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Restart Druid

KubeDB supports restarting the Druid database via a DruidOpsRequest. Restarting is useful if some pods are got stuck in some phase, or they are not working correctly. This tutorial will show you how to use that.

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 KubeDB cli on your workstation and 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 ns demo
  namespace/demo created

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

Deploy Druid

In this section, we are going to deploy a Druid database using KubeDB.

Create External Dependency (Deep Storage)

Before proceeding further, we need to prepare deep storage, which is one of the external dependency of Druid and used for storing the segments. It is a storage mechanism that Apache Druid does not provide. Amazon S3, Google Cloud Storage, or Azure Blob Storage, S3-compatible storage (like Minio), or HDFS are generally convenient options for deep storage.

In this tutorial, we will run a minio-server as deep storage in our local kind cluster using minio-operator and create a bucket named druid in it, which the deployed druid database will use.


$ helm repo add minio https://operator.min.io/
$ helm repo update minio
$ helm upgrade --install --namespace "minio-operator" --create-namespace "minio-operator" minio/operator --set operator.replicaCount=1

$ helm upgrade --install --namespace "demo" --create-namespace druid-minio minio/tenant \
--set tenant.pools[0].servers=1 \
--set tenant.pools[0].volumesPerServer=1 \
--set tenant.pools[0].size=1Gi \
--set tenant.certificate.requestAutoCert=false \
--set tenant.buckets[0].name="druid" \
--set tenant.pools[0].name="default"

Now we need to create a Secret named deep-storage-config. It contains the necessary connection information using which the druid database will connect to the deep storage.

apiVersion: v1
kind: Secret
metadata:
  name: deep-storage-config
  namespace: demo
stringData:
  druid.storage.type: "s3"
  druid.storage.bucket: "druid"
  druid.storage.baseKey: "druid/segments"
  druid.s3.accessKey: "minio"
  druid.s3.secretKey: "minio123"
  druid.s3.protocol: "http"
  druid.s3.enablePathStyleAccess: "true"
  druid.s3.endpoint.signingRegion: "us-east-1"
  druid.s3.endpoint.url: "http://myminio-hl.demo.svc.cluster.local:9000/"

Let’s create the deep-storage-config Secret shown above:

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.9.30/docs/guides/druid/restart/yamls/deep-storage-config.yaml
secret/deep-storage-config created

Now, lets go ahead and create a druid database.

apiVersion: kubedb.com/v1alpha2
kind: Druid
metadata:
  name: druid-cluster
  namespace: demo
spec:
  version: 28.0.1
  deepStorage:
    type: s3
    configSecret:
      name: deep-storage-config
  topology:
    routers:
      replicas: 1
  deletionPolicy: Delete

Let’s create the Druid CR we have shown above,

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.9.30/docs/guides/druid/update-version/yamls/druid-cluster.yaml
druid.kubedb.com/druid-cluster created

Apply Restart opsRequest

apiVersion: ops.kubedb.com/v1alpha1
kind: DruidOpsRequest
metadata:
  name: restart
  namespace: demo
spec:
  type: Restart
  databaseRef:
    name: druid-cluster
  timeout: 5m
  apply: Always

spec.type specifies the Type of the ops Request
spec.databaseRef holds the name of the Druid CR. It should be available in the same namespace as the opsRequest
The meaning of spec.timeout & spec.apply fields will be found here

Let’s create the DruidOpsRequest CR we have shown above,

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.9.30/docs/guides/druid/restart/restart.yaml
druidopsrequest.ops.kubedb.com/restart created

Now the Ops-manager operator will first restart the controller pods, then broker of the referenced druid.

$ kubectl get drops -n demo
NAME      TYPE      STATUS       AGE
restart   Restart   Successful   2m11s

