Commit graph

4 commits

Author SHA1 Message Date
Eelco Dolstra 2df9cbeb47 Provide random access to cached NARs
E.g.

  $ time nix cat-store --store https://cache.nixos.org?local-nar-cache=/tmp/nars \
    /nix/store/b0w2hafndl09h64fhb86kw6bmhbmnpm1-blender-2.79/share/icons/hicolor/scalable/apps/blender.svg > /dev/null
  real    0m4.139s

  $ time nix cat-store --store https://cache.nixos.org?local-nar-cache=/tmp/nars \
    /nix/store/b0w2hafndl09h64fhb86kw6bmhbmnpm1-blender-2.79/share/icons/hicolor/scalable/apps/blender.svg > /dev/null
  real    0m0.024s

(Before, the second call took ~0.220s.)

This will use a NAR listing in
/tmp/nars/b0w2hafndl09h64fhb86kw6bmhbmnpm1.ls containing all metadata,
including the offsets of regular files inside the NAR. Thus, we don't
need to read the entire NAR. (We do read the entire listing, but
that's generally pretty small. We could use a SQLite DB by borrowing
some more code from nixos-channel-scripts/file-cache.hh.)

This is primarily useful when Hydra is serving files from an S3 binary
cache, in particular when you have giant NARs. E.g. we had some 12 GiB
NARs, so accessing individuals files was pretty slow.
2017-12-07 01:07:07 +01:00
Eelco Dolstra 4db0a9555e
nix ls-{nar,store} --json: Respect -R 2017-11-14 14:31:38 +01:00
Eelco Dolstra bac8055652
nix ls-{store,nar}: Add --json flag 2017-11-14 14:23:53 +01:00
Eelco Dolstra 1042c10fd0 Add NAR / Store accessor abstraction
This is primary to allow hydra-queue-runner to extract files like
"nix-support/hydra-build-products" from NARs in binary caches.
2016-02-25 17:43:19 +01:00