Suggestion: multistage Docker builds

Currently the docker image for external-auth-server sits at just over 1.04GB. This can be reduced using multi-staged builds. Here’s an initial pass at a Dockerfile for eas:

FROM node:10 AS builder

WORKDIR /root
COPY package*.json ./
RUN npm install

FROM node:10-alpine AS release

# Run as a non-root user
RUN adduser --disabled-password eas \
        && mkdir /home/eas/app \
        && chown -R eas: /home/eas
WORKDIR /home/eas/app
USER eas

COPY --from=builder --chown=eas:eas /root/node_modules ./node_modules
COPY --chown=eas:eas . .

EXPOSE 8080

CMD [ "npm", "start" ]

Using node:10-alpine the resultant image ends up being just under 200MB:

docker images external-auth-server:slim
REPOSITORY                           TAG                 IMAGE ID            CREATED             SIZE
external-auth-server                 slim              bfc66bf5f94c        38 seconds ago      194MB

I haven’t tested to see if eas will work with this change, but I thought I’d at least suggest a way to reduce the current eas image by 4/5ths.

[travisghansen]

Implemented with v0.10.0.

[travisghansen]

For binary compatibility with some pre-built npm stuff I think we’ll stick with glibc over musl based system.