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Eelco Dolstra 11800e6198 download-from-binary-cache: parallelise fetching of NAR info files
Getting substitute information using the binary cache substituter has
non-trivial latency overhead.  A package or NixOS system configuration
can have hundreds of dependencies, and in the worst case (when the
local info cache is empty) we have to do a separate HTTP request for
each of these.  If the ping time to the server is t, getting N info
files will take tN seconds; e.g., with a ping time of 0.1s to
nixos.org, sequentially downloading 1000 info files (a typical NixOS
config) will take at least 100 seconds.

To fix this problem, the binary cache substituter can now perform
requests in parallel.  This required changing the substituter
interface to support a function querySubstitutablePathInfos() that
queries multiple paths at the same time, and rewriting queryMissing()
to take advantage of parallelism.  (Due to local caching,
parallelising queryMissing() is sufficient for most use cases, since
it's almost always called before building a derivation and thus fills
the local info cache.)

For example, parallelism speeds up querying all 1056 paths in a
particular NixOS system configuration from 116s to 2.6s.  It works so
well because the eccentricity of the top-level derivation in the
dependency graph is only 9.  So we only need 10 round-trips (when
using an unlimited number of parallel connections) to get everything.

Currently we do a maximum of 150 parallel connections to the server.
Thus it's important that the binary cache server (e.g. nixos.org) has
a high connection limit.  Alternatively we could use HTTP pipelining,
but WWW::Curl doesn't support it and libcurl has a hard-coded limit of
5 requests per pipeline.
2012-07-06 19:08:20 -04:00
corepkgs Fix xz compression 2012-07-01 21:57:25 -04:00
doc Update release notes 2012-06-23 14:59:13 -04:00
misc fixes to nix-worker systemd service descriptor: - remove commented-out lines - register the file for distribution in Makefile.am 2012-05-31 08:59:36 -04:00
perl nix-push: Always generate base-32 hashes 2012-07-02 18:05:57 -04:00
scripts download-from-binary-cache: parallelise fetching of NAR info files 2012-07-06 19:08:20 -04:00
src download-from-binary-cache: parallelise fetching of NAR info files 2012-07-06 19:08:20 -04:00
tests Urgh, modified the wrong file... 2012-04-14 19:52:58 +02:00
.gitignore First attempt at the manifest-less substituter 2012-06-29 18:28:52 -04:00
AUTHORS * Put something in here. 2004-11-07 20:30:02 +00:00
bootstrap.sh bootstrap: Simplify & make more robust. 2011-09-06 12:11:05 +00:00
build.nix Add an experimental nix-make file 2012-05-21 09:43:01 -04:00
configure.ac Use XZ compression in binary caches 2012-06-29 15:24:52 -04:00
COPYING * Change this to LGPL to keep the government happy. 2006-04-25 16:41:06 +00:00
INSTALL * Autoconf / Automake configuration and building. 2003-04-04 16:14:56 +00:00
Makefile.am fixes to nix-worker systemd service descriptor: - remove commented-out lines - register the file for distribution in Makefile.am 2012-05-31 08:59:36 -04:00
nix.conf.example * Document --cores in the manual. 2010-08-17 07:22:05 +00:00
nix.spec.in On systems with SystemD, install the service descriptor for nix-worker, and enable and start it 2012-05-31 08:59:36 -04:00
README * Install documentation in $(docdir) (i.e. share/doc/nix). 2008-11-19 13:19:09 +00:00
release.nix Add Emacs to the disk image 2012-05-31 09:50:58 -04:00
substitute.mk Use XZ compression in binary caches 2012-06-29 15:24:52 -04:00
version Bump version number 2012-05-12 00:07:08 -04:00

Nix is a purely functional package manager.  For installation and
usage instructions, please read the manual, which can be found in
`docs/manual/manual.html', and additionally at the Nix website at
<http://nixos.org/>.


Acknowledgments

This product includes software developed by the OpenSSL Project for
use in the OpenSSL Toolkit (http://www.OpenSSL.org/).