Flink on K8s

StreamPark Flink Kubernetes is based on Flink Native Kubernetes and support deployment modes as below：

• Native-Kubernetes Application
• Native-Kubernetes Session At now, one StreamPark only supports one Kubernetes cluster.You can submit Fearure Request Issue , when multiple Kubernetes clusters are needed.

Environments requirement

Additional operating environment to run StreamPark Flink-Kubernetes is as below:

• Kubernetes
• Maven（StreamPark runNode）
• Docker（StreamPark runNode）

StreamPark entity can be deployed on Kubernetes nodes, and can also be deployed on node out of Kubernetes cluster when there are smooth network between the node and cluster.

Preparation for integration

configuration for connecting Kubernetes

StreamPark connects to Kubernetes cluster by default connection credentials ～/.kube/config .User can copy .kube/config from Kubernetes node to StreamPark nodes,or download it from Kubernetes provided by cloud service providers.If considering Permission constraints, User also can generate custom account`s configuration by themselves.

kubectl cluster-info

configuration for coKubernetes RBAC

User can configure RBAC for Kubernetes Namespace by referring to Flink-Docs：https://ci.apache.org/projects/flink/flink-docs-stable/docs/deployment/resource-providers/native_kubernetes/#rbac

When Flink Namespace is flink-dev and there are no needed to explicitly specify Kubernetes accounts, user can allocate resource to clusterrolebinding by the way as below

kubectl create clusterrolebinding flink-role-binding-default --clusterrole=edit --serviceaccount=flink-dev:default

Configuration for remote Docker service

On Setting page of StreamPark, user can configure the connection information for Docker service of Kubernetes cluster.

Building a Namespace named streampark(other name should be set at Setting page of StreamPark) at remote Docker.The namespace is push/pull space of StreamPark Flink image and Docker Register User should own pull/push permission of this namespace.

# verify access
docker login --username=<your_username> <your_register_addr>
# verify push permission
docker pull busybox
docker tag busybox <your_register_addr>/streampark/busybox
docker push <your_register_addr>/streampark/busybox
# verify pull permission
docker pull <your_register_addr>/streampark/busybox

Job submit

Application Job release

parameter descriptions are as below：

• Flink Base Docker Image： Base Flink Docker Image Tag can be obtained from DockerHub - offical/flink .And user can also use private image when Docker Register Account owns pull permission of it.

• Rest-Service Exposed Type：Description of candidate values for native Flink Kubernetes configuration kubernetes.rest-service.exposed.type ：

  • ClusterIP：ip that StreamPark can access；
  • LoadBalancer：resource of LoadBalancer should be allocated in advance， Flink Namespace own permission of automatic binding，and StreamPark can access LoadBalancer`s gateway；
  • NodePort：StreamPark can access all Kubernetes nodes；

• Kubernetes Pod Template: This is Flink's custom configuration of pod-template. The container-name must be flink-main-container. If the Kubernetes pod needs a secret key to pull the Docker image, please fill in the information about the secret key in the pod template file. Below is an example of pod-template:

  apiVersion: v1
  kind: Pod
  metadata:
    name: pod-template
  spec:
    serviceAccount: default
    containers:
    - name: flink-main-container
      image:
    imagePullSecrets:
    - name: regsecret

• Dynamic Option: Dynamic options of Flink on Kubernetes (part of parameters can also be defined in pod-template). Options should start with -D. Details can be found at Flink on Kubernetes parameters.

After the job is started, it is supported to directly access the corresponding Flink Web UI page on the Detail page of the task：

Session job release

The additional configuration of Flink-Native-Kubernetes Session Job will be decided by Flink-Session cluster.More details can be find in Flink-Doc：https://ci.apache.org/projects/flink/flink-docs-stable/docs/deployment/resource-providers/native_kubernetes

other configuration

StreamPark parameters related to Flink-Kubernetes in applicaton.yml are as below. And in most conditions, there is no need to change it.

Configuration item	Description	Default value
streampark.docker.register.image-namespace	namespace of Remote docker service repository， flink-job image will be pushed here	null
streampark.flink-k8s.tracking.polling-task-timeout-sec.job-status	timeout in seconds of flink state tracking task	120
streampark.flink-k8s.tracking.polling-task-timeout-sec.cluster-metric	timeout in seconds of flink metrics tracking task	120
streampark.flink-k8s.tracking.polling-interval-sec.job-status	interval in seconds of flink state tracking task.To maintain accuracy, please set below 5s, the best setting is 2-3s	5
streampark.flink-k8s.tracking.polling-interval-sec.cluster-metric	interval in seconds of flink metrics tracking task	10
streampark.flink-k8s.tracking.silent-state-keep-sec	fault tolerance time in seconds of silent metrics	60