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You are looking at the documentation of a prior release. To read the documentation of the latest release, please visit here.

New to KubeDB? Please start here.

Druid QuickStart

This tutorial will show you how to use KubeDB to run an Apache Druid.

  lifecycle

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 and make sure install with helm command including the flags --set global.featureGates.Druid=true to ensure Druid CRD and --set global.featureGates.ZooKeeper=true to ensure ZooKeeper CRD as Druid depends on ZooKeeper for external dependency.

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 guides/druid/quickstart/overview/yamls folder in GitHub repository kubedb/docs.

We have designed this tutorial to demonstrate a production setup of KubeDB managed Apache Druid. If you just want to try out KubeDB, you can bypass some safety features following the tips here.

Find Available StorageClass

We will have to provide StorageClass in Druid CRD 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                  14h

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

Find Available DruidVersion

When you install the KubeDB operator, it registers a CRD named DruidVersion. The installation process comes with a set of tested DruidVersion objects. Let’s check available DruidVersions by,

$ kubectl get druidversion
NAME     VERSION   DB_IMAGE                               DEPRECATED   AGE
28.0.1   28.0.1    ghcr.io/appscode-images/druid:28.0.1                4h47m

Notice the DEPRECATED column. Here, true means that this DruidVersion is deprecated for the current KubeDB version. KubeDB will not work for deprecated DruidVersion. You can also use the short from drversion to check available DruidVersions.

In this tutorial, we will use 28.0.1 DruidVersion CR to create a Druid cluster.

Get External Dependencies Ready

Metadata Storage

Druid uses the metadata store to house various metadata about the system, but not to store the actual data. The metadata store retains all metadata essential for a Druid cluster to work. Apache Derby is the default metadata store for Druid, however, it is not suitable for production. MySQL and PostgreSQL are more production suitable metadata stores.

Luckily, PostgreSQL and MySQL both are readily available in KubeDB as CRD and can easily be deployed using the MySQL-Guide and PostgreSQL-Guide.

In this tutorial, we will use a MySQL named mysql-demo in the demo namespace and create a database named druid inside it using initialization script.

Let’s create a ConfigMap with initialization script first and then create the mysql-demo database,

$ kubectl create configmap -n demo my-init-script \
--from-literal=init.sql="$(curl -fsSL https://github.com/kubedb/docs/raw/v2024.6.4/docs/examples/druid/quickstart/mysql-init-script.sql)"
configmap/my-init-script created

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.6.4/docs/examples/druid/quickstart/mysql-demo.yaml
mysql.kubedb.com/mysql-demo created

ZooKeeper

Apache Druid uses Apache ZooKeeper (ZK) for management of current cluster state i.e. internal service discovery, coordination, and leader election.

Fortunately, KubeDB also has support for ZooKeeper and can easily be deployed using the guide here

In this tutorial, we will create a ZooKeeper named zk-demo in the demo namespace.

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.6.4/docs/examples/druid/quickstart/zk-demo.yaml
zookeeper.kubedb.com/zk-demo created

Deep Storage

Another external dependency of Druid is deep storage where the segments are stored. 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/v2024.6.4/docs/examples/druid/quickstart/deep-storage-config.yaml
secret/deep-storage-config created

You can also use options like Amazon S3, Google Cloud Storage, Azure Blob Storage or HDFS and create a connection information Secret like this, and you are good to go.

Create a Druid Cluster

The KubeDB operator implements a Druid CRD to define the specification of Druid.

The Druid instance used for this tutorial:

apiVersion: kubedb.com/v1alpha2
kind: Druid
metadata:
  name: druid-quickstart
  namespace: demo
spec:
  version: 28.0.1
  deepStorage:
    type: s3
    configSecret:
      name: deep-storage-config
  metadataStorage:
    name: mysql-demo
    namespace: demo
    createTables: true
  zookeeperRef:
    name: zk-demo
    namespace: demo
  topology:
    coordinators:
      replicas: 1
    brokers:
      replicas: 1
    historicals:
      replicas: 1
      storageType: Durable
      storage:
        accessModes:
          - ReadWriteOnce
        resources:
          requests:
            storage: 1Gi
        storageClassName: standard
    middleManagers:
      replicas: 1
      storageType: Durable
      storage:
        accessModes:
          - ReadWriteOnce
        resources:
          requests:
            storage: 1Gi
        storageClassName: standard
    routers:
      replicas: 1
  deletionPolicy: Delete
  serviceTemplates:
    - alias: primary
      spec:
        type: LoadBalancer
        ports:
          - name: routers
            port: 8888

