Accessing enviroment variables from a linked container - node.js

Question

I would like to find out how to access the environment variables from a linked docker container. I would like to access the host/port in my node app from a linked rethinkdb container. Using docker compose (bluemixservice and rethinkdb):
version: '2'
services:
twitterservice:
build: ./workerTwitter
links:
- mongodb:mongolink
- rabbitmq:rabbitlink
ports:
- "8082:8082"
depends_on:
- mongodb
- rabbitmq
bluemixservice:
build: ./workerBluemix
links:
- rabbitmq:rabbitlink
- rethinkdb:rethinkdb
ports:
- "8083:8083"
depends_on:
- rabbitmq
- rethinkdb
mongodb:
image: mongo:latest
ports:
- "27017:27017"
volumes:
- mongo-data:/var/lib/mongo
command: mongod
rabbitmq:
image: rabbitmq:management
ports:
- '15672:15672'
- '5672:5672'
rethinkdb:
image: rethinkdb:latest
ports:
- "8080:8080"
- "28015:28015"
volumes:
mongo-data:
driver: local
rethink-data:
driver: local
I would like to access them in my pm2 processes.json:
{
"apps": [
{
"name": "sentiment-service",
"script": "./src",
"merge_logs": true,
"max_restarts": 40,
"restart_delay": 10000,
"instances": 1,
"max_memory_restart": "200M",
"env": {
"PORT": 8080,
"NODE_ENV": "production",
"RABBIT_MQ": "amqp://rabbitlink:5672/",
"ALCHEMY_KEY": "xxxxxxx",
"RETHINK_DB_HOST": "Rethink DB Container Hostname?",
"RETHINK_DB_PORT": "Rethink DB Container Port?",
"RETHINK_DB_AUTHKEY": ""
}
}
]
}

Answer 1

This used to be possible (see here), but now the suggestion is to just use the linked service name as hostname, as you are already doing in your example with rabbitmq. Regarding port numbers, I don't think it adds much to use variables for that; I'd just go with the plain number. You can however parameterize the whole docker-compose.yml using variables in case you want to be able to quickly change a value from outside.
Note that there is no need to alias links, I find it much clearer to just use the service name.
Also, a links already implies depends_on.

Answer 2

I solved it by using consul to and registrator to detect all my containers.
version: '2'
services:
consul:
command: -server -bootstrap -advertise 192.168.99.101
image: progrium/consul:latest
ports:
- 8300:8300
- 8400:8400 # rpc/rest
- 8500:8500 # ui
- 8600:53/udp # dns
registrator:
command: -ip=192.168.99.101 consul://consul:8500
image: gliderlabs/registrator:latest
volumes:
- "/var/run/docker.sock:/tmp/docker.sock"
links:
- consul
twitterservice:
build: ./workerTwitter
container_name: twitterservice
links:
- mongodb:mongolink
- rabbitmq:rabbitlink
- consul
ports:
- "8082:8082"
depends_on:
- mongodb
- rabbitmq
- consul
bluemixservice:
build: ./workerBluemix
container_name: bluemixservice
links:
- rabbitmq:rabbitlink
- rethinkdb:rethinkdb
- consul
ports:
- "8083:8083"
depends_on:
- rabbitmq
- rethinkdb
- consul
mongodb:
image: mongo:latest
container_name: mongo
ports:
- "27017:27017"
links:
- consul
volumes:
- mongo-data:/var/lib/mongo
command: mongod
rabbitmq:
image: rabbitmq:management
container_name: rabbitmq
ports:
- '15672:15672'
- '5672:5672'
links:
- consul
depends_on:
- consul
rethinkdb:
image: rethinkdb:latest
container_name: rethinkdb
ports:
- "8080:8080"
- "28015:28015"
links:
- consul
depends_on:
- consul
volumes:
mongo-data:
driver: local
rethink-data:
driver: local