Python
We recommend reviewing Docker’s best practices before attempting to create a custom plugin.
We recommend that all plugins be placed inside a scratch image.
Overview
From Python documentation:
Python is a programming language that lets you work quickly and integrate systems more effectively.
Code
To create a plugin using Python, we’ll need to first decide what task we want this plugin to accomplish.
For this example, we’re going to create a program that makes an HTTP request from the provided input:
#!/usr/bin/env python
import http.client
import os
import urlparse
# import method parameter from environment
method = os.getenv['PARAMETER_METHOD']
# import body parameter from environment
body = os.getenv['PARAMETER_BODY']
# import url parameter from environment
url = os.getenv['PARAMETER_URL']
# capture full URI from url
uri = urlparse(url)
# create new HTTP connection from URL
conn = http.client.HTTPSConnection(uri.hostname, uri.port)
# create headers to be added to request
headers = {}
# send HTTP request
conn.request(method, uri.path, body, headers)
# capture the response
response = conn.getresponse()
# output the response
print(response.read().decode("utf-8"))
Image
Once we have the script needed to accomplish our plugin’s task, we need to create a Dockerfile to produce an image.
This image should contain the script and be setup to run that script when the plugin is executed:
FROM python:alpine
RUN apk add --update --no-cache ca-certificates
COPY vela-sample.py /bin/vela-sample.py
ENTRYPOINT ["python", "/bin/vela-sample.py"]
Publishing
In order to run the plugin in a pipeline, we’ll need to make sure we build and publish it to a Docker registry:
# build the image
docker build -t target/vela-sample:python .
# publish the image
docker push target/vela-sample:python
Troubleshooting
To verify that the plugin performs the desired task, it can be executed locally via the command line:
docker run --rm \
-e PARAMETER_BODY="This is a sample Vela plugin written with Python" \
-e PARAMETER_METHOD="POST" \
-e PARAMETER_URL="http://vela.localhost.com" \
target/vela-sample:python
Usage
After publishing the image to a Docker registry, it can be referenced in a pipeline:
version: "1"
steps:
- name: sample python plugin
image: target/vela-sample:python
pull: always
parameters:
url: http://vela.localhost.com
method: POST
body: |
This is a sample Vela plugin written with Python