How-To

Get started with the Octavia Ingress Controller for Kubernetes

Lingxian Kong, senior developer at Catalyst Cloud, offers this guide.

May 8, 2018
image

This guide explains how to deploy and configure the octavia-ingress-controller in Kubernetes cluster on top of an OpenStack cloud.

What’s an Ingress Controller, anyway?

In Kubernetes, Ingress allows external users and client applications access to HTTP services. Ingress consists of two components:

  • Ingress Resource is a collection of rules for the inbound traffic to reach Services. These are Layer 7 (L7) rules that allow hostnames (and optionally paths) to be directed to specific Services in Kubernetes.
  • Ingress Controller acts on the rules set by the Ingress Resource, typically via an HTTP or L7 load balancer.

It’s vital that both pieces are properly configured to route traffic from an outside client to a Kubernetes Service.

1. Benefits of using the octavia-ingress-controller

As an OpenStack-based public cloud provider, one of our goals at Catalyst Cloud is to continuously provide customers with the capability to innovate by delivering robust and comprehensive cloud services. After deploying Octavia and Magnum services in the public cloud, we’re now thinking about how to help customers to develop their applications running on the Kubernetes cluster and making their services accessible to the public in a high-performance way.

After creating a Kubernetes cluster in Magnum, the most common way to expose the application to the outside world is to use a LoadBalancer service. In the OpenStack cloud, Octavia (LBaaS v2) is the default implementation of LoadBalancer type service, as a result, for each LoadBalancer type service, there is a load balancer created in the cloud tenant account. There are a few drawbacks of this approach:

  • The cost of Kubernetes Service is a little bit high if it’s one-to-one mapping from the service to Octavia load balancer and the customers have to pay for a load balancer per exposed service, which can get expensive.
  • There is no filtering, no routing, etc. for the service. That means you can send almost any kind of traffic to it, like HTTP, TCP, UDP, WebSockets, gRPC, or whatever.
  • The traditional ingress controllers such as the NGINX ingress controller, HAProxy ingress controller, Træfik, etc. don’t make much sense in the cloud environment because the user still needs to expose the service for the ingress controller itself which may increase the network delay and decrease the performance of the application.

The octavia-ingress-controller can solve all of the above problems in an OpenStack environment by creating a single load balancer for multiple NodePort type services in an Ingress. In order to use the octavia-ingress-controller in Kubernetes cluster, use the value openstack for the annotation kubernetes.io/ingress.class in the metadata section of the Ingress Resource as shown below:

annotations: kubernetes.io/ingress.class: openstack

2. How to deploy the octavia-ingress-controller

2.1 Prepare the kubeconfig file

The kubeconfig file is used to configure access to Kubernetes clusters. This is a generic way of referring to configuration files in Kubernetes. The following commands are performed in a Kubernetes cluster created using kubeadm.

  • Install cfssl tools, which are used for generating TLS certs
wget https://pkg.cfssl.org/R1.2/cfssl_linux-amd64 && chmod +x cfssl_linux-amd64 && mv cfssl_linux-amd64 /usr/local/bin/cfssl
wget https://pkg.cfssl.org/R1.2/cfssljson_linux-amd64 && chmod +x cfssljson_linux-amd64 && mv cfssljson_linux-amd64 /usr/local/bin/cfssljson
wget https://pkg.cfssl.org/R1.2/cfssl-certinfo_linux-amd64 && chmod +x cfssl-certinfo_linux-amd64 && mv cfssl-certinfo_linux-amd64 /usr/local/bin/cfssl-certinfo
  • Re-use the CA cert and key in the existing cluster
pushd /etc/kubernetes/pki
cat > ca-config.json <<EOF
{
  "signing": {
    "default": {
      "expiry": "87600h"
    },
    "profiles": {
      "kubernetes": {
        "usages": [
            "signing",
            "key encipherment",
            "server auth",
            "client auth"
        ],
        "expiry": "87600h"
      }
    }
  }
}
EOF
cat > ingress-openstack-csr.json <<EOF
{
  "CN": "octavia-ingress-controller",
  "hosts": [],
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "NZ",
      "ST": "Wellington",
      "L": "Wellington",
      "O": "Catalyst",
      "OU": "Lingxian"
    }
  ]
}
EOF
cfssl gencert -ca=ca.crt -ca-key=ca.key -config=ca-config.json -profile=kubernetes ingress-openstack-csr.json | cfssljson -bare ingress-openstack
# You can take a look at the files generated by cfssl
ls -l | grep ingress-openstack
  • Create a kubeconfig file for the octavia-ingress-controller
ca_data=$(cat ca.crt | base64 | tr -d '\n')
client_cert_data=$(cat ingress-openstack.pem | base64 | tr -d '\n')
client_key_data=$(cat ingress-openstack-key.pem | base64 | tr -d '\n')
cat <<EOF > /etc/kubernetes/ingress-openstack.conf
apiVersion: v1
kind: Config
clusters:
- cluster:
    certificate-authority-data: ${ca_data}
    server: https://${k8s_master_ip}:6443
  name: kubernetes
preferences: {}
users:
- name: octavia-ingress-controller
  user:
    client-certificate-data: ${client_cert_data}
    client-key-data: ${client_key_data}
contexts:
- context:
    cluster: kubernetes
    user: octavia-ingress-controller
  name: octavia-ingress-controller@kubernetes
current-context: octavia-ingress-controller@kubernetes
EOF
popd

2.2 Configure role-based access control (RBAC) for the octavia-ingress-controller user

For testing purpose, grant the cluster-admin role for octavia-ingress-controller as user so that the user has full access to the Kubernetes cluster.

