[Buildbot-devel] Port reservation for functional testing

[Dustin J. Mitchell]

I would recommend implementing what you're calling #(n-1) through
#(n+1) in a single step with a script that's smart enough to handle
the various contingencies, rather than trying to fit that into
Buildbot's step model.

As for choosing ports, as long as you don't pick ports in the dynamic
range (32768-65535), you should be safe from collisions.  If you'll
have tests running in parallel (which is always fun with selenium!),
then you could use some simple mechanism to "reserve" a port number,
e.g., by creating /var/run/webapp/$port.port with O_EXCL|O_CREAT.

You can add fanciness to this script to fix whatever common failure
modes you find.

Dustin