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Version: v1.5

GangScheduling

Introduction

We provide Gang mechanism for the scheduler to control pods binding opportunity. User can declare a resource-collection-minimum number, only when assigned-resources reach the given limitation can trigger the binding. We provide Strict and NonStrict to control the resource-accumulation-process by a configuration. We also provide a two-level Gang description for better matching the real scenario, which is different from community.

Setup

Prerequisite

  • Kubernetes >= 1.18
  • Koordinator >= 0.70

Installation

Please make sure Koordinator components are correctly installed in your cluster. If not, please refer to Installation.

Configurations

GangScheduling is Enabled by default. You can use it without any modification on the koord-scheduler config.

Use GangScheduling

Quick Start

apply gang through gang crd

1.create pod-group

apiVersion: scheduling.sigs.k8s.io/v1alpha1
kind: PodGroup
metadata:
name: gang-example
namespace: default
spec:
scheduleTimeoutSeconds: 100
minMember: 2
$ kubectl get pgs -n default
NAME AGE
gang-example 13s

2.create child pod1

apiVersion: v1
kind: Pod
metadata:
name: pod-example1
namespace: default
labels:
pod-group.scheduling.sigs.k8s.io: gang-example
spec:
schedulerName: koord-scheduler
containers:
- command:
- sleep
- 365d
image: busybox
imagePullPolicy: IfNotPresent
name: curlimage
resources:
limits:
cpu: 40m
memory: 40Mi
requests:
cpu: 40m
memory: 40Mi
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
restartPolicy: Always
$ kubectl get pod -n default
NAME READY STATUS RESTARTS AGE
pod-example1 0/1 Pending 0 7s

3.create child pod2

apiVersion: v1
kind: Pod
metadata:
name: pod-example2
namespace: default
labels:
pod-group.scheduling.sigs.k8s.io: gang-example
spec:
schedulerName: koord-scheduler
containers:
- command:
- sleep
- 365d
image: busybox
imagePullPolicy: IfNotPresent
name: curlimage
resources:
limits:
cpu: 40m
memory: 40Mi
requests:
cpu: 40m
memory: 40Mi
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
restartPolicy: Always
$ kubectl get pod -n default
NAME READY STATUS RESTARTS AGE
pod-example1 1/1 Running 0 53s
pod-example2 1/1 Running 0 5s
$ kubectl get pg gang-example -n default -o yaml
apiVersion: scheduling.sigs.k8s.io/v1alpha1
kind: PodGroup
metadata:
creationTimestamp: "2022-10-09T09:08:17Z"
generation: 6
spec:
minMember: 1
scheduleTimeoutSeconds: 100
status:
phase: Running
running: 2
scheduled: 2

apply gang through annotation

1.create child pod1

apiVersion: v1
kind: Pod
metadata:
name: pod-example1
namespace: default
annotations:
gang.scheduling.koordinator.sh/name: "gang-example"
gang.scheduling.koordinator.sh/min-available: "2"
spec:
schedulerName: koord-scheduler
containers:
- command:
- sleep
- 365d
image: busybox
imagePullPolicy: IfNotPresent
name: curlimage
resources:
limits:
cpu: 40m
memory: 40Mi
requests:
cpu: 40m
memory: 40Mi
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
restartPolicy: Always
$ kubectl get pod -n default
NAME READY STATUS RESTARTS AGE
pod-example1 0/1 Pending 0 7s

2.create child pod2

apiVersion: v1
kind: Pod
metadata:
name: pod-example2
namespace: default
annotations:
gang.scheduling.koordinator.sh/name: "gang-example"
gang.scheduling.koordinator.sh/min-available: "2"
spec:
schedulerName: koord-scheduler
containers:
- command:
- sleep
- 365d
image: busybox
imagePullPolicy: IfNotPresent
name: curlimage
resources:
limits:
cpu: 40m
memory: 40Mi
requests:
cpu: 40m
memory: 40Mi
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
restartPolicy: Always
$ kubectl get pod -n default
NAME READY STATUS RESTARTS AGE
pod-example1 1/1 Running 0 53s
pod-example2 1/1 Running 0 5s
$ kubectl get pg gang-example -n default -o yaml
apiVersion: scheduling.sigs.k8s.io/v1alpha1
kind: PodGroup
metadata:
creationTimestamp: "2022-10-09T09:08:17Z"
generation: 6
spec:
minMember: 1
scheduleTimeoutSeconds: 100
status:
phase: Running
running: 2
scheduled: 2

device resource debug api:

