Heterogeneous Kubernetes cluster on top of OVN

Author: Paulo Pires [email protected]

This document describes, step-by-step, how to provision a Kubernetes cluster comprised of:

One Linux machine acting as Kubernetes master node and OVN central database.
One Linux machine acting as Kubernetes worker node.
One Windows machine acting as Kubernetes worker node.

Many thanks to the great people that helped achieve this, namely:

Alin Serdean (Cloudbase Solutions)
Alin Balutoiu (Cloudbase Solutions)
Feng Min (Google)
Peter Hornyack (Google)
The authors of https://github.com/openvswitch/ovn-kubernetes

TODO

The following items are to be implemented and are not sorted by importance!

Copy CA files from master.
Add other cloud providers documentation, e.g. AWS.
Add gateway node instructions for enabling pod containers Internet access.
Setup OVS TLS.
Add Windows node TLS support.

Requirements

At the time of this writing, the instructions are meant to be run on Google Compute Engine, but apart from gcloud calls and a few networking details, everything detailed below should work regardless of the adopted cloud-provider.

Having that said, here are the requirements:

Use Google Cloud Platform (GCP), namely Google Compute Engine (GCE) VMs.
- gcloud CLI tool
Linux machines(s) run Ubuntu 16.04 with latest updates.
Windows machine(s) run Windows Server 2016 with latest updates.
Administrator access to all VMs, i.e. root in Linux machines.

Master (Linux)

Node set-up

Let's provision the master VM:

gcloud compute instances create "sig-windows-master" \
    --zone "us-east1-d" \
    --machine-type "custom-2-2048" \
    --can-ip-forward \
    --tags "https-server" \
    --image "ubuntu-1604-xenial-v20170125" \
    --image-project "ubuntu-os-cloud" \
    --boot-disk-size "50" \
    --boot-disk-type "pd-ssd" \

When it's ready, SSH into it:

gcloud compute ssh --zone "us-east1-d" "sig-windows-master"

ATTENTION: From now on, it's assumed you're logged-in as root.

Let's install OVS/OVN:

curl -fsSL https://yum.dockerproject.org/gpg | apt-key add -
echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" > sudo tee /etc/apt/sources.list.d/docker.list

apt update
apt install -y docker.io dkms

cd ~
git clone https://github.com/apprenda/kubernetes-ovn-heterogeneous-cluster
cd kubernetes-ovn-heterogeneous-cluster/deb

dpkg -i openvswitch-common_2.6.2-1_amd64.deb \
openvswitch-datapath-dkms_2.6.2-1_all.deb \
openvswitch-switch_2.6.2-1_amd64.deb \
ovn-common_2.6.2-1_amd64.deb \
ovn-central_2.6.2-1_amd64.deb \
ovn-docker_2.6.2-1_amd64.deb \
ovn-host_2.6.2-1_amd64.deb \
python-openvswitch_2.6.2-1_all.deb

We'll need to make sure vport_geneve kernel module is loaded at boot:

echo vport_geneve >> /etc/modules-load.d/modules.conf

Finally, reboot:

reboot

SSH again into the machine and let's proceed.

ATTENTION:

From now on, it's assumed you're logged-in as root.
Pay attention to the environment variables below, particularly:
- LOCAL_IP must be the public IP of this node

Create the OVS bridge interface:

export TUNNEL_MODE=geneve
export LOCAL_IP=10.142.0.2
export MASTER_IP=$LOCAL_IP

ovs-vsctl set Open_vSwitch . external_ids:ovn-remote="tcp:$MASTER_IP:6642" \
  external_ids:ovn-nb="tcp:$MASTER_IP:6641" \
  external_ids:ovn-encap-ip="$LOCAL_IP" \
  external_ids:ovn-encap-type="$TUNNEL_MODE"

ovs-vsctl get Open_vSwitch . external_ids

You should see something like:

{hostname=sig-windows-master.c.apprenda-project-one.internal, ovn-encap-ip="10.142.0.2", ovn-encap-type=geneve, ovn-nb="tcp:10.142.0.2:6641", ovn-remote="tcp:10.142.0.2:6642", system-id="e7af27f6-a218-40bb-8d4f-af67600abd17"}

We are now ready to set-up Kubernetes master node.