Here,

  • spec.version - is the name of the DruidVersion CR. Here, a Druid of version 28.0.1 will be created.
  • spec.storageType - specifies the type of storage that will be used for Kafka. It can be Durable or Ephemeral. The default value of this field is Durable. If Ephemeral is used then KubeDB will create the Druid using EmptyDir volume. In this case, you don’t have to specify spec.storage field. This is useful for testing purposes.
  • spec.storage specifies the StorageClass of PVC dynamically allocated to store data for this Druid instance. This storage spec will be passed to the PetSet created by the KubeDB operator to run Druid pods. You can specify any StorageClass available in your cluster with appropriate resource requests. If you don’t specify spec.storageType: Ephemeral, then this field is required.
  • spec.deletionPolicy specifies what KubeDB should do when a user try to delete Druid CR. Deletion policy Delete will delete the database pods and PVC when the Druid CR is deleted.

Note: spec.storage section is used to create PVC for database pod. It will create PVC with storage size specified in the storage.resources.requests field. Don’t specify limits here. PVC does not get resized automatically.

Let’s create the Druid CR that is shown above:

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.6.4/docs/examples/druid/quickstart/druid-quickstart.yaml
druid.kubedb.com/druid-quickstart created

The Druid’s STATUS will go from Provisioning to Ready state within few minutes. Once the STATUS is Ready, you are ready to use the newly provisioned Druid cluster.

$ kubectl get druid -n demo -w
NAME               TYPE                  VERSION   STATUS         AGE
druid-quickstart   kubedb.com/v1alpha2   28.0.1    Provisioning   17s
druid-quickstart   kubedb.com/v1alpha2   28.0.1    Provisioning   28s
.
.
druid-quickstart   kubedb.com/v1alpha2   28.0.1    Ready          82s

