First Steps With the Kubernetes Operator

This article demonstrates how you can use the Operator Lifecycle Manager to deploy a Kubernetes Operator to your cluster.

Sudip Sengupta

CORE ·

Aug. 14, 20 · Tutorial

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This blog post demonstrates how you can use the Operator Lifecycle Manager to deploy a Kubernetes Operator to your cluster. Then, you will use the Operator to spin up an Elastic Cloud on Kubernetes (ECK) cluster.

An operator is a software extension that uses custom resources (extension of the Kubernetes API) to manage complex applications on behalf of users.

The artifacts that come with an operator are:

A set of CRDs that extend the behavior of the cluster without making any change in the code
A controller that supervises the CRDs, and performs various activities such as spinning up a pod, take a backup, and so on.

The complexity encapsulated within an Operator can vary, as shown in the below diagram:

Operator Maturity Model. Retrieved from https://docs.openshift.com/container-platform/4.1/applications/operators/olm-what-operators-are.html

Prerequisites

A Kubernetes cluster (v1.7 or newer) with a control plane and two workers. If you don’t have a running Kubernetes cluster, refer to the “Create a Kubernetes Cluster with Kind” section below.

Create a Kubernetes Cluster With Kind (Optional)

Kind is a tool for running local Kubernetes clusters using Docker container "nodes". Follow the steps in this section if you don't have a running Kubernetes cluster:

Install kind by following the steps from the Kind Quick Start page.
Place the following spec into a file named kind-es-cluster.yaml :

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kind: Cluster 
apiVersion: kind.x-k8s.io/v1alpha4 
nodes:
 - role: control-plane
 - role: worker
 - role: worker

Create a cluster with a control plane and two worker nodes by running the Kind create cluster command followed by the --config flag and the name of the configuration file:

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kind create cluster --config kind-es-cluster.yaml

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Creating cluster "kind" ...
 ✓ Ensuring node image (kindest/node:v1.16.3) ��
 ✓ Preparing nodes ��
 ✓ Writing configuration ��
 ✓ Starting control-plane ��️
 ✓ Installing CNI ��
 ✓ Installing StorageClass ��
 ✓ Joining worker nodes ��
Set kubectl context to "kind-kind"
You can now use your cluster with:
kubectl cluster-info --context kind-kind
Have a nice day! ��

At this point, you can retrieve the list of services that were started on your cluster:

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kubectl cluster-info

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Kubernetes master is running at https://127.0.0.1:53519 
KubeDNS is running at https://127.0.0.1:53519/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy 
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

Install the Operator Lifecycle Manager

In this section, you'll install the Operator Lifecycle Manager ("OLM"), a tool that helps you manage the Operators deployed to your cluster in an automated fashion.

Run the following commands to install OLM:

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curl -sL https://github.com/operator-framework/operator-lifecycle-manager/releases/download/0.13.0/install.sh | bash -s 0.13.0

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customresourcedefinition.apiextensions.k8s.io/clusterserviceversions.operators.coreos.com created 
customresourcedefinition.apiextensions.k8s.io/installplans.operators.coreos.com created 
customresourcedefinition.apiextensions.k8s.io/subscriptions.operators.coreos.com created 
customresourcedefinition.apiextensions.k8s.io/catalogsources.operators.coreos.com created 
customresourcedefinition.apiextensions.k8s.io/operatorgroups.operators.coreos.com created 
namespace/olm created 
namespace/operators created 
clusterrole.rbac.authorization.k8s.io/system:controller:operator-lifecycle-manager created 
serviceaccount/olm-operator-serviceaccount created 
clusterrolebinding.rbac.authorization.k8s.io/olm-operator-binding-olm created 
deployment.apps/olm-operator created 
deployment.apps/catalog-operator created 
clusterrole.rbac.authorization.k8s.io/aggregate-olm-edit created 
clusterrole.rbac.authorization.k8s.io/aggregate-olm-view created 
operatorgroup.operators.coreos.com/global-operators created 
operatorgroup.operators.coreos.com/olm-operators created 
clusterserviceversion.operators.coreos.com/packageserver created 
catalogsource.operators.coreos.com/operatorhubio-catalog created 
Waiting for deployment "olm-operator" rollout to finish: 0 of 1 updated replicas are available... 
deployment "olm-operator" successfully rolled out 
deployment "catalog-operator" successfully rolled out 
Package server phase: Installing 
Package server phase: Succeeded 
deployment "packageserver" successfully rolled out

Install the ECK Operator

The ECK Operator provides support for managing and monitoring multiple clusters, upgrading to new stack versions, scaling cluster capacity, etc. This section walks through installing the ECK Operator to your Kubernetes cluster:

