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Plugins and Command Templates

Objectives

  • Present the Plugins and Library system added in version 1.2.0

About the Library

The Library is a concept inside csm-orc that allow developers to make common CommandTemplate available to users without needing to copy-paste an external file.

For a user only writing .json orchestrator file it will simply allow him to gain some time in writing by using ready-made CommandTemplate, for a library developer it is a way to package new CommandTemplate for csm-orc in his own work.

The content of the Library is easily displayable with the command csm-orc list-templates that will list every existing template in the Library and display their origin.

What is a Plugin ?

A Plugin is a precisely defined python library. By following a given format it is automatically picked up by the Library and made available to the users.

How to create a Plugin ?

A Plugin needs the following structure

A plugin structure 
cosmotech/
└── orchestrator_plugins/
    └── my_plugin
        ├── __init__.py
        └── templates
            └── ...
cosmotech/orchestrator_plugins/my_plugin/__init__.py
from cosmotech.orchestrator.templates.plugin import Plugin

plugin = Plugin(__file__)

__all__ = [plugin]

And in the templates folder you can put any .json file containing either one single CommandTemplate or an orchestration file containing valid CommandTemplate

{
  "id": "Example",
  "command": "echo"
}

{
  "commandTemplates": [
    {
      "id": "Example1",
      "command": "echo"
    },
    {
      "id": "Example2",
      "command": "ls"
    }
  ]
}

And that is all you need to create a Plugin.

How to make a plugin available ?

The Library make use of the Implicit Namespace Packages of python as defined by the PEP-420.

To summarize, we can define Namespaces that will be able to be filled across multiple Packages and here we define the namespace cosmotech.orchestrator_plugins to contain all future Plugins.

We can easily add our Plugin by making the cosmotech/ folder part of the PYTHONPATH.

To do so we can : - Define a standalone python package for our Plugin and users just need to install said package in their python environment to get access to the Plugin. - Add the cosmotech folder inside the installation of our python package so that when users install the package from any source the Plugin gets installed alongside it - Copy the cosmotech folder in the working directory