Ruby #

Ruby sering dicap sebagai bahasa yang “berat” di Docker. Image Ruby identik dengan:

• ratusan MB
• banyak OS package
• build lama

Padahal, Ruby bisa dibuat sangat ramping dan production-grade jika diperlakukan dengan disiplin yang sama seperti Java (distroless), Node.js (bundling), Python (build/runtime split), dan Go (static binary mindset).

Artikel ini membahas strategi Docker image Ruby yang kecil, aman, dan siap production, dengan fokus rasional engineering, bukan sekadar trik Docker.

Realita Ukuran Docker Image Ruby #

Tanpa Strategi #

Dengan Strategi yang Benar #

Masalah Utama Ruby di Docker #

1. Ruby Adalah Runtime + Toolchain #

• Ruby interpreter
• Bundler
• Native extension compiler

Tanpa pemisahan, semua ikut ke runtime.

2. Native Gem Membengkakkan Image #

Contoh gem:

• nokogiri
• pg
• grpc

Mereka butuh:

• compiler
• libc
• OS library

3. Rails Membawa Dunia Sendiri #

Rails production sering:

• membawa test
• membawa asset source
• membawa build tools

Prinsip Utama Image Ruby Production #

Runtime image hanya berisi Ruby interpreter + gem production + app code.

Yang harus mati di runtime:

• gcc / make
• header library
• gem documentation
• test & development dependency

Strategi 1: Ruby Slim + Multi-stage Build #

Dockerfile Dasar #

FROM ruby:3.3-slim AS builder
WORKDIR /app

RUN apt-get update && apt-get install -y \
  build-essential \
  libpq-dev \
  && rm -rf /var/lib/apt/lists/*

COPY Gemfile Gemfile.lock ./
RUN bundle config set without 'development test' \
 && bundle config set path 'vendor/bundle' \
 && bundle install

COPY . .

FROM ruby:3.3-slim
WORKDIR /app

COPY --from=builder /app /app

ENV RACK_ENV=production
ENV RAILS_ENV=production

CMD ["bundle", "exec", "puma", "-C", "config/puma.rb"]

Ukuran tipikal: 200–300 MB.

Strategi 2: Alpine Ruby (Lebih Kecil, Lebih Rumit) #

FROM ruby:3.3-alpine AS builder
WORKDIR /app

RUN apk add --no-cache \
  build-base \
  postgresql-dev

COPY Gemfile Gemfile.lock ./
RUN bundle config set without 'development test' \
 && bundle install

COPY . .

FROM ruby:3.3-alpine
WORKDIR /app
COPY --from=builder /app /app
CMD ["bundle", "exec", "puma"]

Ukuran: 120–180 MB.

Catatan:

• musl libc
• native gem bisa lebih tricky

Strategi 3: Distroless Ruby (Production-Oriented) #

Ruby tidak resmi didukung distroless, tapi bisa:

FROM ruby:3.3-slim AS builder
WORKDIR /app

RUN apt-get update && apt-get install -y \
  build-essential libssl-dev libpq-dev

COPY Gemfile Gemfile.lock ./
RUN bundle config set without 'development test' \
 && bundle install

COPY . .

FROM gcr.io/distroless/base-debian12
WORKDIR /app

COPY --from=builder /usr/local /usr/local
COPY --from=builder /app /app

ENV PATH="/usr/local/bin:$PATH"
CMD ["ruby", "app.rb"]

Ukuran realistis: 80–130 MB.

Trade-off:

• debugging sulit
• harus paham dependency runtime

Asset Compilation (Rails) #

Lakukan di build stage:

RAILS_ENV=production bundle exec rails assets:precompile

Runtime tidak boleh:

• nodejs
• yarn

Optimasi Bundler #

bundle config set deployment 'true'
bundle config set without 'development test'
bundle config set clean 'true'

Tambahan:

• bundle install --no-cache
• disable documentation

gem: --no-document

Security & Production Readiness #

Non-root User #

Tambahkan user manual atau gunakan distroless base.

###** Logging

• STDOUT
• structured logging

###** Healthcheck

Gunakan HTTP endpoint, bukan shell.

Perbandingan Strategi #

Kapan Strategi Mana Digunakan? #

Penutup #

Ruby bukan masalah di Docker. Yang sering jadi masalah adalah:

• toolchain bocor ke runtime
• native dependency tak dikontrol
• build & runtime dicampur

Dengan disiplin build boundary, Ruby bisa:

• image <150 MB
• aman di Kubernetes
• layak untuk sistem besar

Ruby image besar bukan takdir, tapi keputusan engineering.