From 48a4ee0ad645322228f425c101e02840774e5790 Mon Sep 17 00:00:00 2001
From: Karsten Heymann <karsten.heymann@gmail.com>
Date: Wed, 10 Jul 2019 14:01:42 +0200
Subject: [PATCH] Update dockerfile to create 90% smaller image

This change uses the 2.4-alpine base image variant and a two-stage docker build to reduce the size of the resulting image from 700 MB to around 70 MB with no obvious loss of functionality.
---
 Dockerfile | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/Dockerfile b/Dockerfile
index 64def2e..22ddd18 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,6 +1,21 @@
-FROM ruby:2.4
+# Phase 1: Build the gem and all dependencies, needs C compiler
+FROM ruby:2.4-alpine as builder
 
-RUN gem install redis-stat
+RUN apk add --no-cache build-base
+
+ENV GEM_HOME "/gems"
+
+RUN gem install -N redis-stat
+
+# Phase 2: Build the actual docker image, needs no C compiler -> much smaller image
+FROM ruby:2.4-alpine
+
+RUN apk add --no-cache ncurses
+
+ENV GEM_HOME "/gems"
+ENV PATH $GEM_HOME/bin:$GEM_HOME/gems/bin:$PATH
+
+COPY --from=builder /gems /gems
 
 EXPOSE 63790
 ENTRYPOINT ["redis-stat"]