forked from lix-project/lix
ca580bec35
This speeds up commands like "nix cat-store". For example: $ time nix cat-store --store https://cache.nixos.org?local-nar-cache=/tmp/nar-cache /nix/store/i60yncmq6w9dyv37zd2k454g0fkl3arl-systemd-234/etc/udev/udev.conf real 0m4.336s $ time nix cat-store --store https://cache.nixos.org?local-nar-cache=/tmp/nar-cache /nix/store/i60yncmq6w9dyv37zd2k454g0fkl3arl-systemd-234/etc/udev/udev.conf real 0m0.045s The primary motivation is to allow hydra-server to serve files from S3 binary caches. Previously Hydra had a hack to do "nix-store -r <path>", but that fetches the entire closure so is prohibitively expensive. There is no garbage collection of the NAR cache yet. Also, the entire NAR is read when accessing a single member file. We could generate the NAR listing to provide random access. Note: the NAR cache is indexed by the store path hash, not the content hash, so NAR caches should not be shared between binary caches, unless you're sure that all your builds are binary-reproducible.
74 lines
1.8 KiB
C++
74 lines
1.8 KiB
C++
#include "remote-fs-accessor.hh"
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#include "nar-accessor.hh"
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namespace nix {
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RemoteFSAccessor::RemoteFSAccessor(ref<Store> store, const Path & cacheDir)
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: store(store)
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, cacheDir(cacheDir)
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{
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if (cacheDir != "")
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createDirs(cacheDir);
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}
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std::pair<ref<FSAccessor>, Path> RemoteFSAccessor::fetch(const Path & path_)
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{
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auto path = canonPath(path_);
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auto storePath = store->toStorePath(path);
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std::string restPath = std::string(path, storePath.size());
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if (!store->isValidPath(storePath))
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throw InvalidPath(format("path '%1%' is not a valid store path") % storePath);
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auto i = nars.find(storePath);
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if (i != nars.end()) return {i->second, restPath};
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StringSink sink;
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Path cacheFile = cacheDir != "" ? fmt("%s/%s.nar", cacheDir, storePathToHash(storePath)) : "";
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try {
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if (cacheFile != "")
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*sink.s = nix::readFile(cacheFile);
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} catch (SysError &) { }
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if (sink.s->empty()) {
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store->narFromPath(storePath, sink);
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if (cacheFile != "")
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/* FIXME: do this asynchronously. */
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writeFile(cacheFile, *sink.s);
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}
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auto accessor = makeNarAccessor(sink.s);
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nars.emplace(storePath, accessor);
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return {accessor, restPath};
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}
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FSAccessor::Stat RemoteFSAccessor::stat(const Path & path)
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{
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auto res = fetch(path);
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return res.first->stat(res.second);
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}
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StringSet RemoteFSAccessor::readDirectory(const Path & path)
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{
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auto res = fetch(path);
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return res.first->readDirectory(res.second);
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}
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std::string RemoteFSAccessor::readFile(const Path & path)
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{
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auto res = fetch(path);
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return res.first->readFile(res.second);
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}
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std::string RemoteFSAccessor::readLink(const Path & path)
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{
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auto res = fetch(path);
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return res.first->readLink(res.second);
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}
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}
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