                               ( current / target )
  resource memory on pods:                             &lt;unknown&gt; / 8000Mi
  resource cpu on pods  (as a percentage of request):  &lt;unknown&gt; / 5%
Min replicas:                                          3
Max replicas:                                          5
Conditions:
  Type         Status  Reason          Message
  ----         ------  ------          -------
  AbleToScale  False   FailedGetScale  the HPA controller was unable to get the target's current scale: could not fetch the scale for deployments.extensions good-elephant-kafka: deployments/scale.extensions "good-elephant-kafka" not found
Events:
  Type     Reason          Age   From                       Message
  ----     ------          ----  ----                       -------
  Warning  FailedGetScale  9s    horizontal-pod-autoscaler  could not fetch the scale for deployments.extensions good-elephant-kafka: deployments/scale.extensions "good-elephant-kafka" not found
</code></pre>

<p>Output from metrics server pod</p>

<pre><code>$ kubectl describe pods metrics-server-55cbf87bbb-vm2v5
Name:           metrics-server-55cbf87bbb-vm2v5
Namespace:      default
Node:           docker-for-desktop/192.168.65.3
Start Time:     Fri, 18 Jan 2019 11:26:33 +0530
Labels:         app=metrics-server
            pod-template-hash=1176943666
            release=metrics-server
Annotations:    &lt;none&gt;
Status:         Running
IP:             10.1.0.119
Controlled By:  ReplicaSet/metrics-server-55cbf87bbb
Containers:
  metrics-server:
    Container ID:  docker://ee4b3d9ed1b15c2c8783345b0ffbbc565ad25f1493dec0148f245c9581443631
    Image:         gcr.io/google_containers/metrics-server-amd64:v0.3.1
    Image ID:      docker-pullable://gcr.io/google_containers/metrics-server-amd64@sha256:78938f933822856f443e6827fe5b37d6cc2f74ae888ac8b33d06fdbe5f8c658b
    Port:          &lt;none&gt;
    Host Port:     &lt;none&gt;
    Command:
      /metrics-server
      --kubelet-insecure-tls
      --kubelet-preferred-address-types=InternalIP
      --logtostderr
    State:          Running
  Started:      Fri, 18 Jan 2019 11:26:35 +0530
    Ready:          True
    Restart Count:  0
    Environment:    &lt;none&gt;
    Mounts:
  /var/run/secrets/kubernetes.io/serviceaccount from metrics-server-token-d2g7b (ro)
Conditions:
  Type           Status
  Initialized    True 
  Ready          True 
  PodScheduled   True 
Volumes:
  metrics-server-token-d2g7b:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  metrics-server-token-d2g7b
    Optional:    false
    QoS Class:       BestEffort
Node-Selectors:  &lt;none&gt;
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
             node.kubernetes.io/unreachable:NoExecute for 300s
Events:          &lt;none&gt;
</code></pre>

<p>Guys please feel free to clear my understanding as well if I am going wrong somewhere.</p>

<p>Help on this would be highly appreciated.</p>

<p>You need to add the following command in your <code>metrics-server</code> deployment file:</p>

<pre><code>containers:
   - command:
     - /metrics-server
     - --metric-resolution=30s
     - --kubelet-insecure-tls
     - --kubelet-preferred-address-types=InternalIP
     name: metrics-server
</code></pre>

<p>I believe metrics-server couldn't find the kubelet with <code>InternalIP</code>, hence the issue. For more information, check my following answer for step by step instruction to setup HPA.</p>

<p><a href="https://stackoverflow.com/questions/53725248/how-to-enable-kubeapi-server-for-hpa-autoscaling-metrics/53727101#53727101">How to Enable KubeAPI server for HPA Autoscaling Metrics</a></p>
