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How to Configure Kubernetes Resources for Flink Pods in Ververica Platform

Question

I need to configure some Kubernetes resources (e.g., labels, environment variables, volumes, init containers, sidecar containers, etc.) for my Flink pods in Ververica Platform. Could you show me some examples?

Answer

Note: This section applies to Ververica Platform 2.0 - 2.8.

Ververica Platform supports two ways to configure Kubernetes resources for Flink pods running in Ververica Platform. See the Ververica Plaform's documentation for more details. This article focuses on examples and is complementary to the official documentation. Here is an overview of both approaches.

kind: Deployment  # Ververica Platform Deployment (not the Kubernetes one)
spec:
  template:
    spec:
      kubernetes:
        pods: <KubernetesPodOptions>  # (1) 
        jobManagerPodTemplate: <V1PodTemplateSpec>  # (2)
        taskManagerPodTemplate: <V1PodTemplateSpec> # (2)

1) Simplified pod options

The options configured via this approach apply to both jobmanager and taskmanager pods. This approach supports only annotations, labels, nodeSelector, affinity, tolerations, imagePullSecrets, volumeMounts, securityContext, and environment variables.

2) Full-fledged pod templates (Recommended)

This approach is supported in Ververica Platform 2.4 and later. You configure jobmanager and taskmanager pods individually here. This approach provides full flexibility by exposing the complete Kubernetes V1PodTemplateSpec API and is our recommendation for Ververica Platform 2.4 and later.

Note: You can use only one of two approaches in a deployment. If you have some options configured via the simplified approach, and now need some advanced options like init containers, you will have to convert them to use the full-fledged approach.

The following sections will show you some often used examples.

Environment Variables

Full-fledged Pod Templates (Recommended)

kind: Deployment 
spec:
  template:
    spec:
      kubernetes:
        taskManagerPodTemplate: # or "jobManagerPodTemplate"
          spec:
            containers:    # or "initContainers"
              - name: flink-taskmanager # or "flink-jobmanager"
                env:
                  - name: VAR1
                    value: Hello
                  - name: VAR2
                    valueFrom:
                      secretKeyRef: # or "configMapKeyRef"
                        name: mysecret
                        key: password
                # envFrom is supported only in the full-fledged approach
                envFrom: # expose all key-value pairs in a configMap
                  - configMapRef:
                      name: myconfig

Simplified Pod Options

kind: Deployment
spec:
  template:
    spec:
      kubernetes:
        pods:
          envVars: # not "env" but "envVars"!
            - name: VAR1
              value: Hello
            - name: VAR2
              valueFrom:
                secretKeyRef: # or "configMapKeyRef"
                  name: mysecret
                  key: password

Volumes & VolumeMounts

Full-fledged Pod Templates (Recommended)

kind: Deployment
spec:
  template:
    spec:
      kubernetes:
        taskManagerPodTemplate: # or "jobManagerPodTemplate"
          spec:
            containers:    # or "initContainers"
              - name: flink-taskmanager # or "flink-jobmanager"
                volumeMounts:
                  - name: volume-config
                    mountPath: /config
                  - name: volume-secret
                    mountPath: /secret
                  - name: volume-data
                    mountPath: /data 
            volumes:
              - name: volume-config
                configMap:
                  name: myapp-config
              - name: volume-secret
                secret:
                  secretName: userpass
              - name: volume-data
                persistentVolumeClaim:
                  claimName: myapp-data

Simplified Pod Options

kind: Deployment
spec:
  template:
    spec:
      kubernetes:
        pods:
          volumeMounts:
            - name: volume-secret
              volume:
                name: volume-secret
                secret:  # mount a volume from a secret 
                  secretName: mysecret
              volumeMount:
                name: volume-secret
                mountPath: /secret
            - name: volume-config
              volume:
                name: volume-config
                configMap: # mount a volume from a configMap 
                  name: myapp-config
              volumeMount:
                name: volume-config
                mountPath: /config
            - name: volume-data
              volume:
                name: volume-data
                persistentVolumeClaim: # mount a volume from a PVC
                  claimName: myapp-data
              volumeMount:
                name: volume-data
                mountPath: /data

Labels & Annotations

Full-fledged Pod Templates (Recommended)

kind: Deployment
spec:
  template:
    spec:
      kubernetes:
        taskManagerPodTemplate: # or "jobManagerPodTemplate"
          metadata:
            labels:
              appverion: 1.0
              region: 'europe'
            annotations:
              prometheus.io/port: '9249'
              prometheus.io/scrape: 'true'

Simplified Pod Options

kind: Deployment
spec:
  template:
    spec:
      kubernetes:
        pods:
          labels:
            appverion: 1.0
            region: 'europe'
          annotations:
            prometheus.io/port: '9249'
            prometheus.io/scrape: 'true'

Init Containers

This example is only supported by the full-fledged pod templates. It uses an init container (image: alpine:latest) to download myfile.txt before taskmanager starts and make it available to taskmanager under /myapp-file:

kind: Deployment
spec:
  template:
    spec:      
      kubernetes:
        taskManagerPodTemplate: # or "jobManagerPodTemplate"
          spec:
            containers:
              - name: flink-taskmanager # or "flink-jobmanager"
                volumeMounts:
                  - name: myapp-file
                    mountPath: /myapp-file # myfile.txt is available under /myapp-file            
            initContainers:
              - name: myapp-init
                image: 'alpine:latest'        
                command: 
                  - sh
                  - '-c'
                  - >-
                    wget -q --no-check-certificate -P /myapp-file
                    https://path/to/myfile.txt
                volumeMounts:
                  - name: myapp-file
                    mountPath: /myapp-file
            volumes:
              - name: myapp-file
                emptyDir: {}

Sidecar Containers

This example is taken from Ververica Platform's doc and is supported only by the full-fledged pod templates. It adds an additional sidecar container named my-logging-sidecar to both the JobManager and TaskManager pods.

kind: Deployment
spec:
  template:
    spec:
      kubernetes:
        jobManagerPodTemplate:
          spec:
            containers:
              - name: my-logging-sidecar
                image: registry.acme.org/logging:3.2.1
        taskManagerPodTemplate:
          spec:
            containers:
              - name: my-logging-sidecar
                image: registry.acme.org/logging:3.2.1

Set Resource Requests & Limits

This example is supported only by the full-fledged pod templates. It sets container resource requests and limits to different values:

kind: Deployment
spec:
  template:
    spec:
      kubernetes:
        taskManagerPodTemplate: # or jobManagerPodTemplate
          spec:
            containers:
              - name: flink-taskmanager # or flink-jobmanager
                resources:
                  requests:
                    cpu: 0.5
                    memory: 500Mi
                    ephemeral-storage: 2Gi
                  limits:
                    cpu: 1
                    memory: 1Gi
                    ephemeral-storage: 4Gi
              - name: mysidecar
                resources: # similar for sidecar containers
            initContainers:              
              - name: myinit
                resources: # similar for init containers

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