[Tutorial] Installing Kubernetes with CDK and using auto-configured storage


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This is in connection to the topic of Using Kubernetes with Juju. See that page for background information.

This tutorial will demonstrate how to install the Charmed Distribution of Kubernetes (CDK) and take advantage of the auto-configuration of Kubernetes dynamic persistent volumes (PVs) for use with Kubernetes-specific charms. This is normally done when your backing cloud has a storage type that is supported natively by Kubernetes. Here, we’ll build our cluster with Juju via the CDK bundle using AWS as a backing cloud. The cluster will then be added, as a cloud, to the Juju client’s local cache, after which a controller will be created to manage it.

Prerequisites

The following prerequisites are assumed as a starting point for this tutorial:

  • You’re using Ubuntu 18.04 LTS.
  • Juju v.2.6.0 is installed. See the Installing Juju page.
  • A credential for the ‘aws’ cloud has been added to Juju. See the Using Amazon AWS with Juju page.
  • Sufficient permissions are assigned to the above credential in order for ‘aws-integrator’ to perform operations (see Permissions Requirements; this tutorial assigns the IAM security policy of ‘AdministratorAccess’).

Installing Kubernetes

Begin by creating a controller. We’ll call it ‘aws’:

juju bootstrap aws aws

We’ll deploy Kubernetes using the ‘canonical-kubernetes’ bundle (CDK), which will give us a decently sized cluster. We’ll add an integrator charm by means of an overlay bundle that we’ll store in file k8s-aws-overlay.yaml:

applications:
  aws-integrator:
    charm: cs:~containers/aws-integrator
    num_units: 1
relations:
  - ['aws-integrator', 'kubernetes-master']
  - ['aws-integrator', 'kubernetes-worker']

See Overlay bundles for details on overlays.

We can now deploy the cluster:

juju deploy canonical-kubernetes --overlay k8s-aws-overlay.yaml
juju trust aws-integrator

The trust command grants ‘aws-integrator’ access to the credential used in the bootstrap command. This charm acts as a proxy for the Juju machines, acting as Kubernetes nodes, to create and attach dynamic storage volumes in the AWS backing cloud.

When a cluster is not built, but merely added, such as one originating from a public Kubernetes service like Azure’s AKS or Google’s GKE, then an integrator charm is not required. Ready-made clusters have storage built in.

It will take about 20 minutes to arrive at a stable status command output:

Model    Controller  Cloud/Region   Version  SLA          Timestamp
default  aws         aws/us-east-1  2.6-rc2  unsupported  20:07:50Z

App                    Version   Status  Scale  Charm                  Store       Rev  OS      Notes
aws-integrator         1.16.148  active      1  aws-integrator         jujucharms   10  ubuntu  
easyrsa                3.0.1     active      1  easyrsa                jujucharms  235  ubuntu  
etcd                   3.2.10    active      3  etcd                   jujucharms  415  ubuntu  
flannel                0.10.0    active      5  flannel                jujucharms  404  ubuntu  
kubeapi-load-balancer  1.14.0    active      1  kubeapi-load-balancer  jujucharms  628  ubuntu  exposed
kubernetes-master      1.14.1    active      2  kubernetes-master      jujucharms  654  ubuntu  
kubernetes-worker      1.14.1    active      3  kubernetes-worker      jujucharms  519  ubuntu  exposed

Unit                      Workload  Agent  Machine  Public address  Ports           Message
aws-integrator/0*         active    idle   0        52.91.184.172                   Ready
easyrsa/0*                active    idle   1        34.201.167.3                    Certificate Authority connected.
etcd/0                    active    idle   2        52.91.39.43     2379/tcp        Healthy with 3 known peers
etcd/1*                   active    idle   3        54.166.185.173  2379/tcp        Healthy with 3 known peers
etcd/2                    active    idle   4        3.94.148.234    2379/tcp        Healthy with 3 known peers
kubeapi-load-balancer/0*  active    idle   5        34.200.233.4    443/tcp         Loadbalancer ready.
kubernetes-master/0       active    idle   6        107.22.102.161  6443/tcp        Kubernetes master running.
  flannel/4               active    idle            107.22.102.161                  Flannel subnet 10.1.64.1/24
kubernetes-master/1*      active    idle   7        54.197.30.23    6443/tcp        Kubernetes master running.
  flannel/3               active    idle            54.197.30.23                    Flannel subnet 10.1.40.1/24
kubernetes-worker/0*      active    idle   8        3.84.152.194    80/tcp,443/tcp  Kubernetes worker running.
  flannel/0*              active    idle            3.84.152.194                    Flannel subnet 10.1.51.1/24
kubernetes-worker/1       active    idle   9        18.234.242.121  80/tcp,443/tcp  Kubernetes worker running.
  flannel/1               active    idle            18.234.242.121                  Flannel subnet 10.1.10.1/24
kubernetes-worker/2       active    idle   10       34.229.148.230  80/tcp,443/tcp  Kubernetes worker running.
  flannel/2               active    idle            34.229.148.230                  Flannel subnet 10.1.83.1/24

