Utilize multi-stage build to improve the image size

Dockerfile

@@ -1,6 +1,4 @@
-FROM alpine:3.13
-
-LABEL MAINTAINERS="Guillaume Scheibel <[email protected]>, Damien DUPORTAL <[email protected]>"
+FROM alpine:3.13 AS base
 
 ARG asciidoctor_version=2.0.12
 ARG asciidoctor_confluence_version=0.0.2
@@ -20,8 +18,86 @@ ENV ASCIIDOCTOR_VERSION=${asciidoctor_version} \
   ASCIIDOCTOR_MATHEMATICAL_VERSION=${asciidoctor_mathematical_version} \
   ASCIIDOCTOR_REVEALJS_VERSION=${asciidoctor_revealjs_version} \
   KRAMDOWN_ASCIIDOC_VERSION=${kramdown_asciidoc_version} \
-  ASCIIDOCTOR_BIBTEX_VERSION=${asciidoctor_bibtex_version} \
-  PATH="/root/.cabal/bin/:${PATH}"
+  ASCIIDOCTOR_BIBTEX_VERSION=${asciidoctor_bibtex_version}
+
+# # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+# Ruby build for: asciidoctor, asciidoctor-pdf, and all kinds of associated tools
+# # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+
+FROM base AS build-ruby
+RUN echo "building Ruby dependencies" # keep here to help --cache-from along
+
+RUN apk add --no-cache \
+      build-base \
+      libxml2-dev \
+      ruby-dev \
+      cmake \
+      bison \
+      flex \
+      python3 \
+      glib-dev \
+      cairo-dev \
+      pango-dev \
+      gdk-pixbuf-dev
+
+RUN gem install --no-document \
+      --install-dir /usr/lib/ruby/gems \
+      --bindir      /usr/lib/ruby/bin \
+      "asciidoctor:${ASCIIDOCTOR_VERSION}" \
+      "asciidoctor-confluence:${ASCIIDOCTOR_CONFLUENCE_VERSION}" \
+      "asciidoctor-diagram:${ASCIIDOCTOR_DIAGRAM_VERSION}" \
+      "asciidoctor-epub3:${ASCIIDOCTOR_EPUB3_VERSION}" \
+      "asciidoctor-mathematical:${ASCIIDOCTOR_MATHEMATICAL_VERSION}" \
+      asciimath \
+      "asciidoctor-pdf:${ASCIIDOCTOR_PDF_VERSION}" \
+      "asciidoctor-revealjs:${ASCIIDOCTOR_REVEALJS_VERSION}" \
+      bigdecimal \
+      coderay \
+      epubcheck-ruby:4.2.4.0 \
+      haml \
+      "kramdown-asciidoc:${KRAMDOWN_ASCIIDOC_VERSION}" \
+      pygments.rb \
+      rouge \
+      slim \
+      thread_safe \
+      tilt \
+      text-hyphen \
+      "asciidoctor-bibtex:${ASCIIDOCTOR_BIBTEX_VERSION}"
+
+RUN rm -rf /usr/lib/ruby/gems/cache/*
+
+# # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+# Haskell build for: erd
+# # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+
+FROM base AS build-haskell
+RUN echo "building Haskell dependencies" # keep here to help --cache-from along
+
+RUN apk add --no-cache \
+    alpine-sdk \
+    cabal \
+    ghc-dev \
+    ghc \
+    gmp-dev \
+    gnupg \
+    libffi-dev \
+    linux-headers \
+    perl-utils \
+    wget \
+    xz \
+    zlib-dev
+
+RUN cabal v2-update \
+ && cabal v2-install erd
+
+# # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+# Final image
+# # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+
+FROM base AS main
+RUN echo "building main image" # keep here to help --cache-from along
+
+LABEL MAINTAINERS="Guillaume Scheibel <[email protected]>, Damien DUPORTAL <[email protected]>"
 
 # Installing package required for the runtime of
 # any of the asciidoctor-* functionnalities
@@ -32,8 +108,10 @@ RUN apk add --no-cache \
     findutils \
     font-bakoma-ttf \
     git \
+    gmp \
     graphviz \
     inotify-tools \
+    libffi \
     make \
     openjdk8-jre \
     python3 \
@@ -49,35 +127,6 @@ RUN apk add --no-cache \
     unzip \
     which
 
