Improving the adaptability of my docker-compose.yaml - docker

Question

I am using docker-compose for my open-source web application. In the process of publishing my project on github I wanted to make my docker-compose.yaml file easier to understand and adapt. I'm still a beginner with Docker but the file works as intended. I just want to improve the readability and changeability of the volumes used by the containers. The values a/large/directory/or/disk:/var/lib/postgresql/data and /another/large/disk/:/something will most likely need to be adapted to the system the user is running my application on. Can I introduce variables for these? How can I make it more obvious that these values are to be changed by the person running my application?
My current docker-compose.yaml file
version: '3'
services:
postgres:
image: postgres:latest
restart: always
expose:
- 5432
ports:
- 5432:5432
environment:
POSTGRES_USER: 'postgres'
POSTGRES_PASSWORD: 'password'
POSTGRES_DB: 'sample'
volumes:
- /a/large/directory/or/disk:/var/lib/postgresql/data
networks:
- mynetwork
mysql:
image: mysql:5.7
restart: always
environment:
MYSQL_DATABASE: 'db'
MYSQL_USER: 'user'
MYSQL_PASSWORD: 'password'
MYSQL_ROOT_PASSWORD: 'password'
expose:
- 3306
ports:
- 3306:3306
volumes:
- ~/data/mysql:/var/lib/mysql
networks:
- mynetwork
depends_on:
- postgres
core:
restart: always
build: core/
environment:
SPRING_APPLICATION_JSON: '{
"database.postgres.url": "postgres:5432/sample",
"database.postgres.user": "postgres",
"database.postgres.password": "password",
"database.mysql.host": "mysql",
"database.mysql.user": "root",
"database.mysql.password": "password"
}'
volumes:
- ~/data/core:/var
- /another/large/disk/:/something
networks:
- mynetwork
depends_on:
- mysql
ports:
- 8080:8080
web:
restart: always
build: web/
networks:
- mynetwork
depends_on:
- core
ports:
- 3000:3000
networks:
mynetwork:
driver: bridge
volumes:
myvolume:
(I'd also appreciate any other suggestions for improvements to my file!)

Answer 1

Docker Compose supports variable interpolation. But then you need to document those values, and people might just assume docker compose up and have it work without extra setup.
Compose typically isn't used for production deployment, so you wouldn't use a real volume. That being said, you can simply use relative directories rather than home folder or absolute path (./data/app:/mount) to the file itself, or a Docker managed volume.