website/content/en/docs/setup/independent/high-availability.md at release-1.10

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Mario Kleinsasser 9ca357177d Add missing "Set up master Load Balancer" heading (#9219 )

This heading is missing in the 1.10 documentations which makes it hard to find the needed information because the anchor  `setting up a master load balancer` points to nowhere. This was working in the 1.19 documentation and it was really useful.

2018-06-25 06:32:03 -07:00

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Creating HA clusters with kubeadm

templates/task

This guide shows you how to install and set up a highly available Kubernetes cluster using kubeadm.

This document shows you how to perform setup tasks that kubeadm doesn't perform: provision hardware; configure multiple systems; and load balancing.

{{< note >}} Note: This guide is only one potential solution, and there are many ways to configure a highly available cluster. If a better solution works for you, please use it. If you find a better solution that can be adopted by the community, feel free to contribute it back. {{< /note >}}

Three machines that meet kubeadm's minimum requirements for the masters
Three machines that meet kubeadm's minimum requirements for the workers
Optional: At least three machines that meet kubeadm's minimum requirements if you intend to host etcd on dedicated nodes (see information below)
1GB or more of RAM per machine (any less will leave little room for your apps)
Full network connectivity between all machines in the cluster (public or private network is fine)

Installing prerequisites on masters

For each master that has been provisioned, follow the installation guide on how to install kubeadm and its dependencies. At the end of this step, you should have all the dependencies installed on each master.

Setting up an HA etcd cluster

For highly available setups, you will need to decide how to host your etcd cluster. A cluster is composed of at least 3 members. We recommend one of the following models:

Hosting etcd cluster on separate compute nodes (Virtual Machines)
Hosting etcd cluster on the master nodes.

While the first option provides more performance and better hardware isolation, it is also more expensive and requires an additional support burden.

For Option 1: create 3 virtual machines that follow CoreOS's hardware recommendations. For the sake of simplicity, we will refer to them as etcd0, etcd1 and etcd2.

For Option 2: you can skip to the next step. Any reference to etcd0, etcd1 and etcd2 throughout this guide should be replaced with master0, master1 and master2 accordingly, since your master nodes host etcd.

Create etcd CA certs

Install cfssl and cfssljson on all etcd nodes:

curl -o /usr/local/bin/cfssl https://pkg.cfssl.org/R1.2/cfssl_linux-amd64
curl -o /usr/local/bin/cfssljson https://pkg.cfssl.org/R1.2/cfssljson_linux-amd64
chmod +x /usr/local/bin/cfssl*

SSH into etcd0 and run the following:

mkdir -p /etc/kubernetes/pki/etcd
cd /etc/kubernetes/pki/etcd

cat >ca-config.json <<EOF
{
  "signing": {
      "default": {
          "expiry": "43800h"
      },
      "profiles": {
          "server": {
              "expiry": "43800h",
              "usages": [
                  "signing",
                  "key encipherment",
                  "server auth",
                  "client auth"
              ]
          },
          "client": {
              "expiry": "43800h",
              "usages": [
                  "signing",
                  "key encipherment",
                  "client auth"
              ]
          },
          "peer": {
              "expiry": "43800h",
              "usages": [
                  "signing",
                  "key encipherment",
                  "server auth",
                  "client auth"
              ]
          }
      }
  }
}
EOF

cat >ca-csr.json <<EOF
{
   "CN": "etcd",
   "key": {
       "algo": "rsa",
       "size": 2048
   }
}
EOF

{{< note >}}Optional: You can modify ca-csr.json to add a section for names. See the CFSSL wiki for an example. {{< /note >}}

Next, generate the CA certs:

cfssl gencert -initca ca-csr.json | cfssljson -bare ca -

Generate etcd client certs

Generate the client certificates. While on etcd0, run the following:

cat >client.json <<EOF
{
  "CN": "client",
  "key": {
      "algo": "ecdsa",
      "size": 256
  }
}
EOF

cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=client client.json | cfssljson -bare client

Both client.pem and client-key.pem are created.

Create SSH access

In order to copy certs between machines, you must enable SSH access for scp.

