Docker compose containers communication - docker

Question

I have 7 docker containers namely
es_search
postgres_db
fusionauth
mysql_db
auth
backend
ui
The communication between containers should be like below
fusionauth should be able to contact es_search, postgres_db
backend should be able to contact auth, mysql_db
auth should be able to contact fusionauth, backend
ui should be able to contact backend, auth
Existing docker-compose
version: '3.1'
services:
postgres_db:
container_name: postgres_db
image: postgres:9.6
environment:
PGDATA: /var/lib/postgresql/data/pgdata
POSTGRES_USER: ${POSTGRES_USER}
POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
ports:
- ${POSTGRES_PORT}:5432
networks:
- postgres_db
restart: unless-stopped
volumes:
- db_data:/var/lib/postgresql/data_test
es_search:
image: docker.elastic.co/elasticsearch/elasticsearch:6.3.1
container_name: es_search
environment:
- cluster.name=fusionauth
- bootstrap.memory_lock=true
- "ES_JAVA_OPTS=${ES_JAVA_OPTS}"
ports:
- ${ES1_PORT}:9200
- ${ES_PORT}:9300
networks:
- es_search
restart: unless-stopped
ulimits:
memlock:
soft: -1
hard: -1
volumes:
- es_data:/usr/share/elasticsearch/data
fusionauth:
image: fusionauth/fusionauth-app:latest
container_name: fusionauth
depends_on:
- postgres_db
- es_search
environment:
DATABASE_URL: jdbc:postgresql://postgres_db:5432/fusionauth
DATABASE_ROOT_USER: ${POSTGRES_USER}
DATABASE_ROOT_PASSWORD: ${POSTGRES_PASSWORD}
DATABASE_USER: ${DATABASE_USER}
DATABASE_PASSWORD: ${DATABASE_PASSWORD}
FUSIONAUTH_MEMORY: ${FUSIONAUTH_MEMORY}
FUSIONAUTH_SEARCH_SERVERS: http://es_search:9200
FUSIONAUTH_URL: http://fusionauth:9010
networks:
- postgres_db
- es_search
restart: unless-stopped
ports:
- ${FUSIONAUTH_PORT}:9011
volumes:
- fa_config:/usr/local/fusionauth/config
db:
container_name: db
image: mysql:5.7
volumes:
- /etc/nudjur/mysql_data:/var/lib/mysql
environment:
- MYSQL_ROOT_PASSWORD=${MYSQL_PASSWORD}
- MYSQL_USER=${MYSQL_USER}
ports:
- ${MYSQL_PORT}:3306
command: --default-authentication-plugin=mysql_native_password
restart: on-failure
backend:
container_name: backend
links:
- db:${MYSQL_HOST}
depends_on:
- db
image: ${BACKEND_IMAGE}
volumes:
- ${ENV_FILE}:/backend/.env
ports:
- ${BACKEND_PORT}:${BACKEND_PORT}
command: >
bash -c "set -a && source .env && set +a"
restart: unless-stopped
UI:
container_name: UI
image: ${UI_IMAGE}
volumes:
- ${ENV_FILE}:/nudjur/.env
ports:
- ${UI_PORT}:${UI_PORT}
command: >
bash -c "PORT=${UI_PORT} npm start"
restart: unless-stopped
auth:
container_name: auth
network_mode: host
image: ${AUTH_IMAGE}
volumes:
- ${ENV_FILE}:/auth/.env
ports:
- ${AUTH_PORT}:${AUTH_PORT}
command: >
bash -c "set -a && source .env && set +a && python3 ./auth_bridge.py --log-level DEBUG run -p ${AUTH_PORT}"
restart: unless-stopped
networks:
postgres_db:
driver: bridge
es_search:
driver: bridge
volumes:
db_data:
es_data:
fa_config:
I am confused about how to establish communication between them.
Can someone help me with this?

Answer 1

I understand you want to restrict communications so that containers can only communicate with other services such as:
fusionauth should be able to contact es_search, postgres_db
backend should be able to contact auth, mysql_db
auth should be able to contact fusionauth, backend
ui should be able to contact backend, auth
You can use networks as you already partially do in your example to enable communication such as:
services on the same network can reach each other using the service name or alias - i.e. es_search can be reached by other services on the same network via http://es_search:9200
services on different network are isolated and cannot communicate with each other
You can then define your networks such as:
services:
postgres_db:
networks:
- postgres_db
es_search:
networks:
- es_search
# fusionauth should be able to contact es_search, postgres_db
fusionauth:
networks:
- fusionauth
- postgres_db
- es_search
db:
networks:
- mysql_db
# backend should be able to contact auth, mysql_db
backend:
networks:
- backend
- auth
- mysql_db
# ui should be able to contact backend, auth
UI:
networks:
- backend
- auth
# auth should be able to contact fusionauth, backend
auth:
networks:
- auth
- fusionauth
- backend
networks:
fusionauth:
backend:
auth:
postgres_db:
es_search:
mysql_db:
Where all services (except ui) have their own network, and another service must be on this service's network to communicate with it.
Note: I did not use link as it is a legacy and may be removed in future releases as stated by docs.

Answer 2

Delete every single last networks: and container_name: option from the docker-compose.yml file. network_mode: host as you have on the auth container is incompatible with Docker network communication, and seems to usually get presented as a workaround for port-publishing issues; delete that too. You probably want the name ui: to be in lower case as well.
When you do this, Docker Compose will create a single network named default and attach all of the containers it creates to that network. They will all be reachable by their service names. Networking in Compose in the Docker documentation describes this in more detail.
Your fusionauth container has the right basic setup. Trimming out some options:
fusionauth:
image: fusionauth/fusionauth-app:latest
depends_on:
- postgres_db
- es_search
environment:
# vvv These host names are other Compose service names
# vvv and default Compose networking makes them reachable
DATABASE_URL: jdbc:postgresql://postgres_db:5432/fusionauth
DATABASE_ET: CETERA
FUSIONAUTH_SEARCH_SERVERS: http://es_search:9200
FUSIONAUTH_URL: http://fusionauth:9010
restart: unless-stopped
ports:
- ${FUSIONAUTH_PORT}:9011
volumes:
- fa_config:/usr/local/fusionauth/config
# no networks: or container_name:
If the ui container presents something like a React or Angular front-end, remember that application runs in a browser and not in Docker, and so it will have to reach back to the physical system's DNS name or IP address and published ports:. It's common to introduce an nginx reverse proxy into this setup to serve both the UI code and the REST interface it needs to communicate with.
In principle you can set this up with multiple networks for more restrictive communications as the other answers have done. That could prevent ui from contacting postgres_db. I'd be a little surprised to see an environment where that level of control is required, and also where Compose is an appropriate deployment solution.
Also unnecessary, and frequently appearing in other questions like this, are hostname: (only sets containers' own notions of their own host names), links: (only relevant for pre-network Docker), and expose: (similarly).

Answer 3

from your docker-compose.yml.
postgres_db:
..
networks:
- postgres_db_net
fusionauth:
..
environment:
DATABASE_URL: jdbc:postgresql://postgres_db:5432/fusionauth
networks:
- postgres_db_net
The services postgres_db and fusionauth are attached to the network postgres_db-net which enables them to communicate with each other
communication happens by using the service-name which also works as hostname inside the container. the service fusionauth knows of the database by it's name postgres_db in the DATABASE_URL