[Bug 1837254] [NEW] ubuntu-cpc parallel builds produce unused files

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Robert C Jennings (rcj):

[Impact]

In parallel builds where a list of image targets are provided, the build
may produce binaries that are not part of the named set of targets but
are created by series dependencies.  These implicitly created binaries
may be generated by multiple builds but are unused as our convention for
the ubuntu-cpc project is to only consume binaries from the explicitly
named image targets; this avoids overwriting the same object by multiple
parallel builds.  The problem is that as we build out parallel jobs for
a number of image targets (multiplied by each supported architecture)
we're wasting a lot of resources.

[Test Case]

 * Specify an image target within the ubuntu-cpc project for a build

 * Observe artifacts in addition to the ones for the named image target
are produced and downloaded

[Regression Potential]

 * An artifact from an explicitly named artifact is missing and builds
will begin to remove desired output.  Testing is being done to address
this regression.

[Other Info]

 * This has been running in production in Eoan for a few weeks and we're
satisfied with the results.  We have seen overall time reduced by 20-50%
on some builds.

[Original Description]

In parallel builds where a list of image targets are provided, the build
may produce binaries that are not part of the named set of targets but
are created by series dependencies.  These implicitly created binaries
may be generated by multiple builds but are unused as our convention for
the ubuntu-cpc project is to only consume binaries from the explicitly
named image targets; this avoids overwriting the same object by multiple
parallel builds.  The problem is that as we build out parallel jobs for
a number of image targets (multiplied by each supported architecture)
we're wasting a lot of resources.

** Affects: livecd-rootfs (Ubuntu)
     Importance: Undecided
         Status: Fix Released

** Affects: livecd-rootfs (Ubuntu Xenial)
     Importance: Undecided
         Status: New

** Affects: livecd-rootfs (Ubuntu Bionic)
     Importance: Undecided
         Status: New

** Affects: livecd-rootfs (Ubuntu Disco)
     Importance: Undecided
         Status: New


** Tags: id-5d31721934a49770eea1ff43
-- 
ubuntu-cpc parallel builds produce unused files
https://bugs.launchpad.net/bugs/1837254
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