Kubernetes set-up

ATTENTION:

From now on, it's assumed you're logged-in as root.
Pay attention to the environment variables below, particularly:
- MASTER_INTERNAL_IP must be an IP within K8S_NODE_POD_SUBNET subnet
- K8S_DNS_SERVICE_IP must be an IP within K8S_SERVICE_SUBNET subnet

cd ~/kubernetes-ovn-heterogeneous-cluster/master

rm -rf tmp
mkdir tmp
cp -R make-certs openssl.cnf kubedns-* manifests systemd tmp/

export HOSTNAME=`hostname`
export K8S_VERSION=1.5.3
export K8S_POD_SUBNET=10.244.0.0/16
export K8S_NODE_POD_SUBNET=10.244.1.0/24
export K8S_SERVICE_SUBNET=10.100.0.0/16
export K8S_API_SERVICE_IP=10.100.0.1
export K8S_DNS_VERSION=1.13.0
export K8S_DNS_SERVICE_IP=10.100.0.10
export K8S_DNS_DOMAIN=cluster.local
export ETCD_VERSION=3.1.1

# The following is needed for now, because OVS can't route from pod network to node.
export MASTER_INTERNAL_IP=10.244.1.2

sed -i"*" "s|__K8S_VERSION__|$K8S_VERSION|g" tmp/manifests/*.yaml
sed -i"*" "s|__K8S_VERSION__|$K8S_VERSION|g" tmp/systemd/kubelet.service

sed -i"*" "s|__ETCD_VERSION__|$ETCD_VERSION|g" tmp/systemd/etcd3.service

sed -i"*" "s|__MASTER_IP__|$MASTER_IP|g" tmp/manifests/*.yaml
sed -i"*" "s|__MASTER_IP__|$MASTER_IP|g" tmp/systemd/kubelet.service
sed -i"*" "s|__MASTER_IP__|$MASTER_IP|g" tmp/openssl.cnf

sed -i"*" "s|__MASTER_INTERNAL_IP__|$MASTER_INTERNAL_IP|g" tmp/manifests/*.yaml

sed -i"*" "s|__HOSTNAME__|$HOSTNAME|g" tmp/manifests/proxy.yaml
sed -i"*" "s|__HOSTNAME__|$HOSTNAME|g" tmp/systemd/kubelet.service
sed -i"*" "s|__HOSTNAME__|$HOSTNAME|g" tmp/make-certs
sed -i"*" "s|__HOSTNAME__|$HOSTNAME|g" tmp/openssl.cnf

sed -i"*" "s|__K8S_API_SERVICE_IP__|$K8S_API_SERVICE_IP|g" tmp/openssl.cnf

sed -i"*" "s|__K8S_POD_SUBNET__|$K8S_POD_SUBNET|g" tmp/manifests/*.yaml
sed -i"*" "s|__K8S_SERVICE_SUBNET__|$K8S_SERVICE_SUBNET|g" tmp/manifests/*.yaml

sed -i"*" "s|__K8S_DNS_SERVICE_IP__|$K8S_DNS_SERVICE_IP|g" tmp/systemd/kubelet.service
sed -i"*" "s|__K8S_DNS_DOMAIN__|$K8S_DNS_DOMAIN|g" tmp/systemd/kubelet.service

sed -i"*" "s|__K8S_DNS_SERVICE_IP__|$K8S_DNS_SERVICE_IP|g" tmp/kubedns-service.yaml
sed -i"*" "s|__K8S_DNS_VERSION__|$K8S_DNS_VERSION|g" tmp/kubedns-deployment.yaml
sed -i"*" "s|__K8S_DNS_DOMAIN__|$K8S_DNS_DOMAIN|g" tmp/*.*

cp -R tmp/systemd/*.service /etc/systemd/system/
systemctl daemon-reload
systemctl enable etcd3
systemctl start etcd3

cd tmp
chmod +x make-certs
./make-certs
cd ..

