Kubernetes.io Blog: KubeDirector: The easy way to run complex stateful applications on Kubernetes



Author: Thomas Phelan (BlueData)

KubeDirector is an open source project designed to make it easy to run complex stateful scale-out application clusters on Kubernetes.

KubeDirector is built using the custom resource definition (CRD) framework and leverages the native Kubernetes API extensions and design philosophy. This enables transparent integration with Kubernetes user/resource management as well as existing clients and tools.

We recently introduced the KubeDirector project, as part of a broader open source Kubernetes initiative we call BlueK8s. I’m happy to announce that the pre-alpha code for KubeDirector is now available. And in this blog post, I’ll show how it works.

KubeDirector provides the following capabilities: * The ability to run non-cloud native stateful applications on Kubernetes without modifying the code. In other words, it’s not necessary to decompose these existing applications to fit a microservices design pattern. * Native support for preserving application-specific configuration and state. * An application-agnostic deployment pattern, minimizing the time to onboard new stateful applications to Kubernetes.

KubeDirector enables data scientists familiar with data-intensive distributed applications such as Hadoop, Spark, Cassandra, TensorFlow, Caffe2, etc. to run these applications on Kubernetes – with a minimal learning curve and no need to write GO code. The applications controlled by KubeDirector are defined by some basic metadata and an associated package of configuration artifacts. The application metadata is referred to as a KubeDirectorApp resource.

To understand the components of KubeDirector, clone the repository on GitHub using a command similar to:

git clone http://<userid>@[github.com/bluek8s/kubedirector](http://github.com/bluek8s/kubedirector).

The KubeDirectorApp definition for the Spark 2.2.1 application is located in the file kubedirector/deploy/example_catalog/cr-app-spark221e2.json.

 ~> cat kubedirector/deploy/example_catalog/cr-app-spark221e2.json { "apiVersion": "[kubedirector.bluedata.io/v1alpha1](http://kubedirector.bluedata.io/v1alpha1)    ", "kind": "KubeDirectorApp", "metadata": { "name" : "spark221e2" }, "spec" : { "systemctlMounts": true, "config": { "node_services": [ { "service_ids": [ "ssh", "spark", "spark_master", "spark_worker" ], …

The configuration of an application cluster is referred to as a KubeDirectorCluster resource. The KubeDirectorCluster definition for a sample Spark 2.2.1 cluster is located in the file kubedirector/deploy/example_clusters/cr-cluster-spark221.e1.yaml.

~> cat kubedirector/deploy/example_clusters/cr-cluster-spark221.e1.yaml apiVersion: "[kubedirector.bluedata.io/v1alpha1](http://kubedirector.bluedata.io/v1alpha1)  " kind: "KubeDirectorCluster" metadata: name: "spark221e2" spec: app: spark221e2 roles: - name: controller replicas: 1 resources: requests: memory: "4Gi" cpu: "2" limits: memory: "4Gi" cpu: "2" - name: worker replicas: 2 resources: requests: memory: "4Gi" cpu: "2" limits: memory: "4Gi" cpu: "2" - name: jupyter …

Running Spark on Kubernetes with KubeDirector

With KubeDirector, it’s easy to run Spark clusters on Kubernetes.

First, verify that Kubernetes (version 1.9 or later) is running, using the command kubectl version

~> kubectl version Client Version: version.Info{Major:"1", Minor:"11", GitVersion:"v1.11.3", GitCommit:"a4529464e4629c21224b3d52edfe0ea91b072862", GitTreeState:"clean", BuildDate:"2018-09-09T18:02:47Z", GoVersion:"go1.10.3", Compiler:"gc", Platform:"linux/amd64"} Server Version: version.Info{Major:"1", Minor:"11", GitVersion:"v1.11.3", GitCommit:"a4529464e4629c21224b3d52edfe0ea91b072862", GitTreeState:"clean", BuildDate:"2018-09-09T17:53:03Z", GoVersion:"go1.10.3", Compiler:"gc", Platform:"linux/amd64"}

Deploy the KubeDirector service and the example KubeDirectorApp resource definitions with the commands:

cd kubedirector make deploy

These will start the kubedirector pod:

~> kubectl get pods NAME READY STATUS RESTARTS AGE kubedirector-58cf59869-qd9hb 1/1 Running 0 1m

