In this mode, the following restrictions apply:
* The builtins currentTime, currentSystem and storePath throw an
error.
* $NIX_PATH and -I are ignored.
* fetchGit and fetchMercurial require a revision hash.
* fetchurl and fetchTarball require a sha256 attribute.
* No file system access is allowed outside of the paths returned by
fetch{Git,Mercurial,url,Tarball}. Thus 'nix build -f ./foo.nix' is
not allowed.
Thus, the evaluation result is completely reproducible from the
command line arguments. E.g.
nix build --pure-eval '(
let
nix = fetchGit { url = https://github.com/NixOS/nixpkgs.git; rev = "9c927de4b179a6dd210dd88d34bda8af4b575680"; };
nixpkgs = fetchGit { url = https://github.com/NixOS/nixpkgs.git; ref = "release-17.09"; rev = "66b4de79e3841530e6d9c6baf98702aa1f7124e4"; };
in (import (nix + "/release.nix") { inherit nix nixpkgs; }).build.x86_64-linux
)'
The goal is to enable completely reproducible and traceable
evaluation. For example, a NixOS configuration could be fully
described by a single Git commit hash. 'nixos-rebuild' would do
something like
nix build --pure-eval '(
(import (fetchGit { url = file:///my-nixos-config; rev = "..."; })).system
')
where the Git repository /my-nixos-config would use further fetchGit
calls or Git externals to fetch Nixpkgs and whatever other
dependencies it has. Either way, the commit hash would uniquely
identify the NixOS configuration and allow it to reproduced.
* Look for both 'brotli' and 'bro' as external command,
since upstream has renamed it in newer versions.
If neither are found, current runtime behavior
is preserved: try to find 'bro' on PATH.
* Limit amount handed to BrotliEncoderCompressStream
to ensure interrupts are processed in a timely manner.
Testing shows negligible performance impact.
(Other compression sinks don't seem to require this)
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.
propagated-user-env-packages files in nixpkgs aren't all terminated by
newlines, as buildenv expected. Now it does not require a terminating
newline; note that this introduces a behaviour change: propagated user
env packages may now be spread across multiple lines. However, nix
1.11.x still expects them to be on a single line so this shouldn't be
used in nixpkgs for now.
The storeUri variable in the build-remote hook is declared very much to
the start of the main function and a bunch of lines later, the same
variable gets checked via hasPrefix() but it gets assigned *after* that
check when the most suitable machine for the build was choosen.
So I guess this was just a typo in d16fd24973
and what we really want is to either checkd the prefix *after* assigning
storeUri or use bestMachine->storeUri directly.
I choose the latter, because the former could introduce even more
regressions if the try block where the variable gets assigned terminates
early.
Nevertheless, the reason why the log output didn't work is because
hasPrefix() checked for "ssh://" in front of storeUri, but if the
storeUri isn't set correctly (or at all), we don't get the log file
descriptor set up properly, leading to no log output.
I've adjusted the remote-builds test to include a regression test for
this, so that we can make sure we get a build output when using remote
builds.
In addition to that I've tested this with two of my build farms and the
build logs are emitted correctly again.
Signed-off-by: aszlig <aszlig@nix.build>
The name had become a misnomer since it's not only for substitution
from binary caches, but when adding/copying any
(non-content-addressed) path to a store.
Linus Heckemann