mkdir -p /etc/kubernetes
cp -R tmp/manifests /etc/kubernetes/

systemctl enable kubelet
systemctl start kubelet

curl -Lskj -o /usr/bin/kubectl https://storage.googleapis.com/kubernetes-release/release/v$K8S_VERSION/bin/linux/amd64/kubectl
chmod +x /usr/bin/kubectl

kubectl config set-cluster default-cluster --server=https://$MASTER_IP --certificate-authority=/etc/kubernetes/tls/ca.pem
kubectl config set-credentials default-admin --certificate-authority=/etc/kubernetes/tls/ca.pem --client-key=/etc/kubernetes/tls/admin-key.pem --client-certificate=/etc/kubernetes/tls/admin.pem
kubectl config set-context local --cluster=default-cluster --user=default-admin
kubectl config use-context local

Attention: the API server will take a minute or more to come up, depending on the CPUs available and networking speed. So, before proceeding make sure the API server came up. Run kubectl get nodes until you see something like:

NAME           STATUS                     AGE
pires-master   Ready,SchedulingDisabled   7s

After making sure the API server is up & running, you need to configure pod networking for this node:

export TOKEN=$(kubectl describe secret $(kubectl get secrets | grep default | cut -f1 -d ' ') | grep -E '^token' | cut -f2 -d':' | tr -d '\t')

ovs-vsctl set Open_vSwitch . \
  external_ids:k8s-api-server="https://$MASTER_IP" \
  external_ids:k8s-api-token="$TOKEN"

ln -fs /etc/kubernetes/tls/ca.pem /etc/openvswitch/k8s-ca.crt

apt install -y python-pip

pip install --upgrade pip

cd ~
git clone https://github.com/openvswitch/ovn-kubernetes
cd ovn-kubernetes

pip install --upgrade --prefix=/usr/local --ignore-installed .

ovn-k8s-overlay master-init \
  --cluster-ip-subnet="$K8S_POD_SUBNET" \
  --master-switch-subnet="$K8S_NODE_POD_SUBNET" \
  --node-name="$HOSTNAME"

systemctl enable ovn-k8s-watcher
systemctl start ovn-k8s-watcher

And deploy Kubernetes DNS:

cd ~/kubernetes-ovn-heterogeneous-cluster/master
kubectl create -f tmp/kubedns-deployment.yaml
kubectl create -f tmp/kubedns-service.yaml

Note though that Kubernetes DNS will only become available when a schedulable Kubernetes node joins the cluster.

By this time, the master node is ready:

kubectl get nodes
kubectl -n kube-system get pods

You should see something like:

NAME                                 READY     STATUS    RESTARTS   AGE
kube-apiserver-10.142.0.2            1/1       Running   0          9m
kube-controller-manager-10.142.0.2   1/1       Running   0          9m
kube-dns-555682531-5pp48             0/3       Pending   0          1m
kube-proxy-10.142.0.2                1/1       Running   0          9m
kube-scheduler-10.142.0.2            1/1       Running   0          9m

Let's proceed to set-up the worker nodes.

Worker (Linux)

Node set-up

Let's provision the Linux worker VM:

gcloud compute instances create "sig-windows-worker-linux" \
    --zone "us-east1-d" \
    --machine-type "custom-2-2048" \
    --can-ip-forward \
    --image "ubuntu-1604-xenial-v20170125" \
    --image-project "ubuntu-os-cloud" \
    --boot-disk-size "50" \
    --boot-disk-type "pd-ssd" \

When it's ready, SSH into it:

gcloud compute ssh --zone "us-east1-d" "sig-windows-worker-linux"

ATTENTION: From now on, it's assumed you're logged-in as root.

