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To implement binary caches efficiently, Hydra needs to be able to map
the hash part of a store path (e.g. "gbg...zr7") to the full store
path (e.g. "/nix/store/gbg...kzr7-subversion-1.7.5"). (The binary
cache mechanism uses hash parts as a key for looking up store paths to
ensure privacy.) However, doing a search in the Nix store for
/nix/store/<hash>* is expensive since it requires reading the entire
directory. queryPathFromHashPart() prevents this by doing a cheap
database lookup.
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querySubstitutablePaths() takes a set of paths, so this greatly
reduces daemon <-> client latency.
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queryValidPaths() combines multiple calls to isValidPath() in one.
This matters when using the Nix daemon because it reduces latency.
For instance, on "nix-env -qas \*" it reduces execution time from 5.7s
to 4.7s (which is indistinguishable from the non-daemon case).
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Also removed querySubstitutablePathInfo().
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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.
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I.e. when multiple non-derivation arguments are passed to ‘nix-store
-r’ to be substituted, do them in parallel.
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We can't open a SQLite database if the disk is full. Since this
prevents the garbage collector from running when it's most needed, we
reserve some dummy space that we can free just before doing a garbage
collection. This actually revives some old code from the Berkeley DB
days.
Fixes #27.
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to disable use of substitutes; i.e., force building from source.
Fixes Nix/221.
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We don't need this anymore now that current filesystems support more
than 32,000 files in a directory.
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stream it's now necessary for the daemon to process the entire
sequence of exported paths, rather than letting the client do it.
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(way fewer roundtrips) by allowing the client to send data in bigger
chunks.
* Some refactoring.
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* Buffer the HashSink. This speeds up hashing a bit because it
prevents lots of calls to the hash update functions (e.g. nix-hash
went from 9.3s to 8.7s of user time on the closure of my
/var/run/current-system).
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system calls / context switches when dumping a NAR and in the worker
protocol.
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daemon (which is an error), print a nicer error message than
"Connection reset by peer" or "broken pipe".
* In the daemon, log errors that occur during request parameter
processing.
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derivation paths
This required adding a queryOutputDerivationNames function in the store API
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character. (Nix/216)
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daemon.
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will approximately require.
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size of the NAR serialisation of the path, i.e., `nix-store --dump
PATH'). This is useful for Hydra.
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hook script proper, and the stdout/stderr of the builder. Only the
latter should be saved in /nix/var/log/nix/drvs.
* Allow the verbosity to be set through an option.
* Added a flag --quiet to lower the verbosity level.
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An "using namespace std" was added locally in those functions that refer to
names from <cstring>. That is not pretty, but it's a very portable solution,
because strcpy() and friends will be found in both the 'std' and in the global
namespace.
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`nix-store --query-failed-paths'.
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which requires more I/O.
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(Linux) machines no longer maintain the atime because it's too
expensive, and on the machines where --use-atime is useful (like the
buildfarm), reading the atimes on the entire Nix store takes way too
much time to make it practical.
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read-only operations (like nix-env -qa) work properly when the
daemon isn't running.
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SHA-256 outputs of fixed-output derivations. I.e. they now produce
the same store path:
$ nix-store --add x
/nix/store/j2fq9qxvvxgqymvpszhs773ncci45xsj-x
$ nix-store --add-fixed --recursive sha256 x
/nix/store/j2fq9qxvvxgqymvpszhs773ncci45xsj-x
the latter being the same as the path that a derivation
derivation {
name = "x";
outputHashAlgo = "sha256";
outputHashMode = "recursive";
outputHash = "...";
...
};
produces.
This does change the output path for such fixed-output derivations.
Fortunately they are quite rare. The most common use is fetchsvn
calls with SHA-256 hashes. (There are a handful of those is
Nixpkgs, mostly unstable development packages.)
* Documented the computation of store paths (in store-api.cc).
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build progress.
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when upgrading Nix.
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* --dry-run: print the paths that we don't know how to build/substitute.
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again. (After the previous substituter mechanism refactoring I
didn't update the code that obtains the references of substitutable
paths.) This required some refactoring: the substituter programs
are now kept running and receive/respond to info requests via
stdin/stdout.
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* The garbage collector now also prints the number of blocks freed.
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This isn't usually a problem, except that it causes tests to fail
when performed in a directory with a very long path name. So chdir
to the socket directory and use a relative path name.
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* nix-store --register-validity: option to supply the content hash of
each path.
* Removed compatibility with Nix <= 0.7 stores.
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* queryDeriver in daemon mode: don't barf if the other side returns an
empty string (which means there is no deriver).
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in multi-user Nix (NIX-72).
* Client/worker: exchange a protocol version number for future
compatibility.
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