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Topology Cluster

An Elasticsearch topology cluster is a group of Elasticsearch nodes ( >= 3 ) where each node is assigned with a dedicated role such as master, data, and ingest. In a topology cluster, there has to be at least one master node, one data node, and one ingest node.

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. If you do not already have a cluster, you can create one by using kind.

Now, install the KubeDB operator in your cluster following the steps here.

To keep things isolated, this tutorial uses a separate namespace called demo throughout this tutorial.

$ kubectl create namespace demo
namespace/demo created

$ kubectl get namespace
NAME                 STATUS   AGE
demo                 Active   9s

Note: YAML files used in this tutorial are stored in here in GitHub repository kubedb/docs.

Find Available StorageClass

We will have to provide StorageClass in Elasticsearch CR specification. Check available StorageClass in your cluster using the following command,

$ kubectl get storageclass
NAME                 PROVISIONER             RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
standard (default)   rancher.io/local-path   Delete          WaitForFirstConsumer   false                  1h

Here, we have standard StorageClass in our cluster from Local Path Provisioner.

Create Dedicated Elasticsearch Cluster

We are going to create a dedicated Elasticsearch cluster in topology mode. Our cluster will be consist of 2 master nodes, 3 data nodes, and 2 ingest nodes. We will the Elasticsearch image provided by the SearchGurad ( searchguard-7.9.3 ) for this demo. To learn more about the Elasticsearch CR, visit here.

apiVersion: kubedb.com/v1alpha2
kind: Elasticsearch
metadata:
  name: es-topology
  namespace: demo
spec:
  enableSSL: true 
  version: searchguard-7.9.3
  storageType: Durable
  topology:
    master:
      replicas: 2
      storage:
        storageClassName: "standard"
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 1Gi
    data:
      replicas: 3
      storage:
        storageClassName: "standard"
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 1Gi
    ingest:
      replicas: 2
      storage:
        storageClassName: "standard"
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 1Gi

Here,

spec.version - is the name of the ElasticsearchVersion CR. Here, an Elasticsearch of version 7.9.3 will be created with SearchGuard security plugin.
spec.enableSSL - specifies whether the HTTP layer is secured with certificates or not.
spec.storageType - specifies the type of storage that will be used for Elasticsearch database. It can be Durable or Ephemeral. The default value of this field is Durable. If Ephemeral is used then KubeDB will create the Elasticsearch database using EmptyDir volume. In this case, you don’t have to specify spec.storage field. This is useful for testing purposes.
spec.topology - specifies the node-specific properties for the Elasticsearch cluster.
- topology.master - specifies the properties of master nodes.
  - master.replicas - specifies the number of master nodes.
  - master.storage - specifies the master node storage information that passed to the StatefulSet.
- topology.data - specifies the properties of data nodes.
  - master.replicas - specifies the number of data nodes.
  - master.storage - specifies the data node storage information that passed to the StatefulSet.
- topology.ingest - specifies the properties of ingest nodes.
  - master.replicas - specifies the number of ingest nodes.
  - master.storage - specifies the ingest node storage information that passed to the StatefulSet.

Let’s deploy the above example by the following command:

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.08.23/docs/guides/elasticsearch/clustering/topology-cluster/yamls/es-topology.yaml
elasticsearch.kubedb.com/es-topology created

Watch the bootstrap progress:

$ kubectl get elasticsearch -n demo -w
NAME          VERSION             STATUS         AGE
es-topology   searchguard-7.9.3   Provisioning   15s
es-topology   searchguard-7.9.3   Provisioning   25s
es-topology   searchguard-7.9.3   Provisioning   33s
es-topology   searchguard-7.9.3   Provisioning   2m9s 
es-topology   searchguard-7.9.3   Ready          2m11s

Hence the cluster is ready to use.

