chore: make the docker image much smaller. (#223)

Author: matrushka

Dockerfile

@@ -1,9 +1,9 @@
-FROM node:lts-buster
+FROM node:lts-alpine as node
+
+FROM node as builder
 
 # Install deps
-RUN apt-get update && apt-get install -y \
-  libssl-dev \
-  ca-certificates
+RUN apk add --update git build-base python3 libressl-dev ca-certificates
 
 # Setup directories for the `node` user
 RUN mkdir -p /home/node/app/webrtc-star/node_modules && chown -R node:node /home/node/app/webrtc-star
@@ -13,12 +13,21 @@ WORKDIR /home/node/app/webrtc-star
 # Install node modules
 COPY package.json ./
 # Switch to the node user for installation
-USER node
 RUN npm install --production
 
 # Copy over source files under the node user
-COPY --chown=node:node ./src ./src
-COPY --chown=node:node ./README.md ./
+COPY ./src ./src
+COPY ./README.md ./
+
+# Start from a clean node image
+FROM node as server
+
+# Prepare the working dir
+RUN mkdir -p /home/node/app/webrtc-star/node_modules && chown -R node:node /home/node/app/webrtc-star
+WORKDIR /home/node/app/webrtc-star
+
+# Copy installed and compiled modules w/o build dependencies
+COPY --from=builder --chown=node:node /home/node/app/webrtc-star /home/node/app/webrtc-star
 
 # webrtc-star defaults to 9090
 EXPOSE 9090