First, open new tabs in your shell for etcd1 and etcd2. Ensure you are SSHed into all three machines and then run the following (it will be a lot quicker if you use tmux syncing - to do this in iTerm enter cmd+shift+i):
```
export PEER_NAME=$(hostname)
export PRIVATE_IP=$(ip addr show eth1 | grep -Po 'inet \K[\d.]+')
```
Make sure that eth1 corresponds to the network interface for the IPv4 address of the private network. This might vary depending on your networking setup, so please check by running echo $PRIVATE_IP before continuing.
Next, generate some SSH keys for the boxes:
```
ssh-keygen -t rsa -b 4096 -C "<email>"
```
Make sure to replace <email> with your email, a placeholder, or an empty string. Keep hitting enter until files exist in ~/.ssh.
Output the contents of the public key file for etcd1 and etcd2:
```
cat ~/.ssh/id_rsa.pub
```
Finally, copy the output for each and paste them into etcd0's ~/.ssh/authorized_keys file. This will permit etcd1 and etcd2 to SSH in to the machine.

Generate etcd server and peer certs

In order to generate certs, each etcd machine needs the root CA generated by etcd0. On etcd1 and etcd2, run the following:

mkdir -p /etc/kubernetes/pki/etcd
cd /etc/kubernetes/pki/etcd
scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/ca.pem .
scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/ca-key.pem .
scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/client.pem .
scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/client-key.pem .
scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/ca-config.json .

Where <etcd0-ip-address> corresponds to the public or private IPv4 of etcd0.

Once this is done, run the following on all etcd machines:

cfssl print-defaults csr > config.json
sed -i '0,/CN/{s/example\.net/'"$PEER_NAME"'/}' config.json
sed -i 's/www\.example\.net/'"$PRIVATE_IP"'/' config.json
sed -i 's/example\.net/'"$PEER_NAME"'/' config.json

cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=server config.json | cfssljson -bare server
cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=peer config.json | cfssljson -bare peer

The above will replace the default configuration with your machine's hostname as the peer name, and its IP addresses. Make sure these are correct before generating the certs. If you found an error, reconfigure config.json and re-run the cfssl commands.

This results in the following files: peer.pem, peer-key.pem, server.pem, server-key.pem.

{{% tab name="Choose one..." %}} Please select one of the tabs to see installation instructions for the respective way to set up a virtual IP. {{% /tab %}} {{% tab name="systemd" %}}

First, install etcd binaries:
```
export ETCD_VERSION="v3.1.12" 
curl -sSL https://github.com/coreos/etcd/releases/download/${ETCD_VERSION}/etcd-${ETCD_VERSION}-linux-amd64.tar.gz | tar -xzv --strip-components=1 -C /usr/local/bin/
```
It is worth noting that etcd v3.1.12 is the preferred version for Kubernetes v1.10. For other versions of Kubernetes please consult the changelog.

Also, please realize that most distributions of Linux already have a version of etcd installed, so you will be replacing the system default.

Next, generate the environment file that systemd will use:

touch /etc/etcd.env
echo "PEER_NAME=${PEER_NAME}" >> /etc/etcd.env
echo "PRIVATE_IP=${PRIVATE_IP}" >> /etc/etcd.env

Now copy the systemd unit file:

cat >/etc/systemd/system/etcd.service <<EOF
[Unit]
Description=etcd
Documentation=https://github.com/coreos/etcd
Conflicts=etcd.service
Conflicts=etcd2.service

[Service]
EnvironmentFile=/etc/etcd.env
Type=notify
Restart=always
RestartSec=5s
LimitNOFILE=40000
TimeoutStartSec=0

ExecStart=/usr/local/bin/etcd --name <name> --data-dir /var/lib/etcd --listen-client-urls https://<etcd-listen-ip>:2379 --advertise-client-urls https://<etcd-listen-ip>:2379 --listen-peer-urls https://<etcd-listen-ip>:2380 --initial-advertise-peer-urls https://<etcd-listen-ip>:2380 --cert-file=/etc/kubernetes/pki/etcd/server.pem --key-file=/etc/kubernetes/pki/etcd/server-key.pem --client-cert-auth --trusted-ca-file=/etc/kubernetes/pki/etcd/ca.pem --peer-cert-file=/etc/kubernetes/pki/etcd/peer.pem --peer-key-file=/etc/kubernetes/pki/etcd/peer-key.pem --peer-client-cert-auth --peer-trusted-ca-file=/etc/kubernetes/pki/etcd/ca.pem --initial-cluster <etcd0>=https://<etcd0-ip-address>:2380,<etcd1>=https://<etcd1-ip-address>:2380,<etcd2>=https://<etcd2-ip-address>:2380 --initial-cluster-token my-etcd-token --initial-cluster-state new

