Ruby
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 Ruby documentation:
Ruby is…
A dynamic, open source programming language with a focus on simplicity and productivity. It has an elegant syntax that is natural to read and easy to write.
Code
To create a plugin using Ruby, 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 ruby
require 'net/http'
require 'uri'
# import method parameter from environment
method = ENV['PARAMETER_METHOD']
# import body parameter from environment
body = ENV['PARAMETER_BODY']
# import url parameter from environment
url = ENV['PARAMETER_URL']
# capture full URI from url
uri = URI(url)
# create new HTTP client from URI
http = Net::HTTP.new(uri.host, uri.port)
# send HTTP request and capture response
response = http.send_request(
method,
uri.path,
body,
)
# output the response
puts response.read_body
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 ruby:alpine
RUN apk add --update --no-cache ca-certificates
COPY vela-sample.rb /bin/vela-sample.rb
ENTRYPOINT ["ruby", "/bin/vela-sample.rb"]
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:ruby .
# publish the image
docker push target/vela-sample:ruby
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 Ruby" \
-e PARAMETER_METHOD="POST" \
-e PARAMETER_URL="http://vela.localhost.com" \
target/vela-sample:ruby
Usage
After publishing the image to a Docker registry, it can be referenced in a pipeline:
version: "1"
steps:
- name: sample ruby plugin
image: target/vela-sample:ruby
pull: always
parameters:
url: http://vela.localhost.com
method: POST
body: |
This is a sample Vela plugin written with Ruby