A sample to showcase how to create a k8s scheduler extender.
if you cluster is installed by kubeadm，maybe your kube-scheduler's yaml like this:
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
component: kube-scheduler
tier: control-plane
name: kube-scheduler
namespace: kube-system
spec:
containers:
- command:
- kube-scheduler
- --authentication-kubeconfig=/etc/kubernetes/scheduler.conf
- --authorization-kubeconfig=/etc/kubernetes/scheduler.conf
- --bind-address=127.0.0.1
- --kubeconfig=/etc/kubernetes/scheduler.conf
- --leader-elect=true
- --config=/etc/kubernetes/scheduler-extender.yaml
- --v=9
image: gcr.azk8s.cn/google_containers/kube-scheduler:v1.16.2
imagePullPolicy: IfNotPresent
livenessProbe:
failureThreshold: 8
httpGet:
host: 127.0.0.1
path: /healthz
port: 10251
scheme: HTTP
initialDelaySeconds: 15
timeoutSeconds: 15
name: kube-scheduler
resources:
requests:
cpu: 100m
volumeMounts:
- mountPath: /etc/kubernetes/scheduler.conf
name: kubeconfig
readOnly: true
- mountPath: /etc/kubernetes/scheduler-extender.yaml
name: extender
readOnly: true
- mountPath: /etc/kubernetes/scheduler-extender-policy.yaml
name: extender-policy
readOnly: true
hostNetwork: true
priorityClassName: system-cluster-critical
volumes:
- hostPath:
path: /etc/kubernetes/scheduler.conf
type: FileOrCreate
name: kubeconfig
- hostPath:
path: /etc/kubernetes/scheduler-extender.yaml
type: FileOrCreate
name: extender
- hostPath:
path: /etc/kubernetes/scheduler-extender-policy.yaml
type: FileOrCreate
name: extender-policy
status: {}You must mount scheduler-extender.yaml 和 scheduler-extender-policy.yaml to Pod.
-
Because
k8s.io/kubernetespkg is not intended to be used with go get,so we need use go modules replace to depend these modules, so you must replacego.modto your local k8s path .
-
Prioritize webhook won't be triggered if it's running on an one-node cluster. As it makes no sense to run priorities logic when there is only one candidate:
// from k8s.io/kubernetes/pkg/scheduler/core/generic_scheduler.go
func (g *genericScheduler) Schedule(pod *v1.Pod, nodeLister algorithm.NodeLister) (string, error) {
...
// When only one node after predicate, just use it.
if len(filteredNodes) == 1 {
metrics.SchedulingAlgorithmPriorityEvaluationDuration.Observe(metrics.SinceInMicroseconds(startPriorityEvalTime))
return filteredNodes[0].Name, nil
}
...
}
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