The Charmed Distribution of Kubernetes

Overview

This is a scaled-out Kubernetes cluster composed of the following components and features:

• Multiple Kubernetes master and worker nodes
• Load balancer for master nodes
• Multi-node etcd cluster
• Intra-node TLS by default
• Flannel CNI plugin
• Ingress controller
• Dashboard addon with Heapster for metrics

For a more minimal cluster suitable for development and testing, deploy the smaller
kubernetes-core bundle via conjure-up kubernetes-core.

Usage

Installation has been automated via conjure-up:

sudo snap install conjure-up --classic
conjure-up charmed-kubernetes

Conjure-up will prompt you for deployment options (AWS, GCE, Azure, etc.) and credentials.

Proxy configuration

If you are deploying the Charmed Distribution of Kubernetes behind a proxy
(i.e., your charms are running in a limited-egress environment and can not
reach IP addresses external to their network), please refer to the
documentation for
Proxy configuration.

Alternate deployment methods

Deploying with Juju directly

juju deploy charmed-kubernetes

Note: If you're deploying on lxd, use conjure-up instead, as described
above. It configures your lxd profile to support running Kubernetes on lxd.

This will deploy the Charmed Distribution of Kubernetes with default
machine constraints. This is useful for lab environments, but for real-world use
you should provide more CPU and memory to kubernetes-worker units.

You can increase the constraints by downloading and editing the
bundle.yaml
to fit your needs. Customize the bundle constraints by following this
guide.

To deploy your customized bundle:

juju deploy ./bundle.yaml

Note: If you're operating behind a proxy, remember to set the kubernetes-worker
proxy configuration options as described in the Proxy configuration section
above.

This bundle exposes the kubeapi-load-balancer and kubernetes-worker charms by
default, so they are accessible through their public addresses.

If you would like to remove external access, unexpose them:

juju unexpose kubeapi-load-balancer
juju unexpose kubernetes-worker

To get the status of the deployment, run juju status. For constant updates,
combine it with the watch command:

watch -c juju status --color

Using with your own resources

In order to support restricted-network deployments, the charms in this bundle
support
juju resources.

This allows you to juju attach the resources built for the architecture of
your cloud.

juju attach kubernetes-master kubectl=/path/to/kubectl.snap
juju attach kubernetes-master kube-apiserver=/path/to/kube-apiserver.snap
juju attach kubernetes-master kube-controller-manager=/path/to/kube-controller-manager.snap
juju attach kubernetes-master kube-scheduler=/path/to/kube-scheduler.snap
juju attach kubernetes-master cdk-addons=/path/to/cdk-addons.snap

juju attach kubernetes-worker kubectl=/path/to/kubectl.snap
juju attach kubernetes-worker kubelet=/path/to/kubelet.snap
juju attach kubernetes-worker kube-proxy=/path/to/kube-proxy.snap
juju attach kubernetes-worker cni=/path/to/cni.tgz

Using a specific Kubernetes version

You can select a specific version or series of Kubernetes by configuring CDK
to use a specific snap channel. For example, to use the 1.6 series:

juju config kubernetes-master channel=1.6/stable
juju config kubernetes-worker channel=1.6/stable

After changing the channel, you'll need to manually execute the upgrade action
on each kubernetes-worker and kubernetes-master unit, e.g.:

juju run-action kubernetes-master/0 upgrade
...
juju run-action kubernetes-worker/0 upgrade
juju run-action kubernetes-worker/1 upgrade
juju run-action kubernetes-worker/2 upgrade
...

By default, the channel is set to stable on the current minor version of Kubernetes, for example, 1.6/stable. This means your cluster will receive automatic upgrades for new patch releases (e.g. 1.6.2 -> 1.6.3), but not for new minor versions (e.g. 1.6.3 -> 1.7). To upgrade to a new minor version, configure the channel manually as described above.

Interacting with the Kubernetes cluster

After the cluster is deployed you may assume control over the Kubernetes
cluster from any kubernetes-master or kubernetes-worker node.

To download the credentials and client application to your local workstation:

Create the kubectl config directory.

mkdir -p ~/.kube

Copy the kubeconfig file to the default location.

juju scp kubernetes-master/0:config ~/.kube/config

Install kubectl locally.

snap install kubectl --classic

Query the cluster.

kubectl cluster-info

Accessing the Kubernetes dashboard

The Kubernetes dashboard addon is installed by default, along with Metrics Server,
Heapster, Grafana and InfluxDB for cluster monitoring. The dashboard addons can be
enabled or disabled by setting the enable-dashboard-addons config on the
kubernetes-master application:

juju config kubernetes-master enable-dashboard-addons=true

To access the dashboard, you may establish a secure tunnel to your cluster with
the following command:

kubectl proxy

By default, this establishes a proxy running on your local machine and the
kubernetes-master unit. To reach the Kubernetes dashboard, visit
http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/ if using 1.16 or newer or
http://localhost:8001/api/v1/namespaces/kube-system/services/https:kubernetes-dashboard:/proxy/ if using an older version.

