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Version: v0.9

Share Data across Namespace (Sidecar mode)

This tutorial is used to show how to use a Dataset cache across Namespace.

  • In Namespace ns-a, create Dataset demo and AlluxioRuntime demo
  • In Namespace ns-b create Dataset demo-ref. The mountPoint of demo-ref is dataset://ns-a/demo

Prerequests​

Before running this tutorial, please refer to the installation documentation to complete the installation and check that the components of Fluid are working properly:

$ kubectl get pod -n fluid-system
alluxioruntime-controller-5b64fdbbb-84pc6 1/1 Running 0 8h
csi-nodeplugin-fluid-fwgjh 2/2 Running 0 8h
csi-nodeplugin-fluid-ll8bq 2/2 Running 0 8h
dataset-controller-5b7848dbbb-n44dj 1/1 Running 0 8h
thinruntime-controller-7dcbf5f45-xsf4p 1/1 Running 0 8h

Where thinruntime-controller is used to support Dataset sharing across Namespace and alluxioruntime-controller is the actual cache.

Share Dataset cache across Namespace through CSI mechanism​

1. Create Dataset and Cache Runtime​

In default Namespace,create phy Dataset and AlluxioRuntime.

$ cat<<EOF >ds.yaml
apiVersion: data.fluid.io/v1alpha1
kind: Dataset
metadata:
name: phy
spec:
mounts:
- mountPoint: https://mirrors.bit.edu.cn/apache/spark/
name: spark
---
apiVersion: data.fluid.io/v1alpha1
kind: AlluxioRuntime
metadata:
name: phy
spec:
replicas: 1
tieredstore:
levels:
- mediumtype: MEM
path: /dev/shm
quota: 1Gi
high: "0.95"
low: "0.7"
EOF

$ kubectl create -f ds.yaml

2. Create referenced Dataset and Runtime​

In Namespace ref, create:

  • the referenced dataset refdemo, whose mountPoint format is dataset://${origin-dataset-namespace}/${origin-dataset-name}.
  • ThinRuntime refdemo, and its Spec fields don't need to be filled.

Note:

  1. Currently, the referenced Dataset only supports single mount and its form must be dataset:// (i.e. the creation of a dataset fails when dataset:// and other forms both appear), and other fields in the Spec are invalid.
  2. The fields in Spec of the referenced Runtime corresponding to the Dataset are invalid.
$ kubectl create ns ref

$ cat<<EOF >ds-ref.yaml
apiVersion: data.fluid.io/v1alpha1
kind: Dataset
metadata:
name: refdemo
spec:
mounts:
- mountPoint: dataset://default/phy
name: fusedemo
path: "/"
EOF

$ kubectl create -f ds-ref.yaml -n ref

Create Pod and Check the data​

In Namespace ref, create a Pod:
Need to enable serverless injection, set pod tag serverless.fluid.io/inject=true

$ cat<<EOF >app-ref.yaml
apiVersion: v1
kind: Pod
metadata:
name: nginx
labels:
serverless.fluid.io/inject: "true"
spec:
containers:
- name: nginx
image: nginx
volumeMounts:
- mountPath: /data_spark
name: spark-vol
volumes:
- name: spark-vol
persistentVolumeClaim:
claimName: refdemo
EOF

$ kubectl create -f app-ref.yaml -n ref

In default Namespace, check the Pod information.

  • Only one AlluxioRuntime cluster exists, i.e. there is only one cache.
  • The sidecar mechanism is used, so there is no fuse pod.
$ kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
phy-master-0 2/2 Running 0 7m2s 172.16.1.10 work02 <none> <none>
phy-worker-0 2/2 Running 0 6m29s 172.16.1.10 work02 <none> <none>

In Namespace ref, check the status of the app nginx pod.

$ kubectl get pods -n ref -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx 1/1 Running 0 11m 10.233.109.66 work02 <none> <none>

Check the yaml of the app nginx pod under the ref namespace and you can see that the fuse container is injected.

$ kubectl get pods nginx -n ref -o yaml
...
spec:
containers:
- image: fluidcloudnative/alluxio-fuse:release-2.8.1-SNAPSHOT-0433ade
...
- image: nginx
...

Known Issues​

For the Fuse Sidecar scenario, some ConfigMap is created under the referenced namespace (ref).

NAME                                    DATA   AGE
check-fluid-mount-ready 1 6d14h
phy-config 7 6d15h
refdemo-fuse.alluxio-fuse-check-mount 1 6d14h
  • check-fluid-mount-ready is shared by all Datasets under that namespace.
  • refdemo-fuse.alluxio-fuse-check-mount is generated based on the Dataset name and Runtime type.
  • phy-config is the ConfigMap required by AlluxioRuntime's Fuse Container and is therefore copied from the default namespace to the ref namespace.
    • If a Dataset named phy using AlluxioRuntime previously existed under the ref namespace, then the use of the refdemo Dataset will be wrong.