Describe the Elasticsearch object to observe the progress if something goes wrong or the status is not changing for a long period of time:

$ kubectl describe elasticsearch -n demo es-topology 
Name:         es-topology
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  kubedb.com/v1alpha2
Kind:         Elasticsearch
Metadata:
  Creation Timestamp:  2021-03-02T09:26:51Z
  Finalizers:
    kubedb.com
  Generation:  3
  Resource Version:  153315
  UID:               0b1aa286-ccf0-4ac8-bc4f-593eb9df4955
Spec:
  Auth Secret:
    Name:      es-topology-admin-cred
  Enable SSL:  true
  Internal Users:
    Admin:
      Backend Roles:
        admin
      Reserved:  true
    Kibanaro:
    Kibanaserver:
      Reserved:  true
    Logstash:
    Readall:
    Snapshotrestore:
  Kernel Settings:
    Privileged:  true
    Sysctls:
      Name:   vm.max_map_count
      Value:  262144
  Pod Template:
    Controller:
    Metadata:
    Spec:
      Affinity:
        Pod Anti Affinity:
          Preferred During Scheduling Ignored During Execution:
            Pod Affinity Term:
              Label Selector:
                Match Expressions:
                  Key:       ${NODE_ROLE}
                  Operator:  Exists
                Match Labels:
                  app.kubernetes.io/instance:    es-topology
                  app.kubernetes.io/managed-by:  kubedb.com
                  app.kubernetes.io/name:        elasticsearches.kubedb.com
              Namespaces:
                demo
              Topology Key:  kubernetes.io/hostname
            Weight:          100
            Pod Affinity Term:
              Label Selector:
                Match Expressions:
                  Key:       ${NODE_ROLE}
                  Operator:  Exists
                Match Labels:
                  app.kubernetes.io/instance:    es-topology
                  app.kubernetes.io/managed-by:  kubedb.com
                  app.kubernetes.io/name:        elasticsearches.kubedb.com
              Namespaces:
                demo
              Topology Key:  failure-domain.beta.kubernetes.io/zone
            Weight:          50
      Resources:
      Service Account Name:  es-topology
  Storage Type:              Durable
  Termination Policy:        Delete
  Tls:
    Certificates:
      Alias:  ca
      Private Key:
        Encoding:   PKCS8
      Secret Name:  es-topology-ca-cert
      Subject:
        Organizations:
          kubedb
      Alias:  transport
      Private Key:
        Encoding:   PKCS8
      Secret Name:  es-topology-transport-cert
      Subject:
        Organizations:
          kubedb
      Alias:  http
      Private Key:
        Encoding:   PKCS8
      Secret Name:  es-topology-http-cert
      Subject:
        Organizations:
          kubedb
      Alias:  admin
      Private Key:
        Encoding:   PKCS8
      Secret Name:  es-topology-admin-cert
      Subject:
        Organizations:
          kubedb
      Alias:  archiver
      Private Key:
        Encoding:   PKCS8
      Secret Name:  es-topology-archiver-cert
      Subject:
        Organizations:
          kubedb
  Topology:
    Data:
      Replicas:  3
      Resources:
        Limits:
          Cpu:     500m
          Memory:  1Gi
        Requests:
          Cpu:     500m
          Memory:  1Gi
      Storage:
        Access Modes:
          ReadWriteOnce
        Resources:
          Requests:
            Storage:         1Gi
        Storage Class Name:  standard
      Suffix:                data
    Ingest:
      Replicas:  2
      Resources:
        Limits:
          Cpu:     500m
          Memory:  1Gi
        Requests:
          Cpu:     500m
          Memory:  1Gi
      Storage:
        Access Modes:
          ReadWriteOnce
        Resources:
          Requests:
            Storage:         1Gi
        Storage Class Name:  standard
      Suffix:                ingest
    Master:
      Replicas:  2
      Resources:
        Limits:
          Cpu:     500m
          Memory:  1Gi
        Requests:
          Cpu:     500m
          Memory:  1Gi
      Storage:
        Access Modes:
          ReadWriteOnce
        Resources:
          Requests:
            Storage:         1Gi
        Storage Class Name:  standard
      Suffix:                master
  Version:                   searchguard-7.9.3
Status:
  Conditions:
    Last Transition Time:  2021-03-02T09:26:51Z
    Message:               The KubeDB operator has started the provisioning of Elasticsearch: demo/es-topology
    Reason:                DatabaseProvisioningStartedSuccessfully
    Status:                True
    Type:                  ProvisioningStarted
    Last Transition Time:  2021-03-02T09:27:24Z
    Message:               All desired replicas are ready.
    Reason:                AllReplicasReady
    Status:                True
    Type:                  ReplicaReady
    Last Transition Time:  2021-03-02T09:28:59Z
    Message:               The Elasticsearch: demo/es-topology is accepting client requests.
    Observed Generation:   3
    Reason:                DatabaseAcceptingConnectionRequest
    Status:                True
    Type:                  AcceptingConnection
    Last Transition Time:  2021-03-02T09:29:00Z
    Message:               The Elasticsearch: demo/es-topology is ready.
    Observed Generation:   3
    Reason:                ReadinessCheckSucceeded
    Status:                True
    Type:                  Ready
    Last Transition Time:  2021-03-02T09:29:02Z
    Message:               The Elasticsearch: demo/es-topology is successfully provisioned.
    Observed Generation:   3
    Reason:                DatabaseSuccessfullyProvisioned
    Status:                True
    Type:                  Provisioned
  Observed Generation:     3
  Phase:                   Ready
Events:
  Type    Reason      Age   From                    Message
  ----    ------      ----  ----                    -------
  Normal  Successful   9m   Elasticsearch operator  Successfully  governing service
  Normal  Successful   9m   Elasticsearch operator  Successfully patched Elasticsearch

