Hello! Sree Harsha Totakura <sreehar...@totakura.in> skribis:
> On 03/28/2014 10:26 PM, Ludovic Courtès wrote: >> Sree Harsha Totakura <sreehar...@totakura.in> skribis: >> >>> From the sources, I found that build-aux/hydra/*.scm convert packages into a >>> format hydra understands for building them. >> >> Yes. Specifically, build-aux/hydra/*.scm return a list of “jobs”, where >> each job is represented as an alist with a number of compulsory items, >> such as ‘derivation’ (see ‘package->alist’.) >> > > OK, so the list of jobs is what is termed as a jobset in Hydra. Jobset is a > collection of jobs + configuration for when to rebuild the jobset and where to > get the jobset's inputs (sources). > > The file build-aux/hydra/gnu-system.scm prepares the jobset which contains all > packages currently in Guix. This jobset is configured in hydra.gnu.org to > initiate a build whenever there is a new commit in Guix source repository. > > The file build-aux/hydra/guix.scm is a jobset to build Guix iteself. Yes. >> The result of those scripts is then consumed by Hydra’s >> hydra-eval-guile-jobs: >> >> >> https://github.com/NixOS/hydra/blob/master/src/script/hydra-eval-guile-jobs.in >> >> hydra-eval-guile-jobs is itself called by hydra-evaluator, from here: >> >> >> https://github.com/NixOS/hydra/blob/master/src/lib/Hydra/Helper/AddBuilds.pm >> > > Aye, this is where the magic happens. So it looks at the file extension of > the > jobset's recipe and if it is .scm, then it uses Guix. Exactly (strictly speaking, it uses Guile, Guix being just a Guile library.) >>> Hydra refuses to install without nix-store. So Nix has to be installed as >>> well. >>> I'm guessing Hydra uses nix-store command to build and retrieve store paths >>> for >>> packages given to it. Is it true? >> >> Yes. ‘nix-store’ is essentially a client of {guix,nix}-daemon, just >> like ‘guix build’. Hydra passes ‘nix-store’ a .drv file name, a >> low-level representation of the build process; ‘nix-store’ doesn’t have >> to care whether it was produced by Guix or Nix, and can’t tell the >> difference. (Similarly, ‘guix build’ can be passed a .drv produced by >> Nix.) >> >>> If so, how can hydra nix-store compile Guix packages? >> >> Just like this. :-) > > Ah, so the derivations, when sent to {guix,nix}-daemon are expressed in the > same > format? `guix build' converts our guile code into this format. Right. Try cat $(guix build -d emacs) to see what it looks like. Quoth the manual (info "(guix) Programming Interface"): Lower-level APIs are available to interact with the daemon and the store. To instruct the daemon to perform a build action, users actually provide it with a "derivation". A derivation is a low-level representation of the build actions to be taken, and the environment in which they should occur—derivations are to package definitions what assembly is to C programs. > So, when Hydra sees a .scm file as input, it asks Guix to convert the jobset > into derivations which are then sent to the {guix,nix}-daemon via 'nix-store'. Yes. > Does this mean that {guix,nix}-daemon are interchangeable? Yes and no. The core functionality is the same, but the command-line interface is different, and the default settings is different (for instance, guix-daemon uses chroot builds by default, with nothing in /bin, whereas nix-daemon uses non-chroot builds by default.) > Can Hydra run with the setup: guix clients, nix clients, guix-daemon, > Hydra? Or does it need a nix-daemon? No, no need for nix-daemon. On hydra.gnu.org, we have guix-daemon running, and Guix and Nix clients, the latter being there for Hydra. HTH! Ludo’.
