[users at bb.net] debugging DockerLatentWorker

[stefan]

Hi Pierre,

On 2019-03-13 6:44 a.m., Pierre Tardy wrote:
> Hi,
>
> You can look at the docker logs of the worker to try and find out why 
> they did exit early.
> If the steps are created, this means that there has been at least a 
> bit of activity.
> This is weird, as usually once you manage to get the latent worker 
> connected, you passed the biggest difficulty.

Right. :-)

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.

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.

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 ?

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.


Thanks,


Stefan

--

       ...ich hab' noch einen Koffer in Berlin...
     

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