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

$ kubectl describe druid -n demo druid-quickstart
Name:         druid-quickstart
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  kubedb.com/v1alpha2
Kind:         Druid
Metadata:
  Creation Timestamp:  2024-05-02T10:00:12Z
  Finalizers:
    kubedb.com/druid
  Generation:  1
  Managed Fields:
    API Version:  kubedb.com/v1alpha2
    Fields Type:  FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .:
          f:kubectl.kubernetes.io/last-applied-configuration:
      f:spec:
        .:
        f:deepStorage:
          .:
          f:configSecret:
          f:type:
        f:healthChecker:
          .:
          f:failureThreshold:
          f:periodSeconds:
          f:timeoutSeconds:
        f:metadataStorage:
          .:
          f:createTables:
          f:name:
          f:namespace:
        f:storageType:
        f:topology:
          .:
          f:brokers:
            .:
            f:podPlacementPolicy:
            f:replicas:
          f:coordinators:
            .:
            f:podPlacementPolicy:
            f:replicas:
          f:historicals:
            .:
            f:podPlacementPolicy:
            f:replicas:
            f:storage:
              .:
              f:accessModes:
              f:resources:
                .:
                f:requests:
                  .:
                  f:storage:
              f:storageClassName:
          f:middleManagers:
            .:
            f:podPlacementPolicy:
            f:replicas:
            f:storage:
              .:
              f:accessModes:
              f:resources:
                .:
                f:requests:
                  .:
                  f:storage:
              f:storageClassName:
          f:routers:
            .:
            f:podPlacementPolicy:
            f:replicas:
        f:version:
        f:zookeeperRef:
          .:
          f:name:
          f:namespace:
    Manager:      kubectl-client-side-apply
    Operation:    Update
    Time:         2024-05-02T10:00:12Z
    API Version:  kubedb.com/v1alpha2
    Fields Type:  FieldsV1
    fieldsV1:
      f:metadata:
        f:finalizers:
          .:
          v:"kubedb.com/druid":
    Manager:      kubedb-provisioner
    Operation:    Update
    Time:         2024-05-02T10:00:12Z
    API Version:  kubedb.com/v1alpha2
    Fields Type:  FieldsV1
    fieldsV1:
      f:status:
        .:
        f:conditions:
        f:phase:
    Manager:         kubedb-provisioner
    Operation:       Update
    Subresource:     status
    Time:            2024-05-02T10:01:34Z
  Resource Version:  68607
  UID:               7759adad-4e49-4f44-80ae-fc04cc474813
Spec:
  Auth Secret:
    Name:  druid-quickstart-admin-cred
  Deep Storage:
    Config Secret:
      Name:          deep-storage-config
    Type:            s3
  Disable Security:  false
  Health Checker:
    Failure Threshold:  3
    Period Seconds:     30
    Timeout Seconds:    10
  Metadata Storage:
    Create Tables:  true
    Name:           mysql-demo
    Namespace:      druid
  Pod Template:
    Controller:
    Metadata:
    Spec:
  Storage Type:        Ephemeral
  Deletion Policy:     Delete
  Topology:
    Brokers:
      Pod Placement Policy:
        Name:  default
      Pod Template:
        Controller:
        Metadata:
        Spec:
          Containers:
            Name:  druid
            Resources:
              Limits:
                Memory:  1Gi
              Requests:
                Cpu:     500m
                Memory:  1Gi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Init Containers:
            Name:  init-druid
            Resources:
              Limits:
                Memory:  512Mi
              Requests:
                Cpu:     200m
                Memory:  512Mi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Security Context:
            Fs Group:  1000
      Replicas:        1
    Coordinators:
      Pod Placement Policy:
        Name:  default
      Pod Template:
        Controller:
        Metadata:
        Spec:
          Containers:
            Name:  druid
            Resources:
              Limits:
                Memory:  1Gi
              Requests:
                Cpu:     500m
                Memory:  1Gi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Init Containers:
            Name:  init-druid
            Resources:
              Limits:
                Memory:  512Mi
              Requests:
                Cpu:     200m
                Memory:  512Mi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Security Context:
            Fs Group:  1000
      Replicas:        2
    Historicals:
      Pod Placement Policy:
        Name:  default
      Pod Template:
        Controller:
        Metadata:
        Spec:
          Containers:
            Name:  druid
            Resources:
              Limits:
                Memory:  1Gi
              Requests:
                Cpu:     500m
                Memory:  1Gi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Init Containers:
            Name:  init-druid
            Resources:
              Limits:
                Memory:  512Mi
              Requests:
                Cpu:     200m
                Memory:  512Mi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Security Context:
            Fs Group:  1000
      Replicas:        1
      Storage:
        Access Modes:
          ReadWriteOnce
        Resources:
          Requests:
            Storage:         1Gi
        Storage Class Name:  standard
    Middle Managers:
      Pod Placement Policy:
        Name:  default
      Pod Template:
        Controller:
        Metadata:
        Spec:
          Containers:
            Name:  druid
            Resources:
              Limits:
                Memory:  2560Mi
              Requests:
                Cpu:     500m
                Memory:  2560Mi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Init Containers:
            Name:  init-druid
            Resources:
              Limits:
                Memory:  512Mi
              Requests:
                Cpu:     200m
                Memory:  512Mi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Security Context:
            Fs Group:  1000
      Replicas:        1
      Storage:
        Access Modes:
          ReadWriteOnce
        Resources:
          Requests:
            Storage:         1Gi
        Storage Class Name:  standard
    Routers:
      Pod Placement Policy:
        Name:  default
      Pod Template:
        Controller:
        Metadata:
        Spec:
          Containers:
            Name:  druid
            Resources:
              Limits:
                Memory:  1Gi
              Requests:
                Cpu:     500m
                Memory:  1Gi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Init Containers:
            Name:  init-druid
            Resources:
              Limits:
                Memory:  512Mi
              Requests:
                Cpu:     200m
                Memory:  512Mi
            Security Context:
              Allow Privilege Escalation:  false
              Capabilities:
                Drop:
                  ALL
              Run As Non Root:  true
              Run As User:      1000
              Seccomp Profile:
                Type:  RuntimeDefault
          Security Context:
            Fs Group:  1000
      Replicas:        1
  Version:             28.0.1
  Zookeeper Ref:
    Name:       zk-demo
    Namespace:  druid
Status:
  Conditions:
    Last Transition Time:  2024-05-02T10:00:12Z
    Message:               The KubeDB operator has started the provisioning of Druid: demo/druid-quickstart
    Observed Generation:   1
    Reason:                DatabaseProvisioningStartedSuccessfully
    Status:                True
    Type:                  ProvisioningStarted
    Last Transition Time:  2024-05-02T10:00:40Z
    Message:               All desired replicas are ready.
    Observed Generation:   1
    Reason:                AllReplicasReady
    Status:                True
    Type:                  ReplicaReady
    Last Transition Time:  2024-05-02T10:01:11Z
    Message:               The Druid: demo/druid-quickstart is accepting client requests and nodes formed a cluster
    Observed Generation:   1
    Reason:                DatabaseAcceptingConnectionRequest
    Status:                True
    Type:                  AcceptingConnection
    Last Transition Time:  2024-05-02T10:01:34Z
    Message:               The Druid: demo/druid-quickstart is ready.
    Observed Generation:   1
    Reason:                ReadinessCheckSucceeded
    Status:                True
    Type:                  Ready
    Last Transition Time:  2024-05-02T10:01:34Z
    Message:               The Druid: demo/druid-quickstart is successfully provisioned.
    Observed Generation:   1
    Reason:                DatabaseSuccessfullyProvisioned
    Status:                True
    Type:                  Provisioned
  Phase:                   Ready
Events:                    <none>

