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02_actions_native.md

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Convert this into a StackStorm native action

We can do better than simple copy/paste. Since StackStorm is written in Python there is great support for creating actions using Python code.

Some of the benefits of using Python actions in StackStorm:

  • python module dependency management (via requirements.txt)
  • access to a built-in logger
  • support for **kwargs in def run()
  • support for native python types (int, bool, dict, list)
  • automatic conversion of native python types to structured output (int, bool, dict, list)
  • access to the pack config
  • access to the key/value datastore

In this demo we're going to convert the action we just created into a StackStorm native python action that receives the benefits above.

Convert the action metadata

First, we need to create an Action Metadata with runner_type: python-script. This will tell StackStorm we're using a native Python action. It also defines our input parameters for the action (this will allow us to remove all of our argparse code within the script).

Delete all of the content in the file /opt/stackstorm/packs/tutorial/actions/nasa_apod.yaml :

# hint: delete all of the content in the file
echo "" > /opt/stackstorm/packs/tutorial/actions/nasa_apod.yaml

Edit /opt/stackstorm/packs/tutorial/actions/nasa_apod.yaml and add the following content:

---
name: nasa_apod
pack: tutorial
description: "Queries NASA's APOD (Astronomy Picture Of the Day) API to get the link to the picture of the day."
runner_type: "python-script"
enabled: true
entry_point: nasa_apod.py
parameters:
  api_key:
    type: string
    description: "API key to use for api.nasa.gov."
    default: "DEMO_KEY"
  hd:
    type: boolean
    description: "Retrieve the high resolution image."
    default: false
  date:
    type: string
    description: "The date [YYYY-MM-DD] of the APOD image to retrieve."

You can see in this metadata file that our datatypes are defined along with the same defaults and descriptions from the original python script. We're going to show you how these definitions make the argparse code in the python script no longer necessary!

NOTE If you're struggling and just need the answer, simply copy the file from our answers directory:

cp /opt/stackstorm/packs/tutorial/etc/answers/actions/nasa_apod_native.yaml /opt/stackstorm/packs/tutorial/actions/nasa_apod.yaml

Convert the action python

Next, we'll need to convert our Python code over to something compatible with StackStorm. For native Python actions the following rules need to be met:

  • The python script must contain a one and only one class that inherits from st2common.runners.base_action.Action
  • The Action sub-class must define a def run(self) function.

Example of the most basic action:

from st2common.runners.base_action import Action


class HelloWorld(Action):

    def run(self):
        return "hello world"

The final code in /opt/stackstorm/packs/tutorial/actions/nasa_apod.py should look like:

#!/usr/bin/env python
#
# Description:
#   Queries NASA's APOD (Astronomy Picture Of the Day) API to get the link to the picture
#   of the day.
#
import json
import requests
from st2common.runners.base_action import Action

API_URL = "https://api.nasa.gov/planetary/apod"


class Apod(Action):

    def run(self, api_key, date, hd):
        params = {'api_key': api_key,
                  'hd': hd}
        if date is not None:
            params['date'] = date

        response = requests.get(API_URL, params=params)
        response.raise_for_status()
        data = response.json()
        if hd:
            data['url'] = data['hdurl']
        return data

NOTE If you're struggling and just need the answer, simply copy the file from our answers directory:

cp /opt/stackstorm/packs/tutorial/etc/answers/actions/nasa_apod_native.py /opt/stackstorm/packs/tutorial/actions/nasa_apod.py

Let's register with StackStorm

st2ctl reload --register-actions

And test!

st2 run tutorial.nasa_apod date=2018-07-04