f3f661bac1
Previously, if the queue monitor thread encounters a build that Hydra has previously built, it downloaded the output paths from the binary cache, just to determine the build products and metrics. This is very inefficient. In particular, when doing something like merging nixpkgs:staging into nixpkgs:master, the queue monitor thread will be locked up for a long time fetching files from S3, causing the build farm to be mostly idle. Of course this is entirely unnecessary, since the build products/metrics are already in the Hydra database. So now we just look up a previous build with the same output path, and copy the products/metrics.
To start hacking on Hydra, run:
$ nix-shell
$ ./configure $configureFlags --prefix=/opt/hydra
$ make
$ make install
Or, if you just want to build from source (on x86_64-linux):
$ nix-build -A build.x86_64-linux release.nix