distbuild: Check cache status each time we enqueue new artifacts

This fixes an issue where distbuild would build the same artifact more
than once. The problem occurs with a single distbuild controller, if
multiple initiators request builds of the same thing at roughly the
same time (which scripts/release-build in definitions.git does).

This change also means that multiple distbuild controllers sharing a
single artifact cache will be smart about sharing built artifacts. It
does not mean that distbuild can handle having built artifacts removed
from the cache while it is building stuff.

The number of HTTP requests made to the shared artifact cache is higher
with this patch, but these seem to take no more than 1 second and we
only ever need to run one request before starting more builds, so there
should be no noticable impact on performance.

Change-Id: Ib3246219a10ca95d40b8a21bd0fe53f32e46c1c9

0 files changed, 0 insertions, 0 deletions