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'Graceful' fallback when one or more substituters fail #1061

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opened 2025-12-02 13:16:24 +00:00 by cyrneko · 5 comments

cyrneko commented

2025-12-02 13:16:24 +00:00

Yes, nix/lix entirely fails if one or more subsituters isn't reachable. This was fixed upstream in cppnix with this PR: https://github.com/nixos/nix/pull/13301

Describe the solution you'd like

A fallback to other substituters, or just plain copying upstream's solution would be nice.

Describe alternatives you've considered

uh, switching back to cppnix?????? /hj

Additional context

N/A

## Is your feature request related to a problem? Please describe. Yes, nix/lix entirely fails if one or more subsituters isn't reachable. This was fixed upstream in cppnix with this PR: https://github.com/nixos/nix/pull/13301 ## Describe the solution you'd like A fallback to other substituters, or just plain copying upstream's solution would be nice. ## Describe alternatives you've considered uh, switching back to cppnix?????? /hj ## Additional context N/A

raito commented

2025-12-02 14:30:32 +00:00

Owner

@cyrneko do you have a reproducer? I closed a similar issue recently because I was unable to reproduce this issue on modern Lix.

raito added the

bug

label

2025-12-02 14:30:39 +00:00

cyrneko commented

2025-12-03 21:59:09 +00:00

Author

I can give https://git.vulpecula.zone/tasiaiso/nixos-config, where it happens when cache.vulpecula.zone is down

I can give https://git.vulpecula.zone/tasiaiso/nixos-config, where it happens when `cache.vulpecula.zone` is down

raito added the

Release Blocking

Urgent

label

2025-12-05 01:15:47 +00:00

raito added this to the 2.95 milestone

2025-12-05 01:15:53 +00:00

raito commented

2026-02-07 22:28:39 +00:00

Owner

Reproducer (courtesy of @pennae)

$ NIX_REMOTE=/tmp/store nix-build --no-link --builders '' -E 'with import <nixpkgs> {}; runCommand "foo" {} "touch $out"'
$ NIX_REMOTE=/tmp/store nix copy [INSERT THE DRV YOU JUST GOT] --to 'file:///tmp/sub?compression=none' --no-check-sigs
$ NIX_REMOTE=/tmp/store nix-collect-garbage
$ truncate -s0 /tmp/sub/nar/*.nar                                                   
$ NIX_REMOTE=/tmp/store nix-build --builders '' --no-link -E 'with import <nixpkgs> {}; runCommand "foo" {} "touch $out"' --substituters 'file:///tmp/sub https://cache.nixos.org' --no-require-sigs

Reproducer (courtesy of @pennae) ``` $ NIX_REMOTE=/tmp/store nix-build --no-link --builders '' -E 'with import <nixpkgs> {}; runCommand "foo" {} "touch $out"' $ NIX_REMOTE=/tmp/store nix copy [INSERT THE DRV YOU JUST GOT] --to 'file:///tmp/sub?compression=none' --no-check-sigs $ NIX_REMOTE=/tmp/store nix-collect-garbage $ truncate -s0 /tmp/sub/nar/*.nar $ NIX_REMOTE=/tmp/store nix-build --builders '' --no-link -E 'with import <nixpkgs> {}; runCommand "foo" {} "touch $out"' --substituters 'file:///tmp/sub https://cache.nixos.org' --no-require-sigs ```

raito added the

E/help wanted

E/reproducible

labels

2026-02-07 22:28:49 +00:00

pennae commented

2026-02-08 17:11:29 +00:00

Owner

much better reproducer:

export NIX_REMOTE=/tmp/store

rm -rf /tmp/sub
nix copy nixpkgs#bat --to 'file:///tmp/sub?compression=none'
nix-collect-garbage
chmod -r /tmp/sub/*.narinfo
nix build nixpkgs#bat -v --no-link --substituters 'file:///tmp/sub https://cache.nixos.org' --no-require-sigs

much better reproducer: ``` export NIX_REMOTE=/tmp/store rm -rf /tmp/sub nix copy nixpkgs#bat --to 'file:///tmp/sub?compression=none' nix-collect-garbage chmod -r /tmp/sub/*.narinfo nix build nixpkgs#bat -v --no-link --substituters 'file:///tmp/sub https://cache.nixos.org' --no-require-sigs ```

lix-bot commented

2026-02-08 18:24:21 +00:00

Member

This issue was mentioned on Gerrit on the following CLs:

commit message in cl/5128 ("libstore: treat more substituter failures as recoverable")

This issue was mentioned on Gerrit on the following CLs: * commit message in [cl/5128](https://gerrit.lix.systems/c/lix/+/5128) ("libstore: treat more substituter failures as recoverable")