没有故障转移/负载平衡器的情况下，使用kubeadm的Kubernetes是否可以实现高可用性？

Question

I am trying to achieve the k8s high availability using kubeadm. I am following the document k8s HA using kubeadm

In the official document, it is recommended to have the failover mechanism/load balancer for the kube-apiserver. I tried keepalived but, in case of setup on aws/gcp instaces, it lands in split brain situation as multicast is not supported and so I am not allowed to use it. Is there any way out for this?

Answer 1

No, you need a loadbalancer to have HA with kubeadm.

If you're using AWS/GCP, why not consider using the native loadbalancers for those environments, like ELB or a Google Cloud Load Balancer?

Answer 2

Kubernetes is a container-orchestration system for automating deployment, scaling, and management of containerized applications. Kubernetes play best in High Available and Load Balancing environments.

As @jaxxstorm mentioned, cloud providers give you a possibility to use native load balancers, and I also suggest it is a good pole position with High Availability attempt. You may be interested in GCP documentation.

Kubeadm on Kubernetes homebrewed environment requires some additional work, and from my point of view, it is good to set up Kubernetes The Hardway then starts to play with Kubeadm .

OK, I assume servers for the installation are ready. To create a not complex installation of multi-master cluster, you need 3 masters node (10.0.0.50-52) and Load Balancer (10.0.0.200) .

Generate token and save the output to file:

kubeadm token generate

Create a kubeadm config file:

apiVersion: kubeadm.k8s.io/v1alpha1
kind: MasterConfiguration
etcd:
  endpoints:
  - "http://10.0.0.50:2379"
  - "http://10.0.0.51:2379"
  - "http://10.0.0.52:2379"
apiServerExtraArgs:
  apiserver-count: "3"
apiServerCertSANs:
- "10.0.0.50"
- "10.0.0.51"
- "10.0.0.52"
- "10.0.0.200"
- "127.0.0.1"
token: "YOUR KUBEADM TOKEN"
tokenTTL: "0"

Copy the config file to all nodes.

Do initialization on the first master instance:

kubeadm init --config /path/to/config.yaml

The new master instance, will have all the certificates and keys necessary for our master cluster.

Copy directory structure /etc/kubernetes/pki to other masters to the same location.

On other master servers:

kubeadm init --config /path/to/config.yaml

Now let's start to set up load balancer:

Copy /etc/kubernetes/admin.conf into $HOME/.kube/config

next, edit $HOME/.config and replace

server:10.0.0.50

with

server:10.0.0.200

Check if nodes are working fine:

kubectl get nodes

On all workers execute:

kubeadm join --token YOUR_CLUSTER_TOKEN 10.0.0.200:6443 --discovery-token-ca-cert-hash sha256:89870e4215b92262c5093b3f4f6d57be8580c3442ed6c8b00b0b30822c41e5b3

And that's it! If everything was setup cleanly, you should now have a highly available cluster.

I found "HA Kubernetes cluster via Kubeadm" tutorial useful, thank you @Nate Baker for inspiration.

Answer 3

您绝对需要nginx / haproxy + keepalived来实现故障转移和高可用性