Optimize docker build

Dockerfile

@@ -1,18 +1,49 @@
-FROM keymetrics/pm2:latest-stretch
-# Create app directory
+########
+# BASE
+########
+FROM keymetrics/pm2:12-alpine as base
 WORKDIR /usr/src/markbot
 
-# Install app dependencies
+COPY package*.json ./
+# Install build tools for erlpack, then install prod deps only, then remove build tools
+RUN apk add --no-cache make gcc g++ python && \
+    npm ci --only=production && \
+    apk del make gcc g++ python
+
+########
+# BUILD
+########
+FROM base as build
+
+# Copy all *.json, *.js, *.ts
+COPY . .
+# Prod deps already installed, add dev deps
+RUN npm i
+
+RUN npm run build
+
+########
+# DEPLOY
+########
+FROM keymetrics/pm2:12-alpine as deploy
+WORKDIR /usr/src/markbot
+
+ENV NPM_CONFIG_LOGLEVEL warn
+
+# Steal node_modules from base image
+COPY --from=base /usr/src/markbot/node_modules ./node_modules/
+
+# Steal compiled code from build image
+COPY --from=build /usr/src/markbot/dist ./
+
+# Copy package.json for version number
 COPY package*.json ./
 
-# If you are building your code for production
-ENV NPM_CONFIG_LOGLEVEL warn
-RUN npm ci --only=production
+# Copy PM2 config
+COPY ecosystem.config.js .
 
-# Bundle app source
-COPY . .
 RUN mkdir config
 
-RUN ls -al
+# RUN ls -al
 
 CMD [ "pm2-runtime", "start", "ecosystem.config.js" ]