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 your
compose.yaml
file in an IDE or text editor.Uncomment the database related instructions. The following is the updated
compose.yaml
file.Important
For this section, don't run
docker compose up
until you are instructed to. Running the command at intermediate points may incorrectly initialize your database.compose.yaml# Comments are provided throughout this file to help you get started. # If you need more help, visit the Docker Compose reference guide at # https://docs.docker.com/go/compose-spec-reference/ # Here the instructions define your application as a service called "server". # This service is built from the Dockerfile in the current directory. # You can add other services your application may depend on here, such as a # database or a cache. For examples, see the Awesome Compose repository: # https://github.com/docker/awesome-compose services: server: build: context: . environment: NODE_ENV: production ports: - 3000:3000 # The commented out section below is an example of how to define a PostgreSQL # database that your application can use. `depends_on` tells Docker Compose to # start the database before your application. The `db-data` volume persists the # database data between container restarts. The `db-password` secret is used # to set the database password. You must create `db/password.txt` and add # a password of your choosing to it before running `docker-compose up`. depends_on: db: condition: service_healthy 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.
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. Thecompose.yaml
file doesn't have these variables defined yet.Add the environment variables that specify the database configuration. The following is the updated
compose.yaml
file.compose.yaml# Comments are provided throughout this file to help you get started. # If you need more help, visit the Docker Compose reference guide at # https://docs.docker.com/go/compose-spec-reference/ # Here the instructions define your application as a service called "server". # This service is built from the Dockerfile in the current directory. # You can add other services your application may depend on here, such as a # database or a cache. For examples, see the Awesome Compose repository: # https://github.com/docker/awesome-compose 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 # The commented out section below is an example of how to define a PostgreSQL # database that your application can use. `depends_on` tells Docker Compose to # start the database before your application. The `db-data` volume persists the # database data between container restarts. The `db-password` secret is used # to set the database password. You must create `db/password.txt` and add # a password of your choosing to it before running `docker-compose up`. depends_on: db: condition: service_healthy 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
Add the
secrets
section under theserver
service so that your application securely handles the database password. The following is the updatedcompose.yaml
file.compose.yaml# Comments are provided throughout this file to help you get started. # If you need more help, visit the Docker Compose reference guide at # https://docs.docker.com/go/compose-spec-reference/ # Here the instructions define your application as a service called "server". # This service is built from the Dockerfile in the current directory. # You can add other services your application may depend on here, such as a # database or a cache. For examples, see the Awesome Compose repository: # https://github.com/docker/awesome-compose 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 # The commented out section below is an example of how to define a PostgreSQL # database that your application can use. `depends_on` tells Docker Compose to # start the database before your application. The `db-data` volume persists the # database data between container restarts. The `db-password` secret is used # to set the database password. You must create `db/password.txt` and add # a password of your choosing to it before running `docker-compose up`. 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
In the
docker-nodejs-sample
directory, create a directory nameddb
.In the
db
directory, create a file namedpassword.txt
. This file will contain your database password.You should now have at least 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
Open the
password.txt
file in an IDE or text editor, and specify a password of your choice. Your password must be on a single line with no additional lines. Ensure that the file doesn't contain any newline characters or other hidden characters.Ensure that you save your changes to all the files that you have modified.
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:3000.
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.$ docker compose rm
Run
docker compose up
to run your application again.$ docker compose up --build
Refresh http://localhost:3000 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:${NODE_VERSION}-alpine as base
WORKDIR /usr/src/app
EXPOSE 3000
FROM base as dev
RUN --mount=type=bind,source=package.json,target=package.json \
--mount=type=bind,source=package-lock.json,target=package-lock.json \
--mount=type=cache,target=/root/.npm \
npm ci --include=dev
USER node
COPY . .
CMD npm run dev
FROM base as prod
RUN --mount=type=bind,source=package.json,target=package.json \
--mount=type=bind,source=package-lock.json,target=package-lock.json \
--mount=type=cache,target=/root/.npm \
npm ci --omit=dev
USER node
COPY . .
CMD node src/index.js
In the Dockerfile, you first add a label as base
to the FROM node:${NODE_VERSION}-alpine
statement. This lets you refer to this build stage
in other build stages. Next, you add a new build stage labeled dev
to install
your development 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. All comments have been removed.
services:
server:
build:
context: .
target: dev
ports:
- 3000:3000
- 9229:9229
environment:
NODE_ENV: production
POSTGRES_HOST: db
POSTGRES_USER: postgres
POSTGRES_PASSWORD_FILE: /run/secrets/db-password
POSTGRES_DB: example
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:3000.
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:3000 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 documentation.
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.