Actual results:
the es nodeCount in elasticsearch CRD instance isn't changed after changing es nodeCount from 3 to n (n>3) in the clusterlogging CRD instance

Expected results:
the es node count should be the same as it in the clusterlogging CRD instance.

Additional info:
Scaling up es nodes from 1 or 2 to n(n>=3), no issue.
Scaling up es nodes from 4 or 5 to 6, no issue.

This issue only happens when scaling up from 3 nodes to n(n > 3) nodes

The workaround is: 
1. change es nodeCount in clusterlogging CRD instance, 
2. use `oc delete elasticsearch elasticsearch -n openshift-logging` to delete elasticsearch CRD instance, then the elasticsearch would be recreated, and the nodeCount is what it set in the clusterlogging CRD instance.

this should likely be cloned+backported to 4.1.z

The issue isn't fixed.

Got error msg in EO pod after change es node count from 3 to 4 in clusterlogging CR instance.

{"level":"error","ts":1561442637.229709,"logger":"kubebuilder.controller","msg":"Reconciler error","controller":"elasticsearch-controller","request":"openshift-logging/elasticsearch","error":"Failed to reconcile Elasticsearch deployment spec: Unsupported change to UUIDs made: Previously used GenUUID \"jw91ctq6\" is no longer found in Spec.Nodes","stacktrace":"github.com/go-logr/zapr.(*zapLogger).Error\n\t/go/src/github.com/openshift/elasticsearch-operator/_output/src/github.com/go-logr/zapr/zapr.go:128\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem\n\t/go/src/github.com/openshift/elasticsearch-operator/_output/src/sigs.k8s.io/controller-runtime/pkg/internal/controller/controller.go:217\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func1\n\t/go/src/github.com/openshift/elasticsearch-operator/_output/src/sigs.k8s.io/controller-runtime/pkg/internal/controller/controller.go:158\nk8s.io/apimachinery/pkg/util/wait.JitterUntil.func1\n\t/go/src/github.com/openshift/elasticsearch-operator/_output/src/k8s.io/apimachinery/pkg/util/wait/wait.go:133\nk8s.io/apimachinery/pkg/util/wait.JitterUntil\n\t/go/src/github.com/openshift/elasticsearch-operator/_output/src/k8s.io/apimachinery/pkg/util/wait/wait.go:134\nk8s.io/apimachinery/pkg/util/wait.Until\n\t/go/src/github.com/openshift/elasticsearch-operator/_output/src/k8s.io/apimachinery/pkg/util/wait/wait.go:88"}

$ oc get elasticsearch -oyaml
apiVersion: v1
items:
- apiVersion: logging.openshift.io/v1
  kind: Elasticsearch
  metadata:
    creationTimestamp: "2019-06-25T03:39:34Z"
    generation: 37
    name: elasticsearch
    namespace: openshift-logging
    ownerReferences:
    - apiVersion: logging.openshift.io/v1
      controller: true
      kind: ClusterLogging
      name: instance
      uid: d67cda8e-96fa-11e9-a275-06e6146aca30
    resourceVersion: "431049"
    selfLink: /apis/logging.openshift.io/v1/namespaces/openshift-logging/elasticsearches/elasticsearch
    uid: d9521b52-96fa-11e9-a275-06e6146aca30
  spec:
    managementState: Managed
    nodeSpec:
      image: image-registry.openshift-image-registry.svc:5000/openshift/ose-logging-elasticsearch5:latest
      resources:
        limits:
          cpu: "1"
          memory: 2Gi
        requests:
          cpu: 200m
          memory: 1Gi
    nodes:
    - nodeCount: 3
      resources: {}
      roles:
      - client
      - data
      - master
      storage:
        size: 10Gi
        storageClassName: gp2
    - nodeCount: 1
      resources: {}
      roles:
      - client
      - data
      storage:
        size: 10Gi
        storageClassName: gp2
    redundancyPolicy: FullRedundancy
  status:
    cluster:
      activePrimaryShards: 17
      activeShards: 23
      initializingShards: 0
      numDataNodes: 3
      numNodes: 3
      pendingTasks: 0
      relocatingShards: 0
      status: green
      unassignedShards: 0
    clusterHealth: ""
    conditions:
    - lastTransitionTime: "2019-06-25T06:03:57Z"
      message: Previously used GenUUID "jw91ctq6" is no longer found in Spec.Nodes
      reason: Invalid Spec
      status: "True"
      type: InvalidUUID
    nodes:
    - deploymentName: elasticsearch-cdm-jw91ctq6-1
      upgradeStatus: {}
    - deploymentName: elasticsearch-cdm-jw91ctq6-2
      upgradeStatus: {}
    - deploymentName: elasticsearch-cdm-jw91ctq6-3
      upgradeStatus: {}
    pods:
      client:
        failed: []
        notReady: []
        ready:
        - elasticsearch-cdm-jw91ctq6-1-fbbd7bfc-nglll
        - elasticsearch-cdm-jw91ctq6-2-564f89f647-bhtvm
        - elasticsearch-cdm-jw91ctq6-3-86dbf67c7-bhwvg
      data:
        failed: []
        notReady: []
        ready:
        - elasticsearch-cdm-jw91ctq6-1-fbbd7bfc-nglll
        - elasticsearch-cdm-jw91ctq6-2-564f89f647-bhtvm
        - elasticsearch-cdm-jw91ctq6-3-86dbf67c7-bhwvg
      master:
        failed: []
        notReady: []
        ready:
        - elasticsearch-cdm-jw91ctq6-1-fbbd7bfc-nglll
        - elasticsearch-cdm-jw91ctq6-2-564f89f647-bhtvm
        - elasticsearch-cdm-jw91ctq6-3-86dbf67c7-bhwvg
    shardAllocationEnabled: all
kind: List
metadata:
  resourceVersion: ""
  selfLink: ""

ose-elasticsearch-operator-v4.2.0-201906241432

ose-cluster-logging-operator-v4.2.0-201906241832

Out of curiosity, how much time did you wait for after the initial creation of the clusterlogging object before updating the elasticsearch node count?

In c4, it's about several hours. The ES cluster was in green status before I updating the elasticsearch node count.

And it alse could be reproduced by: creating clusterlogging instance, waiting for the ES cluster be in Green status, updating the es node count.

I can recreate this, looking into why CLO is dropping the uuids

https://github.com/openshift/cluster-logging-operator/pull/205

Verified in ose-cluster-logging-operator-v4.2.0-201907222219

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2019:2922