[Install]
WantedBy=multi-user.target
EOF

Make sure you replace <etcd0-ip-address>, <etcd1-ip-address> and <etcd2-ip-address> with the appropriate IPv4 addresses. Replace <name> with the name of this etcd member. Replace <etcd-listen-ip> with the IPv4 address of this etcd node. Replace <etcd0>, <etcd1> and <etcd2> with real hostnames of each machine. These machines must be able to reach each other using DNS or by adding records to /etc/hosts.

Finally, launch etcd:

systemctl daemon-reload
systemctl start etcd

Check that it launched successfully:
```
systemctl status etcd
```

{{% /tab %}} {{% tab name="Static Pods" %}} Note: This is only supported on nodes that have the all dependencies for the kubelet installed. If you are hosting etcd on the master nodes, this has already been set up. If you are hosting etcd on dedicated nodes, you should either use systemd or run the installation guide on each dedicated etcd machine.

Run the following to generate the manifest file:

  cat >/etc/kubernetes/manifests/etcd.yaml <<EOF
  apiVersion: v1
  kind: Pod
  metadata:
    labels:
      component: etcd
      tier: control-plane
    name: <name>
    namespace: kube-system
  spec:
    containers:
    - command:
      - etcd --name <name> 
      - --data-dir /var/lib/etcd 
      - --listen-client-urls https://<etcd-listen-ip>:2379 
      - --advertise-client-urls https://<etcd-listen-ip>:2379 
      - --listen-peer-urls https://<etcd-listen-ip>:2380 
      - --initial-advertise-peer-urls https://<etcd-listen-ip>:2380 
      - --cert-file=/certs/server.pem 
      - --key-file=/certs/server-key.pem 
      - --client-cert-auth 
      - --trusted-ca-file=/certs/ca.pem 
      - --peer-cert-file=/certs/peer.pem 
      - --peer-key-file=/certs/peer-key.pem 
      - --peer-client-cert-auth 
      - --peer-trusted-ca-file=/certs/ca.pem 
      - --initial-cluster etcd0=https://<etcd0-ip-address>:2380,etcd1=https://<etcd1-ip-address>:2380,etcd2=https://<etcd2-ip-address>:2380 
      - --initial-cluster-token my-etcd-token 
      - --initial-cluster-state new
      image: k8s.gcr.io/etcd-amd64:3.1.10
      livenessProbe:
        httpGet:
          path: /health
          port: 2379
          scheme: HTTP
        initialDelaySeconds: 15
        timeoutSeconds: 15
      name: etcd
      env:
      - name: PUBLIC_IP
        valueFrom:
          fieldRef:
          fieldPath: status.hostIP
      - name: PRIVATE_IP
        valueFrom:
          fieldRef:
            fieldPath: status.podIP
      - name: PEER_NAME
        valueFrom:
          fieldRef:
            fieldPath: metadata.name
      volumeMounts:
      - mountPath: /var/lib/etcd
        name: etcd
      - mountPath: /certs
        name: certs
  hostNetwork: true
  volumes:
  - hostPath:
      path: /var/lib/etcd
      type: DirectoryOrCreate
    name: etcd
  - hostPath:
      path: /etc/kubernetes/pki/etcd
    name: certs
  EOF

Make sure you replace:

<name> with the name of the node you're running on (for example, etcd0, etcd1 or etcd2)
<etcd-listen-ip> with the public IPv4 address of the node you're running on
<etcd0-ip-address>, <etcd1-ip-address> and <etcd2-ip-address> with the public IPv4s of the other machines that host etcd.

Set up master Load Balancer

{{% tab name="Choose one..." %}} Please select one of the tabs to see installation instructions for the respective way to set up a virtual IP. {{% /tab %}} {{% tab name="Cloud" %}} Some examples of cloud provider solutions are:

You will need to ensure that the load balancer routes to just master0 on port 6443. This is because kubeadm will perform health checks using the load balancer IP. Since master0 is set up individually first, the other masters will not have running apiservers, which will result in kubeadm hanging indefinitely.