Enter the following kubectl apply command to install the ECK Operator:

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kubectl apply -f https://download.elastic.co/downloads/eck/1.0.0/all-in-one.yaml

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customresourcedefinition.apiextensions.k8s.io/apmservers.apm.k8s.elastic.co created 
customresourcedefinition.apiextensions.k8s.io/elasticsearches.elasticsearch.k8s.elastic.co created 
customresourcedefinition.apiextensions.k8s.io/kibanas.kibana.k8s.elastic.co created 
clusterrole.rbac.authorization.k8s.io/elastic-operator created 
clusterrolebinding.rbac.authorization.k8s.io/elastic-operator created 
namespace/elastic-system created statefulset.apps/elastic-operator created 
serviceaccount/elastic-operator created 
validatingwebhookconfiguration.admissionregistration.k8s.io/elastic-webhook.k8s.elastic.co created 
service/elastic-webhook-server created 
secret/elastic-webhook-server-cert created

Remember that the ECK Operator is a Kubernetes resource. Thus, you can display it by using the following command:

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kubectl get CustomResourceDefinition

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NAME                                           CREATED AT 
apmservers.apm.k8s.elastic.co                  2020-01-29T07:02:24Z 
catalogsources.operators.coreos.com            2020-01-29T06:59:21Z 
clusterserviceversions.operators.coreos.com    2020-01-29T06:59:20Z 
elasticsearches.elasticsearch.k8s.elastic.co   2020-01-29T07:02:24Z 
installplans.operators.coreos.com              2020-01-29T06:59:20Z 
kibanas.kibana.k8s.elastic.co                  2020-01-29T07:02:25Z 
operatorgroups.operators.coreos.com            2020-01-29T06:59:21Z 
subscriptions.operators.coreos.com             2020-01-29T06:59:20Z

To see more details about a specific CRD, run the kubectl describe CustomResourceDefinition command followed by the name of the CRD:

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kubectl describe CustomResourceDefinition elasticsearches.elasticsearch.k8s.elastic.co

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Name:         elasticsearches.elasticsearch.k8s.elastic.co 
Namespace: 
Labels:       <none> 
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"apiextensions.k8s.io/v1beta1","kind":"CustomResourceDefinition","metadata":{"annotations":{},"creationTimestamp":null,"name... 
API Version:  apiextensions.k8s.io/v1 
Kind:         CustomResourceDefinition 
Metadata:
  Creation Timestamp:  2020-01-29T07:02:24Z
  Generation:          1
  Resource Version:    1074
  Self Link:           /apis/apiextensions.k8s.io/v1/customresourcedefinitions/elasticsearches.elasticsearch.k8s.elastic.co
  UID:                 2332769c-ead3-4208-b6bd-68b8cfcb3692 
Spec:
  Conversion:
    Strategy:  None
  Group:       elasticsearch.k8s.elastic.co
  Names:
    Categories:
      elastic
    Kind:       Elasticsearch
    List Kind:  ElasticsearchList
    Plural:     elasticsearches
    Short Names:
      es
    Singular:               elasticsearch
  Preserve Unknown Fields:  true
  Scope:                    Namespaced
  Versions:
    Additional Printer Columns:
      Json Path:    .status.health
      Name:         health
      Type:         string
      Description:  Available nodes
      Json Path:    .status.availableNodes

This output was truncated for brevity

You check the progress of the installation with:

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kubectl -n elastic-system logs -f statefulset.apps/elastic-operator

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{"level":"info","@timestamp":"2020-01-27T14:57:57.656Z","logger":"controller-runtime.controller","message":"Starting workers","ver":"1.0.0-6881438d","controller":"license-controller","worker count":1} 
{"level":"info","@timestamp":"2020-01-27T14:57:57.757Z","logger":"controller-runtime.controller","message":"Starting EventSource","ver":"1.0.0-6881438d","controller":"elasticsearch-controller","source":"kind source: /, Kind="} 
{"level":"info","@timestamp":"2020-01-27T14:57:57.758Z","logger":"controller-runtime.controller","message":"Starting EventSource","ver":"1.0.0-6881438d","controller":"elasticsearch-controller","source":"kind source: /, Kind="} 
{"level":"info","@timestamp":"2020-01-27T14:57:57.759Z","logger":"controller-runtime.controller","message":"Starting EventSource","ver":"1.0.0-6881438d","controller":"elasticsearch-controller","source":"channel source: 0xc00003a870"} 
{"level":"info","@timestamp":"2020-01-27T14:57:57.759Z","logger":"controller-runtime.controller","message":"Starting Controller","ver":"1.0.0-6881438d","controller":"elasticsearch-controller"} 
{"level":"info","@timestamp":"2020-01-27T14:57:57.760Z","logger":"controller-runtime.controller","message":"Starting workers","ver":"1.0.0-6881438d","controller":"elasticsearch-controller","worker count":1}

Note that the above output was truncated for brevity.

