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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
Download patch file Download diff file Expand all files Collapse all files

98
src/libstore/store-api.cc
View file

@ -4,6 +4,8 @@
#include "util.hh"
#include "nar-info-disk-cache.hh"
#include <future>
namespace nix {
@ -282,52 +284,80 @@ bool Store::isValidPath(const Path & storePath)
ref<const ValidPathInfo> Store::queryPathInfo(const Path & storePath)
{
std::promise<ref<ValidPathInfo>> promise;
queryPathInfo(storePath,
[&](ref<ValidPathInfo> info) {
promise.set_value(info);
},
[&](std::exception_ptr exc) {
promise.set_exception(exc);
});
return promise.get_future().get();
}
void Store::queryPathInfo(const Path & storePath,
std::function<void(ref<ValidPathInfo>)> success,
std::function<void(std::exception_ptr exc)> failure)
{
auto hashPart = storePathToHash(storePath);
{
auto state_(state.lock());
auto res = state_->pathInfoCache.get(hashPart);
if (res) {
stats.narInfoReadAverted++;
if (!*res)
throw InvalidPath(format("path ‘%s’ is not valid") % storePath);
return ref<ValidPathInfo>(*res);
try {
{
auto res = state.lock()->pathInfoCache.get(hashPart);
if (res) {
stats.narInfoReadAverted++;
if (!*res)
throw InvalidPath(format("path ‘%s’ is not valid") % storePath);
return success(ref<ValidPathInfo>(*res));
}
}
}
if (diskCache) {
auto res = diskCache->lookupNarInfo(getUri(), hashPart);
if (res.first != NarInfoDiskCache::oUnknown) {
stats.narInfoReadAverted++;
auto state_(state.lock());
state_->pathInfoCache.upsert(hashPart,
res.first == NarInfoDiskCache::oInvalid ? 0 : res.second);
if (res.first == NarInfoDiskCache::oInvalid ||
(res.second->path != storePath && storePathToName(storePath) != ""))
throw InvalidPath(format("path ‘%s’ is not valid") % storePath);
return ref<ValidPathInfo>(res.second);
if (diskCache) {
auto res = diskCache->lookupNarInfo(getUri(), hashPart);
if (res.first != NarInfoDiskCache::oUnknown) {
stats.narInfoReadAverted++;
{
auto state_(state.lock());
state_->pathInfoCache.upsert(hashPart,
res.first == NarInfoDiskCache::oInvalid ? 0 : res.second);
if (res.first == NarInfoDiskCache::oInvalid ||
(res.second->path != storePath && storePathToName(storePath) != ""))
throw InvalidPath(format("path ‘%s’ is not valid") % storePath);
}
return success(ref<ValidPathInfo>(res.second));
}
}
} catch (std::exception & e) {
return callFailure(failure);
}
auto info = queryPathInfoUncached(storePath);
queryPathInfoUncached(storePath,
[this, storePath, hashPart, success, failure](std::shared_ptr<ValidPathInfo> info) {
if (diskCache)
diskCache->upsertNarInfo(getUri(), hashPart, info);
if (diskCache)
diskCache->upsertNarInfo(getUri(), hashPart, info);
{
auto state_(state.lock());
state_->pathInfoCache.upsert(hashPart, info);
}
{
auto state_(state.lock());
state_->pathInfoCache.upsert(hashPart, info);
}
if (!info
|| (info->path != storePath && storePathToName(storePath) != ""))
{
stats.narInfoMissing++;
throw InvalidPath(format("path ‘%s’ is not valid") % storePath);
}
if (!info
|| (info->path != storePath && storePathToName(storePath) != ""))
{
stats.narInfoMissing++;
return failure(std::make_exception_ptr(InvalidPath(format("path ‘%s’ is not valid") % storePath)));
}
return ref<ValidPathInfo>(info);
callSuccess(success, failure, ref<ValidPathInfo>(info));
}, failure);
}