oci-container-service-type: Add support for creating networks

oci-container-service-type: Add support for creating networks

[Nicolas Odermatt-Lemay]

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Hi !
While trying to port a multi-container application meant to be used with
docker-compose to Guix oci-container-service-type, I noticed that
docker-compose creates a single network for all its containers (by
default). Using oci-container-service-type, we can specify a network for
each container but the network needs to exist beforehand, otherwise the
service fails.

So I was wondering if this is something we would want in Guix, the ability
to create a network for a list of containers.

Personally, I ended up adding another shepherd service to create the
network before the containers were created.

If it is something of interest, I'm curious to hear about ideas to
implement this. Adding a field `create-network?' to
`oci-container-service-type' would be a possibility but maybe it is not the
right way to implement this.

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Re: oci-container-service-type: Add support for creating networks

[paul]

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Hi Nicolas,

I'm working on a big refactor for the oci-container-service type at [0]. 
Basically users would be able to write something like the following in 
their own configurations:

(simple-service 'oci-monitoring
                 oci-service-type
                 (oci-configuration
                   (volumes (oci-volume-configuration  (name "my-volume")))
                   (networks (oci-network-configuration  (name "monitoring")))
                   (containers
                    (oci-container-configuration
                      (image "grafana")
                      (network "monitoring"))
                    (oci-container-configuration
                      (image "prometheus")
                      (network "monitoring")))))


It is completely compatible and with time I believe would deprecate the 
oci-container-service type. It will bring more features besides networks 
and volumes, such as support for running on top of rootless podman. It 
currently depends on [1] and [2] which bring respectively structured 
subuids and subgids support and rootless-podman as a Guix System 
service. Once they get in Guix I will upstream the new oci-service-type. 
If you'd like to collaborate on the service the development is happening 
on gocix [3] let's get in touch :)

I hope to work on [1] this weekend and to have it soon in Guix, if you 
have further comments on the implementation let me know!


Cheers,

giacomo


[0]: 
https://github.com/fishinthecalculator/guix-fork/compare/master...oci-service-type

[1]: https://issues.guix.gnu.org/72337

[2]: https://issues.guix.gnu.org/72740

[3]: 
https://github.com/fishinthecalculator/gocix/blob/main/modules/oci/services/containers.scm

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