Node cannot find node_modules in dockerized node app

Question

I am new to docker. I tried to dockerize my existing node application. During docker-compose the app throws error stating it cannot find the node_modules.

Here's the error

dockerised-yelpcamp | > dockerised-yelpcamp@1.0.1 start /usr/src/app
dockerised-yelpcamp | > node app.js
dockerised-yelpcamp | 
dockerised-yelpcamp | internal/modules/cjs/loader.js:584
dockerised-yelpcamp |     throw err;
dockerised-yelpcamp |     ^
dockerised-yelpcamp | 
dockerised-yelpcamp | Error: Cannot find module 'express'
dockerised-yelpcamp |     at Function.Module._resolveFilename (internal/modules/cjs/loader.js:582:15)
dockerised-yelpcamp |     at Function.Module._load (internal/modules/cjs/loader.js:508:25)
dockerised-yelpcamp |     at Module.require (internal/modules/cjs/loader.js:637:17)
dockerised-yelpcamp |     at require (internal/modules/cjs/helpers.js:22:18)
dockerised-yelpcamp |     at Object.<anonymous> (/usr/src/app/app.js:1:77)
.
.
.
dockerised-yelpcamp |     at Function.Module._load (internal/modules/cjs/loader.js:531:3)
dockerised-yelpcamp | npm ERR! code ELIFECYCLE
dockerised-yelpcamp | npm ERR! errno 1
dockerised-yelpcamp | npm ERR! dockerised-yelpcamp@1.0.1 start: `node app.js`
dockerised-yelpcamp | npm ERR! Exit status 1
dockerised-yelpcamp | npm ERR! 
dockerised-yelpcamp | npm ERR! Failed at the dockerised-yelpcamp@1.0.1 start script.
dockerised-yelpcamp | npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
dockerised-yelpcamp | npm WARN Local package.json exists, but node_modules missing, did you mean to install?
dockerised-yelpcamp | 
dockerised-yelpcamp | npm ERR! A complete log of this run can be found in:
dockerised-yelpcamp | npm ERR!     /root/.npm/_logs/2019-04-17T11_14_17_109Z-debug.log
dockerised-yelpcamp exited with code 1

docker-compose.yml

version: "3"
services:
  main_app:
    container_name: dockerised-yelpcamp
    restart: always
    build: .
    ports:
      - 80:3000
    links:
      - mongo
    volumes: ["./:/usr/src/app"]
  mongo:
    container_name: mongo
    image: mongo
    ports:
      - 27017:27017

Dockerfile

FROM node:10

WORKDIR /usr/src/app

COPY package.json ./

RUN npm install

COPY . .

EXPOSE 3000

CMD ["npm", "start"]

My docker file contains npm install which is executed successfully while building image.

Answer 1

You copy only package.json, so you need node_modules folder created:

dockerised-yelpcamp | npm WARN Local package.json exists, but node_modules missing, did you mean to install?

if my memory is good, docker container can't respond yes by default. So, he skip creation folder and node_modules stay missing.

Answer 2

Your volumes: directive is hiding everything the Dockerfile does with content from your local system. If you don't have a node_modules directory there or its architecture or library stack is incompatible with what's in the container, this setup simply won't work.

The common workaround seems to be to declare a second anonymous volume to hold node_modules , which will work until you change your package.json file.

My recommendation would be to remove the volumes: directive entirely. Develop your application locally without Docker. Once it works and you've tested it, use this Dockerfile to rebuild the image. This both gives you a simpler non-Docker development setup, and replicates the environment you have in production (where you're not going to copy the application code in addition to the Docker image that contains it).