Running Nodemon in Docker Container - node.js

Question

I'm trying to run Nodemon package in a Docker Network with two services, NodeJs and MongoDB.
When I run the app with npm start, nodemon works: I can connect to localhost:3000 and I have the changes in real time. But as soon as I run npm run docker (docker-compose up --build), I can connect to localhost:3000 but I'm not able to see real-time changes on my application nor console.
docker-compose.yml
version: '3.7'
services:
app:
container_name: NodeJs
build: .
volumes:
- "./app:/usr/src/app/app"
ports:
- 3000:3000
mongo_db:
container_name: MongoDB
image: mongo
volumes:
- mongo_db:/data/db
ports:
- 27017:27017
volumes:
mongo_db:
dockerfile
FROM node:alpine
WORKDIR /app
COPY package.json /.
RUN npm install
COPY . /app
CMD ["npm", "run", "dev"]
package.json
{
"name": "projectvintedapi",
"version": "0.0.0",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1",
"start": "node index.js",
"dev": "nodemon index.js",
"docker": "docker-compose up --build"
},
"license": "ISC",
"dependencies": {
"dotenv": "^16.0.0",
"express": "^4.17.3",
"mongodb": "^4.5.0",
"nodemon": "^2.0.15"
}
}

Answer 1

docker-compose.yml tells Docker to boot a container, the Node.js application. It also tells Docker to mount a host volume:
volumes:
- "./app:/usr/src/app/app"
As a result, Docker will mount the ./app directory on your laptop, which contains your code, into the container at /usr/src/app/app.
Once you’ve changed your code on your laptop/desktop, nodemon detects that change and restarts the process without rebuilding the container. To make this happen, you need to tell Docker to set the entrypoint to nodemon. Do that in the Dockerfile:
FROM node:alpine
WORKDIR /app
COPY . /app
RUN npm install -g nodemon
RUN npm install
#Give the path of your endpoint
ENTRYPOINT ["nodemon", "/usr/src/app/server.js"]
CMD ["npm", "run", "dev"]
With host volumes and nodemon, your code sync is almost instantaneous.

Answer 2

Fixed it: it was for bind mount
dockerfile
FROM node:16.13.2
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci
COPY . ./
CMD ["npm", "run", "start"]
docker-compose.yml
version: '3.7'
services:
app:
container_name: NodeJs
build: .
command: npm run dev
volumes:
- .:/app
ports:
- 3000:3000
mongo_db:
container_name: MongoDB
image: mongo
volumes:
- mongo_db:/data/db
ports:
- 27017:27017
volumes:
mongo_db: