First steps

Once you have followed the steps in the Installation section to install the operator and its dependencies, you will now deploy an HDFS cluster and its dependencies. Afterward, you can verify that it works by creating, verifying and deleting a test file in HDFS.

Setup

Zookeeper

To deploy a Zookeeper cluster create one file called zk.yaml:

---
apiVersion: zookeeper.stackable.tech/v1alpha1
kind: ZookeeperCluster
metadata:
  name: simple-zk
spec:
  image:
    productVersion: 3.9.2
  servers:
    roleGroups:
      default:
        replicas: 1

We also need to define a ZNode that will be used by the HDFS cluster to reference Zookeeper. Create another file called znode.yaml:

---
apiVersion: zookeeper.stackable.tech/v1alpha1
kind: ZookeeperZnode
metadata:
  name: simple-hdfs-znode
spec:
  clusterRef:
    name: simple-zk

Apply both of these files:

kubectl apply -f zk.yaml
kubectl apply -f znode.yaml

The state of the Zookeeper cluster can be tracked with kubectl:

kubectl rollout status --watch --timeout=5m statefulset/simple-zk-server-default

HDFS

An HDFS cluster has three components: the namenode, the datanode and the journalnode. Create a file named hdfs.yaml defining 2 namenodes and one datanode and journalnode each:

---
apiVersion: hdfs.stackable.tech/v1alpha1
kind: HdfsCluster
metadata:
  name: simple-hdfs
spec:
  image:
    productVersion: 3.3.6
  clusterConfig:
    zookeeperConfigMapName: simple-hdfs-znode
    dfsReplication: 1
  nameNodes:
    config:
      listenerClass: external-stable # This exposes your Stacklet outside of Kubernetes. Remove this configuration if this is not desired
    roleGroups:
      default:
        replicas: 2
  dataNodes:
    config:
      listenerClass: external-unstable # This exposes your Stacklet outside of Kubernetes. Remove this configuration if this is not desired
    roleGroups:
      default:
        replicas: 1
  journalNodes:
    roleGroups:
      default:
        replicas: 1

Where:

  • metadata.name contains the name of the HDFS cluster

  • the HDFS version in the Docker image provided by Stackable must be set in spec.image.productVersion

Please note that the version you need to specify for spec.image.productVersion is the desired version of Apache HDFS. You can optionally specify the spec.image.stackableVersion to a certain release like 23.11.0 but it is recommended to leave it out and use the default provided by the operator. For a list of available versions please check our image registry. It should generally be safe to simply use the latest image version that is available.

Create the actual HDFS cluster by applying the file:

kubectl apply -f hdfs.yaml

Track the progress with kubectl as this step may take a few minutes:

kubectl rollout status --watch --timeout=5m statefulset/simple-hdfs-datanode-default
kubectl rollout status --watch --timeout=5m statefulset/simple-hdfs-namenode-default
kubectl rollout status --watch --timeout=5m statefulset/simple-hdfs-journalnode-default

Verify that it works

To test the cluster you can create a new file, check its status and then delete it. We will execute these actions from within a helper pod. Create a file called webhdfs.yaml:

---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: webhdfs
  labels:
    app: webhdfs
spec:
  replicas: 1
  serviceName: webhdfs-svc
  selector:
    matchLabels:
      app: webhdfs
  template:
    metadata:
      labels:
        app: webhdfs
    spec:
      containers:
        - name: webhdfs
          image: docker.stackable.tech/stackable/testing-tools:0.2.0-stackable0.0.0-dev
          stdin: true
          tty: true

Apply it and monitor its progress:

kubectl apply -f webhdfs.yaml
kubectl rollout status --watch --timeout=5m statefulset/webhdfs

To begin with the cluster should be empty: this can be verified by listing all resources at the root directory (which should return an empty array!):

  kubectl exec -n default webhdfs-0 -- curl -s -XGET "http://simple-hdfs-namenode-default-0.simple-hdfs-namenode-default.default.svc.cluster.local:9870/webhdfs/v1/?op=LISTSTATUS"

Creating a file in HDFS using the Webhdfs API requires a two-step PUT (the reason for having a two-step create/append is to prevent clients from sending out data before the redirect). First, create a file with some text in it called testdata.txt and copy it to the tmp directory on the helper pod:

kubectl cp -n default ./testdata.txt webhdfs-0:/tmp

Then use curl to issue a PUT command:

  kubectl exec -n default webhdfs-0 -- \
  curl -s -XPUT -T /tmp/testdata.txt "http://simple-hdfs-namenode-default-0.simple-hdfs-namenode-default.default.svc.cluster.local:9870/webhdfs/v1/testdata.txt?user.name=stackable&op=CREATE&noredirect=true"

This will return a location that will look something like this:

http://simple-hdfs-datanode-default-0.simple-hdfs-datanode-default.default.svc.cluster.local:9864/webhdfs/v1/testdata.txt?op=CREATE&user.name=stackable&namenoderpcaddress=simple-hdfs&createflag=&createparent=true&overwrite=false

You can assign this to a local variable - e.g. $location - or you can copy-and-paste it into the URL, and then issue a second PUT like this:

kubectl exec -n default webhdfs-0 -- curl -s -XPUT -T /tmp/testdata.txt "$location"

Rechecking the status again with:

  kubectl exec -n default webhdfs-0 -- curl -s -XGET "http://simple-hdfs-namenode-default-0.simple-hdfs-namenode-default.default.svc.cluster.local:9870/webhdfs/v1/?op=LISTSTATUS"

will now display some metadata about the file that was created in the HDFS cluster:

{
    "FileStatuses": {
        "FileStatus": [
            {
                "accessTime": 1660821734999,
                "blockSize": 134217728,
                "childrenNum": 0,
                "fileId": 16396,
                "group": "supergroup",
                "length": 597,
                "modificationTime": 1660821735602,
                "owner": "stackable",
                "pathSuffix": "testdata.txt",
                "permission": "644",
                "replication": 3,
                "storagePolicy": 0,
                "type": "FILE"
            }
        ]
    }
}

To clean up, the file can be deleted like this:

  kubectl exec -n default webhdfs-0 -- curl -s -XDELETE "http://simple-hdfs-namenode-default-0.simple-hdfs-namenode-default.default.svc.cluster.local:9870/webhdfs/v1/testdata.txt?user.name=stackable&op=DELETE"

What’s next

Look at the Usage guide to find out more about configuring your HDFS cluster.