Dockerfile RUN doesn't to run in container context - node.js

Question

I'm having an issue trying to generate a dockerfile for my nodejs app:
My dockerfile:
FROM node
WORKDIR /app
COPY . /app
RUN npm install
EXPOSE 3000
CMD ["node", "/app/index.js"]
The nodejs (As part of npm install) needs grpc. When I try to run my app, I get the following error message:
Cannot find module '/app/node_modules/grpc/src/node/extension_binary/node-v57-linux-x64/grpc_node.node'
When I explore the app/node_modules/grpc/src/node/extension_binary/ folder, node-v48-win32-x64 is the only folder inside there. My guess is when npm install ran, it used the context my host machine where it detected windows/x64 and downloaded that binary instead. I'd like to avoid running npm install at runtime. How do I fix this?
My package.json:
{
"name": "microservice-test",
"version": "1.0.0",
"description": "A test microservice.",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "FrankerZ",
"license": "ISC",
"devDependencies": {
"grpcc": "0.0.8",
"gulp-livereload": "^3.8.1"
},
"dependencies": {
"async": "^2.5.0",
"grpc": "^1.6.0",
"gulp": "^3.9.1",
"gulp-run": "^1.7.1",
"gulp-util": "^3.0.8",
"protoc-plugin": "0.0.6"
}
}

Answer 1

What I think is happening is, docker run is copying the local node_modules from your project inside the container at COPY . /app
.
So thus you get the linux-x64 error. It basically copied all the machine specific code from node_modules to the container that must have another OS. To fix this, ignore node_modules by making a .dockerignore file alongside your package.json and add just one line.
node_modules
Read more about it from here.