Use containers for Node.js development
Prerequisites
Complete Containerize a Node.js application.
Overview
In this section, you'll learn how to set up a development environment for your containerized application. This includes:
- Adding a local database and persisting data
- Configuring your container to run a development environment
- Debugging your containerized application
Add a local database and persist data
You can use containers to set up local services, like a database. In this section, you'll update the compose.yaml
file to define a database service and a volume to persist data.
Open the compose.yaml
file in an IDE or text editor. You'll notice it
already contains commented-out instructions for a Postgres database and volume.
Open src/persistence/postgres.js
in an IDE or text editor. You'll notice that
this application uses a Postgres database and requires some environment
variables in order to connect to the database. The compose.yaml
file doesn't
have these variables defined.
You need to update the following items in the compose.yaml
file:
- Uncomment all of the database instructions.
- Add the environment variables under the server service.
- Add
secrets
to the server service for the database password.
The following is the updated compose.yaml
file.
services:
server:
build:
context: .
environment:
NODE_ENV: production
POSTGRES_HOST: db
POSTGRES_USER: postgres
POSTGRES_PASSWORD_FILE: /run/secrets/db-password
POSTGRES_DB: example
ports:
- 3000:3000
depends_on:
db:
condition: service_healthy
secrets:
- db-password
db:
image: postgres
restart: always
user: postgres
secrets:
- db-password
volumes:
- db-data:/var/lib/postgresql/data
environment:
- POSTGRES_DB=example
- POSTGRES_PASSWORD_FILE=/run/secrets/db-password
expose:
- 5432
healthcheck:
test: [ "CMD", "pg_isready" ]
interval: 10s
timeout: 5s
retries: 5
volumes:
db-data:
secrets:
db-password:
file: db/password.txt
Note
To learn more about the instructions in the Compose file, see Compose file reference.
Before you run the application using Compose, notice that this Compose file uses
secrets
and specifies a password.txt
file to hold the database's password.
You must create this file as it's not included in the source repository.
In the cloned repository's directory, create a new directory named db
. Inside the db
directory, create a file named password.txt
. Open password.txt
in an IDE or text editor and add a password of your choice. The password must be on a single line with no additional lines in the file.
You should now have the following contents in your docker-nodejs-sample
directory.
├── docker-nodejs-sample/
│ ├── db/
│ │ └── password.txt
│ ├── spec/
│ ├── src/
│ ├── .dockerignore
│ ├── .gitignore
│ ├── compose.yaml
│ ├── Dockerfile
│ ├── package-lock.json
│ ├── package.json
│ └── README.md
Run the following command to start your application.
$ docker compose up --build
Open a browser and verify that the application is running at http://localhost:3000open_in_new.
Add some items to the todo list to test data persistence.
After adding some items to the todo list, press ctrl+c
in the terminal to stop your application.
In the terminal, run docker compose rm
to remove your containers and then run docker compose up
to run your application again.
$ docker compose rm
$ docker compose up --build
Refresh http://localhost:3000open_in_new in your browser and verify that the todo items persisted, even after the containers were removed and ran again.
Configure and run a development container
You can use a bind mount to mount your source code into the container. The container can then see the changes you make to the code immediately, as soon as you save a file. This means that you can run processes, like nodemon, in the container that watch for filesystem changes and respond to them. To learn more about bind mounts, see Storage overview.
In addition to adding a bind mount, you can configure your Dockerfile and compose.yaml
file to install development dependencies and run development tools.
Update your Dockerfile for development
Open the Dockerfile in an IDE or text editor. Note that the Dockerfile doesn't install development dependencies and doesn't run nodemon. You'll need to update your Dockerfile to install the development dependencies and run nodemon.
Rather than creating one Dockerfile for production, and another Dockerfile for development, you can use one multi-stage Dockerfile for both.
Update your Dockerfile to the following multi-stage Dockerfile.
# syntax=docker/dockerfile:1
ARG NODE_VERSION=18.0.0
FROM node:${NODE_VERSION}-alpine as base
WORKDIR /usr/src/app
EXPOSE 3000
FROM base as dev
RUN --mount=type=bind,source=package.json,target=package.json \
--mount=type=bind,source=package-lock.json,target=package-lock.json \
--mount=type=cache,target=/root/.npm \
npm ci --include=dev
USER node
COPY . .
CMD npm run dev
FROM base as prod
ENV NODE_ENV production
RUN --mount=type=bind,source=package.json,target=package.json \
--mount=type=bind,source=package-lock.json,target=package-lock.json \
--mount=type=cache,target=/root/.npm \
npm ci --omit=dev
USER node
COPY . .
CMD node src/index.js
In the Dockerfile, you first add a label as base
to the FROM node:${NODE_VERSION}-alpine
statement. This allows you to refer to this build
stage in other build stages. Next, you add a new build stage labeled dev
to
install your dev dependencies and start the container using npm run dev
.
Finally, you add a stage labeled prod
that omits the dev dependencies and runs
your application using node src/index.js
. To learn more about multi-stage
builds, see
Multi-stage builds.
Next, you'll need to update your Compose file to use the new stage.
Update your Compose file for development
To run the dev
stage with Compose, you need to update your compose.yaml
file.
Open your compose.yaml
file in an IDE or text editor, and then add the
target: dev
instruction to target the dev
stage from your multi-stage
Dockerfile.
Also, add a new volume to the server service for the bind mount. For this application, you'll mount ./src
from your local machine to /usr/src/app/src
in the container.
Lastly, publish port 9229
for debugging.
The following is the updated Compose file.
services:
server:
build:
context: .
target: dev
environment:
NODE_ENV: production
POSTGRES_HOST: db
POSTGRES_USER: postgres
POSTGRES_PASSWORD_FILE: /run/secrets/db-password
POSTGRES_DB: example
ports:
- 3000:3000
- 9229:9229
depends_on:
db:
condition: service_healthy
secrets:
- db-password
volumes:
- ./src:/usr/src/app/src
db:
image: postgres
restart: always
user: postgres
secrets:
- db-password
volumes:
- db-data:/var/lib/postgresql/data
environment:
- POSTGRES_DB=example
- POSTGRES_PASSWORD_FILE=/run/secrets/db-password
expose:
- 5432
healthcheck:
test: [ "CMD", "pg_isready" ]
interval: 10s
timeout: 5s
retries: 5
volumes:
db-data:
secrets:
db-password:
file: db/password.txt
Run your development container and debug your application
Run the following command to run your application with the new changes to the Dockerfile
and compose.yaml
file.
$ docker compose up --build
Open a browser and verify that the application is running at http://localhost:3000open_in_new.
Any changes to the application's source files on your local machine will now be immediately reflected in the running container.
Open docker-nodejs-sample/src/static/js/app.js
in an IDE or text editor and update the button text on line 109 from Add Item
to Add
.
+ {submitting ? 'Adding...' : 'Add'}
- {submitting ? 'Adding...' : 'Add Item'}
Refresh http://localhost:3000open_in_new in your browser and verify that the updated text appears.
You can now connect an inspector client to your application for debugging. For more details about inspector clients, see the Node.js documentationopen_in_new.
Summary
In this section, you took a look at setting up your Compose file to add a mock database and persist data. You also learned how to create a multi-stage Dockerfile and set up a bind mount for development.
Related information:
Next steps
In the next section, you'll learn how to run unit tests using Docker.