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=232350 --- 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 fixing 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 completes. 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 to 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. -- You are receiving this mail because: You are the assignee for the bug.
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