KubeDB Operator Generated Resources

Let’s check the k8s resources created by the operator on the deployment of Elasticsearch CRO:

$ kubectl get all,secret,pvc -n demo -l 'app.kubernetes.io/instance=es-topology'
NAME                       READY   STATUS    RESTARTS   AGE
pod/es-topology-data-0     1/1     Running   0          5m55s
pod/es-topology-data-1     1/1     Running   0          5m42s
pod/es-topology-data-2     1/1     Running   0          5m31s
pod/es-topology-ingest-0   1/1     Running   0          5m55s
pod/es-topology-ingest-1   1/1     Running   0          5m45s
pod/es-topology-master-0   1/1     Running   0          5m55s
pod/es-topology-master-1   1/1     Running   0          5m42s

NAME                         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
service/es-topology          ClusterIP   10.96.143.113   <none>        9200/TCP   5m57s
service/es-topology-master   ClusterIP   None            <none>        9300/TCP   5m57s
service/es-topology-pods     ClusterIP   None            <none>        9200/TCP   5m57s

NAME                                  READY   AGE
statefulset.apps/es-topology-data     3/3     5m55s
statefulset.apps/es-topology-ingest   2/2     5m55s
statefulset.apps/es-topology-master   2/2     5m55s

NAME                                             TYPE                       VERSION   AGE
appbinding.appcatalog.appscode.com/es-topology   kubedb.com/elasticsearch   7.9.3     5m55s

NAME                                      TYPE                       DATA   AGE
secret/es-topology-admin-cert             kubernetes.io/tls          3      5m57s
secret/es-topology-admin-cred             kubernetes.io/basic-auth   2      5m56s
secret/es-topology-archiver-cert          kubernetes.io/tls          3      5m56s
secret/es-topology-ca-cert                kubernetes.io/tls          2      5m57s
secret/es-topology-config                 Opaque                     3      5m55s
secret/es-topology-http-cert              kubernetes.io/tls          3      5m57s
secret/es-topology-kibanaro-cred          kubernetes.io/basic-auth   2      5m56s
secret/es-topology-kibanaserver-cred      kubernetes.io/basic-auth   2      5m56s
secret/es-topology-logstash-cred          kubernetes.io/basic-auth   2      5m56s
secret/es-topology-readall-cred           kubernetes.io/basic-auth   2      5m56s
secret/es-topology-snapshotrestore-cred   kubernetes.io/basic-auth   2      5m56s
secret/es-topology-transport-cert         kubernetes.io/tls          3      5m57s