List the pods running in the elastic-system namespace with:

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kubectl get pods -n elastic-system

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NAME                 READY   STATUS    RESTARTS   AGE 
elastic-operator-0   1/1     Running   0          11m

Make sure the status is Running before moving on.

Deploy an Elasticsearch Cluster

In this section, we'll walk you through the process of deploying an Elasticsearch cluster with the Kubernetes Operator.

Create a file called elastic-search-cluster.yaml with the following content:

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apiVersion: elasticsearch.k8s.elastic.co/v1 
kind: Elasticsearch 
metadata:
  name: quickstart 
spec:
  version: 7.5.2
  nodeSets:
  - name: default
    count: 2
    config:
      node.master: true
      node.data: true
      node.ingest: true
      node.store.allow_mmap: false

Things to note in the above output:

the version parameter specifies the Elasticsearch version the Operator will deploy
the count parameter sets the number of database nodes. Make sure it's not greater than the number of nodes in your Kubernetes cluster.

Create a two-node Elasticsearch cluster by entering the following command:

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kubectl apply -f elastic-search-cluster.yaml

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elasticsearch.elasticsearch.k8s.elastic.co/quickstart created

Behind the scenes, the Operator automatically creates and manages the resources needed to achieve the desired state.

You can now run the following command to see the status of the newly created Elasticsearch cluster:

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kubectl get elasticsearch

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NAME         HEALTH    NODES   VERSION   PHASE   AGE 
quickstart   unknown           7.5.2             3m51s

Note that the HEALTH status has not been reported yet. It takes a few minutes for the process to complete. Then, the HEALTH status will show as green:

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kubectl get elasticsearch

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NAME         HEALTH   NODES   VERSION   PHASE   AGE 
quickstart   green    2       7.5.2     Ready   8m47s

Check the status of the pods running in your cluster with:

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kubectl get pods --selector='elasticsearch.k8s.elastic.co/cluster-name=quickstart'

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NAME                      READY   STATUS    RESTARTS   AGE 
quickstart-es-default-0   1/1     Running   0          9m18s 
quickstart-es-default-1   1/1     Running   0          9m18s

Verify Your Elasticsearch Installation

To verify the installation, follow these steps.

The Operator exposes the service with a static IP address. Run the following kubectl get service command to see it:

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kubectl get service quickstart-es-http

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NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE 
quickstart-es-http   ClusterIP   10.103.196.28   <none>        9200/TCP   15m

To forward all connections made to localhost:9200 to port 9200 of the pod running the quickstart-es-http service, type the following command in a new terminal window:

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kubectl port-forward service/quickstart-es-http 9200

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Forwarding from 127.0.0.1:9200 -> 9200 
Forwarding from [::1]:9200 -> 9200

Move back to the first terminal window. The password for the elastic user is stored in a Kubernetes secret. Use the following command to retrieve the password, and save it into an environment variable called PASSWORD:

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PASSWORD=$(kubectl get secret quickstart-es-elastic-user -o=jsonpath='{.data.elastic}' | base64 --decode)

At this point, you can use curl to make a request:

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curl -u "elastic:$PASSWORD" -k "https://localhost:9200"

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{
  "name" : "quickstart-es-default-0",
  "cluster_name" : "quickstart",
  "cluster_uuid" : "g0_1Vk9iQoGwFWYdzUqfig",
  "version" : {
    "number" : "7.5.2",
    "build_flavor" : "default",
    "build_type" : "docker",
    "build_hash" : "8bec50e1e0ad29dad5653712cf3bb580cd1afcdf",
    "build_date" : "2020-01-15T12:11:52.313576Z",
    "build_snapshot" : false,
    "lucene_version" : "8.3.0",
    "minimum_wire_compatibility_version" : "6.8.0",
    "minimum_index_compatibility_version" : "6.0.0-beta1"
  },
  "tagline" : "You Know, for Search" 
}

Deploy Kibana

This section walks through creating a new Kibana cluster using the Kubernetes Operator.

