Passing NODE_ENV to docker to run package.json scripts

Question

This is my dockerfile :

FROM node:6-onbuild

RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

COPY package.json /usr/src/app/
RUN npm install
COPY . /usr/src/app

ENV PORT 80
EXPOSE ${PORT}

CMD [ "npm","run", "start" ]

and in package.json I do have this :

"scripts": {
  "start": "node start.js",
  "stagestart": "NODE_ENV=content-staging node start.js"
}

the start script is for production, now I want a way to run the staging script in dockerfile. is there a way to read NODE_ENV inside dockerfile, so I can have one dockerfile which handle staging and production.

Answer 1

Here is two possible implementation.

FYI: you don't need to mention NODE_ENV in package.json if you already set NODE_ENV at the system level or set NODE_ENV during build time or runtime in docker.

Here Dockerfile as same but I used to alpine base image

FROM node:alpine

RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

COPY package.json /usr/src/app/
RUN npm install
COPY . /usr/src/app
ENV PORT 3000
ARG DOCKER_ENV
ENV NODE_ENV=${DOCKER_ENV}
RUN if [ "$DOCKER_ENV" = "stag" ] ; then  echo   your NODE_ENV for stage is $NODE_ENV;  \
else  echo your NODE_ENV for dev is $NODE_ENV; \
fi 


EXPOSE ${PORT}

CMD [ "npm","run", "start" ]

when you build this Dockerfile with this command

docker build --build-arg DOCKER_ENV=stag -t test-node .

You will see at layer

 ---> Running in a6231eca4d0b your NODE_ENV for stage is stag

When you run this docker container and run this command your output will be

/usr/src/app # echo $NODE_ENV

stag

Simplest Approch same image and but set environment variable at run time

Your Dockerfile

FROM node:alpine
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app
COPY package.json /usr/src/app/
RUN npm install
COPY . /usr/src/app
ENV PORT 3000
EXPOSE ${PORT}
CMD [ "npm","run", "start" ]

Run this docker image with this command

docker build -t  test-node .

 docker run  --name test -e NODE_ENV=content-staging  -p 3000:3000 --rm -it test-node ash

So when you run this command at container you will see

/usr/src/app # echo $NODE_ENV
content-staging

So this is how you can start your node application with NODE_ENV without setting environment variable at package.json. So if your nodejs configuration is based on NODE_ENV it should pick configuration according to NODE_ENV .