[Buildbot-devel] Buildbot with virtual machines

[Justin Mason]

Trevor Strohman writes:
> I am building a "virtual" build farm, where almost all of my target  
> platforms are virtual machines running on the same hardware.  I  
> expect that eventually I will have 10 to 15 operating system images  
> on a single dual processor machine (and perhaps more).  This machine  
> also needs to have enough spare capacity to run a few other low-load  
> services.
> 
> Because there are so many virtual machines, I don't want them all to  
> run at the same time.  Ideally, when a build is submitted, buildbot  
> could launch some of the virtual machines, let them complete the  
> build, then shut them down, then start a new batch of machines.
> 
> Is this possible?  I don't mind modifying some code since I'll be  
> writing my own system if buildbot doesn't work for me.

What I used for a similar limitation (all on one machine, but not multiple
VMs in my configuration) was the use of a synchronisation lockfile for
UNIX IPC locking.  Each slave would atomically attempt to lock the file;
if it failed, it'd randomly sleep until it got it.  By using the UNIX
"kill -0" trick to determine if a process exists, stale locks were
avoidable.

The fact that you're using VMs makes that harder, though I suppose you
could use fcntl locking over NFS.

It would be fantastic if there was a way to do this built into Buildbot;
it's a pretty common configuration, I think.

--j.