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Storage Autoscaling of Elasticsearch Combined Cluster
This guide will show you how to use KubeDB
to autoscale the storage of an Elasticsearch combined cluster.
Before You Begin
At first, you need to have a Kubernetes cluster, and the
kubectl
command-line tool must be configured to communicate with your cluster.Install
KubeDB
Community, Enterprise and Autoscaler operator in your cluster following the steps here.Install Prometheus from here
You must have a
StorageClass
that supports volume expansion.You should be familiar with the following
KubeDB
concepts:
To keep everything isolated, we are going to use a separate namespace called demo
throughout this tutorial.
$ kubectl create ns demo
namespace/demo created
Note: YAML files used in this tutorial are stored in this directory of kubedb/docs repository.
Storage Autoscaling of Combined cluster
At first verify that your cluster has a storage class, that supports volume expansion. Let’s check,
$ kubectl get storageclass
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
standard (default) rancher.io/local-path Delete WaitForFirstConsumer false 9h
topolvm-provisioner topolvm.cybozu.com Delete WaitForFirstConsumer true 9h
We can see from the output the topolvm-provisioner
storage class has ALLOWVOLUMEEXPANSION
field as true. So, this storage class supports volume expansion. We can use it. You can install topolvm from here
Now, we are going to deploy a Elasticsearch
combined cluster using a supported version by the KubeDB
operator. Then we are going to apply ElasticsearchAutoscaler
to set up autoscaling.
Deploy Elasticsearch Combined Cluster
In this section, we are going to deploy an Elasticsearch combined cluster with version xpack-8.11.1
. Then, in the next section we will set up autoscaling for this database using ElasticsearchAutoscaler
CRD. Below is the YAML of the Elasticsearch
CR that we are going to create,
apiVersion: kubedb.com/v1
kind: Elasticsearch
metadata:
name: es-combined
namespace: demo
spec:
enableSSL: true
version: xpack-8.11.1
storageType: Durable
replicas: 1
storage:
storageClassName: "topolvm-provisioner"
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
deletionPolicy: WipeOut
Let’s create the Elasticsearch
CRO we have shown above,
$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/guides/elasticsearch/autoscaler/storage/combined/yamls/es-combined.yaml
elasticsearch.kubedb.com/es-combined created
Now, wait until es-combined
has status Ready
. i.e,
$ kubectl get es -n demo -w
NAME VERSION STATUS AGE
es-combined xpack-8.11.1 Provisioning 5s
es-combined xpack-8.11.1 Ready 50s
Let’s check volume size from petset, and from the persistent volume,
$ kubectl get sts -n demo es-combined -o json | jq '.spec.volumeClaimTemplates[].spec.resources'
{
"requests": {
"storage": "1Gi"
}
}
$ kubectl get pv -n demo
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-efe67aee-21bf-4320-9873-5d58d68182ae 1Gi RWO Delete Bound demo/data-es-combined-0 topolvm-provisioner 8m3s
You can see the PetSet has 1GB storage, and the capacity of the persistent volume is also 1GB.
We are now ready to apply the ElasticsearchAutoscaler
CRO to set up storage autoscaling for this database.
Storage Autoscaling
Here, we are going to set up storage autoscaling using a ElasticsearchAutoscaler Object.
Create ElasticsearchAutoscaler Object
To set up vertical autoscaling for the combined cluster nodes, we have to create a ElasticsearchAutoscaler
CRO with our desired configuration. Below is the YAML of the ElasticsearchAutoscaler
object that we are going to create,
apiVersion: autoscaling.kubedb.com/v1alpha1
kind: ElasticsearchAutoscaler
metadata:
name: es-combined-storage-as
namespace: demo
spec:
databaseRef:
name: es-combined
storage:
node:
expansionMode: "Online"
trigger: "On"
usageThreshold: 60
scalingThreshold: 50
Here,
spec.databaseRef.name
specifies that we are performing vertical scaling operation ones-combined
cluster.spec.storage.node.trigger
specifies that storage autoscaling is enabled for the Elasticsearch nodes.spec.storage.node.usageThreshold
specifies storage usage threshold, if storage usage exceeds60%
then storage autoscaling will be triggered.spec.storage.node.scalingThreshold
specifies the scaling threshold. Storage will be scaled to50%
of the current amount.
Let’s create the ElasticsearchAutoscaler
CR we have shown above,
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/guides/elasticsearch/autoscaler/storage/combined/yamls/es-combined-storage-as.yaml
elasticsearchautoscaler.autoscaling.kubedb.com/es-combined-storage-as created
Storage Autoscaling is set up successfully
Let’s check that the elasticsearchautoscaler
resource is created successfully,
$ kubectl get elasticsearchautoscaler -n demo
NAME AGE
es-combined-storage-as 9s
$ kubectl describe elasticsearchautoscaler -n demo es-combined-storage-as
Name: es-combined-storage-as
Namespace: demo
Labels: <none>
Annotations: <none>
API Version: autoscaling.kubedb.com/v1alpha1
Kind: ElasticsearchAutoscaler
Metadata:
Creation Timestamp: 2021-03-22T14:57:58Z
Generation: 1
Resource Version: 7906
UID: f4e6b550-b566-458b-af05-84e0581b93f0
Spec:
Database Ref:
Name: es-combined
Storage:
Node:
Scaling Threshold: 50
Trigger: On
Usage Threshold: 60
Events: <none>
So, the elasticsearchautoscaler
resource is created successfully.
Now, for this demo, we are going to manually fill up the persistent volume to exceed the usageThreshold
using dd
command to see if storage autoscaling is working or not.
