Moving logging subsystem resources with node selectors

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

Moving OpenShift Logging resources

You can configure the Cluster Logging Operator to deploy the pods for logging subsystem components, such as Elasticsearch and Kibana, 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.

Prerequisites

  • The Red Hat OpenShift Logging and Elasticsearch Operators must be installed. These features are not installed by default.

Procedure

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

    1. $ oc edit ClusterLogging instance
    1. apiVersion: logging.openshift.io/v1
    2. kind: ClusterLogging
    4. ...
    6. spec:
    7.   collection:
    8.     logs:
    9.       fluentd:
    10.         resources: null
    11.       type: fluentd
    12.   logStore:
    13.     elasticsearch:
    14.       nodeCount: 3
    15.       nodeSelector: (1)
    16.         node-role.kubernetes.io/infra: ''
    17.       tolerations:
    18.       - effect: NoSchedule
    19.         key: node-role.kubernetes.io/infra
    20.         value: reserved
    21.       - effect: NoExecute
    22.         key: node-role.kubernetes.io/infra
    23.         value: reserved
    24.       redundancyPolicy: SingleRedundancy
    25.       resources:
    26.         limits:
    27.           cpu: 500m
    28.           memory: 16Gi
    29.         requests:
    30.           cpu: 500m
    31.           memory: 16Gi
    32.       storage: {}
    33.     type: elasticsearch
    34.   managementState: Managed
    35.   visualization:
    36.     kibana:
    37.       nodeSelector: (1)
    38.         node-role.kubernetes.io/infra: ''
    39.       tolerations:
    40.       - effect: NoSchedule
    41.         key: node-role.kubernetes.io/infra
    42.         value: reserved
    43.       - effect: NoExecute
    44.         key: node-role.kubernetes.io/infra
    45.         value: reserved
    46.       proxy:
    47.         resources: null
    48.       replicas: 1
    49.       resources: null
    50.     type: kibana
    52. ...
    1Add 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. If you added a taint to the infrasructure node, also add a matching toleration.

Verification

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:

    1. $ oc get pod kibana-5b8bdf44f9-ccpq9 -o wide

    Example output

    1. NAME                      READY   STATUS    RESTARTS   AGE   IP            NODE                                        NOMINATED NODE   READINESS GATES
    2. 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:

    1. $ oc get nodes

    Example output

    1. NAME                                         STATUS   ROLES          AGE   VERSION
    2. ip-10-0-133-216.us-east-2.compute.internal   Ready    master         60m   v1.25.0
    3. ip-10-0-139-146.us-east-2.compute.internal   Ready    master         60m   v1.25.0
    4. ip-10-0-139-192.us-east-2.compute.internal   Ready    worker         51m   v1.25.0
    5. ip-10-0-139-241.us-east-2.compute.internal   Ready    worker         51m   v1.25.0
    6. ip-10-0-147-79.us-east-2.compute.internal    Ready    worker         51m   v1.25.0
    7. ip-10-0-152-241.us-east-2.compute.internal   Ready    master         60m   v1.25.0
    8. ip-10-0-139-48.us-east-2.compute.internal    Ready    infra          51m   v1.25.0

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

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

    Example output

    1. kind: Node
    2. apiVersion: v1
    3. metadata:
    4.   name: ip-10-0-139-48.us-east-2.compute.internal
    5.   selfLink: /api/v1/nodes/ip-10-0-139-48.us-east-2.compute.internal
    6.   uid: 62038aa9-661f-41d7-ba93-b5f1b6ef8751
    7.   resourceVersion: '39083'
    8.   creationTimestamp: '2020-04-13T19:07:55Z'
    9.   labels:
    10.     node-role.kubernetes.io/infra: ''
    11. ...

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

    1. apiVersion: logging.openshift.io/v1
    2. kind: ClusterLogging
    4. ...
    6. spec:
    8. ...
    10.   visualization:
    11.     kibana:
    12.       nodeSelector: (1)
    13.         node-role.kubernetes.io/infra: ''
    14.       proxy:
    15.         resources: null
    16.       replicas: 1
    17.       resources: null
    18.     type: kibana
    1Add 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:

    1. $ oc get pods

    Example output

    1. NAME                                            READY   STATUS        RESTARTS   AGE
    2. cluster-logging-operator-84d98649c4-zb9g7       1/1     Running       0          29m
    3. elasticsearch-cdm-hwv01pf7-1-56588f554f-kpmlg   2/2     Running       0          28m
    4. elasticsearch-cdm-hwv01pf7-2-84c877d75d-75wqj   2/2     Running       0          28m
    5. elasticsearch-cdm-hwv01pf7-3-f5d95b87b-4nx78    2/2     Running       0          28m
    6. fluentd-42dzz                                   1/1     Running       0          28m
    7. fluentd-d74rq                                   1/1     Running       0          28m
    8. fluentd-m5vr9                                   1/1     Running       0          28m
    9. fluentd-nkxl7                                   1/1     Running       0          28m
    10. fluentd-pdvqb                                   1/1     Running       0          28m
    11. fluentd-tflh6                                   1/1     Running       0          28m
    12. kibana-5b8bdf44f9-ccpq9                         2/2     Terminating   0          4m11s
    13. 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:

    1. $ oc get pod kibana-7d85dcffc8-bfpfp -o wide

    Example output

    1. NAME                      READY   STATUS        RESTARTS   AGE   IP            NODE                                        NOMINATED NODE   READINESS GATES
    2. 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.

    1. $ oc get pods

    Example output

    1. NAME                                            READY   STATUS    RESTARTS   AGE
    2. cluster-logging-operator-84d98649c4-zb9g7       1/1     Running   0          30m
    3. elasticsearch-cdm-hwv01pf7-1-56588f554f-kpmlg   2/2     Running   0          29m
    4. elasticsearch-cdm-hwv01pf7-2-84c877d75d-75wqj   2/2     Running   0          29m
    5. elasticsearch-cdm-hwv01pf7-3-f5d95b87b-4nx78    2/2     Running   0          29m
    6. fluentd-42dzz                                   1/1     Running   0          29m
    7. fluentd-d74rq                                   1/1     Running   0          29m
    8. fluentd-m5vr9                                   1/1     Running   0          29m
    9. fluentd-nkxl7                                   1/1     Running   0          29m
    10. fluentd-pdvqb                                   1/1     Running   0          29m
    11. fluentd-tflh6                                   1/1     Running   0          29m
    12. kibana-7d85dcffc8-bfpfp                         2/2     Running   0          62s