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Set up an HA Cluster Using a Load Balancer

You can set up a single-master Kubernetes cluster with KubeSphere installed based on the tutorial of Multi-node Installation. Single-master clusters may be sufficient for development and testing in most cases. For a production environment, however, you need to consider the high availability of the cluster. If key components (for example, kube-apiserver, kube-scheduler, and kube-controller-manager) are all running on the same master node, Kubernetes and KubeSphere will be unavailable once the master node goes down. Therefore, you need to set up a high-availability cluster by provisioning load balancers with multiple master nodes. You can use any cloud load balancer, or any hardware load balancer (for example, F5). In addition, Keepalived and HAproxy, or Nginx is also an alternative for creating high-availability clusters.

This tutorial demonstrates the general configurations of a high-availability cluster as you install KubeSphere on Linux.

Architecture

Make sure you have prepared six Linux machines before you begin, with three of them serving as master nodes and the other three as worker nodes. The following image shows details of these machines, including their private IP address and role. For more information about system and network requirements, see Multi-node Installation.

ha-architecture

Configure a Load Balancer

You must create a load balancer in your environment to listen (also known as listeners on some cloud platforms) on key ports. Here is a table of recommended ports that need to be listened on.

ServiceProtocolPort
apiserverTCP6443
ks-consoleTCP30880
httpTCP80
httpsTCP443

Note

  • Make sure your load balancer at least listens on the port of apiserver.

  • You may need to open ports in your security group to ensure external traffic is not blocked depending on where your cluster is deployed. For more information, see Port Requirements.

  • You can configure both internal and external load balancers on some cloud platforms. After assigning a public IP address to the external load balancer, you can use the IP address to access the cluster.

  • For more information about how to configure load balancers, see Installing on Public Cloud to see specific steps on major public cloud platforms.

Download KubeKey

Kubekey is the next-gen installer which provides an easy, fast and flexible way to install Kubernetes and KubeSphere. Follow the steps below to download KubeKey.

Download KubeKey from its GitHub Release Page or use the following command directly.

curl -sfL https://get-kk.kubesphere.io | VERSION=v1.1.1 sh -

Run the following command first to make sure you download KubeKey from the correct zone.

export KKZONE=cn

Run the following command to download KubeKey:

curl -sfL https://get-kk.kubesphere.io | VERSION=v1.1.1 sh -

Note

After you download KubeKey, if you transfer it to a new machine also with poor network connections to Googleapis, you must run export KKZONE=cn again before you proceed with the steps below.

Note

The commands above download the latest release (v1.1.1) of KubeKey. You can change the version number in the command to download a specific version.

Make kk executable:

chmod +x kk

Create an example configuration file with default configurations. Here Kubernetes v1.20.4 is used as an example.

./kk create config --with-kubesphere v3.1.1 --with-kubernetes v1.20.4

Note

  • Recommended Kubernetes versions for KubeSphere v3.1.1: v1.17.9, v1.18.8, v1.19.8, and v1.20.4. If you do not specify a Kubernetes version, KubeKey will install Kubernetes v1.19.8 by default. For more information about supported Kubernetes versions, see Support Matrix.

  • If you do not add the flag --with-kubesphere in the command in this step, KubeSphere will not be deployed unless you install it using the addons field in the configuration file or add this flag again when you use ./kk create cluster later.

  • If you add the flag --with-kubesphere without specifying a KubeSphere version, the latest version of KubeSphere will be installed.

Deploy KubeSphere and Kubernetes

After you run the commands above, a configuration file config-sample.yaml will be created. Edit the file to add machine information, configure the load balancer and more.

Note

The file name may be different if you customize it.

config-sample.yaml example

spec:
  hosts:
  - {name: master1, address: 192.168.0.2, internalAddress: 192.168.0.2, user: ubuntu, password: Testing123}
  - {name: master2, address: 192.168.0.3, internalAddress: 192.168.0.3, user: ubuntu, password: Testing123}
  - {name: master3, address: 192.168.0.4, internalAddress: 192.168.0.4, user: ubuntu, password: Testing123}
  - {name: node1, address: 192.168.0.5, internalAddress: 192.168.0.5, user: ubuntu, password: Testing123}
  - {name: node2, address: 192.168.0.6, internalAddress: 192.168.0.6, user: ubuntu, password: Testing123}
  - {name: node3, address: 192.168.0.7, internalAddress: 192.168.0.7, user: ubuntu, password: Testing123}
  roleGroups:
    etcd:
    - master1
    - master2
    - master3
    master:
    - master1
    - master2
    - master3
    worker:
    - node1
    - node2
    - node3

For more information about different fields in this configuration file, see Kubernetes Cluster Configurations and Multi-node Installation.

Configure the load balancer

## Public LB config example
## apiserver_loadbalancer_domain_name: "lb.kubesphere.local"
  controlPlaneEndpoint:
    domain: lb.kubesphere.local
    address: "192.168.0.xx"
    port: "6443"

Note

  • The address and port should be indented by two spaces in config-sample.yaml.
  • In most cases, you need to provide the private IP address of the load balancer for the field address. However, different cloud providers may have different configurations for load balancers. For example, if you configure a Server Load Balancer (SLB) on Alibaba Cloud, the platform assigns a public IP address to the SLB, which means you need to specify the public IP address for the field address.
  • The domain name of the load balancer is lb.kubesphere.local by default for internal access.

Persistent storage plugin configurations

For a production environment, you need to prepare persistent storage and configure the storage plugin (for example, CSI) in config-sample.yaml to define which storage service you want to use. For more information, see Persistent Storage Configurations.

Enable pluggable components (Optional)

KubeSphere has decoupled some core feature components since v2.1.0. These components are designed to be pluggable which means you can enable them either before or after installation. By default, KubeSphere will be installed with the minimal package if you do not enable them.

You can enable any of them according to your demands. It is highly recommended that you install these pluggable components to discover the full-stack features and capabilities provided by KubeSphere. Make sure your machines have sufficient CPU and memory before enabling them. See Enable Pluggable Components for details.

Start installation

After you complete the configuration, you can execute the following command to start the installation:

./kk create cluster -f config-sample.yaml

Verify installation

  1. Run the following command to inspect the logs of installation.

    kubectl logs -n kubesphere-system $(kubectl get pod -n kubesphere-system -l app=ks-install -o jsonpath='{.items[0].metadata.name}') -f
    
  2. When you see the following message, it means your HA cluster is successfully created.

    #####################################################
    ###              Welcome to KubeSphere!           ###
    #####################################################
       
    Console: http://192.168.0.3:30880
    Account: admin
    Password: [email protected]
       
    NOTES:
      1. After you log into the console, please check the
         monitoring status of service components in
         the "Cluster Management". If any service is not
         ready, please wait patiently until all components
         are up and running.
      2. Please change the default password after login.
       
    #####################################################
    https://kubesphere.io             2020-xx-xx xx:xx:xx
    #####################################################
    

Thanks for the feedback. If you have a specific question about how to use KubeSphere, ask it on Slack. Open an issue in the GitHub repo if you want to report a problem or suggest an improvement.