List the installed kubedirector applications with kubectl get KubeDirectorApp

~> kubectl get KubeDirectorApp NAME AGE cassandra311 30m spark211up 30m spark221e2 30m

Now you can launch a Spark 2.2.1 cluster using the example KubeDirectorCluster file and the kubectl create -f deploy/example_clusters/cr-cluster-spark211up.yaml command. Verify that the spark cluster has been started:

~> kubectl get pods NAME READY STATUS RESTARTS AGE kubedirector-58cf59869-djdwl 1/1 Running 0 19m spark221e2-controller-zbg4d-0 1/1 Running 0 23m spark221e2-jupyter-2km7q-0 1/1 Running 0 23m spark221e2-worker-4gzbz-0 1/1 Running 0 23m spark221e2-worker-4gzbz-1 1/1 Running 0 23m

The running services now include the spark services:

~> kubectl get service NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubedirector ClusterIP <none> 60000/TCP 1d kubernetes ClusterIP <none> 443/TCP 1d svc-spark221e2-5tg48 ClusterIP None <none> 8888/TCP 21s svc-spark221e2-controller-tq8d6-0 NodePort <none> 22:30534/TCP,8080:31533/TCP,7077:32506/TCP,8081:32099/TCP 20s svc-spark221e2-jupyter-6989v-0 NodePort <none> 22:30632/TCP,8888:30355/TCP 20s svc-spark221e2-worker-d9892-0 NodePort <none> 22:30358/TCP,8081:32144/TCP 20s svc-spark221e2-worker-d9892-1 NodePort <none> 22:30294/TCP,8081:31436/TCP 20s

Pointing the browser at port 31533 connects to the Spark Master UI:

That’s all there is to it! In fact, in the example above we also deployed a Jupyter notebook along with the Spark cluster.

To start another application (e.g. Cassandra), just specify another KubeDirectorApp file:

kubectl create -f deploy/example_clusters/cr-cluster-cassandra311.yaml

See the running cassandra cluster:

~> kubectl get pods NAME READY STATUS RESTARTS AGE cassandra311-seed-v24r6-0 1/1 Running 0 1m cassandra311-seed-v24r6-1 1/1 Running 0 1m cassandra311-worker-rqrhl-0 1/1 Running 0 1m cassandra311-worker-rqrhl-1 1/1 Running 0 1m kubedirector-58cf59869-djdwl 1/1 Running 0 1d spark221e2-controller-tq8d6-0 1/1 Running 0 22m spark221e2-jupyter-6989v-0 1/1 Running 0 22m spark221e2-worker-d9892-0 1/1 Running 0 22m spark221e2-worker-d9892-1 1/1 Running 0 22m

Now you have a Spark cluster (with a Jupyter notebook) and a Cassandra cluster running on Kubernetes. Use kubectl get service to see the set of services.

~> kubectl get service NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubedirector ClusterIP <none> 60000/TCP 1d kubernetes ClusterIP <none> 443/TCP 1d svc-cassandra311-seed-v24r6-0 NodePort <none> 22:31131/TCP,9042:30739/TCP 3m svc-cassandra311-seed-v24r6-1 NodePort <none> 22:30373/TCP,9042:32662/TCP 3m svc-cassandra311-vhh29 ClusterIP None <none> 8888/TCP 3m svc-cassandra311-worker-rqrhl-0 NodePort <none> 22:31832/TCP,9042:31962/TCP 3m svc-cassandra311-worker-rqrhl-1 NodePort <none> 22:31454/TCP,9042:31170/TCP 3m svc-spark221e2-5tg48 ClusterIP None <none> 8888/TCP 24m svc-spark221e2-controller-tq8d6-0 NodePort <none> 22:30534/TCP,8080:31533/TCP,7077:32506/TCP,8081:32099/TCP 24m svc-spark221e2-jupyter-6989v-0 NodePort <none> 22:30632/TCP,8888:30355/TCP 24m svc-spark221e2-worker-d9892-0 NodePort <none> 22:30358/TCP,8081:32144/TCP 24m svc-spark221e2-worker-d9892-1 NodePort <none> 22:30294/TCP,8081:31436/TCP 24m

Get Involved

KubeDirector is a fully open source, Apache v2 licensed, project – the first of multiple open source projects within a broader initiative we call BlueK8s. The pre-alpha code for KubeDirector has just been released and we would love for you to join the growing community of developers, contributors, and adopters. Follow @BlueK8s on Twitter and get involved through these channels: