RemoteFSAccessor: Make the local NAR cache content-addressed #14948
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Do we need to bump a cache version? |
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@Ericson2314 There is no version at the moment. There shouldn't be any upgrade issues since the new file names in the cache have a different length. |
Ericson2314
reviewed
Jan 8, 2026
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| ref<SourceAccessor> RemoteFSAccessor::addToCache(std::string_view hashPart, std::string && nar) | ||
| ref<SourceAccessor> RemoteFSAccessor::addToCache( | ||
| std::string_view hashPart, |
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| std::string_view hashPart, |
Ericson2314
reviewed
Jan 8, 2026
| } | ||
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| auto narAccessor = makeNarAccessor(std::move(nar)); | ||
| nars.emplace(hashPart, narAccessor); |
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| nars.emplace(hashPart, narAccessor); |
Ericson2314
reviewed
Jan 8, 2026
| StringSink sink; | ||
| store->narFromPath(storePath, sink); | ||
| return addToCache(storePath.hashPart(), std::move(sink.s)); | ||
| return addToCache(storePath.hashPart(), cacheFile, listingFile, std::move(sink.s)); |
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| return addToCache(storePath.hashPart(), cacheFile, listingFile, std::move(sink.s)); | |
| auto accessor = addToCache(cacheFile, listingFile, std::move(sink.s)); | |
| narsHashes.emplace(storePath.hashPart(), info->narHash); | |
| nars.emplace(info->narHash, accessor); | |
| return accessor; |
Ericson2314
requested changes
Jan 8, 2026
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There is no version at the moment. There shouldn't be any upgrade issues since the new file names in the cache have a different length.
sounds good
OK generally looks good, but I would make it a double map (see final comment) so we don't end up opening multiple NAR accessors for the same NAR.
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Motivation
Previously, the local NAR cache was indexed by the store path hash. Making it content-addressed (i.e. indexed by NAR hash) provides some potential deduplication, but more importantly, makes it possible to substitute NARs from the local NAR cache with fewer trust issues (see DeterminateSystems#279).
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