cat <<EOF | kc create -f -
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: octavia-ingress-controller
subjects:
  - kind: User
    name: octavia-ingress-controller
roleRef:
  kind: ClusterRole
  name: cluster-admin
  apiGroup: rbac.authorization.k8s.io
EOF

2.3 Prepare the octavia-ingress-controller service configuration

We need credentials of admin user and a normal user (e.g. demo) in OpenStack.

source openrc_admin
project_id=$(openstack project show demo -c id -f value)
auth_url=$(export | grep OS_AUTH_URL | awk -F'"' '{print $2}')
subnet_id=$(openstack subnet show private-subnet -c id -f value)
public_net_id=$(openstack network show public -c id -f value)
cat <<EOF > /etc/kubernetes/ingress-openstack.yaml
kubernetes:
    kubeconfig: /etc/kubernetes/ingress-openstack.conf
openstack:
    username: demo
    password: password
    project_id: ${project_id}
    auth_url: ${auth_url}/v3
    region: RegionOne
octavia:
    subnet_id: ${subnet_id}
    fip_network: ${public_net_id}
EOF

2.4 Setting up the octavia-ingress-controller service

cat <<EOF > /etc/kubernetes/manifests/octavia-ingress-controller.yaml
---
apiVersion: v1
kind: Pod
metadata:
  annotations:
    scheduler.alpha.kubernetes.io/critical-pod: ""
  labels:
    component: octavia-ingress-controller
    tier: control-plane
  name: octavia-ingress-controller
  namespace: kube-system
spec:
  containers:
    - name: octavia-ingress-controller
      image: lingxiankong/openstack-ingress-controller:0.0.2
      imagePullPolicy: Always
      args:
        - /bin/octavia-ingress-controller
        - --config=/etc/kubernetes/ingress-openstack.yaml
      volumeMounts:
      - mountPath: /etc/kubernetes/ingress-openstack.yaml
        name: ingressconfig
        readOnly: true
      - mountPath: /etc/kubernetes/ingress-openstack.conf
        name: kubeconfig
        readOnly: true
      resources:
        requests:
          cpu: 200m
  hostNetwork: true
  volumes:
  - hostPath:
      path: /etc/kubernetes/ingress-openstack.yaml
      type: FileOrCreate
    name: ingressconfig
  - hostPath:
      path: /etc/kubernetes/ingress-openstack.conf
      type: FileOrCreate
    name: kubeconfig
status: {}
EOF

Wait until the octavia-ingress-controller static pod is up and running.

$ kubectl get pod --all-namespaces | grep octavia-ingress-controller
kube-system   octavia-ingress-controller-lingxian-k8s-master   1/1       Running   0          1m

3. Setting up HTTP load balancing with Ingress

3.1 Create a backend service

Create a simple service (echo hostname) that listens on a HTTP server on port 8080.

$ cat <<EOF | kc create -f -
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: hostname-echo-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: hostname-echo
  template:
    metadata:
      labels:
        app: hostname-echo
    spec:
      containers:
        - image: "lingxiankong/alpine-test"
          imagePullPolicy: Always
          name: hostname-echo-container
          ports:
            - containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: hostname-echo-svc
spec:
  ports:
     -  port: 8080
        protocol: TCP
        targetPort: 8080
  selector:
    app: hostname-echo
  type: NodePort
EOF
$ kubectl get svc
NAME                TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)          AGE
hostname-echo-svc   NodePort    10.106.36.88   <none>        8080:32066/TCP   33s

When you create a Service of type NodePort, Kubernetes makes your Service available on a randomly selected high port number (e.g. 32066) on all the nodes in your cluster. Generally, the Kubernetes nodes are not externally accessible by default, so creating this Service does not make your application accessible from the Internet. However, we can verify the service using its CLUSTER-IP on Kubernetes master node:

$ curl http://10.106.36.88:8080
hostname-echo-deployment-698fd44fc8-jptl2

To make your HTTP web server application publicly accessible, you need to create an Ingress resource.

3.2 Create an Ingress resource

The following command defines an Ingress resource that directs traffic that requests http://api.sample.com/hostname to the hostname-echo Service:

cat <<EOF | kc create -f -
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: test-octavia-ingress
  annotations:
    kubernetes.io/ingress.class: "openstack"
spec:
  rules:
  - host: api.sample.com
    http:
      paths:
      - path: /hostname
        backend:
          serviceName: hostname-echo-svc
          servicePort: 8080
EOF

Kubernetes creates an Ingress resource on your cluster. The octavia-ingress-controller service running in your cluster is responsible for creating/maintaining the corresponding resources in Octavia to route all external HTTP traffic (on port 80) to the hostname-echo NodePort Service you exposed.

Verify that the Ingress Resource has been created. Please note that the IP address for the Ingress Resource will not be defined right away (wait a few moments for the ADDRESS field to get populated):

$ kubectl get ing
NAME                   HOSTS            ADDRESS   PORTS     AGE
test-octavia-ingress   api.sample.com             80        12s
$ # Wait until the ingress gets an IP address
$ kubectl get ing
NAME                   HOSTS            ADDRESS      PORTS     AGE
test-octavia-ingress   api.sample.com   172.24.4.9   80        9m

For testing purposes, log in to a host that has a network connection with the OpenStack cloud. To do that, you need to update /etc/hosts file in the host to resolve api.sample.com to the Ingress IP address, then you should be able to access the backend service by sending HTTP request to the domain name specified in the Ingress Resource:

$ echo "172.24.4.9 api.sample.com" >> /etc/hosts
$ curl http://api.sample.com/hostname
hostname-echo-deployment-698fd44fc8-jptl2

Live demo

You can also see a live demo here or below.

Author Lingxian Kong will be heading up four sessions at the Vancouver Summit, check them out here.

Tags: , , , ,

Lingxian Kong
Latest posts by Lingxian Kong (see all)