Description

Kubernetes is an open-source platform for deplying, scaling, and operations
of appliation containers across a cluster of hosts. Kubernetes is portable
in that it works with public, private, and hybrid clouds. Extensible through
a pluggable infrastructure. Self healing in that it will automatically
restart and place containers on healthy nodes if a node ever goes away.

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 trusty/etcd
juju deploy local:trusty/kubernetes
juju add-relation kubernetes etcd

Configuration

For your convenience this charm supports some configuration options to set up
a Kuberentes 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

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.

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.

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

Kubernetes information

Contact

Configuration

root_certificate
(string) The root certificate to use for this grouping of charms. If empty (default) the leader will generate a self signed Certificate Authority (CA). All certificates will be based on the root certificate.
iface
(string) Interface to bind flannel overlay networking to. Defaults to eth0.
eth0
version
(string) The version of Kubernetes to use in this charm. The version is inserted in the configuration files that specify the hyperkube container to use when starting a Kubernetes cluster. Changing this value will restart the Kubernetes cluster.
v1.2.3
etcd_image
(string) The image to pull for the 'etcdctl' command. Recommended to mirror the default on a private registry if connectivity is a concern
gcr.io/google_containers/etcd:2.0.12
dns_domain
(string) The domain name to use for the Kubernetes cluster by the skydns service.
cluster.local
package_status
(string) The status of service-affecting packages will be set to this value in the dpkg database. Valid values are "install" and "hold".
install
flannel_image
(string) The image to pull for running 'flannel'. Recommended to mirror the default on a private registry if connectivity is a concern
quay.io/coreos/flannel:0.5.5
extra_packages
(string) Space separated list of extra deb packages to install.
cidr
(string) Network CIDR to assign to Kubernetes service groups. This must not overlap with any IP ranges assigned to nodes for pods.
10.1.0.0/16
enable-cgroups
(boolean) Enable GRUB cgroup overrides cgroup_enable=memory swapaccount=1. WARNING changing this option will reboot the host - use with caution on production services
install_keys
(string) List of signing keys for install_sources package sources, per charmhelpers standard format (a yaml list of strings encoded as a string). The keys should be the full ASCII armoured GPG public keys. While GPG key ids are also supported and looked up on a keyserver, operators should be aware that this mechanism is insecure. null can be used if a standard package signing key is used that will already be installed on the machine, and for PPA sources where the package signing key is securely retrieved from Launchpad.
install_sources
(string) List of extra apt sources, per charm-helpers standard format (a yaml list of strings encoded as a string). Each source may be either a line that can be added directly to sources.list(5), or in the form ppa:<user>/<ppa-name> for adding Personal Package Archives, or a distribution component to enable.