Could not find a required file - docker

Question

I'm trying to run docker container with create-react-app App. App works fine and here's how my dockerfile looks like.
# base image
FROM node:12.2.0-alpine
# set working directory
WORKDIR ./
# add `//node_modules/.bin` to $PATH
ENV PATH ./node_modules/.bin:$PATH
# install and cache dependencies
COPY package.json ./package.json
COPY ./build/* ./public/
RUN npm install --silent
RUN npm install react-scripts#3.0.1 -g
# start
CMD ["npm", "start"]
When I run docker im getting error
> my-app#0.1.0 start /
> react-scripts start
Could not find a required file.
Name: index.js
Searched in: /src
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! my-app#0.1.0 start: `react-scripts start`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the my-app#0.1.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR! /root/.npm/_logs/2019-07-14T08_29_30_761Z-debug.log
has anybody have any idea?

Answer 1

npm start is for webpack - which serves you as the dev server. you are still using directly the src files, not the minified build (dist), which will only be used on production.
#Dockerfile.dev:
# base image
FROM node:12.2.0-alpine
# set working directory
WORKDIR ./
# add `//node_modules/.bin` to $PATH
ENV PATH ./node_modules/.bin:$PATH
COPY package.json ./package.json
#use the minified build file for production, not now - npm start is for development.
#COPY ./build/* ./public/
#install dependencies:
RUN npm install --silent
RUN npm install react-scripts#3.0.1 -g
#copy your project files: (also bad for development, use volume(https://docs.docker.com/storage/volumes/) instead)
COPY . .
# start
CMD ["npm", "start"]

Answer 2

(This builds on #EfratLevitan's answer, but is a little more production-oriented. Their answer will be better if you want to use Docker as a core part of your development flow.)
If you have a working Webpack setup already, its output is static files that can be served up by any Web server. Once you've successfully run npm run build, you can use anything to serve the resulting build directory – serve it as static content from something like a Flask application, put it in a cloud service like Amazon S3 that can serve it for you, directly host it yourself. Any of the techniques described on the CRA Deployment page will work just fine in conjunction with a Docker-based backend.
If you'd like to serve this yourself via Docker, you don't need Node to serve the build directory, so a plain Web server like nginx will work fine. The two examples from the image description work for you here:
# Just use the image and inject the content as data
docker run -v $PWD/build:/usr/share/nginx/html -p 80:80 nginx
# Build an image with the content "baked in"
cat >Dockerfile <<EOF
FROM nginx
COPY ./build /usr/share/nginx/html
EOF
# Run it
docker build -t me/nginx .
docker run -p 80:80 me/nginx
The all-Docker equivalent to this is to use a multi-stage build to run the Webpack build inside Docker, then copy it out to a production Web server image.
FROM node:12.2.0-alpine AS build
WORKDIR /app
COPY package.json yarn.lock .
RUN npm install --silent
RUN npm install react-scripts#3.0.1 -g
COPY . .
RUN npm run build
FROM nginx
COPY --from=build /app/build /usr/share/nginx/html
In this model you'd develop your front-end code locally. (The Webpack/CRA stack has pretty minimal host dependencies, and since the application runs in the user's browser, it can't depend on Docker-specific networking features.) You'd only build this Dockerfile once you wanted to run an end-to-end test with all of the parts running together before you actually pushed out to production.