As far as I know, volume in Docker is some permanent data for the container, which can map local folder and container folder.
In early day, I am facing Error: Cannot find module 'winston' issue in Docker which mentioned in:
docker - Error: Cannot find module 'winston'
Someone told me in this post:
Remove volumes: - ./:/server from your docker-compose.yml. It overrides the whole directory contains node_modules in the container.
After I remove volumes: - ./:/server, the above problem is solved.
However, another problem occurs.
[solved but want explanation]nodemon --legacy-watch src/ not working in Docker
I solve the above issue by adding back volumes: - ./:/server, but I don't know what is the reason of it
Question
What is the cause and explanation for above 2 issues?
What happen between build and volumes, and what is the relationship between build and volumes in docker-compose.yml
Dockerfile
FROM node:lts-alpine
RUN npm install --global sequelize-cli nodemon
WORKDIR /server
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 3030
CMD ["npm", "run", "dev"]
docker-compose.yml
version: '2.1'
services:
test-db:
image: mysql:5.7
...
test-web:
environment:
- NODE_ENV=local
- PORT=3030
build: . <------------------------ It takes Dockerfile in current directory
command: >
./wait-for-db-redis.sh test-db npm run dev
volumes:
- ./:/server <------------------------ how and when does this line works?
ports:
- "3030:3030"
depends_on:
- test-db
When you don't have any volumes:, your container runs the code that's built into the image. This is good! But, the container filesystem is completely separate from the host filesystem, and the image contains a fixed copy of your application. When you change your application, after building and testing it in a non-Docker environment, you need to rebuild the image.
If you bind-mount a volume over the application directory (.:/server) then the contents of the host directory replace the image contents; any work you do in the Dockerfile gets completely ignored. This also means /server/node_modules in the container is ./node_modules on the host. If the host and container environments don't agree (MacOS host/Linux container; Ubuntu host/Alpine container; ...) there can be compatibility issues that cause this to break.
If you also mount an anonymous volume over the node_modules directory (/server/node_modules) then only the first time you run the container the node_modules directory from the image gets copied into the volume, and then the volume content gets mounted into the container. If you update the image, the old volume contents take precedence (changes to package.json get ignored).
When the image is built only the contents of the build: block have an effect. There are no volumes: mounted, environment: variables aren't set, and the build environment isn't attached to networks:.
The upshot of this is that if you don't have volumes at all:
version: '3.8'
services:
app:
build: .
ports: ['3000:3000']
It is completely disconnected from the host environment. You need to docker-compose build the image again if your code changes. On the other hand, you can docker push the built image to a registry and run it somewhere else, without needing a separate copy of Node or the application source code.
If you have a volume mount replacing the application directory then everything in the image build is ignored. I've seen some questions that take this to its logical extent and skip the image build, just bind-mounting the host directory over an unmodified node image. There's not really benefit to using Docker here, especially for a front-end application; install Node instead of installing Docker and use ordinary development tools.
Related
I am new to Docker and created following files in a large Node project folder:
Dockerfile
# syntax=docker/dockerfile:1
FROM node:16
# Update npm
RUN npm install --global npm
# WORKDIR automatically creates missing folders
WORKDIR /opt/app
# https://stackoverflow.com/a/42019654/15443125
VOLUME /opt/app
RUN useradd --create-home --shell /bin/bash app
COPY . .
RUN chown -R app /opt/app
USER app
ENV NODE_ENV=production
RUN npm install
# RUN npx webpack
CMD [ "sleep", "180" ]
docker-compose.yml
version: "3.9"
services:
app:
build:
context: .
ports:
- "3000:3000"
volumes:
- ./dist/dockerVolume/app:/opt/app
And I run this command:
docker compose up --force-recreate --build
It builds the image, starts a container and I added a sleep to make sure the container stays up for at least 3 minutes. When I open a console for that container and run cd /opt/app && ls, I can verify that there are a lot of files. project/dist/dockerVolume/app gets created by Docker, but nothing is written to it at any point.
There are no errors or warnings or other indications that something isn't set up correctly.
What am I missing?
