Manually rolling out Elasticsearch | Logging | OpenShift Container Platform 4.4

Performing an Elasticsearch rolling cluster restart

OpenShift Container Platform supports the Elasticsearch rolling cluster restart. A rolling restart applies appropriate changes to the Elasticsearch cluster without down time (if three masters are configured). The Elasticsearch cluster remains online and operational, with nodes taken offline one at a time.

Performing an Elasticsearch rolling cluster restart

Perform a rolling restart when you change the elasticsearch configmap or any of the elasticsearch-* deployment configurations.

Also, a rolling restart is recommended if the nodes on which an Elasticsearch pod runs requires a reboot.

Prerequisite

Cluster logging and Elasticsearch must be installed.

Procedure

To perform a rolling cluster restart:

Change to the openshift-logging project:
```
$ oc project openshift-logging
```
Use the following command to extract the CA certificate from Elasticsearch and write to the admin-ca file:
```
$ oc extract secret/elasticsearch --to=. --keys=admin-ca

admin-ca
```

Perform a shard synced flush to ensure there are no pending operations waiting to be written to disk prior to shutting down:

$ oc exec <any_es_pod_in_the_cluster> -c elasticsearch -- curl -s --cacert /etc/elasticsearch/secret/admin-ca --cert /etc/elasticsearch/secret/admin-cert --key /etc/elasticsearch/secret/admin-key -XPOST 'https://localhost:9200/_flush/synced'

For example:

$ oc exec -c elasticsearch-cdm-5ceex6ts-1-dcd6c4c7c-jpw6 -- curl -s --cacert /etc/elasticsearch/secret/admin-ca --cert /etc/elasticsearch/secret/admin-cert --key /etc/elasticsearch/secret/admin-key -XPOST 'https://localhost:9200/_flush/synced'

Prevent shard balancing when purposely bringing down nodes using the OpenShift Container Platform es_util tool:

$ oc exec <any_es_pod_in_the_cluster> -c elasticsearch -- es_util --query=_cluster/settings -XPUT 'https://localhost:9200/_cluster/settings' -d '{ "transient": { "cluster.routing.allocation.enable" : "none" } }'

For example:

$ oc exec elasticsearch-cdm-5ceex6ts-1-dcd6c4c7c-jpw6 -c elasticsearch -- es_util --query=_cluster/settings?pretty=true -XPUT 'https://localhost:9200/_cluster/settings' -d '{ "transient": { "cluster.routing.allocation.enable" : "none" } }'

{
  "acknowledged" : true,
  "persistent" : { },
  "transient" : {
    "cluster" : {
      "routing" : {
        "allocation" : {
          "enable" : "none"
        }
      }
    }
  }
}

Once complete, for each deployment you have for an ES cluster:

By default, the OpenShift Container Platform Elasticsearch cluster blocks rollouts to their nodes. Use the following command to allow rollouts and allow the pod to pick up the changes:

$ oc rollout resume deployment/<deployment-name>

For example:

$ oc rollout resume deployment/elasticsearch-cdm-0-1
deployment.extensions/elasticsearch-cdm-0-1 resumed

A new pod is deployed. Once the pod has a ready container, you can move on to the next deployment.

$ oc get pods | grep elasticsearch-*

NAME                                            READY   STATUS    RESTARTS   AGE
elasticsearch-cdm-5ceex6ts-1-dcd6c4c7c-jpw6k    2/2     Running   0          22h
elasticsearch-cdm-5ceex6ts-2-f799564cb-l9mj7    2/2     Running   0          22h
elasticsearch-cdm-5ceex6ts-3-585968dc68-k7kjr   2/2     Running   0          22h

Once complete, reset the pod to disallow rollouts:

$ oc rollout pause deployment/<deployment-name>

For example:

$ oc rollout pause deployment/elasticsearch-cdm-0-1

deployment.extensions/elasticsearch-cdm-0-1 paused

Check that the Elasticsearch cluster is in green state:

$ oc exec <any_es_pod_in_the_cluster> -c elasticsearch -- es_util --query=_cluster/health?pretty=true

If you performed a rollout on the Elasticsearch pod you used in the previous commands, the pod no longer exists and you need a new pod name here.

For example:

$ oc exec elasticsearch-cdm-5ceex6ts-1-dcd6c4c7c-jpw6 -c elasticsearch -- es_util --query=_cluster/health?pretty=true

{
  "cluster_name" : "elasticsearch",
  "status" : "green", (1)
  "timed_out" : false,
  "number_of_nodes" : 3,
  "number_of_data_nodes" : 3,
  "active_primary_shards" : 8,
  "active_shards" : 16,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 1,
  "delayed_unassigned_shards" : 0,
  "number_of_pending_tasks" : 0,
  "number_of_in_flight_fetch" : 0,
  "task_max_waiting_in_queue_millis" : 0,
  "active_shards_percent_as_number" : 100.0
}

1	Make sure this parameter is `green` before proceeding.

If you changed the Elasticsearch configuration map, repeat these steps for each Elasticsearch pod.

Once all the deployments for the cluster have been rolled out, re-enable shard balancing:

$ oc exec <any_es_pod_in_the_cluster> -c elasticsearch -- es_util --query=_cluster/settings -XPUT 'https://localhost:9200/_cluster/settings' -d '{ "transient": { "cluster.routing.allocation.enable" : "none" } }'

For example:

$ oc exec elasticsearch-cdm-5ceex6ts-1-dcd6c4c7c-jpw6 -c elasticsearch -- es_util --query=_cluster/settings?pretty=true -XPUT 'https://localhost:9200/_cluster/settings' -d '{ "transient": { "cluster.routing.allocation.enable" : "all" } }'

{
  "acknowledged" : true,
  "persistent" : { },
  "transient" : {
    "cluster" : {
      "routing" : {
        "allocation" : {
          "enable" : "all"
        }
      }
    }
  }
}