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Make computeFSClosure() single-threaded again

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The fact that queryPathInfo() is synchronous meant that we needed a
thread for every concurrent binary cache lookup, even though they end
up being handled by the same download thread. Requiring hundreds of
threads is not a good idea. So now there is an asynchronous version of
queryPathInfo() that takes a callback function to process the
result. Similarly, enqueueDownload() now takes a callback rather than
returning a future.

Thus, a command like

  nix path-info --store https://cache.nixos.org/ -r /nix/store/slljrzwmpygy1daay14kjszsr9xix063-nixos-16.09beta231.dccf8c5

that returns 4941 paths now takes 1.87s using only 2 threads (the main
thread and the downloader thread). (This is with a prewarmed
CloudFront.)
This commit is contained in:
Eelco Dolstra 2016-09-16 18:54:14 +02:00
parent 054be50257
commit 75989bdca7
16 changed files with 410 additions and 227 deletions
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62
src/libstore/remote-store.cc
View file

@ -246,36 +246,40 @@ void RemoteStore::querySubstitutablePathInfos(const PathSet & paths,
}
std::shared_ptr<ValidPathInfo> RemoteStore::queryPathInfoUncached(const Path & path)
void RemoteStore::queryPathInfoUncached(const Path & path,
std::function<void(std::shared_ptr<ValidPathInfo>)> success,
std::function<void(std::exception_ptr exc)> failure)
{
auto conn(connections->get());
conn->to << wopQueryPathInfo << path;
try {
conn->processStderr();
} catch (Error & e) {
// Ugly backwards compatibility hack.
if (e.msg().find("is not valid") != std::string::npos)
throw InvalidPath(e.what());
throw;
}
if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 17) {
bool valid = readInt(conn->from) != 0;
if (!valid) throw InvalidPath(format("path ‘%s’ is not valid") % path);
}
auto info = std::make_shared<ValidPathInfo>();
info->path = path;
info->deriver = readString(conn->from);
if (info->deriver != "") assertStorePath(info->deriver);
info->narHash = parseHash(htSHA256, readString(conn->from));
info->references = readStorePaths<PathSet>(*this, conn->from);
info->registrationTime = readInt(conn->from);
info->narSize = readLongLong(conn->from);
if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 16) {
info->ultimate = readInt(conn->from) != 0;
info->sigs = readStrings<StringSet>(conn->from);
info->ca = readString(conn->from);
}
return info;
sync2async<std::shared_ptr<ValidPathInfo>>(success, failure, [&]() {
auto conn(connections->get());
conn->to << wopQueryPathInfo << path;
try {
conn->processStderr();
} catch (Error & e) {
// Ugly backwards compatibility hack.
if (e.msg().find("is not valid") != std::string::npos)
throw InvalidPath(e.what());
throw;
}
if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 17) {
bool valid = readInt(conn->from) != 0;
if (!valid) throw InvalidPath(format("path ‘%s’ is not valid") % path);
}
auto info = std::make_shared<ValidPathInfo>();
info->path = path;
info->deriver = readString(conn->from);
if (info->deriver != "") assertStorePath(info->deriver);
info->narHash = parseHash(htSHA256, readString(conn->from));
info->references = readStorePaths<PathSet>(*this, conn->from);
info->registrationTime = readInt(conn->from);
info->narSize = readLongLong(conn->from);
if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 16) {
info->ultimate = readInt(conn->from) != 0;
info->sigs = readStrings<StringSet>(conn->from);
info->ca = readString(conn->from);
}
return info;
});
}