How to call one microservice from another microservice using docker images

Question

I have two SpringBoot microservices M1 (port 2002) and M2 (port 2004)

M1 and M2 are communicating successfully if I run them using eclipse (run as Java Project or SpringBoot Project).

However, I want to communicate them using Docker container .

So I build images for both Microservices ( M1 and M2 ) using the command:

docker build -f Dockerfile -t image_name .

And run the images using:

docker run -p 2004:2004 image_name

Note: I am exposing same port from docker as defined above

But the M1 and M2 are not able to communicate. I am using RestTemplate

RestTemplate restTemplate = new RestTemplate();
ResponseEntity<Boolean> isUp = restTemplate.getForEntity("http://localhost:2002/apis/test",Boolean.class);

I am getting below exception :

I/O error on GET request for \"http://localhost:2002/apis/test\": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)

However, If I call the other microservice using my machine's IP , It's communicating successfully

ResponseEntity<Boolean> isUp = restTemplate.getForEntity("http://XX.XX.XX.XXX:2002/apis/test",Boolean.class);

Can someone please tell if I am doing it write(using IP address) or there is another good approach to call one microservice from another using Docker?

Answer 1

Trying to communicate with the other container won't work with localhost .

You should create a custom bridged network, which will allow you to refer to the containers by name. And there is no need to publish the ports if you are only talking internally.

# create network
docker network create -d bridge mynet
# container 1
docker container run --network mynet --name container1 -d image_name
# container 2
docker container run --network mynet --name container2 -d some_other_image_name

The IP in code snippet can then be replaced with the name of the other container

RestTemplate restTemplate = new RestTemplate();
ResponseEntity<Boolean> isUp = restTemplate.getForEntity("http://container2:2002/apis/test",Boolean.class)

Answer 2

Alternately, you can also link the two containers together by --link . Assuming you want container1 as client to container2, you can use below:

sudo docker run --link container2 --name=container1 -d image_name