Consider this an EXPERIMENTAL feature mostly because it has not been tested yet on a wide variety of long running Druid clusters.
Apache Druid Extension to enable using Kubernetes API Server for node discovery and leader election. This extension allows Druid cluster deployment on Kubernetes without Zookeeper. It allows running multiple Druid clusters within same Kubernetes Cluster, See clusterIdentifier
config below.
To use this extension please make sure to include druid-kubernetes-extensions
in the extensions load list.
This extension works together with HTTP based segment and task management in Druid. Consequently, following configurations must be set on all Druid nodes.
druid.zk.service.enabled=false
druid.serverview.type=http
druid.coordinator.loadqueuepeon.type=http
druid.indexer.runner.type=httpRemote
druid.discovery.type=k8s
For Node Discovery, Each Druid process running inside a pod “announces” itself by adding few “labels” and “annotations” in the pod spec. Druid process needs to be aware of pod name and namespace which it reads from environment variables POD_NAME
and POD_NAMESPACE
. These variable names can be changed, see configuration below. But in the end, each pod needs to have self pod name and namespace added as environment variables.
Additionally, this extension has following configuration.
Property | Possible Values | Description | Default | required |
---|---|---|---|---|
druid.discovery.k8s.clusterIdentifier | string that matches [a-z0-9][a-z0-9-]*[a-z0-9] | Unique identifier for this Druid cluster in Kubernetes e.g. us-west-prod-druid. | None | Yes |
druid.discovery.k8s.podNameEnvKey | Pod Env Variable | Pod Env variable whose value is that pod's name. | POD_NAME | No |
druid.discovery.k8s.podNamespaceEnvKey | Pod Env Variable | Pod Env variable whose value is that pod's kubernetes namespace. | POD_NAMESPACE | No |
druid.discovery.k8s.leaseDuration | Duration | Lease duration used by Leader Election algorithm. Candidates wait for this time before taking over previous Leader. | PT60S | No |
druid.discovery.k8s.renewDeadline | Duration | Lease renewal period used by Leader. | PT17S | No |
druid.discovery.k8s.retryPeriod | Duration | Retry wait used by Leader Election algorithm on failed operations. | PT5S | No |
apiVersion: rbac.authorization.k8s.io/v1 kind: Role metadata: name: druid-cluster rules: - apiGroups: - "" resources: - pods - configmaps verbs: - '*' --- kind: RoleBinding apiVersion: rbac.authorization.k8s.io/v1 metadata: name: druid-cluster subjects: - kind: ServiceAccount name: default roleRef: kind: Role name: druid-cluster apiGroup: rbac.authorization.k8s.io