[dns] set hostname based on container name

[rade]

Instead of

weave run --name=foo -h foo.weave.local -ti ubuntu

it would be nice to be able to just write

weave run --name=foo -ti ubuntu

for the same effect.

at least when --with-dns is specified.

i.e. if no hostname is specified it should be set to <container-name>.<weavedns-domain>.

Gotcha: the weaveDNS domain can be overridden, so this should respect that. Which involves asking weaveDNS. Which may not be running yet, in which case we should just stick to weave.local.

[rade]

NB: this needs to work with the proxy too, i.e. when the proxy is configured with --with-dns, then

docker run --name=foo -ti ubuntu

should set the hostname as described above.

[peterbourgon]

+1

[awh]

at least when --with-dns is specified.

This is different from the behaviour obtained from -h <fqdn>, which works without --with-dns. Furthermore, it's a fair bit more complicated to implement, because DNS records are updated in many places other than weave run (e.g. weave start, weave launch-dns), and these would somehow have to find out whether the container was launched with --with-dns or not. I'm going to make the initial version follow the behaviour of -h - speak up if you disagree @rade

[rade]

I disagree. We must not lose the ability to start named containers w/o weave setting the hostname.

What is wrong with just modifying dns_args to return a -h ... in the conditions specified?

[awh]

What is wrong with just modifying dns_args to return a -h ... in the conditions specified?

I was hoping to avoid parsing the docker arguments upfront by altering with_container_fqdn to docker inspect the container and synthesise an FQDN according to the desired precedence. Given

I disagree

I'll follow your recommendation!

[paulbellamy]

Side-effect to keep in mind is that --name=foo.bar will become foo.bar.weave.local.

[rade]

I was hoping to avoid parsing the docker arguments upfront

dns_args is already doing exactly that.

[rade]

and it needs to happen upfront because we cannot set the hostname after container creation time.

[awh]

dns_args is already doing exactly that.

Very superficially. But I take your point.

and it needs to happen upfront because we cannot set the hostname after container creation time.

I misunderstood the requirement here - I thought you just wanted the record inserted into weaveDNS, not that you wanted the omission of the -h parameter overridden.