Add setting narinfo-cache-meta-ttl

[edolstra]

Motivation

This makes the current hard-coded 7-day nix-cache-info TTL configurable, making --offline and --refresh do the right thing.

Context

Summary by CodeRabbit

• New Features

  • Added configurable TTL for NarInfo metadata cache (narinfo-cache-meta-ttl), defaulting to 7 days.

• Bug Fixes

  • Improved offline and refresh behavior to correctly invalidate NarInfo metadata cache when requested.

• Tests

  • Added functional tests verifying NarInfo metadata caching with HTTP and the effect of --refresh.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📝 Walkthrough

Walkthrough

A new public setting ttlNarInfoCacheMeta controls the TTL for NarInfo metadata caching (default 7 days). Code now uses this setting instead of a hardcoded constant; defaults are adjusted in disableNet and reset on --refresh. Tests added to verify behavior.

Changes

Cohort / File(s)	Summary
Configuration Setting src/libstore/include/nix/store/globals.hh	Added Setting<unsigned int> ttlNarInfoCacheMeta (default 7243600) with help text for binary cache metadata TTL (narinfo-cache-meta-ttl).
Cache Implementation src/libstore/nar-info-disk-cache.cc	Removed hardcoded cacheInfoTtl field and updated cache cutoff calculation to use settings.ttlNarInfoCacheMeta.
CLI Defaults & Refresh src/nix/main.cc	Set ttlNarInfoCacheMeta to UINT_MAX in disableNet defaulting; reset it to 0 during --refresh handling alongside other TTLs.
Functional Tests tests/functional/binary-cache.sh	Added scenario to validate HTTP metadata caching behavior, persistence after removing nix-cache-info, and the effect of --refresh on metadata TTL/cache usage.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐇 I nibble at TTLs under moonlight bright,
A seven-day morsel, tidy and light.
Settings now dance where constants once lay,
Refresh gives a hop, then clears them away.
Cache and carrot, kept just right. 🥕✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly summarizes the main change: adding a new configurable setting for narinfo cache metadata TTL, which is the primary objective across all modified files.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch eelcodolstra/nix-305-make-nix-store-info-refresh-override-the-7-day-ttl

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[coderabbitai]

🧹 Nitpick comments (1)

tests/functional/binary-cache.sh (1)

330-332: Consider clarifying the expected error condition in the comment.

The comment states the failure is due to "nix-cache-info is gone and the cached metadata TTL is overridden to 0," but the expected error message is "uploading.*is not supported". This suggests the store attempts to create/upload cache info when it can't be fetched, rather than simply failing to read it.

Consider updating the comment to explain this behavior more explicitly for future maintainers:

 # But with --refresh, it should fail because nix-cache-info is gone
-# and the cached metadata TTL is overridden to 0.
+# and the cached metadata TTL is overridden to 0. When nix-cache-info
+# cannot be fetched, the HTTP store falls back to trying to create it,
+# which fails because uploading is not supported.
 _NIX_FORCE_HTTP=1 expectStderr 1 nix store info --store "file://$cacheDir" --refresh | grepQuiet "uploading.*is not supported"

[github-actions]

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