If possible, use a smart load balancing algorithm like "least connections", and use health checks so unhealthy nodes can be removed from circulation. Most providers will provide these features. {{% /tab %}} {{% tab name="On-Site" %}} In an on-site environment there may not be a physical load balancer available. Instead, a virtual IP pointing to a healthy master node can be used. There are a number of solutions for this including keepalived, Pacemaker and probably many others, some with and some without load balancing.

As an example we outline a simple setup based on keepalived. Depending on environment and requirements people may prefer different solutions. The configuration shown here provides an active/passive failover without load balancing. If required, load balancing can by added quite easily by setting up HAProxy, NGINX or similar on the master nodes (not covered in this guide).

Install keepalived, e.g. using your distribution's package manager. The configuration shown here works with version 1.3.5 but is expected to work with may other versions. Make sure to have it enabled (chkconfig, systemd, ...) so that it starts automatically when the respective node comes up.
Create the following configuration file /etc/keepalived/keepalived.conf on all master nodes:
```
! Configuration File for keepalived
global_defs {
 router_id LVS_DEVEL
}

vrrp_script check_apiserver {
 script "/etc/keepalived/check_apiserver.sh"
 interval 3
 weight -2
 fall 10
 rise 2
}

vrrp_instance VI_1 {
   state <STATE>
   interface <INTERFACE>
   virtual_router_id 51
   priority <PRIORITY>
   authentication {
       auth_type PASS
       auth_pass 4be37dc3b4c90194d1600c483e10ad1d
   }
   virtual_ipaddress {
       <VIRTUAL-IP>
   }
   track_script {
       check_apiserver
   }
}
```
In the section vrrp_instance VI_1, change the following lines depending on your setup:
- state is either MASTER (on the first master nodes) or BACKUP (the other master nodes).
- interface is the name of an existing public interface to bind the virtual IP to (usually the primary interface).
- priority should be higher for the first master node, e.g. 101, and lower for the others, e.g. 100.
- auth_pass use any random string here.
- virtual_ipaddresses should contain the virtual IP for the master nodes.

Install the following health check script to /etc/keepalived/check_apiserver.sh on all master nodes:

#!/bin/sh

errorExit() {
   echo "*** $*" 1>&2
   exit 1
}

curl --silent --max-time 2 --insecure https://localhost:6443/ -o /dev/null || errorExit "Error GET https://localhost:6443/"
if ip addr | grep -q <VIRTUAL-IP>; then
   curl --silent --max-time 2 --insecure https://<VIRTUAL-IP>:6443/ -o /dev/null || errorExit "Error GET https://<VIRTUAL-IP>:6443/"
fi

Replace the <VIRTUAL-IP> by your chosen virtual IP.

Restart keepalived. While no Kubernetes services are up yet it will log health check fails on all master nodes. This will stop as soon as the first master node has been bootstrapped. {{% /tab %}} {{< /tabs >}}

Acquire etcd certs

Only follow this step if your etcd is hosted on dedicated nodes (Option 1). If you are hosting etcd on the masters (Option 2), you can skip this step since you've already generated the etcd certificates on the masters.

Generate SSH keys for each of the master nodes by following the steps in the create ssh access section. After doing this, each master will have an SSH key in ~/.ssh/id_rsa.pub and an entry in etcd0's ~/.ssh/authorized_keys file.

Run the following:

mkdir -p /etc/kubernetes/pki/etcd
scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/ca.pem /etc/kubernetes/pki/etcd
scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/client.pem /etc/kubernetes/pki/etcd
scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/client-key.pem /etc/kubernetes/pki/etcd

Run kubeadm init on master0

In order for kubeadm to run, you first need to write a configuration file:

  cat >config.yaml <<EOF
  apiVersion: kubeadm.k8s.io/v1alpha1
  kind: MasterConfiguration
  api:
    advertiseAddress: <virtual-ip>
    controlPlaneEndpoint: <virtual-ip>
  etcd:
    endpoints:
    - https://<etcd0-ip-address>:2379
    - https://<etcd1-ip-address>:2379
    - https://<etcd2-ip-address>:2379
    caFile: /etc/kubernetes/pki/etcd/ca.pem
    certFile: /etc/kubernetes/pki/etcd/client.pem
    keyFile: /etc/kubernetes/pki/etcd/client-key.pem
  networking:
    podSubnet: <podCIDR>
  apiServerCertSANs:
  - <virtual-ip>
  - <private-ip>
  apiServerExtraArgs:
    apiserver-count: "3"
  EOF

