Kubernetes Concepts

The following are key concepts to understand the project:

KubeCtl references

Overview: https://kubernetes.io/docs/reference/kubectl/overview/

Cheat Sheet: https://kubernetes.io/docs/reference/kubectl/cheatsheet/

Hands-on training material: SKA Training on containerisation and orchestration.

K8s Templates


The below names and specifics for the charts are not necessarily up to date and were compiled as reference material while developing the structure of standard Helm charts for SKA. The information is still mostly relevant though.

Template files follow the standard conventions for writing Go templates (see the documentation for details). For example, in the tango-base chart, the following files composes the templates for the generation of valid kubernetes manifest files:

  • tangodb.yaml: define a k8s service for maria db and a statefulset attached to it

  • tangodb-pv.yaml: define a PersistentVolume and a PersistentVolumeClaim for the database service (tangodb.yaml)

  • databaseds.yaml: define a k8s service for the device server Databaseds and a statefulset attached to it

  • itango.yaml: define a k8s pod for interacting with other containers (for local testing purpose)

  • jive.yaml: define a k8s pod for interacting with the tango jive tool (for local development purpose)

  • logviewer.yaml: define a k8s pod for interacting with the tango logviewer tool (for local development purpose)

  • tangotest.yaml: define a k8s pod for the tangotest device server

K8s Tags

Below there are the main tags that constitute every object in the k8s integration.

Metadata tag

Every yaml file has a metadata tag which specify some important information like:

  • name: a string that uniquely identifies this object within the current namespace (see the identifiers docs). This value is used in the path when retrieving an individual object.

  • namespace: a namespace is a DNS compatible label that objects are subdivided into.

  • **labels**: a map of string keys and values that can be used to organize and categorize objects:

    • app: unique name (equals to name above)

    • chart: name of the chart

    • release and heritage: used by helm for install/upgrade


Every yaml file has a spec tag which is used to set all the parameters for a specific object. For instance, in databaseds.yaml the StatefulSet object specifies that the label ‘app’ should match with a specific value and that the related service is the one specified in the tag ‘serviceName’.

    app: databaseds-{{ template "tango-base.name" . }}-{{ .Release.Name }}
serviceName: databaseds-{{ template "tango-base.name" . }}-{{ .Release.Name }}


A Pod can have multiple Containers running apps within it, but it can also have one or more Init Containers, which are run before the app Containers are started. Check k8s documentation for more information.


The containers tag includes the containers that form the specific pod or object whithin k8s.