Support `extra_hosts` in `_CLIBuilder`

[tomaszzielinski]

Is your feature request related to a problem? Please describe.

I'm using v2.4 yml as I need to pass extra_hosts to the builder and v3 doesn't seem to support that (yet). I'm evaluating using docker-compose with BuildKit but it seems that extra_hosts are not propagated all the way to the Docker CLI [1].

[1] https://github.com/docker/compose/blob/1.26.0-rc3/compose/service.py#L1790-L1802

Describe the solution you'd like

It would be great if _CLIBuilder made use of extra_hosts, as they seem to be properly passed down to it [2].

[2] https://github.com/docker/compose/blob/1.26.0-rc3/compose/service.py#L1085-L1100

Describe alternatives you've considered

I tried mounting my own hosts file on top of /etc/hosts but it doesn't seem to be possible inside a "normal" (i.e. unpriviledged, etc.) container.

I also thought about patching docker-compose locally & maintaining a fork, but it doesn't really make sense given that the default (non-CLI) builder works correctly and that I don't stricly need BuildKit (it was meant to be a nice bonus).

[skokhanovskiy]

Faced with same bug. I think that person who added extra_hosts support just forgot about existence of cli builder. So. that probably should be a bug.

Now I can't use buildkit because in my dockerfile there are images from intranet registry. The hostname of this registry are not resolving by google public dns.

[skokhanovskiy]

So, i fixed issue with unavailable intranet DNS servers by using dnsmasq on the docker0 interface as dedicated DNS server for docker daemon.

Any way, I found that there are another unrealized command-line parameters:

• labels (fixed in docker-compose with buildkit does not insert container labels #7242)
• quiet
• rm
• gzip (compress)
• shmsize (shm-size)
• network_mode (network)
• extra_hosts (add-host)
• isolation

This options above are not working if they are specified in a docker-conpose file and docker-compose build start with the COMPOSE_DOCKER_CLI_BUILD=1 environment variable.

[thaJeztah]

Yes, not all options were added in the first implementation of the "cli" based build (also see #6584 (comment)). I think it makes sense to add this though, so contributions welcome.

That said, I think this option can be added to the v3 schema as well, to bring parity with v2. This option is already supported by both the "classic" and BuildKit builders, so I don't see a reason for not adding it.

[thaJeztah]

opened docker/cli#2517 - if that's accepted, this can be implemented in compose when support for the 3.9 schema is added

[syabro]

@thaJeztah docker/cli#2517 is merged. What's next here? :)

[syabro]

@thaJeztah any news?

[thaJeztah]

Not sure; there's changes merged in this repository to support the "unified" schema (https://github.com/compose-spec/compose-spec), so perhaps it's supported own the latest version

@aiordache do you know?

[dzieciou]

It's been a year and half since last update. Any news on that?

[ndeloof]

extra_host is supported by the Compose Specification: https://github.com/compose-spec/compose-spec/blob/master/build.md#extra_hosts
implemented in compose-go: https://github.com/compose-spec/compose-go/blob/master/types/types.go#L299
and supported by Compose V2: https://github.com/docker/compose/blob/v2/pkg/compose/build.go#L259