$ kubectl -n koordinator-system get lease koord-scheduler --no-headers | awk '{print $2}' | cut -d'_' -f1 | xargs -I {} kubectl -n koordinator-system get pod {} -o wide --no-headers | awk '{print $6}'
10.244.0.64

$ curl 10.244.0.64:10251/apis/v1/plugins/Coscheduling/gang/default/gang-example
{
"boundChildren": {
"default/pod-example1": {},
"default/pod-example2": {}
},
"children": {
"default/pod-example1": {},
"default/pod-example2": {}
},
"childrenScheduleRoundMap": {
"default/pod-example1": 2,
"default/pod-example2": 2
},
"createTime": "2022-10-09T07:31:53Z",
"gangFrom": "GangFromPodAnnotation",
"gangGroup": null,
"hasGangInit": true,
"minRequiredNumber": 2,
"mode": "Strict",
"name": "default/gang-example",
"onceResourceSatisfied": true,
"scheduleCycle": 2,
"scheduleCycleValid": true,
"totalChildrenNum": 2,
"waitTime": 600000000000,
"waitingForBindChildren": {}
}

advanced configuration for gang

1.apply through pod-group.

apiVersion: scheduling.sigs.k8s.io/v1alpha1
kind: PodGroup
metadata:
name: gang-example1
namespace: default
annotations:
gang.scheduling.koordinator.sh/total-number: "3"
gang.scheduling.koordinator.sh/mode: "NonStrict"
gang.scheduling.koordinator.sh/groups: "[\"default/gang-example1\", \"default/gang-example2\"]"

spec:
scheduleTimeoutSeconds: 100
minMember: 2

  • gang.scheduling.koordinator.sh/total-number specifies the total children number of the gang. If not specified,it will be set with the minMember
  • gang.scheduling.koordinator.sh/mode defines the Gang Scheduling operation when failed scheduling. Support Strict\NonStrict, default is Strict
  • gang.scheduling.koordinator.sh/groups defines which gangs are bundled as a group. The gang will go to bind only all gangs in one group meet the conditions

2.apply through pod annotations.

apiVersion: v1
kind: Pod
metadata:
name: pod-example2
namespace: default
annotations:
gang.scheduling.koordinator.sh/name: "gang-example1"
gang.scheduling.koordinator.sh/min-available: "2"
gang.scheduling.koordinator.sh/total-number: "3"
gang.scheduling.koordinator.sh/mode: "Strict\NonStrict"
gang.scheduling.koordinator.sh/groups: "[\"default/gang-example1\", \"default/gang-example2\"]"
gang.scheduling.koordinator.sh/waiting-time: "100s"
spec:
schedulerName: koord-scheduler
containers:
- command:
- sleep
- 365d
image: busybox
imagePullPolicy: IfNotPresent
name: curlimage
resources:
limits:
cpu: 40m
memory: 40Mi
requests:
cpu: 40m
memory: 40Mi
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
restartPolicy: Always
  • gang.scheduling.koordinator.sh/total-number specifies the total children number of the gang. If not specified,it will be set with the gang.scheduling.koordinator.sh/min-available
  • gang.scheduling.koordinator.sh/mode defines the Gang Scheduling operation when failed scheduling. Support Strict\NonStrict, default is Strict
  • gang.scheduling.koordinator.sh/groups defines which gangs are bundled as a group. The gang will go to bind only all gangs in one group meet the conditions
  • gang.scheduling.koordinator.sh/waiting-time specifies gang's max wait time in Permit Stage.

advanced configuration for scheduler

you can modify koord-scheduler-config.yaml in helm to adjust Coscheduling configuration as below:

apiVersion: v1
kind: ConfigMap
metadata:
name: koord-scheduler-config
namespace: {{ .Values.installation.namespace }}
data:
koord-scheduler-config: |
apiVersion: kubescheduler.config.k8s.io/v1beta2
kind: KubeSchedulerConfiguration
leaderElection:
leaderElect: true
resourceLock: leases
resourceName: koord-scheduler
resourceNamespace: {{ .Values.installation.namespace }}
profiles:
- pluginConfig:
- name: Coscheduling
args:
apiVersion: kubescheduler.config.k8s.io/v1beta2
kind: CoschedulingArgs
defaultTimeout: 600s
controllerWorkers: 1
- name: ElasticQuota
...