First you should move the VOLUME declaration to the end of the Dockerfile, because:
If any build steps change the data within the volume after it has been declared, those changes will be discarded. (Documentation)
After this you will face the issue of how bind mounts and docker volumes work. Unfortunately if you use a bind mount, the contents of the host directory will always replace the files that are already in the container. Files will only appear in the host directory, if they were created during runtime by the container.
Also see:
Docker docs: bind mounts
Docker docs: volumes
To solve the issue, you could use any of these workarounds, depending on your usecase:
Use volumes in your docker-compose.yml file instead of bind mounts (Documentation)
Create the files you want to run on the host instead of in the image, and bind mount them into the container.
Use a bash script in the container that creates the neccessary files (if they are missing) when the container is starting (so the bind mount is already initialized, and the changes will persist) and after that, it starts your processes.
I am trying to host a development environment on my Windows machine which hosts a frontend and backend container. So far I have only been working on the backend. All files are on the C Drive which is shared via Docker Desktop.
I have the following docker-compose file and Dockerfile, the latter is inside a directory called backend within the root directory.
Dockerfile:
FROM node:12.15.0-alpine
WORKDIR /usr/app
COPY package*.json ./
RUN npm install
EXPOSE 5000
CMD [ "npm", "start" ]
docker-compose.yml:
version: "3"
services:
backend:
container_name: backend
build:
context: ./backend
dockerfile: Dockerfile
volumes:
- ./backend:/usr/app
environment:
- APP_PORT=80
ports:
- '5000:5000'
client:
container_name: client
build:
context: ./client
dockerfile: Dockerfile
volumes:
- ./client:/app
ports:
- '80:8080'
For some reason, when I make changes in my local files they are not reflecting inside the container. I am testing this by slightly modifying the outputs of one of my files, but I am having to rebuild the container each time to see the changes take effect.
I have worked with Docker in PHP applications before, and have basically done the same thing. So I am unsure why this is not working with by Node.js app. I am wondering if I am just missing something glaringly obvious as to why this is not working.
Any help would be appreciated.
The difference between node and PHP here is that php automatically picks up file system changes between requests, but a node server doesn't.
I think you'll see that the file changes get picked up if you restart node by bouncing the container with docker-compose down then up (no need to rebuild things!).
If you want node to pick up file system changes without needing to bounce the server you can use some of the node tooling. nodemon is one: https://www.npmjs.com/package/nodemon. Follow the installation instructions for local installation and update your start script to use nodemon instead of node.
Plus I really do think you have a mistake in your dockerfile and you need to copy the source code into your working directory. I'm assuming you got your initial recipe from here: https://dev.to/alex_barashkov/using-docker-for-nodejs-in-development-and-production-3cgp. This is the docker file is below. You missed a step!
FROM node:10-alpine
WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY . .
CMD [ "npm", "start" ]
There are some similar questions but they haven't answered why docker creates the empty node_modules directory in the repo even though the dockerfile is setup to hold node_modules in the container?
I'm interested to know why directory is created on the host empty, give that yarn already installs packages inside the container within node_modules and how to avoid it.
## Dockerfile
FROM node:8.11.4-alpine
RUN apk update && apk add yarn
RUN yarn global add nodemon
WORKDIR /usr/app
COPY package.json yarn.lock /usr/app/
RUN yarn
EXPOSE 3000
## docker-compose.yml
version: "3.2"
services:
app:
build:
context: .
dockerfile: Dockerfile
command: nodemon index.js
volumes:
- .:/usr/app
- /usr/app/node_modules
ports:
- "3000:3000"
You are right, your image building process is installing the node packages into the node_modules directory in the image. So, after you build your image the image contains node_modules and you can use it to run your application.
You see node_modules on your host machine, because of your volumes setup in your Compose file. There is more to it than you see in the other answer though.
What's happening is that you are mapping .:/usr/app in your first volume definition, which means that you are mapping your current directory on the host to /usr/app in the container.
This will override the /usr/app directory in the image with the current directory on the host. And your host does not have the node_modules directory (unless you installed node_modules on the host, too) and therefore your container will not work with this mapping, beacuse you've overriden /usr/app and there is no node_modules dir in the override. Node will throw an error that it cannot find node modules.
The next volume mapping solves the situation, this is actually a common Node development setup. You create a volume /usr/app/node_modules. Note, that this volume does not have a host part there is no : in the mapping, there is only one directory here. This means that Docker will mount the /usr/app/node_modules directory from the image and add it to the previous mapping where you mapped the host dir to /usr/app.
So in the running container you'll have your source code from the host's current directory PLUS node_modules from the underlying image due to the double mapping.
As a side effect you'll see an empty node_modules directory in your host's current directory.
I am aiming to configure docker so that when I modify a file on the host the change is propagated inside the container file system.
You can think of this as hot reloading for server side node code.
The nodemon file watcher should restart the server in response to file changes.
However these file changes on the host volume don't seem to be reflected inside the container when I inspect the container using docker exec pokerspace_express_1 bash and inspect a modified file the changes are not propagated inside the container from the host.
Dockerfile
FROM node:8
MAINTAINER therewillbecode
# Create app directory
WORKDIR src/app
RUN npm install nodemon -g
# Install app dependencies
COPY package.json .
# For npm#5 or later, copy package-lock.json as well
# COPY package.json package-lock.json ./
RUN npm install
CMD [ "npm", "start" ]
docker-compose.yml
version: '2'
services:
express:
build: .
depends_on:
- mongo
environment:
- MONGO_URL=mongo:27017/test
- SERVER_PORT=3000
volumes:
- ./:/src/app
ports:
- '3000:3000'
links:
- mongo
mongo:
image: mongo
ports:
- '27017:27017'
mongo-seed:
build: ./mongo-seed
links:
- mongo
.dockerignore
.git
.gitignore
README.md
docker-compose.yml
How can I ensure that host volume file changes are reflected in the container?
Try something like this in your Dockerfile:
CMD ["nodemon", "-L"]
Some people had a similar issue and were able to resolve it with passing -L (which means “legacy watch”) to nodemon.
References:
https://github.com/remy/nodemon/issues/419
http://fostertheweb.com/2016/02/nodemon-inside-docker-container/#why-isnt-nodemon-reloading
Right, so with Docker we need to re-build the image or figure out some clever solution.
You probably do not want to rebuild the image every time you make a change to your source code.
Let's figure out a clever solution. Let's generalize the Dockerfile a bit to solve your problem and also help others.
So this is the boilerplate Dockerfile:
FROM node:alpine
WORKDIR '/app'
COPY package.json .
RUN npm install
COPY . .
CMD ["npm", "run", "start"]
Remember, during the image building process we are creating a temporary container. When we make the copies we are essentially taking a snapshot of the contents /src and /public. Its a snapshot that is locked in time and by default will not be updated by making changes to the code.
So in order to get these changes to files /src and /public, we need to abandon doing a straight copy, we are going to adjust the docker run command that we use to start up our container.
We are going to make use of a feature called volume.
With Docker volume we setup a placeholder inside our Docker container, so instead of copying over our entire/src directory we can imagine we are going to put a reference to those files and give us access to the files and folders inside of the local machine.
We are setting up a mapping from a folder inside the container to a folder outside a container. The command to use is a bit painful, but once its documented here you can bookmark this answer.
docker run -p 3000:3000 -v /app/node_modules -v $(pwd):/app <image_id>
-v $(pwd):/app used to set up a volume in present working directory. This is a shortcut. So we are saying get the present working directory, get everything inside of it and map it up to our running container. It's long winded I know.
To implement this you will have to first rebuild your docker image by running:
docker build -f Dockerfile.dev .
Then run:
docker run -p 3000:3000 -v $(pwd):/app <image_id>
Then you are going to very quickly get an error message, the react-scripts not found error. You will see that message because I skipped the -v /app/node_modules.
So what's up with that?
The volume command sets up a mapping and when we do, we are saying take everything inside of our present working directory and map it up to our /appfolder, but the issue is there is no /node_modules folder which is where all our dependencies exist.
So the /node_modules folder got overwritten.
So we are essentially pointing to nothing and thats why we need that -v /app/node_modules with no colon because the colon is to map up the folder inside a container to a folder outside the container. Without the colon we are saying want it to be a placeholder, don't map it up against anything.
