Kubernetes Add-ons


Rancher automatically installs Kubernetes add-ons to help enhance the Kubernetes experience.

  • Helm - A Package Manager for Kubernetes
  • Dashboard - A dashboard web interface for Kubernetes
  • SkyDNS - A DNS server for Kubernetes

Helm

Helm consists of two parts, a server called tiller and a client called helm. Tiller is automatically started by Rancher and is launched in the kube-system namespace. The helm client is installed in the embedded kubectl CLI.

Verifying Helm

Before we start using helm to launch applications, let’s verify that the helm client can talk to helm server( i.e. tiller). Use helm vrsion in the embedded kubectl CLI, which is available in Kubernetes -> CLI.

> helm version
Client: &version.Version{SemVer:"v2.1.3", GitCommit:"5cbc48fb305ca4bf68c26eb8d2a7eb363227e973", GitTreeState:"clean"}
Server: &version.Version{SemVer:"v2.1.3", GitCommit:"5cbc48fb305ca4bf68c26eb8d2a7eb363227e973", GitTreeState:"clean"}

If there is a result for both the client and server, then helm is working properly.

Using Helm

Similar to most package managers, we should confirm we have the latest list of charts.

> helm repo update

Hang tight while we grab the latest from your chart repositories...
...Successfully got an update from the "stable" chart repository
Update Complete. â Happy Helming!â

Using helm search, you can search for different charts that are available to be installed.

> helm search
NAME                    VERSION DESCRIPTION
stable/drupal           0.3.4   One of the most versatile open source content m...
stable/jenkins          0.1.1   A Jenkins Helm chart for Kubernetes.
stable/mariadb          0.5.2   Chart for MariaDB
stable/mysql            0.1.1   Chart for MySQL
stable/redmine          0.3.3   A flexible project management web application.
stable/wordpress        0.3.1   Web publishing platform for building blogs and ...
[email protected]:~$

Once you’ve found the chart that you want to install, run helm install <chart_name> to install the application that you want.

> helm install stable/mysql

Fetched stable/mysql to mysql-0.1.1.tgz
NAME: loping-toad
LAST DEPLOYED: Thu Oct 20 14:54:24 2016
NAMESPACE: default
STATUS: DEPLOYED

RESOURCES:
==> v1/Secret
NAME                TYPE      DATA      AGE
loping-toad-mysql   Opaque    2         3s

==> v1/Service
NAME                CLUSTER-IP   EXTERNAL-IP   PORT(S)    AGE
loping-toad-mysql   192.16.1.5   <none>        3306/TCP   3s

==> extensions/Deployment
NAME                DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
loping-toad-mysql   1         0         0            0           3s

==> v1/PersistentVolumeClaim
NAME                STATUS    VOLUME    CAPACITY   ACCESSMODES   AGE
loping-toad-mysql   Pending                                      3s

After you’ve installed the charts that you want, you can check which applications are running by using helm ls. All services are deployed in the namespace that you are currently using CLI in.

> helm ls

NAME            REVISION        UPDATED                         STATUS          CHART
loping-toad     1               Thu Oct 20 14:54:24 2016        DEPLOYED        mysql-0.1.1

SkyDNS

In Rancher, each service is given a name. Other services can communicate with a service using the DNS service name. The DNS service name is <service_name>.<namespace_name>.svc.cluster.local.

Using the mysql application launched in the helm example, you can get the name and namespace of the mysql service.

> kubectl get pods --all-namespaces=true

NAMESPACE     NAME                                 READY     STATUS    RESTARTS   AGE
default       loping-toad-mysql-1951360640-gxmht   0/1       Pending   0          18m
kube-system   tiller-deploy-2434200834-gvk9m       1/1       Running   0          2h

The mysql application is named loping-toad-mysql. For this instance, the DNS service name is loping-toad-mysql.default.svc.cluster.local.