Ensure that the following placeholders are replaced:

<private-ip> with the private IPv4 of the master server.
<etcd0-ip>, <etcd1-ip> and <etcd2-ip> with the IP addresses of your three etcd nodes
<podCIDR> with your Pod CIDR. Please read the CNI network section of the docs for more information. Some CNI providers do not require a value to be set.
<virtual-ip> with the virtual IP. Please read setting up a master load balancer section of the docs for more information.

{{< note >}}Note: If you are using Kubernetes 1.9+, you can replace the apiserver-count: 3 extra argument with endpoint-reconciler-type: lease. For more information, see the documentation.{{< /note >}}

When this is done, run kubeadm:
```
kubeadm init --config=config.yaml
```

Run kubeadm init on master1 and master2

Before running kubeadm on the other masters, you need to first copy the K8s CA cert from master0. To do this, you have two options:

Option 1: Copy with scp

Follow the steps in the create ssh access section, but instead of adding to etcd0's authorized_keys file, add them to master0.

Once you've done this, run:

scp root@<master0-ip-address>:/etc/kubernetes/pki/* /etc/kubernetes/pki
rm /etc/kubernetes/pki/apiserver*

Option 2: Copy paste

Copy the contents of /etc/kubernetes/pki/ca.crt, /etc/kubernetes/pki/ca.key, /etc/kubernetes/pki/sa.key and /etc/kubernetes/pki/sa.pub and create these files manually on master1 and master2.

When this is done, you can follow the previous step to install the control plane with kubeadm.

Add master1 and master2 to load balancer

Once kubeadm has provisioned the other masters, you can add them to the load balancer pool.

Install CNI network

Follow the instructions here to install the pod network. Make sure this corresponds to whichever pod CIDR you provided in the master configuration file.

Install workers

Next provision and set up the worker nodes. To do this, you will need to provision at least 3 Virtual Machines.

To configure the worker nodes, follow the same steps as non-HA workloads.

Configure workers

Reconfigure kube-proxy to access kube-apiserver via the load balancer:

kubectl get configmap -n kube-system kube-proxy -o yaml > kube-proxy-cm.yaml
sed -i 's#server:.*#server: https://<masterLoadBalancerFQDN>:6443#g' kube-proxy-cm.yaml
kubectl apply -f kube-proxy-cm.yaml --force
# restart all kube-proxy pods to ensure that they load the new configmap
kubectl delete pod -n kube-system -l k8s-app=kube-proxy

Reconfigure the kubelet to access kube-apiserver via the load balancer:

sudo sed -i 's#server:.*#server: https://<masterLoadBalancerFQDN>:6443#g' /etc/kubernetes/kubelet.conf
sudo systemctl restart kubelet

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Installing prerequisites on masters

Setting up an HA etcd cluster

Create etcd CA certs

Generate etcd client certs

Create SSH access

Generate etcd server and peer certs

{{< tabs name="etcd_mode" >}}

Set up master Load Balancer

{{< tabs name="lb_mode" >}}

Acquire etcd certs

Run kubeadm init on master0

Run kubeadm init on master1 and master2

Option 1: Copy with scp

Option 2: Copy paste

Add master1 and master2 to load balancer

Install CNI network

Install workers

Configure workers

23 KiB Raw Permalink Blame History

Installing prerequisites on masters

Setting up an HA etcd cluster

Create etcd CA certs

Generate etcd client certs

Create SSH access

Generate etcd server and peer certs

{{< tabs name="etcd_mode" >}}

Set up master Load Balancer

{{< tabs name="lb_mode" >}}

Acquire etcd certs

Run kubeadm init on master0

Run kubeadm init on master1 and master2

Option 1: Copy with scp

Option 2: Copy paste

Add master1 and master2 to load balancer

Install CNI network

Install workers

Configure workers

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