Fix slow PEX boot time when there are many extras. #1929
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Large extras sets lead to an exponentially scaled collection of fingerprinted distribution objects that need to be de-deduped. The hash codes calculated in doing so are expensive when the distribution metadata contains a large numer of requirements. Cache these hash codes to improve boot time by two orders of magnitude. In order to enable ergonomic caching of hash codes via attrs built in feature for doing this, some new plumbing is added to the third party vendored importer plumbing. Fixes pex-tool#1928
jsirois
commented
Oct 4, 2022
| @attr.s(frozen=True) | ||
| # N.B.: DistributionMetadata can have an expensive hash when a distribution has many requirements; | ||
| # so we cache the hash. See: https://github.com/pantsbuild/pex/issues/1928 | ||
| @attr.s(frozen=True, cache_hash=True) |
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This is the fix. All the rest just allows this to work. The attrs internals do magic when you enable this option and that magic requires being able to import attrs.
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The results for the issue repro case: |
benjyw
approved these changes
Oct 4, 2022
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Large extras sets lead to an exponentially scaled collection of
fingerprinted distribution objects that need to be de-duped. The hash
codes calculated in doing so are expensive when the distribution
metadata contains a large number of requirements. Cache these hash codes
to improve boot time by two orders of magnitude.
In order to enable ergonomic caching of hash codes via attrs built in
feature for doing this, some new plumbing is added to the third party
vendored importer plumbing.
Fixes #1928