nix-super/src/nix-channel
Eelco Dolstra 90ad02bf62 Enable HTTP/2 support
The binary cache store can now use HTTP/2 to do lookups. This is much
more efficient than HTTP/1.1 due to multiplexing: we can issue many
requests in parallel over a single TCP connection. Thus it's no longer
necessary to use a bunch of concurrent TCP connections (25 by
default).

For example, downloading 802 .narinfo files from
https://cache.nixos.org/, using a single TCP connection, takes 11.8s
with HTTP/1.1, but only 0.61s with HTTP/2.

This did require a fairly substantial rewrite of the Downloader class
to use the curl multi interface, because otherwise curl wouldn't be
able to do multiplexing for us. As a bonus, we get connection reuse
even with HTTP/1.1. All downloads are now handled by a single worker
thread. Clients call Downloader::enqueueDownload() to tell the worker
thread to start the download, getting a std::future to the result.
2016-09-14 16:36:02 +02:00
..
local.mk nix-channel: implement in c++ 2016-08-11 11:34:43 -04:00
nix-channel.cc Enable HTTP/2 support 2016-09-14 16:36:02 +02:00