Hi Ludo, Thank you very much. Please ACK my understanding.
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. > 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. >> 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. 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'. Does this mean that {guix,nix}-daemon are interchangeable? Can Hydra run with the setup: guix clients, nix clients, guix-daemon, Hydra? Or does it need a nix-daemon? Sree