KubeDB Operator Generated Resources

On deployment of a Druid CR, the operator creates the following resources:

$ kubectl get all,secret,petset -n demo -l 'app.kubernetes.io/instance=druid-quickstart'
NAME                                    READY   STATUS    RESTARTS   AGE
pod/druid-quickstart-brokers-0          1/1     Running   0          2m4s
pod/druid-quickstart-coordinators-0     1/1     Running   0          2m10s
pod/druid-quickstart-historicals-0      1/1     Running   0          2m8s
pod/druid-quickstart-middlemanagers-0   1/1     Running   0          2m6s
pod/druid-quickstart-routers-0          1/1     Running   0          2m1s

NAME                                    TYPE           CLUSTER-IP      EXTERNAL-IP   PORT(S)                                                 AGE
service/druid-quickstart-brokers        ClusterIP      10.96.28.252    <none>        8082/TCP                                                2m13s
service/druid-quickstart-coordinators   ClusterIP      10.96.52.186    <none>        8081/TCP                                                2m13s
service/druid-quickstart-pods           ClusterIP      None            <none>        8081/TCP,8090/TCP,8083/TCP,8091/TCP,8082/TCP,8888/TCP   2m13s
service/druid-quickstart-routers        LoadBalancer   10.96.134.202   10.86.51.181  8888:32751/TCP                                          2m13s

NAME                                                  TYPE               VERSION   AGE
appbinding.appcatalog.appscode.com/druid-quickstart   kubedb.com/druid   28.0.1    2m1s

NAME                                 TYPE                       DATA   AGE
secret/druid-quickstart-admin-cred   kubernetes.io/basic-auth   2      2m13s

