HttpBinaryCacheStore: Don't ignore 401/407 errors#15877
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The only reason it treats 403 errors as 404s is that S3 returns 403 for files that don't exist if the bucket is unlistable. But we don't want to ignore (and definitely shouldn't cache) 401/407 errors as "file not found". This fixes "token expired" errors from cache.flakehub.com being silently ignored and cached. Now you get: # nix build --dry-run /nix/store/qnfhg5anpfpr4il3jlp9bnkf6vhyzbnj-determinate-nix-3.20.0 error: unable to download 'https://cache.flakehub.com/qnfhg5anpfpr4il3jlp9bnkf6vhyzbnj.narinfo': HTTP error 401 response body: {"code":401,"error":"Unauthorized","message":"Unauthorized.","request_id":"019e3a82-2474-7f80-8564-6e1bc2234654"} don't know how to build these paths: /nix/store/qnfhg5anpfpr4il3jlp9bnkf6vhyzbnj-determinate-nix-3.20.0 i.e. it's a fatal error now unless you use `--fallback`.
xokdvium
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May 21, 2026
kolmodin
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May 30, 2026
HttpBinaryCacheStore: Don't ignore 401/407 errors
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Motivation
The only reason it treats 403 errors as 404s is that S3 returns 403 for files that don't exist if the bucket is unlistable. But we don't want to ignore (and definitely shouldn't cache) 401/407 errors as "file not found".
This fixes "token expired" errors from cache.flakehub.com being silently ignored and cached. Now you get:
i.e. it's a fatal error now unless you use
--fallback.Note: this can "break" systems that have expired/unauthenticated binary caches, but that is the intended behaviour without
--fallback(we don't want fallback to building from source by default).Context
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