This integrates the functionality of the index-debuginfo program in
nixos-channel-scripts to maintain an index of DWARF debuginfo files in
a format usable by dwarffs. Thus the debug info index is updated by
Hydra rather than by the channel mirroring script.
Example usage:
$ nix copy --to 'file:///tmp/binary-cache?index-debug-info=true' /nix/store/vr9mhcch3fljzzkjld3kvkggvpq38cva-nix-2.2.2-debug
$ cat /tmp/binary-cache/debuginfo/036b210b03bad75ab2d8fc80b7a146f98e7f1ecf.debug
{"archive":"../nar/0313h2kdhk4v73xna9ysiksp2v8xrsk5xsw79mmwr3rg7byb4ka8.nar.xz","member":"lib/debug/.build-id/03/6b210b03bad75ab2d8fc80b7a146f98e7f1ecf.debug"}
Fixes#3083.
This reduces memory consumption of
nix copy --from file://... --to ~/my-nix /nix/store/95cwv4q54dc6giaqv6q6p4r02ia2km35-blender-2.79
from 514 MiB to 18 MiB for an uncompressed binary cache, and from 192
MiB to 53 MiB for a bzipped binary cache. It may also be faster
because fetching can happen concurrently with decompression/writing.
Continuation of 48662d151b.
Issue https://github.com/NixOS/nix/issues/1681.
The fact that queryPathInfo() is synchronous meant that we needed a
thread for every concurrent binary cache lookup, even though they end
up being handled by the same download thread. Requiring hundreds of
threads is not a good idea. So now there is an asynchronous version of
queryPathInfo() that takes a callback function to process the
result. Similarly, enqueueDownload() now takes a callback rather than
returning a future.
Thus, a command like
nix path-info --store https://cache.nixos.org/ -r /nix/store/slljrzwmpygy1daay14kjszsr9xix063-nixos-16.09beta231.dccf8c5
that returns 4941 paths now takes 1.87s using only 2 threads (the main
thread and the downloader thread). (This is with a prewarmed
CloudFront.)
