gc: resume GC after a pathinuse error #11922
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Mic92
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Mic92
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Nov 20, 2024
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In that case there should at least be an GitHub issue so we can try to diagnose this (and a comment in the code to link to that issue). |
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Created an issue: #11923 |
First the motivation: I recently faced a bug that I assume is coming from the topoSortPaths function where the GC was trying to delete a path having some alive referrers. I resolved this by manually deleting the faulty path referrers using nix-store --query --referrers. I sadly did not manage to reproduce this bug. This bug alone is not a big deal. However, this bug is triggering a cascading failure: invalidatePathChecked is throwing a PathInUse exception. This exception is not catched and fails the whole GC run. From there, the machine (a builder machine) was unable to GC its Nix store, which led to an almost full disk with no way to automatically delete the dead Nix paths. Instead, I think we should log the error for the specific store path we're trying to delete, specifying we can't delete this path because it still has referrers. Once we're done with logging that, the GC run should continue to delete the dead store paths it can delete.
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Motivation
invalidatePathCheckedis throwing aPathInUseexception. This exception is not catched and fails the whole GC run.Instead, I think we should log the error for the specific store path we're trying to delete, explaining we can't delete this path because it still has referrers. Once we're done with logging that, the GC run should continue to delete the dead store paths it can delete.
Context
I recently faced a bug that I assume is coming from the
topoSortPathsfunction where the GC was trying to delete a path having some alive referrers. The GC run service was constantly failing with the error messageI resolved this by manually deleting the faulty path referrers using
nix-store --query --referrersandnix store delete. I sadly can't reproduce this bug. It seems to happen extremely infrequently.This bug alone is not a massive deal due to its infrequent nature. However, the way it cascades is a serious issue for Nix builders. Because we're throwing an un-catched
PathInUseexception, the full GC run fails. This prevents any automatic garbage collection of the nix store, and the machine disk is slowly but surely filling up. Up until the point where a manual intervention is required to fix the situation.Priorities and Process
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