Merge pull request gate-sso#25 from pieterlange/feature/docker-alpine

Use alpine and optimize image build steps

Author: olttwa

Dockerfile

@@ -1,15 +1,17 @@
-FROM jruby:9.1.7.0
+FROM jruby:9.1-alpine
 LABEL maintainer <vjdhama26@gmail.com>
 
-RUN apt-get update -qq && apt-get install -y build-essential libmysqlclient-dev nodejs
 RUN mkdir /app
 
 WORKDIR /app
 
 COPY Gemfile /app
 COPY Gemfile.lock /app
 
-RUN bundle install
+RUN apk --update add build-base nodejs mariadb-dev mariadb-client-libs tzdata && \
+    bundle install && \
+    apk del build-base mariadb-dev && \
+    rm -rf /tmp/* /var/tmp/* /var/cache/apk/*
 
 ADD . /app