Create a file called kibana.yaml with the following content:

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apiVersion: kibana.k8s.elastic.co/v1 
kind: Kibana 
metadata:
  name: quickstart 
spec:
  version: 7.5.1
  count: 1
  elasticsearchRef:
    name: quickstart
  podTemplate:
    metadata:
      labels:
        foo: kibana
    spec:
      containers:
        - name: kibana
          resources:
            requests:
              memory: 1Gi
              cpu: 0.5
            limits:
              memory: 1Gi
              cpu: 1

Enter the following kubectl apply command to create a Kibana cluster:

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kubectl apply -f kibana.yaml

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kibana.kibana.k8s.elastic.co/quickstart created

During the installation, you can check on the progress by running:

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kubectl get kibana

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NAME         HEALTH   NODES   VERSION   AGE 
quickstart                    7.5.1     3s

Note that in the above output, the HEALTH status hasn't been reported yet.

Once the installation is completed, the HEALTH status will show as green:

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kubectl get kibana

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NAME         HEALTH   NODES   VERSION   AGE 
quickstart   green    1       7.5.1     104s

At this point, you can list the Kibana pods by entering the following kubectl get pods command:

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kubectl get pod --selector='kibana.k8s.elastic.co/name=quickstart'

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NAME                             READY   STATUS    RESTARTS   AGE 
quickstart-kb-7578b8d8fc-ftvbz   1/1     Running   0          70s

Verify Your Kibana Installation

Follow these steps to verify your Kibana installation.

The Kubernetes Operator has created a ClusterIP service for Kibana. You can retrieve it like this:

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kubectl get service quickstart-kb-http

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NAME                 TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE 
quickstart-kb-http   ClusterIP   10.98.126.75   <none>        5601/TCP   11m

To make the service available on your host, type the following command in a new terminal window:

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kubectl port-forward service/quickstart-kb-http 5601

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Forwarding from 127.0.0.1:5601 -> 5601 
Forwarding from [::1]:5601 -> 5601

To access Kibana, you need the password for the elastic user. You've already saved it into an environment variable called PASSWORD in Step 3 of the Verify Your Elasticsearch Installation section. You can now display it with:

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echo $PASSWORD

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vrfr6b6v4687hnldrc72kb4q

In our example, the password is vrfr6b6v4687hnldrc72kb4q but yours will be different.

Now, you can access Kibana by pointing your browser to https://localhost:5601

Manage Your ECK Cluster With the Kubernetes Operator

In this section, you'll learn how to scale down and up your ECK Cluster.

To scale down, modify the number of nodes running Elasticsearch by specifying nodeSets.count: 1 in your elasticsearch.yaml file. Your spec should look like this:

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apiVersion: elasticsearch.k8s.elastic.co/v1 
kind: Elasticsearch 
metadata:
  name: quickstart 
spec:
  version: 7.5.2
  nodeSets:
  - name: default
    count: 1
    config:
      node.master: true
      node.data: true
      node.ingest: true
      node.store.allow_mmap: false

You can apply the spec with:

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kubectl apply -f elastic-search.yaml

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elasticsearch.elasticsearch.k8s.elastic.co/quickstart configured

Behind the scenes, the Operator makes required changes to reach the desired state. This can take a bit of time.

In the meantime, you can display the status of your cluster by entering the following command:

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kubectl get elasticsearch

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NAME         HEALTH   NODES   VERSION   PHASE             AGE 
quickstart   green    1       7.5.2     ApplyingChanges   56m

In the above output, note that there's only one node running Elasticsearch.

You can list the pods running Elasticsearch:

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kubectl get pods --selector='elasticsearch.k8s.elastic.co/cluster-name=quickstart'

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NAME                      READY   STATUS    RESTARTS   AGE quickstart-es-default-0   1/1     Running   0          58m

Similarly, you can scale up your Elasticsearch cluster by specifying nodeSets.count: 2 in your elasticsearch.yaml file:

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apiVersion: elasticsearch.k8s.elastic.co/v1 
kind: Elasticsearch 
metadata:
  name: quickstart 
spec:
  version: 7.5.2
  nodeSets:
  - name: default
    count: 3
    config:
      node.master: true
      node.data: true
      node.ingest: true
      node.store.allow_mmap: false

You can monitor the progress with:

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kubectl get elasticsearch

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NAME         HEALTH   NODES   VERSION   PHASE             AGE 
quickstart   green    1       7.5.2     ApplyingChanges   61m

Once the desired stats is reached, the PHASE column will show as Ready:

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kubectl get elasticsearch

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NAME         HEALTH   NODES   VERSION   PHASE   AGE 
quickstart   green    2       7.5.2     Ready   68m

Congratulations, you've covered a lot of ground, and now you are familiar with the basic principles behind the Kubernetes Operator! In a future post, we'll walk through the process of writing our own Operator.

Thanks for reading!

Kubernetes Operator (extension) Java (programming language) Docker (software)

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