Date: Thu, 15 Nov 2018 15:26:20 +0000 From: bugzilla-noreply@freebsd.org To: pkg@FreeBSD.org Subject: [Bug 232350] ports-mgmt/pkg: periodic pkg-checksum and pkg-backup interfere with 'overnight' port builds Message-ID: <bug-232350-32340-4SmZUeQ3XT@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-232350-32340@https.bugs.freebsd.org/bugzilla/> References: <bug-232350-32340@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D232350 --- Comment #11 from Ian Lepore <ian@FreeBSD.org> --- (In reply to Alex Kozlov from comment #10) It is not an error or a problem to be working on a snapshot of the database taken at the beginning of the periodic run. This is a standard axiom of fi= xing races with lockless (or lock minimization) techniques... it doesn't matter whether you capture the snapshot before or after some arbitrary action, it = only matters that you capture and operate on a consistant snapshot. If updates = are happening to the live database while you run the validation on the snapshot, those updates will be validated in the run the next day, and that situation= is exactly identical to the situation in which running with exclusionary locks prevented the update from happening until after the validation run complete= s. These are not new problems, and the techniques for solving them are not new either. I first ran into these problems and the snapshot-based solutions to them in the 1970s. The main downside to such techniques is that it requires copying the data t= o be validated, and sometimes the size of that data makes that too expensive of = an operation. That could be the case here, I have no idea how much data would have to be copied in this instance. --=20 You are receiving this mail because: You are the assignee for the bug.=
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