Let's install OVS/OVN:

curl -fsSL https://yum.dockerproject.org/gpg | apt-key add -
echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" > sudo tee /etc/apt/sources.list.d/docker.list

apt update
apt install -y docker.io dkms

cd ~
git clone https://github.com/apprenda/kubernetes-ovn-heterogeneous-cluster
cd kubernetes-ovn-heterogeneous-cluster/deb

dpkg -i openvswitch-common_2.6.2-1_amd64.deb \
openvswitch-datapath-dkms_2.6.2-1_all.deb \
openvswitch-switch_2.6.2-1_amd64.deb \
ovn-common_2.6.2-1_amd64.deb \
ovn-central_2.6.2-1_amd64.deb \
ovn-docker_2.6.2-1_amd64.deb \
ovn-host_2.6.2-1_amd64.deb \
python-openvswitch_2.6.2-1_all.deb

We'll need to make sure vport_geneve kernel module is loaded at boot:

echo vport_geneve >> /etc/modules-load.d/modules.conf

Finally, reboot:

reboot

SSH again into the machine, become root and let's proceed.

ATTENTION:

From now on, it's assumed you're logged-in as root.
Pay attention to the environment variables below, particularly:
- LOCAL_IP must be the public IP of this node
- MASTER_IP must be the remote public IP address of the master node

Create the OVS bridge interface:

export TUNNEL_MODE=geneve
export LOCAL_IP=10.142.0.3
export MASTER_IP=10.142.0.2

ovs-vsctl set Open_vSwitch . external_ids:ovn-remote="tcp:$MASTER_IP:6642" \
  external_ids:ovn-nb="tcp:$MASTER_IP:6641" \
  external_ids:ovn-encap-ip="$LOCAL_IP" \
  external_ids:ovn-encap-type="$TUNNEL_MODE"

ovs-vsctl get Open_vSwitch . external_ids

You should see something like:

{hostname=sig-windows-worker-linux-1.c.apprenda-project-one.internal, ovn-encap-ip="10.142.0.3", ovn-encap-type=geneve, ovn-nb="tcp:10.142.0.2:6641", ovn-remote="tcp:10.142.0.2:6642", system-id="c6364c4c-8069-4bfd-ace8-ec701572feb7"}

We are now ready to set-up Kubernetes Linux worker node.

Kubernetes set-up

Attention:

From now on, it's assumed you're logged-in as root.
You must copy the CA keypair that's available in the master node over the following paths:
- /etc/kubernetes/tls/ca.pem
- /etc/kubernetes/tls/ca-key.pem
Pay attention to the environment variables below

cd ~/kubernetes-ovn-heterogeneous-cluster/worker/linux

rm -rf tmp
mkdir tmp
cp -R ../make-certs ../openssl.cnf ../kubeconfig.yaml manifests systemd tmp/

export HOSTNAME=`hostname`
export K8S_VERSION=1.5.3
export K8S_POD_SUBNET=10.244.0.0/16
export K8S_NODE_POD_SUBNET=10.244.2.0/24
export K8S_DNS_SERVICE_IP=10.100.0.10
export K8S_DNS_DOMAIN=cluster.local

sed -i"*" "s|__K8S_VERSION__|$K8S_VERSION|g" tmp/manifests/proxy.yaml
sed -i"*" "s|__K8S_VERSION__|$K8S_VERSION|g" tmp/systemd/kubelet.service

sed -i"*" "s|__MASTER_IP__|$MASTER_IP|g" tmp/manifests/proxy.yaml
sed -i"*" "s|__MASTER_IP__|$MASTER_IP|g" tmp/systemd/kubelet.service
sed -i"*" "s|__MASTER_IP__|$MASTER_IP|g" tmp/openssl.cnf
sed -i"*" "s|__MASTER_IP__|$MASTER_IP|g" tmp/kubeconfig.yaml

