lix/src/libstore/binary-cache-store.cc
Eelco Dolstra 75989bdca7 Make computeFSClosure() single-threaded again
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.)
2016-09-16 18:54:14 +02:00

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#include "archive.hh"
#include "binary-cache-store.hh"
#include "compression.hh"
#include "derivations.hh"
#include "fs-accessor.hh"
#include "globals.hh"
#include "nar-info.hh"
#include "sync.hh"
#include "worker-protocol.hh"
#include "nar-accessor.hh"
#include "nar-info-disk-cache.hh"
#include <chrono>
#include <future>
namespace nix {
BinaryCacheStore::BinaryCacheStore(const Params & params)
: Store(params)
, compression(get(params, "compression", "xz"))
{
auto secretKeyFile = get(params, "secret-key", "");
if (secretKeyFile != "")
secretKey = std::unique_ptr<SecretKey>(new SecretKey(readFile(secretKeyFile)));
StringSink sink;
sink << narVersionMagic1;
narMagic = *sink.s;
}
void BinaryCacheStore::init()
{
std::string cacheInfoFile = "nix-cache-info";
auto cacheInfo = getFile(cacheInfoFile);
if (!cacheInfo) {
upsertFile(cacheInfoFile, "StoreDir: " + storeDir + "\n");
} else {
for (auto & line : tokenizeString<Strings>(*cacheInfo, "\n")) {
size_t colon = line.find(':');
if (colon == std::string::npos) continue;
auto name = line.substr(0, colon);
auto value = trim(line.substr(colon + 1, std::string::npos));
if (name == "StoreDir") {
if (value != storeDir)
throw Error(format("binary cache %s is for Nix stores with prefix %s, not %s")
% getUri() % value % storeDir);
} else if (name == "WantMassQuery") {
wantMassQuery_ = value == "1";
} else if (name == "Priority") {
string2Int(value, priority);
}
}
}
}
void BinaryCacheStore::notImpl()
{
throw Error("operation not implemented for binary cache stores");
}
std::shared_ptr<std::string> BinaryCacheStore::getFile(const std::string & path)
{
std::promise<std::shared_ptr<std::string>> promise;
getFile(path,
[&](std::shared_ptr<std::string> result) {
promise.set_value(result);
},
[&](std::exception_ptr exc) {
promise.set_exception(exc);
});
return promise.get_future().get();
}
Path BinaryCacheStore::narInfoFileFor(const Path & storePath)
{
assertStorePath(storePath);
return storePathToHash(storePath) + ".narinfo";
}
void BinaryCacheStore::addToStore(const ValidPathInfo & info, const std::string & nar,
bool repair, bool dontCheckSigs)
{
if (!repair && isValidPath(info.path)) return;
/* Verify that all references are valid. This may do some .narinfo
reads, but typically they'll already be cached. */
for (auto & ref : info.references)
try {
if (ref != info.path)
queryPathInfo(ref);
} catch (InvalidPath &) {
throw Error(format("cannot add %s to the binary cache because the reference %s is not valid")
% info.path % ref);
}
auto narInfoFile = narInfoFileFor(info.path);
assert(nar.compare(0, narMagic.size(), narMagic) == 0);
auto narInfo = make_ref<NarInfo>(info);
narInfo->narSize = nar.size();
narInfo->narHash = hashString(htSHA256, nar);
if (info.narHash && info.narHash != narInfo->narHash)
throw Error(format("refusing to copy corrupted path %1% to binary cache") % info.path);
/* Compress the NAR. */
narInfo->compression = compression;
auto now1 = std::chrono::steady_clock::now();
auto narCompressed = compress(compression, nar);
auto now2 = std::chrono::steady_clock::now();
narInfo->fileHash = hashString(htSHA256, *narCompressed);
narInfo->fileSize = narCompressed->size();
auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(now2 - now1).count();
printMsg(lvlTalkative, format("copying path %1% (%2% bytes, compressed %3$.1f%% in %4% ms) to binary cache")
% narInfo->path % narInfo->narSize
% ((1.0 - (double) narCompressed->size() / nar.size()) * 100.0)
% duration);
/* Atomically write the NAR file. */
narInfo->url = "nar/" + printHash32(narInfo->fileHash) + ".nar"
+ (compression == "xz" ? ".xz" :
compression == "bzip2" ? ".bz2" :
"");
if (repair || !fileExists(narInfo->url)) {
stats.narWrite++;
upsertFile(narInfo->url, *narCompressed);
} else
stats.narWriteAverted++;
stats.narWriteBytes += nar.size();
stats.narWriteCompressedBytes += narCompressed->size();
stats.narWriteCompressionTimeMs += duration;
/* Atomically write the NAR info file.*/
if (secretKey) narInfo->sign(*secretKey);
upsertFile(narInfoFile, narInfo->to_string());
auto hashPart = storePathToHash(narInfo->path);
{
auto state_(state.lock());
state_->pathInfoCache.upsert(hashPart, std::shared_ptr<NarInfo>(narInfo));
}
if (diskCache)
diskCache->upsertNarInfo(getUri(), hashPart, std::shared_ptr<NarInfo>(narInfo));
stats.narInfoWrite++;
}
bool BinaryCacheStore::isValidPathUncached(const Path & storePath)
{
// FIXME: this only checks whether a .narinfo with a matching hash
// part exists. So f4kb...-foo matches f4kb...-bar, even
// though they shouldn't. Not easily fixed.
