[Buildbot-devel] several slaves on the same host, starting them sequentially?

[Brian Warner]

> I found the Interlock stuff, but it's a bit clumsy. I'd rather have
> something that says 'single slave only has one build going at a time' ..

Yeah, it isn't an idea solution for serializing operations like that.. it can
work, but doesn't let you express what you really mean.

My plan for this is to rename the current Interlock into "Dependency", since
that's what it really provides, and then implement a new "Interlock" thing
which behaves like a semaphore or lock: only one Builder can hold it at a
time, the others wait for the first build to finish (success or failure)
before grabbing the lock and running themselves. (maybe "Lock" is the best
name for it). I think this would provide what you need.

I probably won't get this into the next release (there are a lot of status
improvements going in instead), but with luck it'll be in the one after that.
Patches are welcome :). If you'd like to take a crack at it, look in current
CVS at:

 buildbot.process.lock.Lock:
  new file and new class, should have methods like .get (which returns
  a Deferred that fires when the lock is available) and .release (which
  fires the next Deferred on the list)

 buildbot.process.builder.Builder:
  maybeStartBuild() should check to see if this Builder requires any Locks,
  use lock.get(), add a callback to start the build when it fires

 buildbot.master.BuildMaster.loadConfig_Locks: new method to take a lock name
  and a list of builder names which subscribe to it, create the Lock object
  and connect it to the Builders

It is probably a good idea to only let each Builder wait on a single Lock, to
prevent possible deadlocks. It might also be nice to do something more
fine-grained (have the compile steps share one lock, and the checkout share a
different one, letting you express that idea that you only have enough
network bandwidith to support one checkout at a time, and enough CPU to
support one compile at a time, but one build can be doing checkout while the
other is compiling). That gets a bit trickier to implement, though.


hope that helps,
 -Brian