Reduce docker image size with multistage build

We don't need development dependencies in production. I also added the
BUILD_COMMIT environment variable to the image for convenience.

.travis.yml

@@ -18,7 +18,7 @@ before_install:
   - sudo mv docker-compose /usr/local/bin
 
 install:
-  - docker build --build-arg BUILD_COMMIT=$TRAVIS_COMMIT -t humanconnection/nitro-backend:latest .
+  - docker build --build-arg BUILD_COMMIT=$TRAVIS_COMMIT --target production -t humanconnection/nitro-backend:latest .
   - docker-compose -f docker-compose.yml up -d
 
 script:

Dockerfile

@@ -1,9 +1,11 @@
-FROM node:10-alpine
+FROM node:10-alpine as builder
 LABEL Description="Backend of the Social Network Human-Connection.org" Vendor="Human Connection gGmbH" Version="0.0.1" Maintainer="Human Connection gGmbH (developer@human-connection.org)"
 
 # Expose the app port
 EXPOSE 4000
 
+ARG BUILD_COMMIT
+ENV BUILD_COMMIT=$BUILD_COMMIT
 ARG WORKDIR=/nitro-backend
 RUN mkdir -p $WORKDIR
 WORKDIR $WORKDIR
@@ -11,10 +13,17 @@ WORKDIR $WORKDIR
 # Install the Application Dependencies
 COPY package.json .
 COPY yarn.lock .
-RUN yarn install --production=false --frozen-lockfile --non-interactive
+RUN yarn install --frozen-lockfile --non-interactive
 
 COPY . .
 COPY .env.template .env
 
 RUN yarn run build
 CMD ["yarn", "run", "start"]
+
+# reduce image size with a multistage build
+FROM node:10-alpine as production
+ENV NODE_ENV=production
+COPY --from=builder /nitro-backend/dist ./dist
+COPY package.json yarn.lock ./
+RUN yarn install --frozen-lockfile --non-interactive

docker-compose.override.yml

@@ -2,6 +2,9 @@ version: "3.7"
 
 services:
   backend:
+    build:
+      context: .
+      target: builder
     volumes:
       - .:/nitro-backend
       - /nitro-backend/node_modules

docker-compose.yml

@@ -3,7 +3,9 @@ version: "3.7"
 services:
   backend:
     image: humanconnection/nitro-backend:latest
-    build: .
+    build:
+      context: .
+      target: production
     networks:
       - hc-network
     depends_on: