[Nix-dev] Regarding the unstable channel

[Eric Sagnes]

Hi,

I am using the unstable channel and recently encoutered some issues to update 
the system with `nixos-rebuild`, to list a few:

- flashplayer source not found (PR #11675)
- udevil not building (PR #11702)
- signing-party source not found (PR #11703)

All these issues have in common that the binary substitute was not available 
and they were triggered during source building.
As I understand it, a channel is updated when *all* the packages have been
built and the binary cache is available [1].

I totally understand that issues are expected when using the something labelled 
unstable, but it might confuse some less technical users, or worse give a bad 
impression to people that are trying NixOS.

This problem has no severe consequences as the system stays in a stable 
state, but it is a little unpleasing when trying to update the system with a
a local dev branch rebased on the current unstable and get update failures. 
(maybe this is more a development workflow problem?)

I am not familiar with hydra so I don't know what is possible to improve 
the situation. 
But for example, could it be possible to update the unstable channel when none 
or only a few jobs fail?
Also, I have no idea if it is technically possible, but having an automatic 
weekly digest on the ML with some hydra evaluations statistics and a list of 
"newly failing jobs" could be a way to bring attention on potential issues.

Cheers,
Eric

[1] http://nixos.org/nixos/manual/index.html#sec-upgrading
-- 
Eric Sagnes
サニエ エリック