sed -i"*" "s|__LOCAL_IP__|$LOCAL_IP|g" tmp/manifests/proxy.yaml
sed -i"*" "s|__LOCAL_IP__|$LOCAL_IP|g" tmp/systemd/kubelet.service
sed -i"*" "s|__LOCAL_IP__|$LOCAL_IP|g" tmp/openssl.cnf

sed -i"*" "s|__HOSTNAME__|$HOSTNAME|g" tmp/manifests/proxy.yaml
sed -i"*" "s|__HOSTNAME__|$HOSTNAME|g" tmp/systemd/kubelet.service
sed -i"*" "s|__HOSTNAME__|$HOSTNAME|g" tmp/make-certs

sed -i"*" "s|__K8S_POD_SUBNET__|$K8S_POD_SUBNET|g" tmp/manifests/proxy.yaml

sed -i"*" "s|__K8S_DNS_SERVICE_IP__|$K8S_DNS_SERVICE_IP|g" tmp/systemd/kubelet.service
sed -i"*" "s|__K8S_DNS_DOMAIN__|$K8S_DNS_DOMAIN|g" tmp/systemd/kubelet.service

cd tmp
chmod +x make-certs
./make-certs
cd ..

cp -R tmp/manifests /etc/kubernetes/

cp tmp/kubeconfig.yaml /etc/kubernetes/

cp -R tmp/systemd/*.service /etc/systemd/system/
systemctl daemon-reload

curl -Lskj -o /usr/bin/kubectl https://storage.googleapis.com/kubernetes-release/release/v$K8S_VERSION/bin/linux/amd64/kubectl
chmod +x /usr/bin/kubectl

kubectl config set-cluster default-cluster --server=https://$MASTER_IP --certificate-authority=/etc/kubernetes/tls/ca.pem
kubectl config set-credentials default-admin --certificate-authority=/etc/kubernetes/tls/ca.pem --client-key=/etc/kubernetes/tls/node-key.pem --client-certificate=/etc/kubernetes/tls/node.pem
kubectl config set-context local --cluster=default-cluster --user=default-admin
kubectl config use-context local

Now, let's configure pod networking for this node:

export TOKEN=$(kubectl describe secret $(kubectl get secrets | grep default | cut -f1 -d ' ') | grep -E '^token' | cut -f2 -d':' | tr -d '\t')

ovs-vsctl set Open_vSwitch . \
  external_ids:k8s-api-server="https://$MASTER_IP" \
  external_ids:k8s-api-token="$TOKEN"

ln -fs /etc/kubernetes/tls/ca.pem /etc/openvswitch/k8s-ca.crt

mkdir -p /opt/cni/bin && cd /opt/cni/bin
curl -Lskj -o cni.tar.gz https://github.com/containernetworking/cni/releases/download/v0.4.0/cni-v0.4.0.tgz
tar zxf cni.tar.gz
rm -f cni.tar.gz

apt install -y python-pip

pip install --upgrade pip

cd ~
git clone https://github.com/openvswitch/ovn-kubernetes
cd ovn-kubernetes

pip install --upgrade --prefix=/usr/local --ignore-installed .

ovn-k8s-overlay minion-init \
  --cluster-ip-subnet="$K8S_POD_SUBNET" \
  --minion-switch-subnet="$K8S_NODE_POD_SUBNET" \
  --node-name="$HOSTNAME"

By this time, your Linux worker node is ready to run Kubernetes workloads:

systemctl enable kubelet
systemctl start kubelet
kubectl get nodes
kubectl -n kube-system get pods

Let's proceed to setup the Windows worker node.

Worker (Windows)

Attention:

Connectivity may flicker and you may need to reconnect your RDP session. This is expected at least a couple times when setting up networking interfaces.
Make sure Windows Server 2016 Routing feature is installed. You can find information on how to do it here and if you're following said instructions make sure you just install the feature as there's no need, nor have we tried, enabling LAN Routing, etc.

