[GitHub] [pulsar] stupidusername opened a new issue #5380: Kubernetes deployment: Pods from a service are being scheduled on the same node

[GitBox]

stupidusername opened a new issue #5380: Kubernetes deployment: Pods from a 
service are being scheduled on the same node
URL: https://github.com/apache/pulsar/issues/5380
 
 
   I was trying to deploy pulsar using GKE. While I was deploying the ZooKeeper 
service I noticed that its pods were being scheduled on the same node. I am 
really new to Kubernetes but this looks a little odd to me:
   
   `deployment/kubernetes/google-kubernetes-engine/zookeeper.yaml` 
   
   ```yaml
   spec:
       serviceName: zookeeper
       replicas: 3
       template:
           metadata:
               labels:
                   app: pulsar
                   component: zookeeper
                   cluster: pulsar-gke
               annotations:
                   pod.alpha.kubernetes.io/initialized: "true"
                   prometheus.io/scrape: "true"
                   prometheus.io/port: "8080"
   
           spec:
               # Make sure multiple pods of ZK don't get scheduled on the
               # same node, unless there are no other available nodes
               affinity:
                   podAntiAffinity:
                       preferredDuringSchedulingIgnoredDuringExecution:
                         - weight: 1
                           podAffinityTerm:
                               labelSelector:
                                   matchExpressions:
                                     - key: "app"
                                       operator: In
                                       values:
                                         - zookeeper
                               topologyKey: "kubernetes.io/hostname"
   ```
   
   I read this [Kubernetes affinity 
example](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#an-example-of-a-pod-that-uses-pod-affinity)
 and I think that the `key` used in `matchExpressions`  should be `component`, 
not `app`. When I use `component` as the `key`, all the ZooKeeper pods are 
scheduled on different nodes.
   
   If I am correct, this error is present in all the Kubernetes deployment 
files.
   
   Is there any Kubernetes expert willing to take a look at this?
   
   Thank you!

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