wroclaw-git-backups/nix
1
0
Fork 0
mirror of https://github.com/NixOS/nix synced 2025-07-04 19:41:48 +02:00
Code Activity

Make computeFSClosure() single-threaded again

Browse source 
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

10
src/libstore/download.hh
View file

@ -23,8 +23,6 @@ struct DownloadRequest
struct DownloadResult
{
enum Status { Success, NotFound, Forbidden, Misc, Transient };
Status status;
bool cached;
std::string etag;
std::string effectiveUrl;
@ -38,7 +36,11 @@ struct Downloader
/* Enqueue a download request, returning a future to the result of
the download. The future may throw a DownloadError
exception. */
virtual std::future<DownloadResult> enqueueDownload(const DownloadRequest & request) = 0;
virtual void enqueueDownload(const DownloadRequest & request,
std::function<void(const DownloadResult &)> success,
std::function<void(std::exception_ptr exc)> failure) = 0;
std::future<DownloadResult> enqueueDownload(const DownloadRequest & request);
/* Synchronously download a file. */
DownloadResult download(const DownloadRequest & request);
@ -50,7 +52,7 @@ struct Downloader
Path downloadCached(ref<Store> store, const string & uri, bool unpack, string name = "",
const Hash & expectedHash = Hash(), string * effectiveUri = nullptr);
enum Error { NotFound, Forbidden, Misc, Transient };
enum Error { NotFound, Forbidden, Misc, Transient, Interrupted };
};
/* Return a shared Downloader object. Using this object is preferred