Service definition
- Docker & Kubernetes course
- Beginner
- Lesson 62/82
- 4 min
Add a web service to the compose file.
Service definition
A service can be created from a ready image (image:) or from a Dockerfile in the project (build:). Each docker run option has a Compose counterpart:
services:
api:
build: .
image: api:dev
ports:
- "8000:8000"
environment:
LOG_LEVEL: info
restart: unless-stoppedWhen build and image are written together, the built image is tagged with that name.
Build details
In long form, build can take the context, Dockerfile and build arguments. When the code changes, the image is rebuilt with --build:
services:
api:
build:
context: ./api
dockerfile: Dockerfile
args:
SURUM: "1.0.0"
docker compose up -d --buildCompose uses the project folder's name (or -p) as a prefix: the container name becomes proje-api-1.
Practice The API service
Write the api service in compose.yaml: built from the current folder (build: .); publishing port 8000 with the same number; LOG_LEVEL: info under environment; restart: unless-stopped.
Starter code
# compose.yaml
services:
# buraya yazSample solution
# compose.yaml
services:
api:
build: .
ports:
- "8000:8000"
environment:
LOG_LEVEL: info
restart: unless-stoppedExpected output
[+] Running 2/2 ✔ Image proje-api Built ✔ Container proje-api-1 Started
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What is the Compose counterpart of the docker run -e LOG_LEVEL=info option?
- args: LOG_LEVEL=info
- LOG_LEVEL: info under environment Correct answer
- env: LOG_LEVEL
- vars: [info]
Explanation: environment can be written both as a map and as a list (- NAME=value).
2 Create the service from the Dockerfile in the project.
services:
api:
____: .services:
api:
build: .Explanation: build points at the context folder.
3 Match the docker run counterparts.
| Term | Meaning |
|---|---|
-p 8000:8000 |
ports |
-e NAME=value |
environment |
--restart |
restart |
docker build . |
build: . |