hydra-module.nix: add 'useSubstitutes' option to control use of binary caches

Dependencies

• [2] 36YF4WOZ Remove unnecessary call to hydra-queue-runner --unlock
• [3] CF7QG4IA Make NIX_REMOTE_SYSTEMS configurable
• [4] 2ANV36PB Hackery
• [5] TTZ26BJQ Unify Hydra's NixOS module with the one used for hydra.nixos.org
• [6] 4HDPYRJ6 Update the hydra-queue-runner unit
• [7] ZYEFL36Q Ported/merged properties from the TUD configuration's hydra-module
• [8] 7XOH2DGH hydra-module.nix: Give types to options
• [*] D3MDJONY

Change contents

• edit in hydra-module.nix at line 171
  [3.319]

  [3.319]
  + };

  +

  + useSubstitutes = mkOption {

  + type = types.bool;

  + default = false;

  + description = ''

  + Whether to use binary caches for downloading store paths. Note that

  + binary substitutions trigger (a potentially large number of) additional

  + HTTP requests that slow down the queue monitor thread significantly.

  + Also, this Hydra instance will serve those downloaded store paths to

  + its users with its own signature attached as if it had built them

  + itself, so don't enable this feature unless your active binary caches

  + are absolute trustworthy.

  + '';
• replacement in hydra-module.nix at line 327
  [4.1684]→[2.0:125](∅→∅)
  − { ExecStart = "@${cfg.package}/bin/hydra-queue-runner hydra-queue-runner -v --option build-use-substitutes false";
  [4.1684]

  [4.85]
  + { ExecStart = "@${cfg.package}/bin/hydra-queue-runner hydra-queue-runner -v --option build-use-substitutes ${if optionalString cfg.useSubstitutes then "true" else "false"}";