Let’s exec into the database pod and fill the database volume using the following commands:
$ kubectl exec -it -n demo es-combined-0 -- bash
[root@es-combined-0 elasticsearch]# df -h /usr/share/elasticsearch/data
Filesystem Size Used Avail Use% Mounted on
/dev/topolvm/026b4152-c7d8-47c1-afe2-0a7c7b708857 1014M 40M 975M 4% /usr/share/elasticsearch/data
[root@es-combined-0 elasticsearch]# dd if=/dev/zero of=/usr/share/elasticsearch/data/file.img bs=600M count=1
1+0 records in
1+0 records out
629145600 bytes (629 MB) copied, 1.95767 s, 321 MB/s
[root@es-combined-0 elasticsearch]# df -h /usr/share/elasticsearch/data
Filesystem Size Used Avail Use% Mounted on
/dev/topolvm/026b4152-c7d8-47c1-afe2-0a7c7b708857 1014M 640M 375M 64% /usr/share/elasticsearch/data
So, from the above output, we can see that the storage usage is 64%, which exceeded the usageThreshold
60%.
Let’s watch the elasticsearchopsrequest
in the demo namespace to see if any elasticsearchopsrequest
object is created. After some time you’ll see that a elasticsearchopsrequest
of type VolumeExpansion
will be created based on the scalingThreshold
.
$ kubectl get esops -n demo -w
NAME TYPE STATUS AGE
esops-es-combined-8ub9ca VolumeExpansion Progressing 30s
Let’s wait for the opsRequest to become successful.
$ kubectl get esops -n demo
NAME TYPE STATUS AGE
esops-es-combined-8ub9ca VolumeExpansion Successful 50s
We can see from the above output that the ElasticsearchOpsRequest
has succeeded. If we describe the ElasticsearchOpsRequest
we will get an overview of the steps that were followed to expand the volume of the database.
$ kubectl describe esops -n demo esops-es-combined-8ub9ca
Name: esops-es-combined-8ub9ca
Namespace: demo
Labels: app.kubernetes.io/component=database
app.kubernetes.io/instance=es-combined
app.kubernetes.io/managed-by=kubedb.com
app.kubernetes.io/name=elasticsearches.kubedb.com
Annotations: <none>
API Version: ops.kubedb.com/v1alpha1
Kind: ElasticsearchOpsRequest
Metadata:
Creation Timestamp: 2021-03-22T15:08:54Z
Generation: 1
Owner References:
API Version: autoscaling.kubedb.com/v1alpha1
Block Owner Deletion: true
Controller: true
Kind: ElasticsearchAutoscaler
Name: es-combined-storage-as
UID: f4e6b550-b566-458b-af05-84e0581b93f0
Resource Version: 11064
UID: 65ca8078-ae75-4b90-8e11-c09dc287c993
Spec:
Database Ref:
Name: es-combined
Type: VolumeExpansion
Volume Expansion:
Node: 1594884096
Status:
Conditions:
Last Transition Time: 2021-03-22T15:08:54Z
Message: Elasticsearch ops request is expanding volume of the Elasticsearch nodes.
Observed Generation: 1
Reason: VolumeExpansion
Status: True
Type: VolumeExpansion
Last Transition Time: 2021-03-22T15:09:24Z
Message: successfully expanded combined nodes
Observed Generation: 1
Reason: UpdateCombinedNodePVCs
Status: True
Type: UpdateCombinedNodePVCs
Last Transition Time: 2021-03-22T15:09:39Z
Message: successfully deleted the petSet with orphan propagation policy
Observed Generation: 1
Reason: OrphanPetSetPods
Status: True
Type: OrphanPetSetPods
Last Transition Time: 2021-03-22T15:09:44Z
Message: PetSet is recreated
Observed Generation: 1
Reason: ReadyPetSets
Status: True
Type: ReadyPetSets
Last Transition Time: 2021-03-22T15:09:44Z
Message: Successfully completed the modification process.
Observed Generation: 1
Reason: Successful
Status: True
Type: Successful
Observed Generation: 1
Phase: Successful
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal PauseDatabase 17m KubeDB Enterprise Operator Pausing Elasticsearch demo/es-combined
Normal UpdateCombinedNodePVCs 17m KubeDB Enterprise Operator successfully expanded combined nodes
Normal OrphanPetSetPods 16m KubeDB Enterprise Operator successfully deleted the petSet with orphan propagation policy
Normal ResumeDatabase 16m KubeDB Enterprise Operator Resuming Elasticsearch demo/es-combined
Normal ResumeDatabase 16m KubeDB Enterprise Operator Resuming Elasticsearch demo/es-combined
Normal ReadyPetSets 16m KubeDB Enterprise Operator PetSet is recreated
Normal ResumeDatabase 16m KubeDB Enterprise Operator Resuming Elasticsearch demo/es-combined
Normal Successful 16m KubeDB Enterprise Operator Successfully Updated Database
Now, we are going to verify from the Petset
, and the Persistent Volume
whether the volume of the combined cluster has expanded to meet the desired state, Let’s check,
$ kubectl get sts -n demo es-combined -o json | jq '.spec.volumeClaimTemplates[].spec.resources'
{
"requests": {
"storage": "1594884096"
}
}
$ kubectl get pv -n demo
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-efe67aee-21bf-4320-9873-5d58d68182ae 2Gi RWO Delete Bound demo/data-es-combined-0 topolvm-provisioner 43m
The above output verifies that we have successfully autoscaled the volume of the Elasticsearch combined cluster.
Cleaning Up
To clean up the Kubernetes resources created by this tutorial, run:
$ kubectl delete elasticsearch -n demo es-combined
$ kubectl delete elasticsearchautoscaler -n demo es-combined-storage-as