Without the change llvm build fails on this week's gcc-13 snapshot as:
src/libutil/json.cc: In function 'void nix::toJSON(std::ostream&, const char*, const char*)':
src/libutil/json.cc:33:22: error: 'uint16_t' was not declared in this scope
33 | put(hex[(uint16_t(*i) >> 12) & 0xf]);
| ^~~~~~~~
src/libutil/json.cc:5:1: note: 'uint16_t' is defined in header '<cstdint>'; did you forget to '#include <cstdint>'?
4 | #include <cstring>
+++ |+#include <cstdint>
5 |
This solves the error
error: cannot connect to socket at '/nix/var/nix/daemon-socket/socket': Connection refused
on build farm systems that are loaded but operating normally.
I've seen this happen on an M1 mac running a loaded hercules-ci-agent.
Hercules CI uses multiple worker processes, which may connect to
the Nix daemon around the same time. It's not unthinkable that
the Nix daemon listening process isn't scheduled until after 6
workers try to connect, especially on a system under load with
many workers.
Is the increase safe?
The number is the number of connections that the kernel will buffer
while the listening process hasn't `accept`-ed them yet.
It did not - and will not - restrict the total number of daemon
forks that a client can create.
History
The number 5 has remained unchanged since the introduction in
nix-worker with 0130ef88ea in 2006.
Add a new `file` fetcher type, which will fetch a plain file over
http(s), or from the local file.
Because plain `http(s)://` or `file://` urls can already correspond to
`tarball` inputs (if the path ends-up with a know archive extension),
the URL parsing logic is a bit convuluted in that:
- {http,https,file}:// urls will be interpreted as either a tarball or a
file input, depending on the extensions of the path part (so
`https://foo.com/bar` will be a `file` input and
`https://foo.com/bar.tar.gz` as a `tarball` input)
- `file+{something}://` urls will be interpreted as `file` urls (with
the `file+` part removed)
- `tarball+{something}://` urls will be interpreted as `tarball` urls (with
the `tarball+` part removed)
Fix#3785
Co-Authored-By: Tony Olagbaiye <me@fron.io>
Since a26be9f3b8, the same parser is used
to parse the result of sourcehut’s `HEAD` endpoint (coming from [git
dumb protocol]) and the output of `git ls-remote`. However, they are very
slightly different (the former doesn’t specify the current reference
since it’s implied to be `HEAD`).
Unify both, and make the parser a bit more robust and understandable (by
making it more typed and adding tests for it)
[git dumb protocol]: https://git-scm.com/book/en/v2/Git-Internals-Transfer-Protocols#_the_dumb_protocol
this slightly increases the amount of memory used for any given symbol, but this
increase is more than made up for if the symbol is referenced more than once in
the EvalState that holds it. on average every symbol should be referenced at
least twice (once to introduce a binding, once to use it), so we expect no
increase in memory on average.
symbol tables are limited to 2³² entries like position tables, and similar
arguments apply to why overflow is not likely: 2³² symbols would require as many
string instances (at 24 bytes each) and map entries (at 24 bytes or more each,
assuming that the map holds on average at most one item per bucket as the docs
say). a full symbol table would require at least 192GB of memory just for
symbols, which is well out of reach. (an ofborg eval of nixpks today creates
less than a million symbols!)
PosTable deduplicates origin information, so using symbols for paths is no
longer necessary. moving away from path Symbols also reduces the usage of
symbols for things that are not keys in attribute sets, which will become
important in the future when we turn symbols into indices as well.
Pos objects are somewhat wasteful as they duplicate the origin file name and
input type for each object. on files that produce more than one Pos when parsed
this a sizeable waste of memory (one pointer per Pos). the same goes for
ptr<Pos> on 64 bit machines: parsing enough source to require 8 bytes to locate
a position would need at least 8GB of input and 64GB of expression memory. it's
not likely that we'll hit that any time soon, so we can use a uint32_t index to
locate positions instead.
nix show-config --json was serializing experimental features as ints.
nlohmann::json will automatically use these definitions to serialize
and deserialize ExperimentalFeatures.
Strictly, we don't use the from_json instance yet, it's provided for
completeness and hopefully future use.
This was a problem when writing a fetcher that uses e.g. sha256 hashes
for revisions. This doesn't actually do anything new, but allows for
creating such fetchers in the future (perhaps when support for Git's
SHA256 object format gains more popularity).
Saving the cwd fd didn't actually work well -- prior to this commit, the
following would happen:
: ~/w/vc/nix ; doas outputs/out/bin/nix --experimental-features 'nix-command flakes' run nixpkgs#coreutils -- --coreutils-prog=pwd
pwd: couldn't find directory entry in ‘../../../..’ with matching i-node
: ~/w/vc/nix ; doas outputs/out/bin/nix --experimental-features 'nix-command flakes' develop -c pwd
pwd: couldn't find directory entry in ‘../../../..’ with matching i-node
This doesn't work very well (maybe I'm misunderstanding the desired
implementation):
: ~/w/vc/nix ; doas outputs/out/bin/nix --experimental-features 'nix-command flakes' develop -c pwd
pwd: couldn't find directory entry in ‘../../../..’ with matching i-node
I regularly pass around simple scripts by using nix-shell as the script
interpreter, eg. like this:
#!/usr/bin/env nix-shell
#!nix-shell -p dd_rescue coreutils bash -i bash
While this works most of the time, I recently had one occasion where it
would not and the above would result in the following:
$ sudo ./myscript.sh
bash: ./myscript.sh: No such file or directory
Note the "sudo" here, because this error only occurs if we're root.
The reason for the latter is because running Nix as root means that we
can directly access the store, which makes sure we use a filesystem
namespace to make the store writable. XXX - REWORD!
So when stracing the process, I stumbled on the following sequence:
openat(AT_FDCWD, "/proc/self/ns/mnt", O_RDONLY) = 3
unshare(CLONE_NEWNS) = 0
... later ...
getcwd("/the/real/cwd", 4096) = 14
setns(3, CLONE_NEWNS) = 0
getcwd("/", 4096) = 2
In the whole strace output there are no calls to chdir() whatsoever, so
I decided to look into the kernel source to see what else could change
directories and found this[1]:
/* Update the pwd and root */
set_fs_pwd(fs, &root);
set_fs_root(fs, &root);
The set_fs_pwd() call is roughly equivalent to a chdir() syscall and
this is called when the setns() syscall is invoked[2].
[1]: b14ffae378/fs/namespace.c (L4659)
[2]: b14ffae378/kernel/nsproxy.c (L346)
Impure derivations are derivations that can produce a different result
every time they're built. Example:
stdenv.mkDerivation {
name = "impure";
__impure = true; # marks this derivation as impure
outputHashAlgo = "sha256";
outputHashMode = "recursive";
buildCommand = "date > $out";
};
Some important characteristics:
* This requires the 'impure-derivations' experimental feature.
* Impure derivations are not "cached". Thus, running "nix-build" on
the example above multiple times will cause a rebuild every time.
* They are implemented similar to CA derivations, i.e. the output is
moved to a content-addressed path in the store. The difference is
that we don't register a realisation in the Nix database.
* Pure derivations are not allowed to depend on impure derivations. In
the future fixed-output derivations will be allowed to depend on
impure derivations, thus forming an "impurity barrier" in the
dependency graph.
* When sandboxing is enabled, impure derivations can access the
network in the same way as fixed-output derivations. In relaxed
sandboxing mode, they can access the local filesystem.
Sergei Trofimovich
Robert Hensing
Yorick