Machine  State    DNS             Inst id              Series  AZ          Message
0        started  52.91.184.172   i-06d8c42a33dd53f4c  bionic  us-east-1a  running
1        started  34.201.167.3    i-0ef15a160a8d6aea9  bionic  us-east-1b  running
2        started  52.91.39.43     i-0e97785dce4afad2e  bionic  us-east-1a  running
3        started  54.166.185.173  i-090c7af5f0b0235b7  bionic  us-east-1b  running
4        started  3.94.148.234    i-01a65ce6300b5bda7  bionic  us-east-1c  running
5        started  34.200.233.4    i-099bf4c44cab8200c  bionic  us-east-1c  running
6        started  107.22.102.161  i-0d2a5fbf55a93f94a  bionic  us-east-1b  running
7        started  54.197.30.23    i-05c97ea2ce5a50858  bionic  us-east-1a  running
8        started  3.84.152.194    i-0e6d4f997e0174e3b  bionic  us-east-1b  running
9        started  18.234.242.121  i-044654e51075296c8  bionic  us-east-1c  running
10       started  34.229.148.230  i-0144700b2ef3ebf43  bionic  us-east-1a  running

Adding the cluster to Juju

We’ll now copy over the cluster’s main configuration file and then use the add-k8s command to add the cluster to the Juju client’s list of known clouds. Here, we call the new cloud ‘aws-cluster’:

mkdir ~/.kube
juju scp kubernetes-master/0:config ~/.kube/config
juju add-k8s --local --region=ec2/us-east-1 aws-cluster

The first component of the value of the --region option is “cloud type” (‘ec2’) and its second component is the actual region (‘us-east-1’). The latter was obtained from the output to juju controllers:

Controller  Model       User   Access     Cloud/Region               Models  Nodes    HA  Version
aws         default     admin  superuser  aws/us-east-1                   2     12  none  2.6-rc2

The fact that the cluster was added without error indicates that the auto-configuration of storage was successful for both operator storage and charm storage. It would have failed if the --region option was omitted, as the inclusion of a cloud type and a region permits the AWS backing cloud to be queried.

The success of this operation can be confirmed by running juju clouds --local.

Creating a controller

Since the cluster is now known to Juju as a cloud, a controller can be created to manage it. We’ll call it ‘k8s’:

juju bootstrap aws-cluster k8s

Now run the clouds command (within the context of the newly-created controller):

juju clouds

Sample output:

Clouds on controller "k8s":

Cloud         Regions  Default    Type  Description
aws-cluster         1  us-east-1  k8s

So the ‘k8s’ controller now manages the cluster that was built with the aid of the ‘aws’ controller. The name ‘aws-cluster’ was chosen (during the first invocation of add-k8s) in order to reflect this in the above output.

Adding a model

In contrast to non-Kubernetes controllers, there is no workload model automatically set up for us as part of the controller-creation process (i.e. model ‘default’). Here, we create one called ‘exciter’:

juju add-model exciter

The output to juju models should look like this:

Controller: k8s

Model       Cloud/Region               Type        Status     Access  Last connection
controller  aws-cluster/us-east-1      kubernetes  available  admin   just now
exciter*    aws-cluster                kubernetes  available  admin   never connected

Deploying Kubernetes charms

We can now deploy a Kubernetes charm. We’ll choose one that has storage requirements:

juju deploy cs:~juju/mariadb-k8s --storage database=10M

Because dynamic storage was set up automatically when the cluster was added there is no need to specify a storage pool. If we did, the value for the --storage option would have looked like database=<pool-name>,10M.

The output to juju status should soon look like the following:

Model    Controller  Cloud/Region     Version  SLA          Timestamp
exciter  k8s         aws-cluster      2.6-rc2  unsupported  03:23:20Z

App          Version  Status  Scale  Charm        Store       Rev  OS          Address        Notes
mariadb-k8s           active      1  mariadb-k8s  jujucharms    1  kubernetes  10.152.183.58  

Unit            Workload  Agent  Address    Ports     Message
mariadb-k8s/0*  active    idle   10.1.83.7  3306/TCP

We can inspect the charm storage volume in use with the storage command:

juju storage

Output:

Unit           Storage id  Type        Pool        Size   Status    Message
mariadb-k8s/0  database/0  filesystem  kubernetes  35MiB  attached  Successfully provisioned volume pvc-4ac4...c590 using kubernetes.io/aws-ebs

We can see that storage class ‘aws-ebs’ was chosen during the storage auto-configuration process.

The model configuration options that are used to track storage class values corroborate this:

juju model-config | grep -e Attribute -e storage

Output:

Attribute                     From        Value
operator-storage              controller  aws-ebs
workload-storage              controller  aws-ebs

Next steps

Consider the following tutorials:


Using the aws-integrator charm - tutorial
Tutorials
Juju documentation
New 2.6 feature: Kubernetes cloud enhancements