NAME                                                           AGE
petset.apps.k8s.appscode.com/druid-quickstart-brokers          2m4s
petset.apps.k8s.appscode.com/druid-quickstart-coordinators     2m10s
petset.apps.k8s.appscode.com/druid-quickstart-historicals      2m8s
petset.apps.k8s.appscode.com/druid-quickstart-middlemanagers   2m6s
petset.apps.k8s.appscode.com/druid-quickstart-routers          2m1s
  • PetSet - In topology mode, the operator may create 4 to 6 petSets (depending on the topology you provide as overlords and routers are optional) with name {Druid-Name}-{Sufix}.
  • Services - For topology mode, a headless service with name {Druid-Name}-{pods}. Other than that, 2 to 4 more services (depending on the specified topology) with name {Druid-Name}-{Sufix} can be created.
    • {Druid-Name}-{brokers} - The primary service which is used to connect the brokers with external clients.
    • {Druid-Name}-{coordinators} - The primary service which is used to connect the coordinators with external clients.
    • {Druid-Name}-{overlords} - The primary service is only created if spec.topology.overlords is provided. In the same way, it is used to connect the overlords with external clients.
    • {Druid-Name}-{routers} - Like the previous one, this primary service is only created if spec.topology.routers is provided. It is used to connect the routers with external clients.
  • AppBinding - an AppBinding which hold to connect information for the Druid. Like other resources, it is named after the Druid instance.
  • Secrets - A secret is generated for each Druid cluster.
    • {Druid-Name}-{username}-cred - the auth secrets which hold the username and password for the Druid users. Operator generates credentials for admin user and creates a secret for authentication.

Connect with Druid Database

We will use port forwarding to connect with our routers of the Druid database. Then we will use curl to send HTTP requests to check cluster health to verify that our Druid database is working well. It is also possible to use External-IP to access druid nodes if you make service type of that node as LoadBalancer.

Check the Service Health

Let’s port-forward the port 8888 to local machine:

$ kubectl port-forward -n demo svc/druid-quickstart-routers 8888
Forwarding from 127.0.0.1:8888 -> 8888
Forwarding from [::1]:8888 -> 8888

Now, the Druid cluster is accessible at localhost:8888. Let’s check the Service Health of Routers of the Druid database.

$ curl "http://localhost:8888/status/health"
true

From the retrieved health information above, we can see that our Druid cluster’s status is true, indicating that the service can receive API calls and is healthy. In the same way it possible to check the health of other druid nodes by port-forwarding the appropriate services.

Access the web console

We can also access the web console of Druid database from any browser by port-forwarding the routers in the same way shown in the aforementioned step or directly using the External-IP if the router service type is LoadBalancer.

Now hit the http://localhost:8888 from any browser, and you will be prompted to provide the credential of the druid database. By following the steps discussed below, you can get the credential generated by the KubeDB operator for your Druid database.

Connection information:

  • Username:

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

  • Password:

    $ kubectl get secret -n demo druid-quickstart-admin-cred -o jsonpath='{.data.password}' | base64 -d
LzJtVRX5E8MorFaf

After providing the credentials correctly, you should be able to access the web console like shown below.

  lifecycle

You can use this web console for loading data, managing datasources and tasks, and viewing server status and segment information. You can also run SQL and native Druid queries in the console.

Cleaning up

To clean up the Kubernetes resources created by this tutorial, run:

$ kubectl patch -n demo druid druid-quickstart -p '{"spec":{"deletionPolicy":"WipeOut"}}' --type="merge"
kafka.kubedb.com/druid-quickstart patched

$ kubectl delete dr druid-quickstart  -n demo
druid.kubedb.com "druid-quickstart" deleted

$  kubectl delete namespace demo
namespace "demo" deleted

Tips for Testing

If you are just testing some basic functionalities, you might want to avoid additional hassles due to some safety features that are great for the production environment. You can follow these tips to avoid them.

  1. Use storageType: Ephemeral. Databases are precious. You might not want to lose your data in your production environment if the database pod fails. So, we recommend to use spec.storageType: Durable and provide storage spec in spec.storage section. For testing purposes, you can just use spec.storageType: Ephemeral. KubeDB will use emptyDir for storage. You will not require to provide spec.storage section.
  2. Use deletionPolicy: WipeOut. It is nice to be able to resume the database from the previous one. So, we preserve all your PVCs and auth Secrets. If you don’t want to resume the database, you can just use spec.deletionPolicy: WipeOut. It will clean up every resource that was created with the Druid CR. For more details, please visit here.

Next Steps

  • Use kubedb cli to manage databases like kubectl for Kubernetes.

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