return fileExists(narInfoFileFor(storePath));
}
void BinaryCacheStore::narFromPath(const Path & storePath, Sink & sink)
{
auto info = queryPathInfo(storePath).cast<const NarInfo>();
auto nar = getFile(info->url);
if (!nar) throw Error(format("file %s missing from binary cache") % info->url);
stats.narRead++;
stats.narReadCompressedBytes += nar->size();
/* Decompress the NAR. FIXME: would be nice to have the remote
side do this. */
try {
nar = decompress(info->compression, *nar);
} catch (UnknownCompressionMethod &) {
throw Error(format("binary cache path %s uses unknown compression method %s")
% storePath % info->compression);
}
stats.narReadBytes += nar->size();
printMsg(lvlTalkative, format("exporting path %1% (%2% bytes)") % storePath % nar->size());
assert(nar->size() % 8 == 0);
sink((unsigned char *) nar->c_str(), nar->size());
}
void BinaryCacheStore::queryPathInfoUncached(const Path & storePath,
std::function<void(std::shared_ptr<ValidPathInfo>)> success,
std::function<void(std::exception_ptr exc)> failure)
{
auto narInfoFile = narInfoFileFor(storePath);
getFile(narInfoFile,
[=](std::shared_ptr<std::string> data) {
if (!data) return success(0);
stats.narInfoRead++;
callSuccess(success, failure, (std::shared_ptr<ValidPathInfo>)
std::make_shared<NarInfo>(*this, *data, narInfoFile));
},
failure);
}
Path BinaryCacheStore::addToStore(const string & name, const Path & srcPath,
bool recursive, HashType hashAlgo, PathFilter & filter, bool repair)
{
// FIXME: some cut&paste from LocalStore::addToStore().
/* Read the whole path into memory. This is not a very scalable
method for very large paths, but `copyPath' is mainly used for
small files. */
StringSink sink;
Hash h;
if (recursive) {
dumpPath(srcPath, sink, filter);
h = hashString(hashAlgo, *sink.s);
} else {
auto s = readFile(srcPath);
dumpString(s, sink);
h = hashString(hashAlgo, s);
}
ValidPathInfo info;
info.path = makeFixedOutputPath(recursive, h, name);
addToStore(info, *sink.s, repair);
return info.path;
}
Path BinaryCacheStore::addTextToStore(const string & name, const string & s,
const PathSet & references, bool repair)
{
ValidPathInfo info;
info.path = computeStorePathForText(name, s, references);
info.references = references;
if (repair || !isValidPath(info.path)) {
StringSink sink;
dumpString(s, sink);
addToStore(info, *sink.s, repair);
}
return info.path;
}
/* Given requests for a path /nix/store/<x>/<y>, this accessor will
first download the NAR for /nix/store/<x> from the binary cache,
build a NAR accessor for that NAR, and use that to access <y>. */
struct BinaryCacheStoreAccessor : public FSAccessor
{
ref<BinaryCacheStore> store;
std::map<Path, ref<FSAccessor>> nars;
BinaryCacheStoreAccessor(ref<BinaryCacheStore> store)
: store(store)
{
}
std::pair<ref<FSAccessor>, Path> fetch(const Path & path_)
{
auto path = canonPath(path_);
auto storePath = store->toStorePath(path);
std::string restPath = std::string(path, storePath.size());
if (!store->isValidPath(storePath))
throw InvalidPath(format("path %1% is not a valid store path") % storePath);
auto i = nars.find(storePath);
if (i != nars.end()) return {i->second, restPath};
StringSink sink;
store->narFromPath(storePath, sink);
auto accessor = makeNarAccessor(sink.s);
nars.emplace(storePath, accessor);
return {accessor, restPath};
}
Stat stat(const Path & path) override
{
auto res = fetch(path);
return res.first->stat(res.second);
}
StringSet readDirectory(const Path & path) override
{
auto res = fetch(path);
return res.first->readDirectory(res.second);
}
std::string readFile(const Path & path) override
{
auto res = fetch(path);
return res.first->readFile(res.second);
}
std::string readLink(const Path & path) override
{
auto res = fetch(path);
return res.first->readLink(res.second);
}
};
ref<FSAccessor> BinaryCacheStore::getFSAccessor()
{
return make_ref<BinaryCacheStoreAccessor>(ref<BinaryCacheStore>(
std::dynamic_pointer_cast<BinaryCacheStore>(shared_from_this())));
}
}