Logging in to the dashboard will require either a valid kubeconfig or a basic auth
username and password.

Control the cluster

kubectl is the command line utility to interact with a Kubernetes cluster.

Minimal getting started

To check the state of the cluster:

kubectl cluster-info

List all nodes in the cluster:

kubectl get nodes

Now you can run pods inside the Kubernetes cluster:

kubectl create -f example.yaml

List all pods in the cluster:

kubectl get pods

List all services in the cluster:

kubectl get services

For expanded information on kubectl beyond what this README provides, please
see the
kubectl overview
which contains practical examples and an API reference.

Additionally if you need to manage multiple clusters, there is more information
about configuring kubectl in the
kubectl config guide

Using Ingress

The kubernetes-worker charm supports deploying an NGINX ingress controller.
Ingress allows access from the Internet to containers running web
services inside the cluster.

First allow the Internet access to the kubernetes-worker charm with with the
following Juju command:

juju expose kubernetes-worker

In Kubernetes, workloads are declared using pod, service, and ingress
definitions. An ingress controller is provided to you by default and deployed into
the ingress-nginx-kubernetes-worker namespace
of the cluster (this is derived from the Juju charm's name). If one is not available, you may deploy it with:

juju config kubernetes-worker ingress=true

Ingress resources are DNS mappings to your containers, routed through
endpoints.

As an example for users unfamiliar with Kubernetes, we packaged an action to
both deploy an example and clean itself up.

To deploy 5 replicas of the microbot web application inside the Kubernetes
cluster run the following command:

juju run-action kubernetes-worker/0 microbot replicas=5

This action performs the following steps:

• It creates a deployment titled 'microbots' comprised of 5 replicas defined
  during the run of the action. It also creates a service named 'microbots'
  which binds an 'endpoint', using all 5 of the 'microbots' pods.

• Finally, it will create an ingress resource, which points at a
  xip.io domain to simulate a proper DNS service.

Running the packaged example

Run a Juju action to create the example microbot web application:

$ juju run-action kubernetes-worker/0 microbot replicas=3
Action queued with id: db7cc72b-5f35-4a4d-877c-284c4b776eb8

$ juju show-action-output db7cc72b-5f35-4a4d-877c-284c4b776eb8
results:
  address: microbot.104.198.77.197.xip.io
status: completed
timing:
  completed: 2016-09-26 20:42:42 +0000 UTC
  enqueued: 2016-09-26 20:42:39 +0000 UTC
  started: 2016-09-26 20:42:41 +0000 UTC

Note: Your FQDN will be different and contain the address of the cloud
instance.

At this point, you can inspect the cluster to observe the workload coming
online.

List the pods

$ kubectl get pods
NAME                             READY     STATUS    RESTARTS   AGE
microbot-1855935831-58shp        1/1       Running   0          1h
microbot-1855935831-9d16f        1/1       Running   0          1h
microbot-1855935831-l5rt8        1/1       Running   0          1h
microbot-1855935831-s6x49        1/1       Running   0          1h
microbot-1855935831-wzp7x        1/1       Running   0          1h

List the services and endpoints

$ kubectl get services,endpoints
NAME                       CLUSTER-IP    EXTERNAL-IP   PORT(S)   AGE
svc/default-http-backend   10.1.225.82   <none>        80/TCP    1h
svc/kubernetes             10.1.0.1      <none>        443/TCP   1h
svc/microbot               10.1.44.173   <none>        80/TCP    1h
NAME                      ENDPOINTS                               AGE
ep/default-http-backend   10.1.68.2:80                            1h
ep/kubernetes             172.31.31.139:6443                      1h
ep/microbot               10.1.20.3:80,10.1.68.3:80,10.1.7.4:80   1h

List the ingress resources

$ kubectl get ingress
NAME               HOSTS                          ADDRESS         PORTS     AGE
microbot-ingress   microbot.52.38.62.235.xip.io                   80        1h

When all the pods are listed as Running, you are ready to visit the address listed in the HOSTS column of the ingress listing.

Note: It is normal to see a 502/503 error during initial application deployment.

As you refresh the page, you will be greeted with a microbot web page, serving
from one of the microbot replica pods. Refreshing will show you another
microbot with a different hostname as the requests are load-balanced across
the replicas.

