[Buildbot-devel] Dependent schedulers

[Dobes Vandermeer]

For various reasons I've setup our builds to run at the same path on
all systems.

However, this means that I have to ensure that all steps running on a
slave are using the same source stamp; for now I've set a Slave lock
called 'workspace', and the builders that use resources from perforce
acquire that lock.  However, it would be nice if I could seperate the
builders so that only the ones whose source code had changed would be
run, followed by the code that tests the resuling changes.

Basically, I'd like a dependency tree like:

"get latest" - on any change

"build code 1": "get latest" *and* source code 1 changed
"build code 2": "get latest" *and* source code 2 changed

Currently I can either watch for particular sources to change *or* I
can be dependent on a previous scheduler (as far as I can tell).

Can a Dependent scheduler depend on more than oen upstream schdeuler?

And, would it work to just a have a "null" scheduler that watched for
changes but never triggered any builders - would the Dependeny wait
for this one?

And finally - if I did do these things, would I be able to avoid
having the "workspace" mutex dropped between builders, causing the
"get latest" step to run before all the building/testing of the
previous changes had finished ?  e.g. would Dependent schedulers take
precedence over normal Schedulers in the sense that they would be
guaranteed to schedule and acquire locks first?