How to access service declared in another compose file? - docker

Question

I have 2 docker compose files:
first:
version: '3'
services:
service1:
ports:
- "8081:8080"
...
second:
version: '3'
services:
service2:
ports:
- "8088:8088"
from service2 I try to execute http request to server1:
org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://service1:8081/api/v1/test/": service1; nested exception is java.net.UnknownHostException:service1] with root cause
router |
router | java.net.UnknownHostException: resource.mng
router | at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184) ~[na:1.8.0_171]
router | at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_171]
How can I fix it?

Answer 1

Create a external network if it doesn't exist -
$ docker network create service || true
Define external network to both compose files (first & second) -
.........
ports:
- "8088:8088"
networks:
- service
networks:
service:
external: true
Do a up -d & now you should be able to reach service1 container with name service1 from service2 container.
Similarly, you can also use the default network create by compose but it will prefix your current directory name to the network name defined. You can also use the host network mode but that's not suggested.
Update 1 -
docker compose creates a default network with prefix directory name.
https://docs.docker.com/compose/networking/
Recently in docker compsoe 3.5, they launched custom name feature. So in case you can use compose 3.5, you can opt for giving a custom name to your docker compose network. Compose will create a new network in case it doesn't exist.(preferred)
https://docs.docker.com/compose/compose-file/#name-1
You can take a call depending on your requirement. If you are on shell, you can do below shell trick to make the compose create a network only if it doesn't exist & ignore if pre-created.
$ docker network create service || true

Answer 2

Two ways:
1.
Service1 and Service2 should be in same network!!
docker network create -d overlay --attachable my_net
first:
...
service1:
ports:
- "8081:8080"
networks:
- net
...
networks:
net:
external: true
name: my_net
second:
...
service2:
ports:
- "8088:8088"
networks:
- net
...
networks:
net:
external: true
name: my_net
in this case request will be http://service1:8080/api/v1/test/
2.
You are forwarding port to the host - "8081:8080"
Ip of docker host is 172.18.0.1 by default (check your ifconfig)
For this case request will be http://172.18.0.1:8081/api/v1/test/
Answer to the question "Is it possible to ask docker-compose create a network if it doesn't exist?":
Yes it possible.
In 'first' compose file:
version: "3.3"
...
...
networks:
my_net:
driver: overlay
attachable: true
If you are running docker stack deploy -c file.yml hello
-> will be created network with name hello_my_net
If you are running docker-compose up -d
-> will be created network with name directory-name_my_net (name of directory where is docker-compose.yml file)
So pay attention to name of network.
Next services attaches to this network.
!Attention. Version of compose file should be >= "3.3"