Now, go ahead and run: docker run -p 3000:3000 -v $(pwd):/app <image_id>
Once done, you can make all the changes you want to your project and see them "hot reload" in your browser. No need to figure out how to implement Nodemon.
So whats happening there is any changes made to your local file system is getting propagated into your container, the server inside your container sees the change and updates.
Now, I know its hard and annoying to remember such a long command, in enters Docker Compose.
We can make use of Docker Compose to dramatically simplify the command we have to run to start up the container.
So to implement that you create a Docker Compose file and inside of it you will include the port setting and the two volumes that you need.
Inside your root project, make a new file called docker-compose.yml.
Inside there you will add this:
version: '3'
services:
web:
build: .
ports:
- "3000:3000"
volumes:
- /app/node_modules
- .:/app
Then run: docker-compose up
Daniel's answer partially worked for me, but the hot reloading still doesn't work. I'm using a Windows host and had to change his docker-compose.yml to
version: '3'
services:
web:
build: .
ports:
- "3000:3000"
volumes:
- /App/node_modules
- .:/App
(I changed the volumes arguments from /app/node_modules to /App/node_modules and from .:/app to .:/App. This enables changes to be passed to the container, however the hot reloading still doesn't work. I have to use docker-compose up --build each time I want to refresh the app.)
I've tried every solution from this post and this post
I'm not finding a solution to get rid of the following error when running docker-compose up:
module.js:598
return process.dlopen(module, path._makeLong(filename));
^
Error: /code/node_modules/bcrypt/lib/binding/bcrypt_lib.node: invalid ELF header
Here's my latest attempt docker-compose.yml
version: "2"
services:
app:
build: ./client
ports:
- "3000:3000"
links:
- auth
volumes:
- ./client:/code
auth:
build: ./auth-service
ports:
- "3002:3002"
links:
- db
volumes:
- ./auth-service:/code
db:
...
And my auth service Dockerfile:
FROM node:7.7.1
EXPOSE 3002
WORKDIR /code
COPY package.json /code
RUN npm install
COPY . /code
CMD npm start
After trying each of the solution from the above two links, I rebuild the containers and it always results in the same error.
Also worth noting, the service runs fine locally, when I don't use docker.
How do I get docker to work with bcrypt?
Update
I was able to get it working by doing the following:
finding the id of the container: docker ps
accessing the container: docker exec -t -i containerId /bin/bash
installing bcrypt: npm install bcrypt
This isn't ideal for portability
I spent a few hours trying to solve this and in the end I came up with the following solution.
My compose file looks like this.....
version: "3"
services:
server:
build:
context: ./server
volumes:
- ./server:/usr/src/app
- /usr/src/app/node_modules/
ports:
- 3050:3050
depends_on:
- db
command: ["nodemon", "./bin/www"]
The second volume mount there is the important one as this gets around the local node_module issue.
Just for reference my dockerfile is like this:
FROM node
RUN npm install -g nodemon
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app
COPY package.json /usr/src/app
RUN npm install
EXPOSE 3050
CMD ["nodemon", "./bin/www"]
was struggling with this one few times, the ".dockerignore" solution wont work if you use volumes sadly, since its only related to the "Copy" command and only when you build the container.
the only solution i found which i think makes the most sense, is to volume only what you need, what does it mean - divide your source code and the "configurations" files (such as package.json):
- src
-- morecode
-- morecode2
-- server.js
- index.js
- package.json
- jslint.json
- tsconfig.json
- .env
- .dockerignore
- ... etc
and put the volume only on the "src" folder, that way your builds will also be much faster plus your node modules will be built and installed on the correct operation system, d'ont forget to add .dockerignore to node_modules to prevent builds form taking unnecessary longer time
do note that doing so will require re-build of the application every time your adding new package, but if you use npm best practice and you divide the npm installation in your docker file to be cached, it will be faster
The reason this error occurs is that the node module bcrypt is first compiled on your original machine (specific for your OS) and when an image is built on docker it cannot run since the OS is no longer the same. solution create a .dockerignore file in your root folder and add node_modules to this file.