A container runs an application with its dependencies in an isolated, portable environment. Docker containers have their own processes, network interfaces, and volume mounts, but share the host’s operating-system kernel. Unlike a virtual machine, a container does not include a full operating system. section 12.1.2
A Docker image is the template; a container is an instance started from it. To check the distinction in practice, pull the `hello-world` image and run it with `docker run hello-world`. section 12.2.1
# Use the main rust Docker image FROM rust # copy app into docker image COPY . /app # Set the workdirectory WORKDIR /app # build the app RUN cargo build --release # start the application CMD ["./target/release/docker-rust"]
This first Dockerfile copies a Rust web service into an image, builds a release binary, and sets that binary as the container’s startup command. section 12.2.2
Build and run the service, then address what the first container leaves unresolved:
- Build with `docker build -f Dockerfile-basic . -t docker-rust-basic`, then run with `docker run -p 8080:8080 -t docker-rust-basic`. Check both HTTP routes in a browser. section 12.2.2
- The initial image is 1.32 GB because it retains the Rust compiler and build artifacts. A multistage build can keep only the final binary in the runtime image. section 12.2.2 section 12.6
- Run Postgres in a separate container. Put its data in a Docker volume so records survive stopping and restarting the container. section 12.3.1 section 12.3.2
version: '3'
services:
db: #1
container_name: tutor-postgres
restart: always
image: postgres:latest
environment:
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=postgres
- POSTGRES_DB=ezytutors
volumes:
- tutor-data:/var/lib/postgresql/data
- ./c12-data/initdb.sql:/docker-entrypoint-initdb.d/initdb.sql
- ./c12-data/init-tables.sql:/docker-entrypoint-initdb.d/init-tables.sql
ports:
- 5432:5432
networks:
- tutor-network
api: #2
restart: on-failure
container_name: tutor-webservice
build: #3
context: ./
dockerfile: Dockerfile-tutor-webservice
network: host
environment: #4
- DATABASE_URL=${DATABASE_URL}
- HOST_PORT=${HOST_PORT}
depends_on:
- db #5
ports:
- ":3000:3000" #6
networks:
- tutor-network #7
volumes:
tutor-data:
networks:
tutor-network:
The Compose configuration shows separate database and API services, with image or build settings, environment variables, storage, ports, and networking. section 12.5
Docker Compose builds, starts, and stops the application’s containers as a group. Connect the web service and Postgres through a common Docker network, set the database URL for their connection, and test the running API with `curl localhost:3000/tutors/`. Container packaging does not itself settle production concerns such as secrets, security, monitoring, or backups. section 12.5 section 12.0
