Charmed Kubernetes on OpenStack

Charmed Kubernetes will run seamlessly on OpenStack. With the addition of the openstack-integrator, your cluster will also be able to directly use OpenStack native features.

OpenStack integrator

The openstack-integrator charm simplifies working with Charmed Kubernetes on OpenStack. Using the credentials provided to Juju, it acts as a proxy between Charmed Kubernetes and the underlying cloud, granting permissions to dynamically create, for example, Cinder volumes.

Prerequisites

OpenStack integration requires Octavia to be available in the underlying OpenStack cloud, both to support Kubernetes LoadBalancer services and to support creation of a load balancer for the Kubernetes API.

Installing

When installing Charmed Kubernetes using the Juju bundle, you can add the openstack-integrator at the same time by using the following overlay file (download it here):

description: Charmed Kubernetes overlay to add native OpenStack support.
applications:
  openstack-integrator:
    annotations:
      gui-x: "600"
      gui-y: "300"
    charm: openstack-integrator
    num_units: 1
    trust: true
relations:
  - ['openstack-integrator', 'kubernetes-control-plane:openstack']
  - ['openstack-integrator', 'kubernetes-worker:openstack']

To use the overlay with the Charmed Kubernetes bundle, specify it during deploy like this:

juju deploy charmed-kubernetes --overlay ~/path/openstack-overlay.yaml --trust

… and remember to fetch the configuration file!

juju ssh kubernetes-control-plane/leader -- cat config > ~/.kube/config

For more configuration options and details of the permissions which the integrator uses, please see the charm docs.

<span class="p-notification__title">Note:</span>
<p class="p-notification__message">Resources allocated by Kubernetes or the integrator are usually cleaned up automatically when no
longer needed. However, it is recommended to periodically, and particularly after tearing down a
cluster, use the OpenStack administration tools to make sure all unused resources have been
successfully released.</p>

Using Octavia Load Balancers

There are two ways in which Octavia load balancers can be used with Charmed Kubernetes: load balancers automatically created by Kubernetes for Services which sit in front of Pods and are defined with type=LoadBalancer, and as a replacement for the load balancer in front of the API server itself.

In either case, the load balancers can optionally have floating IPs (FIPs) attached to them to allow for external access.

<span class="p-notification__title">Note:</span>
<p class="p-notification__message">For security reasons, the security groups automatically managed by Juju will not by default allow
traffic into the nodes from external networks which can otherwise reach the FIPs. The easiest way to
allow this is to add a rule to the model security group (named `juju-<model UUID>`) to allow ingress traffic
from the FIP network, according to your security and network traffic policy and needs.
Alternatively, you could create a separate security group to manage the rule(s) across multiple models or
controllers.<br/>
<br/>
Configuring or creating a security group will also be necessary if you wish to have the Amphora instances in a
different subnet from the node instances, since you will need to allow at least traffic on the
NodePort range (30000-32767) from the Amphorae into the nodes.</p>

LoadBalancer-type Pod Services

To use Octavia for LoadBalancer type services in the cluster, you will also need to set the subnet-id config to the appropriate tenant subnet where your nodes reside, and if desired, the floating-network-id config to whatever network you want FIPs created in. See the Charm config docs for more details.

As an example of this usage, this will create a simple application, scale it to five pods, and expose it with a LoadBalancer-type Service:

kubectl create deployment hello-world --image=gcr.io/google-samples/node-hello:1.0
kubectl scale deployment hello-world --replicas=5
kubectl expose deployment hello-world --type=LoadBalancer --name=hello --port 8080

You can verify that the application and replicas have been created with:

kubectl get deployments hello-world

Which should return output similar to:

NAME              READY   UP-TO-DATE   AVAILABLE   AGE
hello-world      5/5               5                            5             2m38s

To check that the service is running correctly:

kubectl get service hello

…which should return output similar to:

NAME    TYPE           CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
hello   LoadBalancer   10.152.183.136   202.49.242.3  8080:32662/TCP   2m

You can see that the External IP is now in front of the five endpoints of the example deployment. You can test the ingress address:

curl  http://202.49.242.3:8080

Hello Kubernetes!

API Server Load Balancer

If desired, the openstack-integrator can also replace kubeapi-load-balancer and create a native OpenStack load balancer for the Kubernetes API server, which simplifies the model and is properly HA, which kubeapi-load-balancer on its own is not. To enable this, use this overlay instead (download it here):

applications:
  kubeapi-load-balancer: null
  openstack-integrator:
    annotations:
      gui-x: "600"
      gui-y: "300"
    charm: openstack-integrator
    num_units: 1
    trust: true
relations:
  - ['openstack-integrator', 'kubernetes-control-plane:loadbalancer']
  - ['openstack-integrator', 'kubernetes-control-plane:openstack']
  - ['openstack-integrator', 'kubernetes-worker:openstack']

You will also need to set the lb-subnet config to the appropriate tenant subnet where your nodes reside, and if desired, the lb-floating-network config to whatever network you want the FIP created in. See the Charm config docs for more details.

Using Cinder Volumes

Many pods you may wish to deploy will require storage. Although you can use any type of storage supported by Kubernetes (see the storage documentation), you also have the option to use Cinder storage volumes, if supported by your OpenStack.

A cdk-cinder storage class will be automatically created when the integrator is used. This storage class can then be used when creating a Persistent Volume Claim:

kubectl create -f - <<EOY
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: testclaim
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi
  storageClassName: cdk-cinder
EOY

This should finish with a confirmation. You can check the current PVCs with:

kubectl get pvc

…which should return something similar to:

NAME        STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
testclaim   Bound    pvc-54a94dfa-3128-11e9-9c54-028fdae42a8c   1Gi        RWO            cinder         9s

This PVC can then be used by pods operating in the cluster. As an example, the following deploys a busybox pod:

kubectl create -f - <<EOY
apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: default
spec:
  containers:
    - image: busybox
      command:
        - sleep
        - "3600"
      imagePullPolicy: IfNotPresent
      name: busybox
      volumeMounts:
        - mountPath: "/pv"
          name: testvolume
  restartPolicy: Always
  volumes:
    - name: testvolume
      persistentVolumeClaim:
        claimName: testclaim
EOY

Using Keystone Authentication / Authorisation

The openstack-integrator also provides an interface for authentication and authorisation using Keystone. This is covered in detail in the Keystone and LDAP documentation.

Upgrading the integrator charm

The openstack-integrator is not specifically tied to the version of Charmed Kubernetes installed and may generally be upgraded at any time with the following command:

juju refresh openstack-integrator

Troubleshooting

If you have any specific problems with the openstack-integrator, you can report bugs on Launchpad.

For logs of what the charm itself believes the world to look like, you can use Juju to replay the log history for that specific unit:

juju debug-log --replay --include openstack-integrator/0