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Chapter 10. Moving the cluster logging resources with node selectors

You can use node selectors to deploy the Elasticsearch, Kibana, and Curator pods to different nodes.

10.1. Moving the cluster logging resources

You can configure the Cluster Logging Operator to deploy the pods for any or all of the Cluster Logging components, Elasticsearch, Kibana, and Curator to different nodes. You cannot move the Cluster Logging Operator pod from its installed location.

For example, you can move the Elasticsearch pods to a separate node because of high CPU, memory, and disk requirements.

Note

You should set your machine set to use at least 6 replicas.

Prerequisites

  • Cluster logging and Elasticsearch must be installed. These features are not installed by default.

Procedure

  1. Edit the ClusterLogging custom resource (CR) in the openshift-logging project: 

    $ oc edit ClusterLogging instance
    apiVersion: logging.openshift.io/v1
kind: ClusterLogging

....

spec:
  collection:
    logs:
      fluentd:
        resources: null
      type: fluentd
  curation:
    curator:
      nodeSelector: 1
          node-role.kubernetes.io/infra: ''
      resources: null
      schedule: 30 3 * * *
    type: curator
  logStore:
    elasticsearch:
      nodeCount: 3
      nodeSelector: 2
          node-role.kubernetes.io/infra: ''
      redundancyPolicy: SingleRedundancy
      resources:
        limits:
          cpu: 500m
          memory: 16Gi
        requests:
          cpu: 500m
          memory: 16Gi
      storage: {}
    type: elasticsearch
  managementState: Managed
  visualization:
    kibana:
      nodeSelector: 3
          node-role.kubernetes.io/infra: '' 4
      proxy:
        resources: null
      replicas: 1
      resources: null
    type: kibana

....
1 2 3 4
Add a nodeSelector parameter with the appropriate value to the component you want to move. You can use a nodeSelector in the format shown or use <key>: <value> pairs, based on the value specified for the node.

Verification steps

To verify that a component has moved, you can use the oc get pod -o wide command.

For example:

  • You want to move the Kibana pod from the ip-10-0-147-79.us-east-2.compute.internal node: 

    $ oc get pod kibana-5b8bdf44f9-ccpq9 -o wide
NAME                      READY   STATUS    RESTARTS   AGE   IP            NODE                                        NOMINATED NODE   READINESS GATES
kibana-5b8bdf44f9-ccpq9   2/2     Running   0          27s   10.129.2.18   ip-10-0-147-79.us-east-2.compute.internal   <none>           <none>

  • You want to move the Kibana Pod to the ip-10-0-139-48.us-east-2.compute.internal node, a dedicated infrastructure node: 

    $ oc get nodes
NAME                                         STATUS   ROLES          AGE   VERSION
ip-10-0-133-216.us-east-2.compute.internal   Ready    master         60m   v1.17.1
ip-10-0-139-146.us-east-2.compute.internal   Ready    master         60m   v1.17.1
ip-10-0-139-192.us-east-2.compute.internal   Ready    worker         51m   v1.17.1
ip-10-0-139-241.us-east-2.compute.internal   Ready    worker         51m   v1.17.1
ip-10-0-147-79.us-east-2.compute.internal    Ready    worker         51m   v1.17.1
ip-10-0-152-241.us-east-2.compute.internal   Ready    master         60m   v1.17.1
ip-10-0-139-48.us-east-2.compute.internal    Ready    infra          51m   v1.17.1

    Note that the node has a node-role.kubernetes.io/infra: '' label: 

    $ oc get node ip-10-0-139-48.us-east-2.compute.internal -o yaml

kind: Node
apiVersion: v1
metadata:
  name: ip-10-0-139-48.us-east-2.compute.internal
  selfLink: /api/v1/nodes/ip-10-0-139-48.us-east-2.compute.internal
  uid: 62038aa9-661f-41d7-ba93-b5f1b6ef8751
  resourceVersion: '39083'
  creationTimestamp: '2020-04-13T19:07:55Z'
  labels:
    node-role.kubernetes.io/infra: ''
....

  • To move the Kibana pod, edit the ClusterLogging CR to add a node selector: 

    apiVersion: logging.openshift.io/v1
kind: ClusterLogging

....

spec:

....

  visualization:
    kibana:
      nodeSelector: 1
        node-role.kubernetes.io/infra: '' 2
      proxy:
        resources: null
      replicas: 1
      resources: null
    type: kibana
    1 2
    Add a node selector to match the label in the node specification.

  • After you save the CR, the current Kibana pod is terminated and new pod is deployed: 

    $ oc get pods
NAME                                            READY   STATUS        RESTARTS   AGE
cluster-logging-operator-84d98649c4-zb9g7       1/1     Running       0          29m
elasticsearch-cdm-hwv01pf7-1-56588f554f-kpmlg   2/2     Running       0          28m
elasticsearch-cdm-hwv01pf7-2-84c877d75d-75wqj   2/2     Running       0          28m
elasticsearch-cdm-hwv01pf7-3-f5d95b87b-4nx78    2/2     Running       0          28m
fluentd-42dzz                                   1/1     Running       0          28m
fluentd-d74rq                                   1/1     Running       0          28m
fluentd-m5vr9                                   1/1     Running       0          28m
fluentd-nkxl7                                   1/1     Running       0          28m
fluentd-pdvqb                                   1/1     Running       0          28m
fluentd-tflh6                                   1/1     Running       0          28m
kibana-5b8bdf44f9-ccpq9                         2/2     Terminating   0          4m11s
kibana-7d85dcffc8-bfpfp                         2/2     Running       0          33s

  • The new pod is on the ip-10-0-139-48.us-east-2.compute.internal node: 

    $ oc get pod kibana-7d85dcffc8-bfpfp -o wide
NAME                      READY   STATUS        RESTARTS   AGE   IP            NODE                                        NOMINATED NODE   READINESS GATES
kibana-7d85dcffc8-bfpfp   2/2     Running       0          43s   10.131.0.22   ip-10-0-139-48.us-east-2.compute.internal   <none>           <none>

  • After a few moments, the original Kibana pod is removed. 

    $ oc get pods
NAME                                            READY   STATUS    RESTARTS   AGE
cluster-logging-operator-84d98649c4-zb9g7       1/1     Running   0          30m
elasticsearch-cdm-hwv01pf7-1-56588f554f-kpmlg   2/2     Running   0          29m
elasticsearch-cdm-hwv01pf7-2-84c877d75d-75wqj   2/2     Running   0          29m
elasticsearch-cdm-hwv01pf7-3-f5d95b87b-4nx78    2/2     Running   0          29m
fluentd-42dzz                                   1/1     Running   0          29m
fluentd-d74rq                                   1/1     Running   0          29m
fluentd-m5vr9                                   1/1     Running   0          29m
fluentd-nkxl7                                   1/1     Running   0          29m
fluentd-pdvqb                                   1/1     Running   0          29m
fluentd-tflh6                                   1/1     Running   0          29m
kibana-7d85dcffc8-bfpfp                         2/2     Running   0          62s
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