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  1. Couchbase Kubernetes
  2. K8S-421

Ability to Balance in Nodes on Provision Failure




      • Set antiaffinity to true in couchbase-cluster.yaml.
      • There is one master node and 2 worker nodes.

      [root@ip-172-31-7-110 couchbase-operator]# kubectl get nodes
      NAME                                         STATUS    ROLES     AGE       VERSION
      ip-172-31-1-197.us-east-2.compute.internal   Ready     <none>    57d       v1.10.2
      ip-172-31-6-25.us-east-2.compute.internal    Ready     <none>    57d       v1.10.2
      ip-172-31-7-110.us-east-2.compute.internal   Ready     master    57d       v1.10.2

      * There are three pods to be scheduled as mentioned in couchbase-cluster.yaml:

          - size: 3
            name: all_services
              - data
              - index
              - query
              - search
              - eventing
              - analytics

      * Since anti-affinity is set to true, there is no worker node for the third pod to be scheduled and the third pod fails to be scheduled as expected. The logs also print out messages appropriately indicating this behavior:

      time="2018-06-29T05:24:57Z" level=info msg="Finish reconciling" cluster-name=cb-example module=cluster
      time="2018-06-29T05:24:57Z" level=error msg="failed to reconcile: Failed to add new node to cluster: unable to schedule pod: 0/3 nodes are available: 1 node(s) had taints that the pod didn't tolerate, 2 node(s) didn't match pod affinity/anti-affinity, 2 node(s) didn't satisfy existing pods anti-affinity rules." cluster-name=cb-example module=cluster

      * The first two pods are scheduled properly and are up and running:

      [root@ip-172-31-7-110 couchbase-operator]# kubectl get pods -o wide
      NAME                                  READY     STATUS    RESTARTS   AGE       IP          NODE
      cb-example-0000                       1/1       Running   0          12m   ip-172-31-6-25.us-east-2.compute.internal
      cb-example-0001                       1/1       Running   0          12m   ip-172-31-1-197.us-east-2.compute.internal
      couchbase-operator-5d7dfb795f-wthfr   1/1       Running   0          2d   ip-172-31-1-197.us-east-2.compute.internal

      * However, after logging into the UI, it appears that the operator left the cluster in an inconsistent state (pending rebalance) as shown below:

      Question: Since 2 pods out of 3 pods are scheduled successfully due to node availability, isn't the operator expected to manage those 2 pods correctly? Is the cluster expected to be left in this state?


        1. inconsistent.png
          309 kB
          Sindhura Palakodety
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            simon.murray Simon Murray
            sindhura.palakodety Sindhura Palakodety (Inactive)
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