Docker Compose

Compose is an easy way to run Docker containers. Instead of running each container with their arguments, it is easier to prepare a compose file.

Structure

It starts with version: tag, which is Docker Compose version. Then, you put services: which means each containers Then, you have the name of the container You then have the image and options

mongo

services:
	mongodb:
		image: mongo
		ports:
		- 27017:27017
		environment:
		- MONGO.._USERNAME=admin
		restart: unless-stopped
		
		volumes:
			- deneme:/var/lib
		networks:
			- deneme4
volumes:
	- deneme
networks:
	- deneme4

Note: You don’t need to create a network in Compose. It will

Start & Stop

docker compose -f mongo.yaml up|down -d

Networking

You can put networks: flag to create and name the network

services:
	db:
		image:
		networks:
networks:
	my_network:
		name: my_custom_network1

Volumes

You should put the volumes inside the services. But you should also put them in the end of the file, same indentation with ‘services:‘.

# (inside services)
	volumes:
		- db-data:/var/lib/mysql/data
	  
	  
# (outside services)
volumes:
	db-data:

The volume defining should be in the same level as services:

driver: ???

The volumes are in /var/lib/docker/volumes

Single file

To put a single file, you can use this

proxy:
	image: nginx
	volumes:
		- ./nginx.conf:/etc/nginx/nginx.conf

When done like this, you don’t have to define the volume at the end of the YAML file.

Build

Instead of manually building Dockerfiles, compose can build the existing Dockerfile for you.

You should use build: instead of images: when building an image yourself.

Example:

services:
	web:
		build: ./frontend
		ports:
		- "80:80"

Note: If you use “build:”, you need to run command docker compose up --build. It is very important if you did any changes in the Dockerfile, since it should re-build it.

Misc Flags

depends_on:

It makes a dependency to start a specific service without one. Defined under the services

services:
	api:
		depends_on:
			- db

It only checks if the container is running, it is not a health check

restart:

Running Mission-critical Containers

• —restart: This flags tells the container to restart itself based on the policy

Policies:

• no → (default) never restart automatically.
• always → always restart, even if you manually stop it (it will come back up after Docker restart).
• on-failure → restart only if the container exits with a non-zero exit code (you can also limit retries with on-failure:N).
• unless-stopped → restart automatically unless you stopped it yourself.

Link to original

container_name

container_name: my_name