For the sake of simplicity when setting up Windows node, we will not be relying on TLS for now.

Node set-up

Let's provision the Windows worker VM:

gcloud compute instances create "sig-windows-worker-windows-1" \
  --zone "us-east1-d" \
  --machine-type "custom-4-4096" \
  --can-ip-forward \
  --image "windows-server-2016-dc-v20170117" \
  --image-project "windows-cloud" \
  --boot-disk-size "50" \
  --boot-disk-type "pd-ssd" \

After VM is provisioned, establish a new connection to it. How one does this is out of the scope of this document.

Now, start a new Powershell session with administrator privileges and execute:

cd \
mkdir ovs
cd ovs

Start-BitsTransfer https://cloudbase.it/downloads/OpenvSwitch_prerelease.msi
Start-BitsTransfer https://cloudbase.it/downloads/k8s_ovn_service_prerelease.zip

cmd /c 'msiexec /i OpenvSwitch_prerelease.msi /qn'

netsh netkvm setparam 0 *RscIPv4 0
netsh netkvm restart 0

Install-Module -Name DockerMsftProvider -Repository PSGallery -Force
Install-Package -Name docker -ProviderName DockerMsftProvider

A reboot is mandatory:

Restart-Computer -Force

Re-establish connection to the VM.

Now, one needs to set-up the overlay (OVN) network. On a per node basis, copy worker/windows/install_ovn.ps1 over to C:\ovs on the Windows node and edit its contents accordingly before running the Powershell script.

Then, start a new Powershell session with administrator privileges and execute:

cd C:\ovs
.\install_ovn.ps1

We are now ready to set-up Kubernetes Windows worker node.

Kubernetes set-up

On a per node basis, copy worker/windows/install_k8s.ps1 over to the Windows node and edit its contents accordingly before running the Powershell script.

Now, let's install Kubernetes:

.\install_k8s.ps1

Attention: While we don't automate Kubernetes components registration as Windows services, one will need to edit the commands below according to the specifics of the cluster in the making.

Run kube-proxy:

New-VMSwitch -Name KubeProxySwitch -SwitchType Internal

cd C:\kubernetes
$env:INTERFACE_TO_ADD_SERVICE_IP = "KubeProxySwitch"
.\kube-proxy.exe -v=3 --proxy-mode=userspace --hostname-override=sig-windows-worker-windows-1 --bind-address=10.142.0.5 --master=http://10.142.0.2:8080 --cluster-cidr=10.244.0.0/16

And the kubelet:

cd C:\kubernetes
$env:CONTAINER_NETWORK = "external"
.\kubelet.exe -v=3 --address=10.142.0.9 --hostname-override=10.142.0.9 --cluster_dns=10.100.0.10 --cluster_domain=cluster.local --pod-infra-container-image="apprenda/pause" --resolv-conf="" --api_servers=http://10.142.0.2:8080

If everything is working, you should see all three nodes and several pods in the output of these kubectl commands:

cd C:\kubernetes
.\kubectl.exe -s 10.142.0.2:8080 get nodes
.\kubectl.exe -s 10.142.0.2:8080 -n kube-system get pods

Troubleshooting

Look in ovn-kubernetes issues first. Some problems we found are:

(Optional) Build packages

OVS/OVN

As root, run:

apt update
apt install -y build-essential fakeroot dkms \
autoconf automake debhelper dh-autoreconf libssl-dev libtool \
python-all python-twisted-conch python-zopeinterface \
graphviz

cd ~
git clone https://github.com/openvswitch/ovs.git
cd ovs
git checkout branch-2.6

dpkg-checkbuilddeps

DEB_BUILD_OPTIONS='nocheck' fakeroot debian/rules binary

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Heterogeneous Kubernetes cluster on top of OVN

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Heterogeneous Kubernetes cluster on top of OVN

TODO

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