(Experimental) Ruby Container size reducing

Dockerfile.large

FROM ruby:2.6.0-slim-stretch

RUN set -ex \
    && apt-get update -qq && apt-get install -y --no-install-recommends \
    build-essential=12.3 \
    libxml2-dev=2.9.4+dfsg1-2.2+deb9u2 \
    libxslt1-dev=1.1.29-2.1 \
    libsqlite3-dev=3.16.2-5+deb9u1 \
    && apt-get clean \
    && apt-get autoclean \
    && rm -rf /var/lib/apt/lists/*

WORKDIR /usr/src/app

COPY Gemfile .
COPY Gemfile.lock .

RUN gem update bundler
RUN bundle install --frozen --jobs=4 --clean

COPY . .

CMD ["ruby", "./url.rb"]

Dockerfile.small

# Build for install dependency RubyGems
FROM ruby:2.6.0-stretch AS bundle

COPY Gemfile .
COPY Gemfile.lock .

RUN gem update bundler
RUN bundle install --frozen --jobs=4 --clean

# Build for run the Ruby
FROM ruby:2.6.0-slim-stretch
COPY --from=bundle /usr/local/bundle /usr/local/bundle

RUN set -ex \
    && apt-get update -qq && apt-get install -y --no-install-recommends \
    libxml2=2.9.4+dfsg1-2.2+deb9u2 \
    libxslt1.1=1.1.29-2.1 \
    libsqlite3-0=3.16.2-5+deb9u1 \
    && apt-get clean \
    && apt-get autoclean \
    && rm -rf /var/lib/apt/lists/*

WORKDIR /usr/src/app
COPY . .

CMD ["ruby", "./url.rb"]

Gemfile

source "https://rubygems.org"

gem "sqlite3"
gem "nokogiri"

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    mini_portile2 (2.4.0)
    nokogiri (1.10.0)
      mini_portile2 (~> 2.4.0)
    sqlite3 (1.3.13)

PLATFORMS
  ruby

DEPENDENCIES
  nokogiri
  sqlite3

BUNDLED WITH
   2.0.1

url.rb

require 'sqlite3'
require 'nokogiri'
require 'open-uri'

URLS = [
  'https://www.google.co.jp',
  'https://www.apple.com'
]

# Initialize Database
db = SQLite3::Database.new 'test.db'
db.results_as_hash = true
db.execute('CREATE TABLE urls (id INTEGER PRIMARY KEY, url TEXT, title TEXT);')

# Create site information from URL list
URLS.each do |url|
  html = Nokogiri::HTML(open(url))
  title = html.search('title').text
  db.execute('INSERT INTO URLS (url, title) values (?, ?)', url, title)
end

# Show URL information
db.execute('SELECT * FROM urls') do |row|
  puts "ID: #{row['id']} | #{row['url']} | #{row['title']}"
end

Compare

$ docker images | grep tomohiro/ruby
tomohiro/ruby               2.6.0-slim-stretch-large   6ffd2344aea4        4 minutes ago       557MB
tomohiro/ruby               2.6.0-slim-stretch-small   cb7d7a51ce43        14 minutes ago      243MB

Build

$ docker build -f ./Dockerfile.small . -t tomohiro/ruby:2.6.0-slim-stretch-small
$ docker build -f ./Dockerfile.large . -t tomohiro/ruby:2.6.0-slim-stretch-large

Result

Large:

$ docker run -it --rm tomohiro/ruby:2.6.0-slim-stretch-large
ID: 1 | https://www.google.co.jp | Google
ID: 2 | https://www.apple.com | Apple

Small:

$ docker run -it --rm tomohiro/ruby:2.6.0-slim-stretch-small
ID: 1 | https://www.google.co.jp | Google
ID: 2 | https://www.apple.com | Apple