-# Installing Ruby Gems needed in the image
-# including asciidoctor itself
-RUN apk add --no-cache --virtual .rubymakedepends \
-    build-base \
-    libxml2-dev \
-    ruby-dev \
-  && gem install --no-document \
-    "asciidoctor:${ASCIIDOCTOR_VERSION}" \
-    "asciidoctor-confluence:${ASCIIDOCTOR_CONFLUENCE_VERSION}" \
-    "asciidoctor-diagram:${ASCIIDOCTOR_DIAGRAM_VERSION}" \
-    "asciidoctor-epub3:${ASCIIDOCTOR_EPUB3_VERSION}" \
-    "asciidoctor-mathematical:${ASCIIDOCTOR_MATHEMATICAL_VERSION}" \
-    asciimath \
-    "asciidoctor-pdf:${ASCIIDOCTOR_PDF_VERSION}" \
-    "asciidoctor-revealjs:${ASCIIDOCTOR_REVEALJS_VERSION}" \
-    bigdecimal \
-    coderay \
-    epubcheck-ruby:4.2.4.0 \
-    haml \
-    "kramdown-asciidoc:${KRAMDOWN_ASCIIDOC_VERSION}" \
-    pygments.rb \
-    rouge \
-    slim \
-    thread_safe \
-    tilt \
-    text-hyphen \
-    "asciidoctor-bibtex:${ASCIIDOCTOR_BIBTEX_VERSION}" \
-  && apk del -r --no-cache .rubymakedepends
-
 # Installing Python dependencies for additional
 # functionnalities as diagrams or syntax highligthing
 RUN apk add --no-cache --virtual .pythonmakedepends \
@@ -91,23 +140,14 @@ RUN apk add --no-cache --virtual .pythonmakedepends \
     seqdiag \
   && apk del -r --no-cache .pythonmakedepends
 
-# ERD
-RUN apk add --no-cache --virtual .haskellmakedepends \
-    alpine-sdk \
-    cabal \
-    ghc-dev \
-    ghc \
-    gmp-dev \
-    gnupg \
-    libffi-dev \
-    linux-headers \
-    perl-utils \
-    wget \
-    xz \
-    zlib-dev \
-  && cabal v2-update \
-  && cabal v2-install erd \
-  && apk del -r --no-cache .haskellmakedepends
+# --target=XYZ --> XYZ/bin --> ln -s XYZ/bin/* /bin/
+# COPY --from=build-python    /usr/local/lib/python3.9/site-packages /usr/local/lib/python3.9/site-packages
+
+COPY --from=build-ruby    /usr/lib/ruby/gems/     /usr/lib/ruby/gems/
+COPY --from=build-ruby    /usr/lib/ruby/bin/      /bin/
+ENV GEM_HOME=/usr/lib/ruby/gems
+
+COPY --from=build-haskell root/.cabal/bin/erd     /bin/
 
 WORKDIR /documents
 VOLUME /documents

build_image.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+
+# Problem: docker doesn't cache multi-stage builds by default,
+#          so the full build time of ~10min hits me on every tinker-rebuild.
+# Solution as per: https://github.com/moby/moby/issues/34715 is to
+#  - force caching with --cache-from,
+#  - use buildkit, and
+#  - tell buildkit to build cacheable images.
+
+export DOCKER_BUILDKIT=1
+
+image_name="adoc-test"
+
+docker build \
+    --target build-ruby \
+    --tag ${image_name}:build-ruby \
+    --build-arg BUILDKIT_INLINE_CACHE=1 \
+    --cache-from=${image_name}:build-ruby \
+    .
+
+docker build \
+    --target build-haskell \
+    --tag ${image_name}:build-haskell \
+    --build-arg BUILDKIT_INLINE_CACHE=1 \
+    --cache-from=${image_name}:build-haskell \
+    .
+
+docker build \
+    --target main \
+    --tag ${image_name} \
+    --build-arg BUILDKIT_INLINE_CACHE=1 \
+    --cache-from=${image_name}:build-ruby \
+    --cache-from=${image_name}:build-haskell \
+    --cache-from=${image_name} \
+    .
+
+