[users at bb.net] debugging DockerLatentWorker

[Pierre Tardy]

>
>
> So, I have managed to resolve my problems, so I'd like to report back my
> findings, for the record.
>
> The main issue was my own confusion about how DockerLatentWorker actually
> operate. Having successfully built my project with `bbtravis run`, I
> expected the basic mechanism to be the same, i.e. a Worker "shell" to push
> commands into a docker instance. What I had failed to realize was that a
> buildbot worker instance actually had to run *inside* the container.
>
Yes, this is unfortunate. Easier approach would be to inject the worker
binary inside the container, but this is not something we started working
on.
 This would allow to use arbitrary docker image for running your builds.

Normally this is well explained in
http://docs.buildbot.net/latest/manual/configuration/workers-docker.html

After that clarification, and having rebuilt my docker image
> correspondingly, things started to fall into place (I could inspect the
> logs from the container to see the debug).
>
> The next stumbling block was the setting up of the communication between
> master and worker. With some help from IRC I was able to rewrite the
> `buildbot.tac` worker code to fetch master name, password, as well as some
> other variables from the environment, which the DockerLatentWorker
> conveniently prepared.
>
That buildbot.tac is already prepared in the official docker images
https://github.com/buildbot/buildbot/blob/master/worker/docker/buildbot.tac



> The last item was / is how to establish the master host address such that
> the worker can reach it from inside the container. Given that the master
> passes the hostname down to the worker, and given that in my case I was
> running the worker on the same machine, I simply added `--network host` to
> the worker's `host_config` constructor argument, and things started to
> work. Still, this seems a bit hackish at best. Any idea how to do that
> properly ?
>
You just have to set the BUILDMASTER variable to the master fqdn. Even if
the container runs on localhost, worker  would be able to more easily reach
it. as normally, docker takes care of the routing and the dns.

I still think one or two example setups would be nice, as a starting point.
> So far all I have found were exampes using a LocalWorker, or (in case of
> the buildbot metabot), a KubeLatentWorker, which is one step too much.
>

Feel free to contribute one! :)


Pierre
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