NAME                                              STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
persistentvolumeclaim/data-es-topology-data-0     Bound    pvc-7cad281b-6b1d-4474-ba76-4347b49cd647   1Gi        RWO            standard       5m55s
persistentvolumeclaim/data-es-topology-data-1     Bound    pvc-64637ae8-48b8-40c8-b0f6-16f52d375b8f   1Gi        RWO            standard       5m42s
persistentvolumeclaim/data-es-topology-data-2     Bound    pvc-2b21c196-e029-4ef6-a515-8b8c2570d00b   1Gi        RWO            standard       5m31s
persistentvolumeclaim/data-es-topology-ingest-0   Bound    pvc-ffc0a0f2-420d-44f2-a075-749f9abaa4d0   1Gi        RWO            standard       5m55s
persistentvolumeclaim/data-es-topology-ingest-1   Bound    pvc-fd9b4f65-00b6-4add-aae9-0f792c1cd620   1Gi        RWO            standard       5m45s
persistentvolumeclaim/data-es-topology-master-0   Bound    pvc-d6f2e28d-92d6-4ea0-b764-a8dc38c013f2   1Gi        RWO            standard       5m55s
persistentvolumeclaim/data-es-topology-master-1   Bound    pvc-74178260-c1d9-47e8-977f-a31ddd97b31d   1Gi        RWO            standard       5m42s

StatefulSet - 3 StatefulSets are created for 3 types Elasticsearch nodes. The StatefulSets are named after the Elasticsearch instance with given suffix: {Elasticsearch-Name}-{Sufix}.
Services - 3 services are generated for each Elasticsearch database.
- {Elasticsearch-Name} - the client service which is used to connect to the database. It points to the ingest nodes.
- {Elasticsearch-Name}-master - the master service which is used to connect to the master nodes. It is a headless service.
- {Elasticsearch-Name}-pods - the node discovery service which is used by the Elasticsearch nodes to communicate each other. It is a headless service.
AppBinding - an AppBinding which hold the connect information for the database. It is also named after the Elastics
Secrets - 3 types of secrets are generated for each Elasticsearch database.
- {Elasticsearch-Name}-{username}-cred - the auth secrets which hold the username and password for the Elasticsearch users.
- {Elasticsearch-Name}-{alias}-cert - the certificate secrets which hold tls.crt, tls.key, and ca.crt for configuring the Elasticsearch database.
- {Elasticsearch-Name}-config - the default configuration secret created by the operator.

Connect with Elasticsearch Database

We will use port forwarding to connect with our Elasticsearch database. Then we will use curl to send HTTP requests to check cluster health to verify that our Elasticsearch database is working well.

Let’s port-forward the port 9200 to local machine:

$ $ kubectl port-forward -n demo svc/es-topology 9200
Forwarding from 127.0.0.1:9200 -> 9200
Forwarding from [::1]:9200 -> 9200

Now, our Elasticsearch cluster is accessible at localhost:9200.

Connection information:

Address: localhost:9200

Username:

$ kubectl get secret -n demo es-topology-admin-cred -o jsonpath='{.data.username}' | base64 -d
admin

Password:

$ kubectl get secret -n demo es-topology-admin-cred -o jsonpath='{.data.password}' | base64 -d
MaBoYQX*KAe4na(f

Now let’s check the health of our Elasticsearch database.

$ curl -XGET -k -u 'admin:MaBoYQX*KAe4na(f' "https://localhost:9200/_cluster/health?pretty"
{
  "cluster_name" : "es-topology",
  "status" : "green",
  "timed_out" : false,
  "number_of_nodes" : 7,
  "number_of_data_nodes" : 3,
  "active_primary_shards" : 6,
  "active_shards" : 13,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 0,
  "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
}

Cleaning Up

TO cleanup the k8s resources created by this tutorial, run:

$ kubectl patch -n demo elasticsearch es-topology -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"

$ kubectl delete elasticsearch -n demo es-topology 

# delete namespace
$ kubectl delete namespace demo

Next Steps

Learn about taking backup of Elasticsearch database using Stash.
Monitor your Elasticsearch database with KubeDB using out-of-the-box builtin-Prometheus.
Monitor your Elasticsearch database with KubeDB using out-of-the-box Prometheus operator.
Detail concepts of Elasticsearch object.
Use private Docker registry to deploy Elasticsearch with KubeDB.
Want to hack on KubeDB? Check our contribution guidelines.

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