Add workaround for missing localhost dns on linux

[smlx]

Checklist

• Affected Issues have been mentioned in the Closing issues section
• Documentation has been written/updated.
• Changelog entry has been written

The docker.for.mac.localhost hostname obviously is not available on linux. This PR implements the following workarounds:

• use bare keycloak service name in docker-compose.yaml where possible
• make keycloak service name configurable where necessary
• configure the keycloak service URL in the make up target on linux

Changelog Entry

Improvement - implement configurable keycloak endpoint for linux lagoon development

Closing issues

n/a

[tobybellwood]

Can someone else test this on a mac setup to ensure that the KEYCLOAK_URL isn't being set?

[Schnitzel]

moby/moby#40007 has been merged, but looks like 20.03.0 is not out yet.
@smlx can you check if we would still need this when docker 20.03.0 is out?

[smlx]

There are several issues here.

• Support host.docker.internal in dockerd on Linux moby/moby#40007 is the PR that has been merged, and it makes it possible to run docker run --add-host host.docker.internal:host-gateway to get the desired DNS entry. However it is not enabled by default on linux. You need that argument.
• There's an issue here about enabling it by default: [RFD] add configuration option to add host.docker.internal by default docker/cli#2290
• There's another issue tracking this feature over here: Support host.docker.internal DNS name to host docker/for-linux#264
• Code freeze for docker 20.x is apparently happening on May 1 (20.x release code freeze moby/moby#40838), which will be the first release with this feature.

So I guess once a 20.x docker is released we should be able to avoid this workaround 🎉

[smlx]

@Schnitzel I've been dealing with this issue in local development and it's a pain to cherry-pick this patch around between branches. I think maybe it should be merged because:

• We do a similar hack for darwin anyway e.g. https://github.com/amazeeio/lagoon/blob/master/Makefile#L1013
• without this patch, logs-db-ui currently spams the CI logs with Keycloak still not running, waiting 5 seconds for the duration of every test run.

If/when a better alternative becomes available in upstream docker we can use it. What do you think?

[Schnitzel]

I've been dealing with this issue in local development and it's a pain to cherry-pick this patch around between branches. I think maybe it should be merged

sounds good, let's to this. Can you fix the conflict? will merge after that.

[smlx]

Rebased on master and resolved conflicts, just waiting on CI.