Reduce docker image size (#394)

Reduce docker image size based on:  https://cadu.dev/reduce-your-docker-images-an-example-with-ruby/

docker/Dockerfile

@@ -1,9 +1,11 @@
-FROM ruby:2.6.5-slim
+# pre-build stage
+FROM ruby:2.6.5-alpine AS pre-builder
 
 # ARG default to production settings
 # For development docker-compose file overrides ARGS
 ARG BUNDLE_WITHOUT="development:test"
 ENV BUNDLE_WITHOUT ${BUNDLE_WITHOUT}
+ENV BUNDLER_VERSION=2.1.2
 
 ARG RAILS_SERVE_STATIC_FILES=true
 ENV RAILS_SERVE_STATIC_FILES ${RAILS_SERVE_STATIC_FILES}
@@ -11,22 +13,20 @@ ENV RAILS_SERVE_STATIC_FILES ${RAILS_SERVE_STATIC_FILES}
 ARG RAILS_ENV=production
 ENV RAILS_ENV ${RAILS_ENV}
 
-RUN apt-get update \
-    && apt-get -qq -y install \
-    build-essential \
-    curl \
-    git \
-    imagemagick \
-    libpq-dev \
+ENV BUNDLE_PATH="/gems"
+
+RUN apk update \
+  && apk add \
+    openssl \
+    tar \
+    build-base \
+    tzdata \
+    postgresql-dev \
     postgresql-client \
-    && curl -L https://deb.nodesource.com/setup_12.x | bash - \
-    && curl https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - \
-    && echo 'deb https://dl.yarnpkg.com/debian stable main' > /etc/apt/sources.list.d/yarn.list \
-    && apt-get update \
-    && apt-get -qq -y install nodejs yarn \
-    && gem install bundler \
-    && apt-get clean \
-    && rm -rf /var/lib/apt/lists/*
+    nodejs \
+    yarn \
+  && mkdir -p /var/app \
+  && gem install bundler
 
 RUN mkdir -p /app
 WORKDIR /app
@@ -47,4 +47,42 @@ COPY . /app
 # generate production assets if production environment
 RUN if [ "$RAILS_ENV" = "production" ]; then \
   SECRET_KEY_BASE=precompile_placeholder bundle exec rake assets:precompile; \
-  fi
+  fi
+
+# final build stage
+FROM ruby:2.6.5-alpine
+
+ARG BUNDLE_WITHOUT="development:test"
+ENV BUNDLE_WITHOUT ${BUNDLE_WITHOUT}
+ENV BUNDLER_VERSION=2.1.2
+
+ARG EXECJS_RUNTIME="Disabled"
+ENV EXECJS_RUNTIME ${EXECJS_RUNTIME}
+
+ARG RAILS_SERVE_STATIC_FILES=true
+ENV RAILS_SERVE_STATIC_FILES ${RAILS_SERVE_STATIC_FILES}
+
+ARG RAILS_ENV=production
+ENV RAILS_ENV ${RAILS_ENV}
+ENV BUNDLE_PATH="/gems"
+
+RUN apk add --update --no-cache \
+    openssl \
+    tzdata \
+    postgresql-client \
+  && gem install bundler
+
+RUN if [ "$RAILS_ENV" = "production" ]; then \
+  rm -rf spec node_modules app/assets vendor/assets tmp/cache; \
+  else apk add nodejs yarn; \
+  fi
+
+COPY --from=pre-builder /gems/ /gems/
+COPY --from=pre-builder /app /app
+
+# Remove unecessary files
+RUN rm -rf /gems/ruby/2.6.0/cache/*.gem \
+  && find /gems/ruby/2.6.0/gems/ -name "*.c" -delete \
+  && find /gems/ruby/2.6.0/gems/ -name "*.o" -delete
+
+WORKDIR /app

docker/entrypoints/rails.sh

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/bin/sh
 
 set -x
 
@@ -17,10 +17,9 @@ done
 
 echo "Database ready to accept connections."
 
-YARN="yarn check --integrity"
 BUNDLE="bundle check"
 
-until $YARN && $BUNDLE
+until $BUNDLE
 do
   sleep 2;
 done

docker/entrypoints/webpack.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 set -e
 
 rm -rf /app/tmp/pids/server.pid
@@ -17,4 +17,4 @@ done
 
 echo "Ready to run webpack development server."
 
-exec "$@"
+exec "$@"