kubernetes worker #22

  • By containers
  • Latest version (#22)
  • xenial
  • Stable
  • Candidate

Kubernetes is an open-source platform for deploying, scaling, and operations
of application 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 Worker


This charm deploys a container runtime, and additionally stands up the Kubernetes
worker applications: kubelet, and kube-proxy.

In order for this charm to be useful, it should be deployed with its companion
charm kubernetes-master
and linked with an SDN-Plugin.

This charm has also been bundled up for your convenience so you can skip the
above steps, and deploy it with a single command:

juju deploy canonical-kubernetes

For more information about Canonical Kubernetes
consult the bundle README.md file.

Scale out

To add additional compute capacity to your Kubernetes workers, you may
juju add-unit scale the cluster of applications. They will automatically
join any related kubernetes-master, and enlist themselves as ready once the
deployment is complete.

Operational actions

The kubernetes-worker charm supports the following Operational Actions:


Pausing the workload enables administrators to both drain and cordon
a unit for maintenance.


Resuming the workload will uncordon a paused unit. Workloads will automatically migrate unless otherwise directed via their application declaration.

Private registry

With the "registry" action that is part for the kubernetes-worker charm, you can very easily create a private docker registry, with authentication, and available over TLS. Please note that the registry deployed with the action is not HA, and uses storage tied to the kubernetes node where the pod is running. So if the registry pod changes is migrated from one node to another for whatever reason, you will need to re-publish the images.

Example usage

Create the relevant authentication files. Let's say you want user userA to authenticate with the password passwordA. Then you'll do :

echo "userA:passwordA" > htpasswd-plain
htpasswd -c -b -B htpasswd userA passwordA

(the htpasswd program comes with the apache2-utils package)

Supposing your registry will be reachable at myregistry.company.com, and that you already have your TLS key in the registry.key file, and your TLS certificate (with myregistry.company.com as Common Name) in the registry.crt file, you would then run :

juju run-action kubernetes-worker/0 registry domain=myregistry.company.com htpasswd="$(base64 -w0 htpasswd)" htpasswd-plain="$(base64 -w0 htpasswd-plain)" tlscert="$(base64 -w0 registry.crt)" tlskey="$(base64 -w0 registry.key)" ingress=true

If you then decide that you want do delete the registry, just run :

juju run-action kubernetes-worker/0 registry delete=true ingress=true

Known Limitations

Kubernetes workers currently only support 'phaux' HA scenarios. Even when configured with an HA cluster string, they will only ever contact the first unit in the cluster map. To enalbe a proper HA story, kubernetes-worker units are encouraged to proxy through a kubeapi-load-balancer
application. This enables a HA deployment without the need to
re-render configuration and disrupt the worker services.

External access to pods must be performed through a Kubernetes
Ingress Resource


                            A comma-separated list of nagios servicegroups.
If left empty, the nagios_context will be used as the servicegroup

                            Deploy the default http backend and ingress controller to handle
ingress requests.

                            URL to use for HTTP_PROXY to be used by Docker. Only useful in closed
environments where a proxy is the only option for routing to the
registry to pull images

                            When true, worker services will not be upgraded until the user triggers
it manually by running the upgrade action.

                            Comma-separated list of destinations (either domain names or IP
addresses) that should be directly accessed, by opposition of going
through the proxy defined above.

                            Toggle installation from ubuntu archive vs the docker PPA

                            Allow privileged containers to run on worker nodes. Supported values are
"true", "false", and "auto". If "true", kubelet will run in privileged
mode by default. If "false", kubelet will never run in privileged mode.
If "auto", kubelet will not run in privileged mode by default, but will
switch to privileged mode if gpu hardware is detected.

                            HTTP/HTTPS web proxy for Snappy to use when accessing the snap store.

                            Labels can be used to organize and to select subsets of nodes in the
cluster. Declare node labels in key=value format, separated by spaces.

                            URL to use for HTTPS_PROXY to be used by Docker. Only useful in closed
environments where a proxy is the only option for routing to the
registry to pull images

                            Used by the nrpe subordinate charms.
A string that will be prepended to instance name to set the host name
in nagios. So for instance the hostname would be something like:
If you're running multiple environments with the same services in them
this allows you to differentiate between them.

                            Extra options to pass to the docker daemon. e.g. --insecure-registry

                            Enable GRUB cgroup overrides cgroup_enable=memory swapaccount=1. WARNING
changing this option will reboot the host - use with caution on production

                            Snap channel to install Kubernetes worker services from