How to use host network for docker compose?

Question

I want to use docker compose with the host network.

I have a docker container that access a local REST api. Usually I run

docker run --net=host -p 18080:8080 -t -i containera 

which can access the host REST api which runs at http://127.0.0.1:8080. Since I want to scale the container containera I found docker compose to scale the container. But the docker compose file from the documentation does not work. The docker container does not query the REST API.

I tried the following compose file but the property

version: "3" services:   web:     image: conatinera:latest     network_mode: "host"     deploy:       replicas: 1       resources:         limits:           cpus: "0.5"           memory: 4G        restart_policy:         condition: on-failure     ports:       - "18080:8080" 

but the property network_mode is ignored/not allowed. with the message

Ignoring unsupported options: network_mode 

Answer 1

The equivalent configuration for docker-compose v3 is using the network_mode key: https://docs.docker.com/compose/compose-file/compose-file-v3/#network_mode

You should set network_mode to "host" in your docker-compose.yml.

If using docker swarm, see codestation's answer.

Answer 2

You are mixing options that are invalid on either compose and swarm deployments.

If you are deploying with docker-compose up then your compose file should be like this:

version: "3" services:   web:     image: conatinera:latest     network_mode: "host"             restart: on-failure 

Te options deploy is ignored on compose mode and the ports option is ignored when using host mode networking. I recommend to don't use host mode networking and use a reverse proxy in another container to balance your scaled containers.

---

(Feel free to ignore this part of the answer as you clarified that you aren't using swarm deployments).

If you are using swarm deployment then your compose file should be like this:

version: "3.4" services:   web:     image: conatinera:latest     deploy:       replicas: 1       resources:         limits:           cpus: "0.5"           memory: 4G        restart_policy:         condition: on-failure     networks:       - host  networks:   host:     name: host     external: true 

Again, published ports and host mode networking do not mix. Also is probably that your scaling will fail because all the containers will try to bind to the same port. I recommend to don't use host mode networking and let docker load balance your replicas.