.. _helm:

Helm
----

You must have Helm 3.0 installed for this functionality to work.

Helm is an automation tool for creating all the Kubernetes resources needed to deploy a single application.
This is done by creating a "Chart" that describes the components of your installation.   When a chart is
instantiated, a "Release" is created.

The helm_install() function makes some assumptions about the environment.   Values for charts are placed
in a subdirectory name **charts/**.   If you don't provide a **release_name**, it is derived from the last
word in the **chart_name**.  For example, if the chart_name is "stable/tomcat", "tomcat" is the release name.

Finally, the YAML file with modified values are stored using the following naming pattern:
**charts/{{release_name}}-values.yaml**

A directory structure would look like this::

    my-project/
        charts/
            tomcat-values.yaml

        deploy.py


Let's say the only thing we want to modify on the Tomcat chart was **ingress** information.  The contents of
**tomcat-values.yaml** would look like this::

    ingress:
      enabled: true
      hosts:
        - tomcat.{{domain}}
      tls:
        - hosts:
            - tomcat.{{domain}}


Note that we are using Jinja2 templating syntax.   When we call **helm_install**, we can provide the value
of all template variables in the **param** parameters.

You can see this in the following example of **deploy.py**::

    from k9.helm import *
    form k9.core import set_default_namespace()

    // Set the namespace to install into
    set_default_namespace('tomcat')
    helm_install('stable/tomcat', {'domain': 'sandbox.simoncomputing.com'})

In the above example, what will happen is the **charts/tomcat-values.yaml** file will be translated
using Jinja to another file **.output/tomcat-values.yaml**.   That file will look like this::

    ingress:
      enabled: true
      hosts:
        - tomcat.sandbox.simoncomputing.com
      tls:
        - hosts:
            - tomcat.sandbox.simoncomputing.com


From that point the **helm** command is called like this::

    helm install -f .output/tomcat-values.yaml tomcat stable/tomcat

**Note** that all Helm functions will throw an exception if an error occurs.

.. autofunction:: k9.helm.helm_repo_add
.. autofunction:: k9.helm.helm_repo_update
.. autofunction:: k9.helm.helm_repo_ls
.. autofunction:: k9.helm.helm_repo_remove

.. autofunction:: k9.helm.helm_install
.. autofunction:: k9.helm.helm_uninstall
.. autofunction:: k9.helm.helm_ls
.. autofunction:: k9.helm.helm_exists