SCHEDULES Optimization for Test Harnesses now live

[Andrew Halberstadt]

In case you missed Dustin's note to 'firefox-ci', bug 1383880 added the
ability
to annotate which tasks a particular file can affect in moz.build. For
example, if a
push only touches Android specific files, the scheduler will only run tasks
on the
Android platform.

Now, bug 1403222 has added some additional annotations for test harnesses.
For
example, if your push *only* touches files under testing/web-platform, then
we will
only run web-platform-test based tasks.

I did a very cursory pass through the tree to annotate test-harness
specific files to
their relevant harness tags, but I likely missed a lot. We also can (and
should)
annotate test files and manifests themselves. This is a little tricky as
test files are
often mixed together, so general top-level rules to determine which test
files belong
to which test suite will be hard to do. But we could still go through and
annotate
files and directories manually. Getting this perfect will require a heroic
effort, but we
could start with some of the larger, nicely isolated test directories. It
doesn't need
to happen all at once.

If you'd like to help improve our scheduling efficiency, it would be great
to have
more people start to annotate test specific files. The list of available
test suites is
here
<https://hg.mozilla.org/mozilla-central/file/tip/python/mozbuild/mozbuild/schedules.py#l27>.
For an example on how to apply these annotations, see here
<https://hg.mozilla.org/mozilla-central/file/tip/testing/web-platform/moz.build#l27>
.

Finally to echo Dustin's request, if you can think of other vectors along
which we
can set up similar optimizations, please let us know or file a bug under
Taskcluster :: Task Configuration.

Thanks,
Andrew