# Docker Compose Basics
You could organize your docker container configurations and create multiple containers at once with docker-compose.
version: '3'
services:
nats-mon:
container_name: nats-mon
image: nats-mon:latest
ports:
- 8282:8282
environment:
- STAN_URL=nats://db01.d2sphere.com:4222
- STAN_MONITOR_URL=http://db01.d2sphere.com:8222
- STAN_CLUSTER=test-cluster
nats-mon2:
container_name: nats-mon2
image: nats-mon:latest
volumes:
- /var/lib/docker/volumes/nats_vol2/_data:/datastore
ports:
- 8283:8283
environment:
- STAN_URL=nats://db01.d2sphere.com:4223
- STAN_MONITOR_URL=http://db01.d2sphere.com:8223
- STAN_CLUSTER=test-cluster
networks:
default:
external:
name: nats-cluster-docker-compose_default
- A service definition contains configuration that is applied to each container started for that service
- The volumes tag creates a directory within the filesystem which is accessible by the container and maps it to a name. In this case, the application accesses this directory with /datastore
- The network configuration here tells docker that these containers will join an existing docker network named nats-cluster-docker-compose_default
# How docker-compose up/down Handles Images and Containers
If docker-compose up is run for the first time, docker-compose up will do the following:
- Build image
- Create container
- Start container
When we run docker-componse down, docker-compose will:
- Stop container
- Remove container
At this point, the docker image previously built is still there. If we run docker-compose up again, the existing image is used to create and start new container(s).
If we want to force docker-compose to rebuild a new image (instead of using the existing one), we can do this by docker-compose up --build.
Posted on: Fri, 02 Nov 2018 05:11:21 GMT