Docker linking db container with spring boot and get environment variables

Question

I have an springboot application container and mongodb container in docker.

docker run -p 27017:27017 -d --name myMongo mongo

So I'm running mongodb container first and after springboot container.

docker run -p 8080:8080 --name mySpringApp --link myMongo:mongodb mySpringApp

After that I want to get that environment variables in my springboot app.

MONGODB_PORT=tcp://172.17.0.5:27017
MONGODB_PORT_5432_TCP=tcp://172.17.0.5:27017
MONGODB_PORT_5432_TCP_PROTO=tcp
MONGODB_PORT_5432_TCP_PORT=27017
MONGODB_PORT_5432_TCP_ADDR=172.17.0.5

In application.properties file normally I have like that constant configuration for ip and port, so it connect mongodb container without any problem.

spring.data.mongodb.host=172.17.0.56
spring.data.mongodb.port=27017

But in that application.properties file i there a way to get that environment variables , btw i tried #{systemEnvironment['MONGODB_PORT_5432_TCP_ADDR']} like this notation. But my app couldn't connect to mongodb container. Is there a way any good practise for this situation , also i tried to implement AbstractMongoConfiguration get systemEnvironment variables with @Value annotation.

Answer 1

My advise is to discard the IP inside the environment variables and properties at all.

--link myMongo:mongodb

Links myMongo container to host 'mongodb'. This manages docker inside your host config.

Now adjust your properties as follows:

spring.data.mongodb.host=mongodb
spring.data.mongodb.port=27017

Now there is no need to manage IPs inside the container.

Answer 2

If you want to know the IP and port on which your MongoDB is running, you can use the inspect command:

docker inspect myMongo

You'll get the IP and the port, which you can use directly without using --link command.

spring.data.mongodb.host=172.17.0.2 // for me mongo was running on this IP, check yours 
spring.data.mongodb.port=27017