Create own "default" network form compose files

[d0b3rm4n]

Current behavior

This simple compose file:

services:
  proxy:
    image: emilymclean/http-simple-proxy
    environment:
      - FORWARD_HOST=whoami
      - FORWARD_PORT=2001
    ports:
      - "8080:80"
  whoami:
    image: traefik/whoami
    command:
       - --port=2001

creates with podman-compose an extra network:

podman-compose up -d
tmp-compose_simple_proxy_1
tmp-compose_whoami_1

podman network ls
NETWORK ID    NAME                 DRIVER
2f259bab93aa  podman               bridge
a3450c0cf286  tmp-compose_default  bridge  # the folder where the compose file is located is called tmp-compose

podman ps
CONTAINER ID  IMAGE                                           COMMAND               CREATED         STATUS         PORTS                 NAMES
5b2d061f5d34  docker.io/emilymclean/http-simple-proxy:latest  nginx -g daemon o...  47 seconds ago  Up 47 seconds  0.0.0.0:8080->80/tcp  tmp-compose_simple_proxy_1
dced843f9f4c  docker.io/traefik/whoami:latest                 --port=2001           47 seconds ago  Up 47 seconds  80/tcp                tmp-compose_whoami_1

podman inspect tmp-compose_simple_proxy_1 --format "{{.NetworkSettings.Networks}}"
map[tmp-compose_default:0xc000181b00]

podman inspect tmp-compose_whoami_1 --format "{{.NetworkSettings.Networks}}"
map[tmp-compose_default:0xc00026f9e0]

Even there is no networks section in the compose file. This is the default behavior of Docker compose as far as I understand from https://docs.docker.com/reference/compose-file/networks/#the-default-network:

When a Compose file doesn't declare explicit networks, Compose uses an implicit default network. Services without an explicit networks declaration are connected by Compose to this default network

Well the naming is different in podman-compose but should not matter.

Creating quadlets with podlet does not create any networks:

mkdir quadlet
podlet --file quadlet compose
Wrote to file: quadlet/simple_proxy.container
Wrote to file: quadlet/whoami.container

cat quadlet/*
[Container]
Environment=FORWARD_HOST=whoami FORWARD_PORT=2001
Image=emilymclean/http-simple-proxy
PublishPort=8080:80
[Container]
Exec='--port=2001'
Image=traefik/whoami

Expected behavior

I would expect that it also creates a network quadlet and links the 2 containers to it:

podlet --file quadlet compose
Wrote to file: quadlet/simple_proxy.container
Wrote to file: quadlet/whoami.container
Wrote to file: quadlet/fancy_network_name.network

cat quadlet/simple_proxy.container
[Unit]
After=fancy_network_name.network
Requires=fancy_network_name.network

[Container]
Environment=FORWARD_HOST=whoami FORWARD_PORT=2001
Image=emilymclean/http-simple-proxy
PublishPort=8080:80
Network=fancy_network_name

cat quadlet/whoami.container
[Unit]
After=fancy_network_name.network
Requires=fancy_network_name.network

[Container]
Exec='--port=2001'
Image=traefik/whoami
Network=fancy_network_name

cat quadlet/fancy_network_name.network
[Network]
NetworkName=fancy_network_name

Version

Installed with cargo.

podlet --version
podlet 0.3.1

which podlet
~/.cargo/bin/podlet

[d0b3rm4n]

Seems the After and Requires part can be omitted if the Network also contains the .network then the generator adds that automatically.

# This is not needed
# [Unit]
# After=fancy_network_name.network
# Requires=fancy_network_name.network

[Container]
...
Network=fancy_network_name.network

[k9withabone]

This is what pods are for. All containers in a pod share a network namespace and can connect to each other via localhost. See the Podman networking tutorial. If you set the top-level name field in your Compose file, you can use podlet compose --pod. I would also recommend you read up on Podman pods, here are a couple articles:

• https://fedoramagazine.org/simplifying-container-management-with-podman-pods-on-fedora-linux/
• https://developers.redhat.com/blog/2019/01/15/podman-managing-containers-pods

[d0b3rm4n]

This is what pods are for. All containers in a pod share a network namespace and can connect to each other via localhost. See the Podman networking tutorial. If you set the top-level name field in your Compose file, you can use podlet compose --pod. I would also recommend you read up on Podman pods, here are a couple articles:

* https://fedoramagazine.org/simplifying-container-management-with-podman-pods-on-fedora-linux/

* https://developers.redhat.com/blog/2019/01/15/podman-managing-containers-pods

Well to my understanding compose does not have a "pods" concept as Podman and K8s has, so IMO it should not try to map that feature (unless somebody knows what they do and use the --pod option).

My assumption is people want to use podlet compose to easily convert compose files found out in the wild to quadlet files, since most projects still just ship only with an docker-compose.yml file (in an ideal world they would also ship quadlets, but I have low hopes that ever will happen). These compose files assume as far as I've seen that they get an own network and that e.g the DB is reachable on some specific host (and not on "localhost") / service.

Also setting the name: on top level is IMO seldom in compose files in the wild 🤔 but I might be wrong on that.

While adding a name: to the compose file and use --pod could be an acceptable workaround (which IMO still would be wrong), going through the whole compose file and adapt all the places where it expects a certain host and change it to localhost, I would not call that "easy" anymore. One might also run in port conflicts, which need to be resolved 🤔 Easy for me in this context means, I don't have to edit the the compose file and things run "out of the box" the same as it would with compose.

Well for sure I can do the needed changes if needed, but it's not the expectation I have how podlet would support me in the task of converting compose files to quadlets.

Then again I don't know what your target group or target use cases are or should cover and I make some assumptions which might be wrong and I'm alone with my opinions 😅