$ kubectl get drops -n demo restart -oyaml
apiVersion: ops.kubedb.com/v1alpha1
kind: DruidOpsRequest
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"ops.kubedb.com/v1alpha1","kind":"DruidOpsRequest","metadata":{"annotations":{},"name":"restart","namespace":"demo"},"spec":{"apply":"Always","databaseRef":{"name":"druid-cluster"},"timeout":"5m","type":"Restart"}}
  creationTimestamp: "2024-10-21T10:30:53Z"
  generation: 1
  name: restart
  namespace: demo
  resourceVersion: "83200"
  uid: 0fcbc7d4-593f-45f7-8631-7483805efe1e
spec:
  apply: Always
  databaseRef:
    name: druid-cluster
  timeout: 5m
  type: Restart
status:
  conditions:
  - lastTransitionTime: "2024-10-21T10:30:53Z"
    message: Druid ops-request has started to restart druid nodes
    observedGeneration: 1
    reason: Restart
    status: "True"
    type: Restart
  - lastTransitionTime: "2024-10-21T10:31:51Z"
    message: Successfully Restarted Druid nodes
    observedGeneration: 1
    reason: RestartNodes
    status: "True"
    type: RestartNodes
  - lastTransitionTime: "2024-10-21T10:31:01Z"
    message: get pod; ConditionStatus:True; PodName:druid-cluster-historicals-0
    observedGeneration: 1
    status: "True"
    type: GetPod--druid-cluster-historicals-0
  - lastTransitionTime: "2024-10-21T10:31:01Z"
    message: evict pod; ConditionStatus:True; PodName:druid-cluster-historicals-0
    observedGeneration: 1
    status: "True"
    type: EvictPod--druid-cluster-historicals-0
  - lastTransitionTime: "2024-10-21T10:31:06Z"
    message: check pod running; ConditionStatus:True; PodName:druid-cluster-historicals-0
    observedGeneration: 1
    status: "True"
    type: CheckPodRunning--druid-cluster-historicals-0
  - lastTransitionTime: "2024-10-21T10:31:11Z"
    message: get pod; ConditionStatus:True; PodName:druid-cluster-middlemanagers-0
    observedGeneration: 1
    status: "True"
    type: GetPod--druid-cluster-middlemanagers-0
  - lastTransitionTime: "2024-10-21T10:31:11Z"
    message: evict pod; ConditionStatus:True; PodName:druid-cluster-middlemanagers-0
    observedGeneration: 1
    status: "True"
    type: EvictPod--druid-cluster-middlemanagers-0
  - lastTransitionTime: "2024-10-21T10:31:16Z"
    message: check pod running; ConditionStatus:True; PodName:druid-cluster-middlemanagers-0
    observedGeneration: 1
    status: "True"
    type: CheckPodRunning--druid-cluster-middlemanagers-0
  - lastTransitionTime: "2024-10-21T10:31:21Z"
    message: get pod; ConditionStatus:True; PodName:druid-cluster-brokers-0
    observedGeneration: 1
    status: "True"
    type: GetPod--druid-cluster-brokers-0
  - lastTransitionTime: "2024-10-21T10:31:21Z"
    message: evict pod; ConditionStatus:True; PodName:druid-cluster-brokers-0
    observedGeneration: 1
    status: "True"
    type: EvictPod--druid-cluster-brokers-0
  - lastTransitionTime: "2024-10-21T10:31:26Z"
    message: check pod running; ConditionStatus:True; PodName:druid-cluster-brokers-0
    observedGeneration: 1
    status: "True"
    type: CheckPodRunning--druid-cluster-brokers-0
  - lastTransitionTime: "2024-10-21T10:31:31Z"
    message: get pod; ConditionStatus:True; PodName:druid-cluster-routers-0
    observedGeneration: 1
    status: "True"
    type: GetPod--druid-cluster-routers-0
  - lastTransitionTime: "2024-10-21T10:31:31Z"
    message: evict pod; ConditionStatus:True; PodName:druid-cluster-routers-0
    observedGeneration: 1
    status: "True"
    type: EvictPod--druid-cluster-routers-0
  - lastTransitionTime: "2024-10-21T10:31:36Z"
    message: check pod running; ConditionStatus:True; PodName:druid-cluster-routers-0
    observedGeneration: 1
    status: "True"
    type: CheckPodRunning--druid-cluster-routers-0
  - lastTransitionTime: "2024-10-21T10:31:41Z"
    message: get pod; ConditionStatus:True; PodName:druid-cluster-coordinators-0
    observedGeneration: 1
    status: "True"
    type: GetPod--druid-cluster-coordinators-0
  - lastTransitionTime: "2024-10-21T10:31:41Z"
    message: evict pod; ConditionStatus:True; PodName:druid-cluster-coordinators-0
    observedGeneration: 1
    status: "True"
    type: EvictPod--druid-cluster-coordinators-0
  - lastTransitionTime: "2024-10-21T10:31:46Z"
    message: check pod running; ConditionStatus:True; PodName:druid-cluster-coordinators-0
    observedGeneration: 1
    status: "True"
    type: CheckPodRunning--druid-cluster-coordinators-0
  - lastTransitionTime: "2024-10-21T10:31:51Z"
    message: Controller has successfully restart the Druid replicas
    observedGeneration: 1
    reason: Successful
    status: "True"
    type: Successful
  observedGeneration: 1
  phase: Successful

Cleaning up

To cleanup the Kubernetes resources created by this tutorial, run:

kubectl delete druidopsrequest -n demo restart
kubectl delete druid -n demo druid-cluster
kubectl delete ns demo

Next Steps

Detail concepts of Druid object.
Different Druid topology clustering modes here.
Monitor your Druid database with KubeDB using out-of-the-box Prometheus operator.

Want to hack on KubeDB? Check our contribution guidelines.

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