Is there a way to know the current leader in a Kubernetes HA cluster?

[Qian Zhang]

Hi,

I have a Kubernetes HA cluster which consists of 3 master nodes, each of them has kube-apiserver, kube-scheduler and kube-controller-manager running, and kube-scheduler and kube-controller-manager are started with the option "--leader-elect", my question is, is there a way to tell the current leader of kube-scheduler/kube-controller-manager? E.g., a Kubernetes API to get such info? Or directly get it from etcd?

Thanks,

Qian Zhang

[Jerzy Szczepkowski]

You can get it from endpoints resource. The endpoint should have an annotation pointing to the leader.

$ kubectl get endpoints kube-controller-manager --namespace=kube-system  -o yaml

apiVersion: v1
kind: Endpoints
metadata:
  annotations:
    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"kubernetes-master","leaseDurationSeconds":15,"acquireTime":"2017-02-14T14:05:57Z","renewTime":"2017-02-14T14:14:42Z","leaderTransitions":0}'

...

Regards,

Jerzy

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[Qian Zhang]

Thanks Jerzy!

Thanks,

Qian Zhang

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[Junaid Subhani]

Hello Jerzy ,

Is there a much more direct way to get just the value of holderIdentity ?

My request :

http://172.29.240.172:8080/api/v1/namespaces/kube-system/endpoints/kube-controller-manager

This gives me :

{ "kind": "Endpoints", "apiVersion": "v1", "metadata": { "name": "kube-controller-manager", "namespace": "kube-system", "selfLink": "/api/v1/namespaces/kube-system/endpoints/kube-controller-manager", "uid": "89e09aae-5dc6-11e7-89c1-0050569b569d", "resourceVersion": "19152", "creationTimestamp": "2017-06-30T19:01:35Z", "annotations": { "control-plane.alpha.kubernetes.io/leader": "{\"holderIdentity\":\"master2\",\"leaseDurationSeconds\":15,\"acquireTime\":\"2017-06-30T19:01:35Z\",\"renewTime\":\"2017-06-30T19:18:01Z\",\"leaderTransitions\":0}" } }, "subsets": [] }

I basically need to configure HAProxy based on the value of holderIdentity

On Tuesday, 14 February 2017 09:18:54 UTC-5, Jerzy Szczepkowski wrote:

You can get it from endpoints resource. The endpoint should have an annotation pointing to the leader.

$ kubectl get endpoints kube-controller-manager --namespace=kube-system  -o yaml

apiVersion: v1
kind: Endpoints
metadata:
  annotations:
    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"kubernetes-master","leaseDurationSeconds":15,"acquireTime":"2017-02-14T14:05:57Z","renewTime":"2017-02-14T14:14:42Z","leaderTransitions":0}'

...

Regards,

Jerzy

On Tue, Feb 14, 2017 at 2:27 PM, Qian Zhang <zhq5...@gmail.com> wrote:

Hi,

I have a Kubernetes HA cluster which consists of 3 master nodes, each of them has kube-apiserver, kube-scheduler and kube-controller-manager running, and kube-scheduler and kube-controller-manager are started with the option "--leader-elect", my question is, is there a way to tell the current leader of kube-scheduler/kube-controller-manager? E.g., a Kubernetes API to get such info? Or directly get it from etcd?

Thanks,

Qian Zhang

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[Andy Xie]

This should definitely be added to the doc.

在 2017年2月15日星期三 UTC+8下午4:51:35，Qian Zhang写道：

Thanks Jerzy!

Thanks,

Qian Zhang

On Tue, Feb 14, 2017 at 10:18 PM, 'Jerzy Szczepkowski' via Kubernetes user discussion and Q&A <kubernet...@googlegroups.com> wrote:

You can get it from endpoints resource. The endpoint should have an annotation pointing to the leader.

$ kubectl get endpoints kube-controller-manager --namespace=kube-system  -o yaml

apiVersion: v1
kind: Endpoints
metadata:
  annotations:
    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"kubernetes-master","leaseDurationSeconds":15,"acquireTime":"2017-02-14T14:05:57Z","renewTime":"2017-02-14T14:14:42Z","leaderTransitions":0}'

...

Regards,

Jerzy

On Tue, Feb 14, 2017 at 2:27 PM, Qian Zhang <zhq5...@gmail.com> wrote:

Hi,

I have a Kubernetes HA cluster which consists of 3 master nodes, each of them has kube-apiserver, kube-scheduler and kube-controller-manager running, and kube-scheduler and kube-controller-manager are started with the option "--leader-elect", my question is, is there a way to tell the current leader of kube-scheduler/kube-controller-manager? E.g., a Kubernetes API to get such info? Or directly get it from etcd?

Thanks,

Qian Zhang

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[Andy Xie]

As the value for `control-plane.alpha.kubernetes.io/leader` is the output of json marshal. So, you can not just use the kubectl command line `kubectl -s http://APISERVER --namespace=kube-system get endpoints kube-controller-manager -o jsonpaata.annotations.control-plane\.alpha\.kubernetes\.io/leader}'` to extract. But be using `jq` you can do this `kubectl -s http://APISERVER --namespace=kube-system get endpoints kube-controller-manager -o jsonpath='{.metadata.annotations.control-plane\.alpha\.kubernetes\.io/leader}'|jq '.holderIdentity'`

在 2017年7月1日星期六 UTC+8上午3:24:20，Junaid Subhani写道：