Containers Kubernetes

  • By Canonical Kubernetes
  • Cloud
Channel Version Revision Published Runs on
latest/stable 10 10 01 Feb 2021
Ubuntu 16.04
latest/edge 8 8 01 Feb 2021
Ubuntu 16.04
juju deploy containers-kubernetes
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Platform:

Ubuntu
16.04

kubernetes

Kubernetes is an open source system for managing application containers across multiple hosts. This version of Kubernetes uses Docker to package, instantiate and run containerized applications.

This charm is an encapsulation of the Running Kubernetes locally via Docker document. The released hyperkube image (gcr.io/google_containers/hyperkube) is currently pulled from a Google owned container repository repository. For this charm to work it will need access to the repository to docker pull the images.

This charm was built from other charm layers using the reactive framework. The layer:docker is the base layer. For more information please read Getting Started Developing charms

Deployment

The kubernetes charms require a relation to a distributed key value store (ETCD) which Kubernetes uses for persistent storage of all of its REST API objects.

juju deploy etcd
juju deploy kubernetes
juju add-relation kubernetes etcd

Configuration

For your convenience this charm supports some configuration options to set up a Kubernetes cluster that works in your environment:

version: Set the version of the Kubernetes containers to deploy. The version string must be in the following format "v#.#.#" where the numbers match with the kubernetes release labels of the kubernetes github project. Changing the version causes the all the Kubernetes containers to be restarted.

cidr: Set the IP range for the Kubernetes cluster. eg: 10.1.0.0/16

dns_domain: Set the DNS domain for the Kubernetes cluster.

Storage

The kubernetes charm is built to handle multiple storage devices if the cloud provider works with Juju storage.

The 16.04 (xenial) release introduced ZFS to Ubuntu. The xenial charm can use ZFS witha raidz pool. A raidz pool distributes parity along with the data (similar to a raid5 pool) and can suffer the loss of one drive while still retaining data. The raidz pool requires a minimum of 3 disks, but will accept more if they are provided.

You can add storage to the kubernetes charm in increments of 3 or greater:

juju add-storage kubernetes/0 disk-pool=ebs,3,1G

Note: Due to a limitation of raidz you can not add individual disks to an existing pool. Should you need to expand the storage of the raidz pool, the additional add-storage commands must be the same number of disks as the original command. At this point the charm will have two raidz pools added together, both of which could handle the loss of one disk each.

The storage code handles the addition of devices to the charm and when it recieves three disks creates a raidz pool that is mounted at the /srv/kubernetes directory by default. If you need the storage in another location you must change the mount-point value in layer.yaml before the charms is deployed.

To avoid data loss you must attach the storage before making the connection to the etcd cluster.

Operational Actions

Microbot - Deploys mini containers that serve up static webpages and identify the container ID that's serving the request. Useful to deploy a phaux workload for visualizations quickly, or to test reverse proxy that does not depend on session affinity.

Pause - Cordon the unit by marking it as unscheduleable. It also drains the workloads from the unit, making it feesible to perform maintenance tasks without disrupting end user experience.

Resume - UnCordon the unit. No workload balancing is done at this time, the kubernetes scheduler will being filling the unit back up with workloads depending on unit-pressure, which is based on resource allocation/uitilization.

State Events

While this charm is meant to be a top layer, it can be used to build other solutions. This charm sets or removes states from the reactive framework that other layers could react appropriately. The states that other layers would be interested in are as follows:

kubelet.available - The hyperkube container has been run with the kubelet service and configuration that started the apiserver, controller-manager and scheduler containers.

proxy.available - The hyperkube container has been run with the proxy service and configuration that handles Kubernetes networking.

kubectl.package.created - Indicates the availability of the kubectl application along with the configuration needed to contact the cluster securely. You will need to download the /home/ubuntu/kubectl_package.tar.gz from the kubernetes leader unit to your machine so you can control the cluster.

kubedns.available - Indicates when the Domain Name System (DNS) for the cluster is operational.

Kubernetes information

Contact

  • Charm Author: Matthew Bruzek <Matthew.Bruzek@canonical.com>
  • Charm Contributor: Charles Butler <Charles.Butler@canonical.com>

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