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Ruby

warning

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
info

An example of this code is provided in the ruby section of the go-vela/vela-tutorials repository.

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"]
info

An example of this image is provided in the target/vela-sample Docker repository.

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
info

This has the added benefit of enabling others in the community to consume your plugin!

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