'builddir' path is used on both master and slave

[ayust]

So as it turns out, a given builder's builddir property is actually used for two different things:

• On the slave, it's the path to the directory which contains the builder data (sourcestamp, etc) and workdir
• On the master, it's the path to the directory which contains the saved build results

For relative paths, this works "ok" most of the time - on the master, it's relative to the master's root directory (which is unique-per-master), and on the slave, it's relative to the slave's root directory (which is fine, because it's unique-per-slave, and slaves are currently unique-per-master).

Problems arise, however, if one of the following is true:

• two different buildbot (masters/slaves) are running on the same machine, and an absolute path is used
• two builders have the same builddir, even if they're on different slaves

Because the builddir path is also used on the master for storing results files, this introduces a potential conflict between paths for multiple builders (potentially even across different masters, in the case of absolute paths) which can result in race conditions and/or combination of data from different builds.

At a bare minimum, Builder should be changed to have separate path settings for the master-side data storage and the slave-side build directory.

[tom.prince]

There is already both builddir and slavebuilddir, with the latter defaulting to the former.

[ayust]

I'd say they should get renamed then, because I definitely expect builddir to refer to the slave directory first. resultsdir would make more sense for the master's version, and it's the one that should get set explicitly if different.

(workdir is relative to builddir, builders are primarily operating on slaves, etc.)

[dustin]

At one point, there were explicit checks for overlapping builddirs, though slavedirs are intentionally allowed to overlap (Use At Your Own Risk).

This check, assuming it's still working, would prevent the second point -- "two builders have the same builddir" -- from occurring.

Since this will be obviated by moving this data to the database, perhaps for the remainder of 0.8.x we should just issue a warning for absolute paths in builddirs?

• minor because while this caused mayhem, it is something of a corner case; and
• simple because adding this warning only requires grokking master/buildbot/config.py.

[Tom Prince]

Add warning about absolute builddir.

Refs #2260.

Changeset: 516d41c436acf2e9fb08a7549c7beb499c2e70d6

[tom.prince]

We now warn about absolute paths, so moving this back to 0.9.0, when results will live in the db.

[Tom Prince]

Add warning about absolute builddir.

Refs #2260.

Changeset: 516d41c436acf2e9fb08a7549c7beb499c2e70d6