Clean up example

There is also an action to clean up the microbot applications. When you are
done using the microbot application you can delete them from the pods with
one Juju action:

juju run-action kubernetes-worker/0 microbot delete=true

If you no longer need Internet access to your workers, remember to unexpose the
kubernetes-worker charm:

juju unexpose kubernetes-worker

To learn more about
Kubernetes Ingress
and how to configure the Ingress Controller beyond defaults (such as TLS and
websocket support) view the
nginx-ingress-controller
project on github.

Scale out Usage

Scaling kubernetes-worker

The kubernetes-worker nodes are the load-bearing units of a Kubernetes cluster.

By default, pods are automatically spread across the kubernetes-worker units
that you have deployed.

To add more kubernetes-worker units to the cluster:

juju add-unit kubernetes-worker

or specify machine constraints to create larger nodes:

juju set-constraints kubernetes-worker cpu-cores=8 mem=32G
juju add-unit kubernetes-worker

Refer to the
machine constraints documentation
for other machine constraints that might be useful for the kubernetes-worker units.

Scaling Etcd

Etcd is the key-value store for the Kubernetes cluster. For reliability
the bundle defaults to three instances in this cluster.

For more scalability, we recommend between 3 and 9 etcd nodes. If you want to
add more nodes:

juju add-unit etcd

The CoreOS etcd documentation has a chart for the
optimal cluster size
to determine fault tolerance.

Adding optional storage

Using Juju Storage, the
Charmed Distribution of Kubernetes allows you to connect with durable
storage devices such as Ceph.

Deploy a minimum of three ceph-mon and three ceph-osd charms:

juju deploy cs:ceph-mon -n 3
juju deploy cs:ceph-osd -n 3

Relate the charms:

juju add-relation ceph-mon ceph-osd

List the storage pools available to Juju for your cloud:

$ juju storage-pools
Name     Provider  Attrs
ebs      ebs
ebs-ssd  ebs       volume-type=ssd
loop     loop
rootfs   rootfs
tmpfs    tmpfs

Note: This listing is for the Amazon Web Services public cloud.
Different clouds will have different pool names.

Add a storage pool to the ceph-osd charm by NAME,SIZE,COUNT:

juju add-storage ceph-osd/0 osd-devices=ebs,10G,1
juju add-storage ceph-osd/1 osd-devices=ebs,10G,1
juju add-storage ceph-osd/2 osd-devices=ebs,10G,1

Next relate the storage cluster with the Kubernetes cluster:

juju add-relation kubernetes-master ceph-mon

We are now ready to enlist
Persistent Volumes
in Kubernetes, which our workloads can use via Persistent Volume Claims (PVC).

juju run-action kubernetes-master/0 create-rbd-pv name=test size=50

This example created a "test" Radios Block Device (rbd) in the size of 50 MB.

You should see the PV become enlisted and be marked as available:

$ watch kubectl get pv

NAME CAPACITY   ACCESSMODES   STATUS    CLAIM              REASON    AGE

test   50M          RWO       Available                              10s

To consume these Persistent Volumes, your pods will need a
Persistent Volume Claim associated with
them, a task that is outside the scope of this README. See the
Persistent Volumes
documentation for more information.

Known Limitations and Issues

The following are known issues and limitations with the bundle and charm code:

• Destroying the the easyrsa charm will result in loss of public key
  infrastructure (PKI).

• Deployment locally on LXD will require the use of conjure-up to tune
  settings on the host's LXD installation to support Docker and other
  components.

• If resources fail to download during initial deployment for any reason, you
  will need to download and install them manually. For example, if
  kubernetes-master is missing its resources, download them from the resources
  section of the sidebar here
  and install them by running, for example:

juju attach kubernetes-master kube-apiserver=/path/to/snap.

You can find resources for the charmed-kubernetes charms here:

• kubernetes-master
• kubernetes-worker
• easyrsa
• etcd
• flannel

Charmed Kubernetes Reference

• Docs
• Source Code
• Bug tracker
• Demos
• Third-party Integrations

Flannel

Flannel is a virtual network that gives a subnet to each host for use with
container runtimes.

Configuration

iface The interface to configure the flannel SDN binding. If this value is
empty string or undefined the code will attempt to find the default network
adapter similar to the following command:

route | grep default | head -n 1 | awk {'print $8'}

cidr The network range to configure the flannel SDN to declare when
establishing networking setup with etcd. Ensure this network range is not active
on the vlan you're deploying to, as it will cause collisions and odd behavior
if care is not taken when selecting a good CIDR range to assign to flannel.

Known Limitations

This subordinate does not support being co-located with other deployments of
the flannel subordinate (to gain 2 vlans on a single application). If you
require this support please file a bug.

This subordinate also leverages juju-resources, so it is currently only available
on juju 2.0+ controllers.

Further information

• Flannel Charm Resource
• Flannel Homepage