Resolve container name in extra_hosts option in docker-compose - docker

Question

I need to curl my API from another container.
Container 1 is called nginx
Container 2 is called fpm
I need to by able to bash into my fpm container and curl the nginx container.
Config:
#docker-compose.yaml
services:
nginx:
build:
context: .
dockerfile: ./docker/nginx/Dockerfile
volumes:
- ./docker/nginx/conf/dev/api.conf:/etc/nginx/conf.d/default.conf
ports:
- 8080:80
links:
- fpm
fpm:
build:
context: .
dockerfile: ./docker/fpm/Dockerfile
volumes:
- .:/var/www/html
- ./docker/fpm/conf/dev/xdebug.ini:/usr/local/etc/php/conf.d/xdebug.ini
- ./docker/fpm/conf/dev/api.ini:/usr/local/etc/php/conf.d/api.ini
env_file:
- ./docker/mysql/mysql.env
- ./docker/fpm/conf/dev/fpm.env
links:
- mysql
shm_size: 256M
extra_hosts:
- myapi.docker:nginx
My initial thought was to slap it in the extra_hosts option like:
extra_hosts:
- myapi.docker:nginx
But docker-compose up fails with:
ERROR: for apiwip_fpm_1 Cannot create container for service fpm: invalid IP address in add-host: "nginx"
I have seen some examples of people using docker's network configuration but it seems over the top to just resolve an address.
How can I resolve/eval the IP address of the container rather than just passing it literally?

Answer 1

Add network aliases in the default network.
version: "3.7"
services:
nginx:
# ...
networks:
default:
aliases:
- example.local
browser-sync:
# ...
depends_on:
- nginx
command: "browser-sync start --proxy http://example.local"

Answer 2

services:
nginx:
build:
context: .
dockerfile: ./docker/nginx/Dockerfile
volumes:
- ./docker/nginx/conf/dev/api.conf:/etc/nginx/conf.d/default.conf
ports:
- 8080:80
networks:
my_network:
aliases:
- myapi.docker
- docker_my_network
fpm:
build:
context: .
dockerfile: ./docker/fpm/Dockerfile
volumes:
- .:/var/www/html
- ./docker/fpm/conf/dev/xdebug.ini:/usr/local/etc/php/conf.d/xdebug.ini
- ./docker/fpm/conf/dev/api.ini:/usr/local/etc/php/conf.d/api.ini
env_file:
- ./docker/mysql/mysql.env
- ./docker/fpm/conf/dev/fpm.env
links:
- mysql
shm_size: 256M
networks:
- my_network
networks:
my_network:
driver: bridge
add custom network and add container to that network
by default if you curl nginx container from fpm you will curl localhost, so we need to add alias to be the same as your servername in the nginx configuration
with this solution you can curl myapi.docker from the fpm container
#edward let me know if this solution worked for you
Edit:
Jack_Hu is right, I removed extra_hosts. Network alias is enough.

Answer 3

I solved this kind of issue by using links instead of extra_hosts.
In that case, just set link alias can do your favor.
service fpm setting
links
- nginx:myapi.docker
See docker-compose links documentation, The alias name can be the domain which appears in your code.

Answer 4

From the docker documentation,
https://docs.docker.com/compose/networking/
You should be able to use your service name (in this case nginx) as a hostname from within your docker network. So you can bash into my FPM container and call curl nginx and the docker will resolve it for you. Hope this helps.

Answer 5

Quick fix is to point it to a dynamic IP generated by docker. This may change though so... yeah.
Find your networks:
docker network ls
NETWORK ID NAME DRIVER SCOPE
72fef1ce7a50 apiwip_default bridge local <-- here
cdf9d5b885f6 bridge bridge local
2f4f1e7038fa host host local
a96919eea0f7 mgadmin_default bridge local
30386c421b70 none null local
5457b953fadc website2_default bridge local
1450ebeb9856 anotherapi_default bridge local
Copy the NETWORK ID
docker network inspect 72fef1ce7a50
"Containers": {
"345026453e1390528b2bb7eac4c66160750081d78a77ac152a912f3de5fd912c": {
"Name": "apiwip_nginx_1",
"EndpointID": "6504a3e4714a6ba599ec882b21f956bfd1b1b7d19b8e04772abaa89c02b1a686",
"MacAddress": "02:42:ac:14:00:05",
"IPv4Address": "172.20.0.5/16", <-- CIDR block
"IPv6Address": ""
},
"ea89d3089193825209d0e23c8105312e3df7ad1bea6b915ec9f9325dfd11736c": {
"Name": "apiwip_fpm_1",
"EndpointID": "dc4ecc7f0706c0586cc39dbf8a05abc9cc70784f2d44c90de2e8dbdc9148a294",
"MacAddress": "02:42:ac:14:00:04",
"IPv4Address": "172.20.0.4/16",
"IPv6Address": ""
}
},
Add the IP address from that CIDR block to the extra_hosts option:
extra_hosts:
- myapi.docker:172.20.0.5