compose.yaml & service names

Declare two services with Compose

Lesson 13 of 20 · 12 min · Module 4: Artifact and stack design

A declarative file can describe the relationships of a small application stack.

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Describe the desired service graph
Keep YAML data types visible

The idea

Compose describes services and their relationships as YAML mappings and sequences. Read the whole service graph, including access and storage boundaries.

services:
  frontend:
    image: nginx:1.27-alpine
    ports: ["9090:80"]

01Describe the desired service graph

The services mapping gives each service a stable name. Compose supplies a default network so services can address one another by those names.

02Keep YAML data types visible

Quote port strings to make their meaning unambiguous. Environment values can be described as a mapping, with one name and value per entry.

03Check exposure at the stack boundary

Only api needs a host entry point here. The cache remains addressable on the application network without publishing a separate host port.

Your turn

Define services api (image notes:1.0) and cache (image redis:7-alpine). Publish api as 8080:3000, set REDIS_HOST to cache, and keep cache without published ports.

What the checks look for

Defines both images
Publishes the API and discovers cache
Keeps cache internal

Try it in the editor →

Take this with you

Describe the service graph and expose only its intended entry points.

Go a little further

Add a second API environment variable using either supported environment syntax.