From 0aca127062b2770009dc7ad3acb8146d6a7bac75 Mon Sep 17 00:00:00 2001
From: Brandur <brandur@brandur.org>
Date: Wed, 21 Mar 2018 15:28:18 -0700
Subject: [PATCH] Leaner Docker image through the use of multi-stage builds
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In #50 I was able to successfully push an image to Docker Hub, but quite
a large one -- weighing in at 91 MB, which is pretty heavy for this
small program.

Here we lean out the final image by switching `Dockerfile` to use a
multi-phase build strategy. This creates one image initially based off
of a Go image which is used to build the final release program, then
creates a second image based on the lightweight Alpine Linux and copies
over the release binary.

This has the effect of reducing the final image's size from 91 MB to a
lean 13.7 MB, which is faster/cheaper for users to pull.

A smaller optimization is to add a `.dockerignore` file which prevents
us from having to copy a number of extraneous files into the Docker
daemon for the initial build. This will help nominally to speed things
up.

One slight loss is that I've removed testing within the Go image from
`.travis.yml` because we no longer have a Go runtime with which to run
`go test ./...`. I think this is okay because we're already running
tests elsewhere in the Travis build, and it's unlikely that running them
in a Docker container is going to surface anything extra.

Here's me running the image locally:

```
$ docker run -d --name stripe-mock-container -p 12112:12111 stripemock/stripe-mock
bc71abebe5f6d80a9af2d1d53c86777d8c50b2e9a8d4de4a8b25d66c32a5d44b

$ docker ps
CONTAINER ID        IMAGE                    COMMAND                  CREATED             STATUS              PORTS                    NAMES
bc71abebe5f6        stripemock/stripe-mock   "/bin/sh -c /stripe-…"   26 seconds ago      Up 28 seconds       0.0.0.0:12112->12111/tcp stripe-mock-container
```

And a successful cURL:

```
$ curl http://localhost:12112
{
  "error": {
    "message": "Please authenticate by specifying an `Authorization` header with any valid looking testmode secret API key. For example, `Authorization: Bearer sk_test_123`. Authorization was ''.",
    "type": "invalid_request_error"
  }
}
```
---
 .dockerignore |  6 ++++++
 .travis.yml   |  1 -
 Dockerfile    | 30 +++++++++++++++++++++++++-----
 3 files changed, 31 insertions(+), 6 deletions(-)
 create mode 100644 .dockerignore

diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 00000000..894a046a
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,6 @@
+README.md
+LICENSE
+Makefile
+dist/
+goreleaser.yml
+openapi/
diff --git a/.travis.yml b/.travis.yml
index 5b4059cc..eb93ecef 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,7 +24,6 @@ script:
   - docker build -t "$DOCKER_REPO" .
   - docker run -d --name stripe-mock-container -p 12111:12111 "$DOCKER_REPO"
   - docker ps -a
-  - docker exec -it stripe-mock-container /bin/sh -c "cd /go/src/github.com/stripe/stripe-mock/; go test ./..."
 
 deploy:
   provider: script
diff --git a/Dockerfile b/Dockerfile
index c7eb34fd..01a066d6 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,9 +1,29 @@
-FROM golang:1.9-alpine
+# -*- mode: dockerfile -*-
+#
+# A multi-stage Dockerfile that builds a Linux target then creates a small
+# final image for deployment.
 
-ADD . /go/src/github.com/stripe/stripe-mock
+#
+# STAGE 1
+#
+# Uses a Go image to build a release binary.
+#
 
-RUN go install github.com/stripe/stripe-mock
+FROM golang:1.9-alpine AS builder
+WORKDIR /go/src/github.com/stripe/stripe-mock/
+ADD ./ ./
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o stripe-mock .
 
-EXPOSE 12111
+#
+# STAGE 2
+#
+# Use a tiny base image (alpine) and copy in the release target. This produces
+# a very small output image for deployment.
+#
 
-ENTRYPOINT /go/bin/stripe-mock
+FROM alpine:latest
+RUN apk --no-cache add ca-certificates
+WORKDIR /
+COPY --from=builder /go/src/github.com/stripe/stripe-mock/stripe-mock .
+ENTRYPOINT /stripe-mock
+EXPOSE 12111