Cooldown Protection Plugin User Guide

Background

When we need to enable elastic training or serving, preemptible job’s pods can be preempted or back to running repeatedly, if no cooldown protection set, these pods can be preempted again after they just started for a short time, this may cause service stability dropped. So we add “cdp” plugin to ensure preemptible job’s pods can run for at least some time set by user.

Environment setup

Install volcano

Refer to Install Guide to install volcano.

Update scheduler configmap

After installed, update the scheduler configuration:

kubectl edit configmap -n volcano-system volcano-scheduler-configmap

Register cdp plugin in configmap while enable preempt action

kind: ConfigMap
apiVersion: v1
metadata:
  name: volcano-scheduler-configmap
  namespace: volcano-system
data:
  volcano-scheduler.conf: |
    actions: "enqueue, allocate, preempt, backfill"
    tiers:
    - plugins:
      - name: priority
      - name: gang
      - name: conformance
      - name: cdp
    - plugins:
      - name: drf
      - name: predicates
      - name: task-topology
        arguments:
          task-topology.weight: 10
      - name: proportion
      - name: nodeorder
      - name: binpack

Running Jobs

Take a simple volcano job as sample.

original job yaml is as below, which has “ps” and “worker” task

apiVersion: batch.volcano.sh/v1alpha1
kind: Job
metadata:
  name: test-job
spec:
  minAvailable: 3
  schedulerName: volcano
  priorityClassName: high-priority
  plugins:
    ssh: []
    env: []
    svc: []
  maxRetry: 5
  queue: default
  volumes:
    - mountPath: "/myinput"
    - mountPath: "/myoutput"
      volumeClaimName: "testvolumeclaimname"
      volumeClaim:
        accessModes: [ "ReadWriteOnce" ]
        storageClassName: "my-storage-class"
        resources:
          requests:
            storage: 1Gi
  tasks:
    - replicas: 6
      name: "worker"
      template:
        metadata:
          name: worker
        spec:
          containers:
            - image: nginx
              imagePullPolicy: IfNotPresent
              name: nginx
              resources:
                requests:
                  cpu: "1"
          restartPolicy: OnFailure
    - replicas: 2
      name: "ps"
      template:
        metadata:
          name: ps
        spec:
          containers:
            - image: nginx
              imagePullPolicy: IfNotPresent
              name: nginx
              resources:
                requests:
                  cpu: "1"
          restartPolicy: OnFailure

Edit yaml of vcjob

1. add annotations in volcano job in format below.

   1. volcano.sh/preemptable annotation indicates that job or task is preemptable

   2. volcano.sh/cooldown-time annotation indicates cooldown time for the entire job or dedicated task. Value for the annotation indicates cooldown time, valid time units are “ns”, “us” (or “µs”), “ms”, “s”, “m”, “h”.

          volcano.sh/preemptable: "true"
          volcano.sh/cooldown-time: "600s"
      

Example 1

Add annotation to entire job, then “ps” and “worker” task can be preempted and all have cooldown time support.

apiVersion: batch.volcano.sh/v1alpha1
kind: Job
metadata:
  name: test-job
  annotations:
    volcano.sh/preemptable: "true"
    volcano.sh/cooldown-time: "600s"
spec:
  ... # below keep the same

Example 2

Add annotation to dedicated task, as shown below, only “worker” can be preempted and have cooldown time support.

apiVersion: batch.volcano.sh/v1alpha1
kind: Job
metadata:
  name: test-job
spec:
  minAvailable: 3
  schedulerName: volcano
  priorityClassName: high-priority
  plugins:
    ssh: []
    env: []
    svc: []
  maxRetry: 5
  queue: default
  volumes:
    - mountPath: "/myinput"
    - mountPath: "/myoutput"
      volumeClaimName: "testvolumeclaimname"
      volumeClaim:
        accessModes: [ "ReadWriteOnce" ]
        storageClassName: "my-storage-class"
        resources:
          requests:
            storage: 1Gi
  tasks:
    - replicas: 6
      name: "worker"
      template:
        metadata:
          name: worker
          annotations:     # add annotation in tasks
            volcano.sh/preemptable: "true"
            volcano.sh/cooldown-time: "600s"
        spec:
          containers:
            - image: nginx
              imagePullPolicy: IfNotPresent
              name: nginx
              resources:
                requests:
                  cpu: "1"
          restartPolicy: OnFailure
    - replicas: 2
      name: "ps"
      template:
        metadata:
          name: ps
        spec:
          containers:
            - image: nginx
              imagePullPolicy: IfNotPresent
              name: nginx
              resources:
                requests:
                  cpu: "1"
          restartPolicy: OnFailure